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So, I have an S2 7.9. I really like the boat, it's a good shorthanded boat, especially for someone dumb like me. It's simple. Simple is good. Lots of strings just confuse me. Anyway, the ONLY complaint I have about the boat is that the one-design rudder has exactly zero directional stability. I mean, it never loads up really badly, even when you're going sideways, over on your ear.  It's never a huge wrestling match because it's got a bunch of the blade in front of the axis of rotation. However, you absolutely can NOT let go of the tiller for even a second. No matter what, it will INSTANTLY head for the leeward side and you will round up. 

For a guy who singlehands a lot, that's not so good.  Also I figure on taking this boat 'waaay off the coast of California and I know of several boats who've sheared their 1-D kick-up rudders off.  The guys on "Arturo the Aquaboy", an S-2 7.9 that did the Pacific Cup doublehanded back in 2008 told me to get a one-piece rudder to make the trip. They tried with the one-design rudder and busted it off, about 400 miles off the coast.  Not good.  So, since floating in 8 inches of water isn't a high priority for me, I thought I'd make a rudder.

I had some specs I wanted.  I wanted it to be at least as deep as the 1-D rudder, which is about 44 inches of submerged blade.  I wanted a 15.5 - 16 inch chord.  I wanted it thick and strong, seeing as the !-D rudder is actually 3-freaking inches thick at the top.    If I could manage a fancy elliptical rudder, I'd love that, but I think that's beyond my skills.  So I went looking.  Custom Composites (Phils Foils) will do a semi-elliptical but it's going to set me back about $2K to $2.4K  in Canadian dollars. Ouch.   For me, that's just al little too much "ouch".   Rudder Craft makes a rudder that's the right size, but it's made out of HDPE, which bends. They have a wood core rudder, but it's just a bit smaller than what I wanted. Honestly, it would probably work, but I'm stubborn.  They also offer balanced rudders for J-29's / J-30's, which are about the size I want but they're $2100 USA.  Ouch, again.

So I decided to make my own.

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Did you actually build it?

The prices quoted seem reasonable for a one-off elliptical rudder blade. Lowest price I could do that job for would be well into the $1000 price range. I think your best bet is to either re-use a rudder that someone else has done for a similar size production boat, or get some other S-2 7.9 owners together and get some molds cut.

The amount of carbon in these blades can be staggering. I'm counting ~25 layers per side in a blade I've been working on on and off over the last year (its a 2nd spare, so not in a hurry to finish the job).

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First off...buy some wood.  I went down to our local good lumberyard, NOT Home Depot... and bought $217 worth of straight grain douglas fir. That got ripped into 2-inch-wide pieces. Because I'm a stupid git, and my shortest piece was 7 feet long, I cut them all to 7 feet. Fuckup.  I mean, I had 8 foot and 9 foot pieces. OK, me = dumbass.  Anyway, I mixed up some TAP Plastics marine epoxy, and bought a couple more bar clamps and put it all together on my garage floor.

rudder-final-glue.jpg.1988c8b0688e4a41997f1bd390eeb840.jpg

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What you're seeing there is some offset joints, so that the total length of the rudder is about 7' 10".   I'm not worried about the short bits at the bottom, as that's the bottom of the rudder and there's no real load down there.

Sanc99us - I don't think there will be any carbon in this. It's 2 1/8 inches thick doug fir, and will have a layer of 8 or 10 oz cloth over it.  That will be heavy, but it will be a positive lightweight compared to the one-deign appendage. This will be a straight foil, nothing elliiptical here.

Most of the blade is  clamped while the epoxy sets, I stuck some little bits on that will be hardly loaded, they're really there for fairing purposes with blue tape. Honest.  There are few pieces of wood stuck in the are at odd angles for support.

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Next up is to define the foil shape.

Well, if you read THIS article on Duckworks - http://www.duckworksmagazine.com/09/howto/foils/index.htm

 

you get the idea on what I'm going here. Also, the author made a nifty little spreadsheet in excel that will plot a router template for a given router bit depth, and NACA foil section chosen.  I learned, however, that while that spreadsheet and it's pattern is really accurate, your PRINTER may not be. Turns out that both printers I had access to printed out patterns that were stretched in both X And Y  directions.  I had to "fake it" by printing off a foil that was supposed to be about a cm. less chord than I planned on and with 3 mm less router bit depth. 

Anyway, here's what the template printout looks like.

 

rudder-excel-template.jpg

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OK, so I cut up some scrap plywood, printed out my template and taped the paper on top of the plywood. I then used a thumbtack to prick holes through the template line into the plywood. Then, a fresh "curve cutting" blade on the jigsaw and some careful sawing later., I had my two foil templates.  All this was glued up on the garage floor, my usual high-accuracy workspace.

 

rudder-router-jig.jpg

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All -pin one photo of finished router jig...

The dark plywood was scavenged for a lap table I made for the Mrs. when she had her hip replacement done. She hasn't used it in three years, so it's mine, all mine, now.  The rest is all scrap wood.

rudder-router-jig-and-diagram.jpg

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THen you need a REALLY flat table to do the routing on. OK, can do.  A visit to Home Depot..some chipboard, a couple of dry 2 x 4's, my sawhorses and a couple of little wedges to level things out and....

rudder-table.jpg

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Does the template fit?  Yes...but the rudder edges are not perfectly parallel, there's about 1/4 inch variation from the top (waterline) to the bottom of the rudder. I'll ahve to shim it a bit as the template gets near the bottom.
I was all ready to start routing, only to discover that "regular" router bits don't reach out to the offset I put into the Excel spreadsheet that generaled my foil jig. !@#$%^....so I ordered some "extra long" router bits off of Amazon. They arrived yesterday. If it doesn't rain, I'll do some routing out of the foil shape this weekend and will update.

rudder-jig-and-table.jpg

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2 minutes ago, daddle said:

Why the goofy beveled trailing edge on the guide template?

The router will never get back that far, so I just cut off the foil templates.  I could have cut  them off  at right angles or whatever, I suppose.   Hey "goofy" is in the eye of the beholder!

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BTW, I'd like to be clear about something.  I do NOT mean that I think that a Custom Composites rudder isn't worth the money.  I have no doubt, whatsoever that they deliver good value for the money and their product is first class. Not only that, but their CNC machine is capable of generating much more complex and sophisticated shapes than I can with a router and a flat table in my driveway. Their lamination guys have years of experience. Me?  Not so much.

It's just that two bills is a lot of money for moi, for a boat that I paid five bills for, to start with. (Yes, I stole it, that's a preposterous price for an S-2 7.9...)

It's an 80's boat. I'll be putting an 80's style, 12% balanced  constant-chord rudder on it. I'm fine with that.

Regarding carbon.

OoooOOOoooOOooo  "carbon". If it's carbon, it must be good, right? Carbon is the BEST, for *Everything*.  Right? Right?   Hm. I am very much not so sure. Engineered carbon structures, put together by someone who knows what they're doing, engineered by someone who knows what they're doing are lovely things. Oddly enough, though, wood rudders have been around for a very long time.  This is an S-2 7.9, not a J-70. Baby will surf down a water-hill, she don't really plane. So I'm willing to give up a bit of drag, meaning having a fat rudder, for A.) more attached flow, for longer when the shitski hits the fan and it's roundup time  B.) low-tech build that I can do myself.

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I like your router jig. Another option that we do for hand shaping, is cutting vertical depth strips with a circular/table saw and then using an electric hand plane to remove the material to those depths. Your jig may be a bit slower but will make it impossible to screw up, and will nail your profile. 

Also $2400 is a steal for a one-off rudder. 

I would consider upping your laminate to two layers of 12oz biaxial cloth if I were you -- bagged preferably. 

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I've used a similar template / jig to build a daggerboard with a wood core. In Fiji, on my foredeck. Prepare for a lot of noise and sawdust!

I also had a CNC cut set of foam rudder cores (left/right split) made in Australia. Less than $400. Good value - the hard work is all in shaping the core.

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NIce Allan, always fun to do it yourself.

remember not to route the whole profile, you need to turn it around and need flat spots or it would hard to shim stable.

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Alan,

How'd you settle on 12% balance?  What is the balance area of the existing OD rudder?  My most recent boat was an S2 9.1, with exactly the same issue plus  if motoring you couldn't let go of the tiller for a second either or she would instantly and quickly swing to port...and I always wondered if it was an issue of too much balance area of original rudder vice not enough balance area...

Crash

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1 hour ago, Crash said:

Alan,

How'd you settle on 12% balance?  What is the balance area of the existing OD rudder?  My most recent boat was an S2 9.1, with exactly the same issue plus  if motoring you couldn't let go of the tiller for a second either or she would instantly and quickly swing to port...and I always wondered if it was an issue of too much balance area of original rudder vice not enough balance area...

Crash

In Beill Belchers book on Windvane self-steering systems, he uses 20% balance for both his servo-pendulum oars and for his trim-tab auxiliary rudder. Now, that's for small, auxiliary steering where helmsman "feel" is irrelevant. The goal is to maintain a stable rudder/pendulum and minimize the amount of force needed to turn it.

However, if you look at a Monitor windvane paddle, you'll see that it's not very balanced at all, maybe 5%. Ditto for the Auto  Helm trim-tab vane's aux rudder. Look at a Hydrovane steering rudder, it's about 5% balanced.  So, how to make sense of this?  Why would the commercial windvanes, including two auxiliary rudder-type vanes use a much less balanced rudder than Belcher recommends?

Glen-L has this discussion page. http://www.glen-l.com/weblettr/webletters-4/wl38-rudders.html     For the type of rudder we use as most sailboaters, looks like they want 15-17%.

BoatDesign.net has several discussions on rudder design, and specifically how much balance to build into a spade rudder. The answer is that lots of people have opinions, it varies on the kind of sailing you're doing, and probably anything from 10-20% will work. I wanted to opt for a little more "feel" and a little more rudder stability and I'm willing to trade off a bit of helming effort for that. After all, the problem I'm trying to correct is a rudder which has a very light "feel", doesn't ever load up, but is wickedly UN-stable.  So going for 20% makes no sense.  I could have just as easily chosen 15%.

Calculating the percent of balance in the One Design rudder is pretty difficult, as the thickness varies wildly from top to bottom, but just going from profile, it's about 18%.
 

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https://www.jamestowndistributors.com/userportal/pdfs/WestSystem/Rudder_Blades_and_Centerboards_000_448.pdf

 

Read this. Build it this way. Ideally you should do the carbon fiber inlay and wrap it with a continuous layer of 12oz biax. If you don't do the carbon. Do a continuous layer of triaxial glass. Continuous meaning  you support the whole rudder on edge. leading edge up. drape the cloth over both side. Its a good idea to make the first 10mm and last 10mm of solid glass/resin filler. 

10 oz regular cloth will waterproof it. Not much strength happening there.

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Alan H

 

The way you are making the blank and shaping it is great and is a good method for the home builder and a great start. 

 

If I was building a rudder / fin for one of my clients then I would use a laminated timber core and then sheath it in glass in the lay up and I  use vinyl ester resin in the lay up and I would fill and fair the blade in gel coat / flow coat 

I know that this method sounds low tech and old school and heavier than other methods. The thing is it’s simple and cost affective and by the time you fill and fair and then paint the blade it’s still only 1-2 kgs heavier and far more longer lasting finish than paint. As far as the extra weight of the blade, I’m shore you can put your boat on a diet and remove more than that in crap out of the Boat.

 

The advantage in using vinyl ester resin in doing this job is it’s easier to use than epoxy resins and cheaper. Vinyl ester resin works like polyester resin when fibreglassing and has epoxy resin properties in water proofing and strength and is 1/2 the price of epoxy resin. 

As far as using carbon in the layup, I think that you would be spending more money that you don’t need too spend. Rule of thumb. The thinker the glass layup the stiffer and stronger the laminate will be.

 

Ive had no trouble in the rudders that I’ve make using the following method with a timber core. If you felt that you needed more glass then I’d put 1 extra layer on the leading edge all the way down the blade 200 mm wide 

 

When I make a rudder blade 6' - 7’ long this is how I make them

I make and shape the timber blank and shape it and make the trailing edge short by 40-50 mm.

I then cut a grove into the trailing edge f the blade and then glue in a solid strip of fibreglass to the trailing edge. The Advantage of doing this is I can get the trailing edge razor sharp and no air bubbles.

I then make allowances for glass overlaps on the leading edge of about 100 mm /4" 

I lay the blade on a flat surface and mix up a resin and acetone mix and per coat the timber 

Then I glass the blade with 600 double bias on one side over lapping the leading edge 100mm. When the resin has gelled I turn the blade over and glass the other side.

When the blade has cured l grind the over laps in the glass and then apply gel coat or flow coat all over the board. 2-3 coats of flow coat 

I then fill and fair the gel coat / flow coat I apply more gel coat / flow coat if needed.

I then polish and buff the gel/ flow coat surface.

job done and ready for use no painting required.

 

I’ve  found that this method works very well and that the gel / flow coat surface is long lasting and that the rudder blades tend not to get scratches or chips in them. On 1 Boat a 24’ footers that  I made a swing rudder on 10 years ago is still in very good condition and we sail in shallow water and touch bottom all the time when racing. After all rubbing in racing in shallow water. 

Thats what I'd do and I've been building boats for almost 30 years 

pulpit 

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15 hours ago, CaptainAhab said:

https://www.jamestowndistributors.com/userportal/pdfs/WestSystem/Rudder_Blades_and_Centerboards_000_448.pdf

 

Read this. Build it this way. Ideally you should do the carbon fiber inlay and wrap it with a continuous layer of 12oz biax. If you don't do the carbon. Do a continuous layer of triaxial glass. Continuous meaning  you support the whole rudder on edge. leading edge up. drape the cloth over both side. Its a good idea to make the first 10mm and last 10mm of solid glass/resin filler. 

10 oz regular cloth will waterproof it. Not much strength happening there.

That's basically what I'm doing, with a few differences. I'm considering picking up a few feet of unidirectional carbon/graphite today and routing in a channel for a few layers of it.  I keep going back and forth - yes/no as to whether to do it. It's not much work or expense, so I probably should.

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11 hours ago, pulpit said:

Alan H

 

The way you are making the blank and shaping it is great and is a good method for the home builder and a great start. 

 

If I was building a rudder / fin for one of my clients then I would use a laminated timber core and then sheath it in glass in the lay up and I  use vinyl ester resin in the lay up and I would fill and fair the blade in gel coat / flow coat 

I know that this method sounds low tech and old school and heavier than other methods. The thing is it’s simple and cost affective and by the time you fill and fair and then paint the blade it’s still only 1-2 kgs heavier and far more longer lasting finish than paint. As far as the extra weight of the blade, I’m shore you can put your boat on a diet and remove more than that in crap out of the Boat.

 

The advantage in using vinyl ester resin in doing this job is it’s easier to use than epoxy resins and cheaper. Vinyl ester resin works like polyester resin when fibreglassing and has epoxy resin properties in water proofing and strength and is 1/2 the price of epoxy resin. 

As far as using carbon in the layup, I think that you would be spending more money that you don’t need too spend. Rule of thumb. The thinker the glass layup the stiffer and stronger the laminate will be.

 

Ive had no trouble in the rudders that I’ve make using the following method with a timber core. If you felt that you needed more glass then I’d put 1 extra layer on the leading edge all the way down the blade 200 mm wide 

 

When I make a rudder blade 6' - 7’ long this is how I make them

I make and shape the timber blank and shape it and make the trailing edge short by 40-50 mm.

I then cut a grove into the trailing edge f the blade and then glue in a solid strip of fibreglass to the trailing edge. The Advantage of doing this is I can get the trailing edge razor sharp and no air bubbles.

I then make allowances for glass overlaps on the leading edge of about 100 mm /4" 

I lay the blade on a flat surface and mix up a resin and acetone mix and per coat the timber 

Then I glass the blade with 600 double bias on one side over lapping the leading edge 100mm. When the resin has gelled I turn the blade over and glass the other side.

When the blade has cured l grind the over laps in the glass and then apply gel coat or flow coat all over the board. 2-3 coats of flow coat 

I then fill and fair the gel coat / flow coat I apply more gel coat / flow coat if needed.

I then polish and buff the gel/ flow coat surface.

job done and ready for use no painting required.

 

I’ve  found that this method works very well and that the gel / flow coat surface is long lasting and that the rudder blades tend not to get scratches or chips in them. On 1 Boat a 24’ footers that  I made a swing rudder on 10 years ago is still in very good condition and we sail in shallow water and touch bottom all the time when racing. After all rubbing in racing in shallow water. 

Thats what I'd do and I've been building boats for almost 30 years 

pulpit 

That's a very complete answer and helpful, thank you. I will see if I can get 600  biaxial  glass here at TAP plastics. If not, I'll order it.  I don't mind the expense of epoxy. This whole blade will probably cost me about $450-$500, which is 1/4 to 1/2  of what a custom rudder would cost. Add in another $200 for the welding and materials for the gudgeons.

I note that both you and Cap'n Ahab recommend biaxial cloth. OK, then....

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3 hours ago, Alan H said:

That's a very complete answer and helpful, thank you. I will see if I can get 600  biaxial  glass here at TAP plastics. If not, I'll order it.  I don't mind the expense of epoxy. This whole blade will probably cost me about $450-$500, which is 1/4 to 1/2  of what a custom rudder would cost. Add in another $200 for the welding and materials for the gudgeons.

I note that both you and Cap'n Ahab recommend biaxial cloth. OK, then....

Alan H 

 

I use double bias and not biaxial cloth.

The difference is that cloth weaves run in different directions

biaxial cloth weave runs  0 /90 degrees 

double bias weave runs 45 / 45 degrees 

 

I find that the double bias mat just raps better around the leading edge and rounds of the blades far better than the biaxial cloth. As far as adding carbon into the laminate, I feel that this is over kill. If I was using a foam core then the carbon makes sense as the foam core has no balls in it to keep it from bending so the extra laminate would be needed. You are using a timber core so the glass is really only sheathing the timber. If it needs more laminate then I’d only add extra laminate to the leading edge as it’s the thickest part of the blade.

 

pulpit 

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I was going to post a video of myself, happily routering-away, removing wood at a great pace and forming a perfect foil this afternoon. Haha! From things I've read in the Wooden Boat Forum  I was expecting an hour or so per side and done....

NOT.

After 4 hours of work I have about 3/5ths of one side done.You know how it is, about 1/3rd of the way through the job you figure out the best way to do the job.

Gaaaa.... I discovered that router bits drift in the chuck after a while. You have to check them every 10-15 minutes. Imagine how I figured that out. Except for the godawful area where the bit moved, which will have to be faired, bigtime, most of the body of the thing is tolerable. "Precise", I'm not so sure, but tolerable. The trailing edge is OK. The leading edge is disgraceful. Now I know why the guy in the YouTube video used an elliptical edging bit for his leading edge. I'll be able to fill with epoxy and wood dough and fair it, and it will be fine, but yeeeecccchhhh.

I refuse to show you all photographs of this mess.

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Late to the game here, and have made a couple of rudders myself.  My contribution is Soller Composites as a source for hard-to-source cloth, at reasonable prices.  They have all kinds of weird stuff.  Good luck and more pics!

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Wood core? Leading edges are easily cleaned up with a hand plane. But.... Since you laminated strips together, watch the grain direction. 

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Warned you. Try doing a 6' deep section, 24" chord - with a stupid little 1/4" router and a tiny straight bit (only thing I could find in Nadi, Fiji).

daggerboard-1.jpg.603bf46306adfc8099685bffa8a1deb3.jpg

Then scarfing a 2" thick section to the remaining good part of the daggerboard...Total length of board is about 11'. Do not, do not repeat do scarf joints on 2" thick wood. Stupid idea. Much faster to just have built a 11' daggerboard and machine the bottom part into a foil.

.daggerboard-2.jpg.15f5bf0bd37ae7044eed2d986c18e201.jpg

Here's a little CNC foam core for a new rudder. Much, much easier to have a more sophisticated foil shape with a section that changes with depth.

daggerboard-3.jpg.3a85c1d3d050aa0a5476e943e31d5583.jpg

And have the router cut out the foam for the stock and tangs.

daggerboard-4.jpg.4279f8b9d68f74d95a943b8a03265d34.jpgdaggerboard-5.jpg.ea3d69d4b5ba3f40982b6b151e73181a.jpg

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11 hours ago, Zonker said:

Warned you. Try doing a 6' deep section, 24" chord - with a stupid little 1/4" router and a tiny straight bit (only thing I could find in Nadi, Fiji).

daggerboard-1.jpg.603bf46306adfc8099685bffa8a1deb3.jpg

 

OUCH! Doing a job that size with a laminate trimmer. :blink:

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On 11/18/2017 at 10:59 PM, Zonker said:

Warned you. Try doing a 6' deep section, 24" chord - with a stupid little 1/4" router and a tiny straight bit (only thing I could find in Nadi, Fiji).

daggerboard-1.jpg.603bf46306adfc8099685bffa8a1deb3.jpg

Then scarfing a 2" thick section to the remaining good part of the daggerboard...Total length of board is about 11'. Do not, do not repeat do scarf joints on 2" thick wood. Stupid idea. Much faster to just have built a 11' daggerboard and machine the bottom part into a foil.

.daggerboard-2.jpg.15f5bf0bd37ae7044eed2d986c18e201.jpg

Here's a little CNC foam core for a new rudder. Much, much easier to have a more sophisticated foil shape with a section that changes with depth.

daggerboard-3.jpg.3a85c1d3d050aa0a5476e943e31d5583.jpg

And have the router cut out the foam for the stock and tangs.

daggerboard-4.jpg.4279f8b9d68f74d95a943b8a03265d34.jpgdaggerboard-5.jpg.ea3d69d4b5ba3f40982b6b151e73181a.jpg

OK, you got me beat in the "annoying as fuck"  and "will I ever be done?" departments.  Also, my GOOD sections look about like yours.

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Alan H,

 

Are you taking the trailing edge of the board all the way to a fine point and then wrapping the glass around the trailing edge ?

 

From what I’ve seen in the photo that is the case, if so please think about cutting the trailing edge short 50 mm - 2” short and fit a solid fibreglass strip in its place. It will make fibreglassing much easier and quicker and give you a far stronger trailing edge. 

 

The problem with wrapping the fibreglass around a to tighter curve is you always get air bubbles in it or sand through the glass when fairing and when you bounce the board on the bottom will end up denting it as well and always repairing it.

 

Pulpit 

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9 hours ago, pulpit said:

Alan H,

Are you taking the trailing edge of the board all the way to a fine point and then wrapping the glass around the trailing edge ?

From what I’ve seen in the photo that is the case, if so please think about cutting the trailing edge short 50 mm - 2” short and fit a solid fibreglass strip in its place. It will make fibreglassing much easier and quicker and give you a far stronger trailing edge. 

The problem with wrapping the fibreglass around a to tighter curve is you always get air bubbles in it or sand through the glass when fairing and when you bounce the board on the bottom will end up denting it as well and always repairing it.

Pulpit 

+1 on this.  I did something similar to this on a CF/foam core rudder I built.  I didn't cut 50 mm off the trailing edge (more like 15-20mm), then wedged in a strip of CF tape I had already epoxied out and let cure.  With some additional glass and fairing compound, worked a treat.

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I was going to leave the trailing edge at about 1/4 inch thick and pull the layer of glass straight back from that.

I don't have any of the stuff to vacuum bag, and the Mrs. will revolt if I take over our garage for stinky stuff like that, so I'll be putting the glass on, outside.  I'll suspend the board by the ends and drape the cloth over it, leading edge up. Before that, I'll put a coating of thinned epoxy over the whole board and let it sit for an hour or so.  Anyway, I bought a little roller today, along with the epoxy and some gel coat so hopefully I can get a good bond.

How am I planning on doing the trailing edge?

 

The submerged part of the blade...the formed part is about 45 inches long. I'll take two, 1 x 1 x 48 inch bits of lumber and wrap 'em in saran wrap. I have about 8 pretty lightweight .. and in 1/2 pound... plastic wood clamps. I figure on overlapping the trailing edges by about an inch or so... maybe two inches, so the excess cloth, wetted out, will drape below the rudder. I then clamp the cloth shut  behind the trailing edge of the wood with the two 46-inch long bits of wood, held tight by the clamps.   The plastic wrap should keep the epoxy from bonding to the wood.

Wait until it all cures...sand..fair... sand. Gel Coat.   That's the plan.

I discovered today that TAP plastics does not carry 600 gm bi-directional glass. They have linear knytex, which I used for my last emergency rudder, crude as it was, 10 years ago.  So I'll have to order it online...no biggie.

 

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While I was at it,  I grabbed some lumber that's been sitting down the street, in an empty lot that used to have a house on it, a few years ago. This stuff has been outside for 18 months-plus.  I thought it was doug fir, or "construction hemlock" but when I cut it, come to find out that it's redwood. Hmm. This is for an emergency rudder, that will go in a low-tech cassette.

Anyway, I cut the bits out and put in two pieces of mahogany from Home Depot to add some stiffness. I carefully chose bits of redwood with the fewest knots, and actually scored pretty well, there are almost none in the rudder.  And then in a fit of cheap, I edge-glued them with Loctite PL100  polyurethane because I had a tube of that lying around but no epoxy.

Before everybody loses their minds over the  PL100 I have to say that I use the stuff to fix cabers for the Scottish Highland Games and that shit is strong. The sticks stay out in the rain and weather until we finally bust 'em and invariably the wood goes before the PL100- wood bond breaks. AND, the stuff is $6 a tube. Cheapo home-builder dudes who knock together semi-disposable plywood boats use PL100 to seal seams and glue stuff together all the time.

I dunno about redwood. You all can lose your minds over that, I suppose.  This will be an experiment. The blade is now 7 feet long overall, but that's because I have to cut the top off at an angle so the rudder can get over my transom. The foil part of the blade is going to be about 40 inches.   While I was at  TAP plastics they had 4 1/2 feet of linear carbon, 12 inches wide in the "2/3rds off" bin. WTF, I bought it.  I'll cut some 2 inch wide strips and lay on there to help the redwood. Then laminate over it all with bi-directional glass like you all tell me to do.  The chord is 13 inches, the stuff is 1.75 inches thick, by the time I fair it and glass it, it will probably be close to 2 inches thick. Beef, I think.  It might not be pretty but it will be strong.

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Actually, it's not that bad.  ---   looking  here:  http://www.woodworkweb.com/woodwork-topics/wood/146-wood-strengths.html

compressive strength perpendicular to grain, which seems like probably the most likely thing that would be applicable..

Doug Fir, depending on where it grows, is 1100 - 1400 psi
Young growth Redwood -  is 1100 psi.   so, in the ballpark.

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5 hours ago, Alan H said:

Anyway, I bought a little roller today, along with the epoxy and some gel coat so hopefully I can get a good bond.

Use a Bondo squeegee after you've rolled out the resin - it will give you a very nice lamination - it will look almost as "dry" as a bagged laminate.

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One thing I found for getting a decent lamination on the trailing edge with fiber glass and carbon tapes was to fold them in half lengthwise and sew them along the fold with a zig zag stitch. The two sides sandwich the trailing edge and air bubbles in the laminate are greatly reduced..catch the epoxy as it cures and use a bondo  knife to make sure every thing stays aligned.  Some Hutchins speed file work feathers the edges and the next layers make a surface to fair. Repeat layers if necessary, hope this helps. 

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Another technique for straight trailing edges is use a fiberglass sail batten as the solid glass trailing edge, with glass covering both sides.

Glass laminations covered with peel ply, trailing edge clamped with Corecell battens:

passport-1.jpg.e1ce415bc71fb9f4b8b3f116a8ceac47.jpg

I trimmed trailing edge of core, laid on 1 layer of glass, added epoxy bog to trailing edge, then laid over the other side of glass. Clamped on top of the peel ply.

Trim with tungsten grit jigsaw blade when cured

passport-1-2.jpg.200c3198eef3a9d2af73e6b2cffffd98.jpg

Cross section of trailing edge. Brown stuff is epoxy/phenolic/colloidal bog.

passport-2.jpg.b2f1838b83767cf3d065e0a33c4df0bc.jpg

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21 hours ago, Alan H said:

Actually, it's not that bad.  ---   looking  here:  http://www.woodworkweb.com/woodwork-topics/wood/146-wood-strengths.html

compressive strength perpendicular to grain, which seems like probably the most likely thing that would be applicable..

Doug Fir, depending on where it grows, is 1100 - 1400 psi
Young growth Redwood -  is 1100 psi.   so, in the ballpark.

It'll be fine. :) The whole point of sheathed composite is the whole is much stronger that the parts. For comparison,  Corecell A500 has compressive strength of 146psi, shear strength of 165psi, and tensile of 229psi (modulii much higher). You'd probably want more glass thickness on foam than on timber, but your core will carry more of the load.  Heavier than glass-over-foam, but a too-light rudder tends to float on ya.

Thanks for this thread, as we also will soon be building a rudder. I've considered a wood core, but one thing I worry about is water infiltration. A daggerboard is one thing, but rudders seem inevitably to leak where the shaft enters the blade.  What's your strategy for preventing that? Cuz one thing about solid wood: when it gets wet, it swells -- and the hydraulic forces involved can split granite boulders. :(

(Our current plan is pour-your-own  foam cores , probably 16lb/cuft urethane, with biaxial glass over that and a scheme of G-Flex epoxy and 5200 at the stock entrance to keep the water out. We molded our own core foam for some cockpit hatches & it worked well, though you need to scuff up the faces to get good epoxy adhesion.)

 

 

 

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On 11/19/2017 at 8:49 AM, pulpit said:

Alan H 

 

I use double bias and not biaxial cloth.

The difference is that cloth weaves run in different directions

biaxial cloth weave runs  0 /90 degrees 

double bias weave runs 45 / 45 degrees 

 

I find that the double bias mat just raps better around the leading edge and rounds of the blades far better than the biaxial cloth. As far as adding carbon into the laminate, I feel that this is over kill. If I was using a foam core then the carbon makes sense as the foam core has no balls in it to keep it from bending so the extra laminate would be needed. You are using a timber core so the glass is really only sheathing the timber. If it needs more laminate then I’d only add extra laminate to the leading edge as it’s the thickest part of the blade.

 

pulpit 

Biaxial cloth is +-45(US)

Double bias cloth is +-45(AU)

Same thing ... different hemisphere

 

 

https://www.jamestowndistributors.com/userportal/show_product.do?pid=1470

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2 hours ago, Diarmuid said:

(Our current plan is pour-your-own  foam cores , probably 16lb/cuft urethane, with biaxial glass over that and a scheme of G-Flex epoxy and 5200 at the stock entrance to keep the water out. We molded our own core foam for some cockpit hatches & it worked well, though you need to scuff up the faces to get good epoxy adhesion.)

Instead of PU foam you might consider expanding epoxy foams.  I believe Sicomen and Pro-Set make these.

Not sure where you would find Sicomen in North America, but Fisheries Supply carries the Pro-Set, although I imagine you could probably source it through any dealer that sells Pro-Set products.

https://www.fisheriessupply.com/proset-epoxy-pro-set-expanding-foam-resin-m1034-1

https://www.fisheriessupply.com/proset-epoxy-pro-set-expanding-foam-hardener-m2037-1

the Pro-Set expands roughly 3-4x so probably about 16 lb/ft3.  Roughly $150 for 1.5 gal of product.

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The model airplane lads and lasses hot-wire cut foam wings all the time. Now, they don't use anything heavy or tough like lastafoam, it's all super-lightweight stuff, but you can get constant chord foam foils from them.

Here...save you some searching. --  https://flyingfoam.com/

In their "quick order cores" you can find NACA symmetrical foils from the NACA 00xx series up to 6 feet long and an 18 inch chord. This is the bomb for emergency rudders... get the core, laminate the shit out of it, then wrap with a couple of layers of plastic and laminate a cassette around the foil.

For about $20 you can make your own hot wire setup and cut your own foils. Doing this, you can make tapered rudders
 



Now, hot to set this all up such that you can put a carbon or steel post in the middle.....I dunno.

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You can hot-wire pink insulation foam from Home Depot / Lowes  Orchard Supply, apparently. I would suspect that sniffing the vapors while you cut might not be the smartest thing in the world.  However, these foams are really low-density and have minimal strength. All they do is provide a form around which you build up your laminate.

I would be concerned about the foam wing bending during layup, but not to worry, the airplane boyz have figured out how to insert small carbon or wood rods into the foam  to stiffen it up. There are about 90 video's on youtube about how to do this.

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This video, even though it's not about anything specific that we might do, shows that the foam foil is shipped inside the blank from which it's cut.  This can be used as an exterior compression mold, as long as you don't lay in a lot of cloth.
 



To stiffen up your super-lightweight rudder core before going to town on your laminate structure, you can slather epoxy on your core. Don't go hog-wild with the epoxy, just get enough to bond one layer of light cloth on there.   Anyway, put the epoxy on the rudder core, then a layer of maybe 6 ounce cloth, roll it out well,  and then a layer of peel-ply. No more than that..... Put the whole thing back inside the blank, and weigh it down a bit on your bench.

When I did this, back in 2007  I didn't know about peel-ply and I used wax paper between the cloth and the blank. Seriously.....

Come back 6-8 hours later and pull the "blank" off of the rudder.

As a complete aside, you now have a foil-shaped "blank" which is somewhat coated with epoxy. I suspect that you can then prep and lightly glass the inside of the blank. Then make yourself a nifty plywood box to hold the  blank, make it come apart, and you can use the glassed-up blank as a mold for expanding foam structure.  I'm just guessing on this last part.

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Now that I'm guessing...  If I wanted to produce a mess of rudders, all the same, I might order a pre-cut flying foam rudder...or hot cut my  own, say if I wanted a tapered rudder.  I would order one that was 1/4 an inch longer than I wanted and probably an NACA section one percent fatter.  If I was cutting my own, I'd make plywood foils about a cm longer in chord and 1/4 inch fatter than the design I was after.

Get my foam, hot cut the foil out of the blank and hot cut the fore and  aft edges so that the two halves of the blank come apart. Save the "core" and laminate it up into another rudder, if you want...or toss it.

Then I would vacuum-bag  down a good solid laminate on the INSIDE of the two halves of the  blank, figuring on about 1/8 inch of  'glass on each side.  When the resin has kicked off, remove from the bag.  What you then have is two very sturdy  female molds which should mate pretty darned close. Build an open-able plywood box for these things, and you can make any number of essentially identical rudders out of this mold from expanding foam.  You can probably pre-build a carbon or s.s. rudder post, hang it inside the mold such that it's centered, and pour expanding foam around it, into the mold.

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5 hours ago, Diarmuid said:

It'll be fine. :) The whole point of sheathed composite is the whole is much stronger that the parts. For comparison,  Corecell A500 has compressive strength of 146psi, shear strength of 165psi, and tensile of 229psi (modulii much higher). You'd probably want more glass thickness on foam than on timber, but your core will carry more of the load.  Heavier than glass-over-foam, but a too-light rudder tends to float on ya.

Thanks for this thread, as we also will soon be building a rudder. I've considered a wood core, but one thing I worry about is water infiltration. A daggerboard is one thing, but rudders seem inevitably to leak where the shaft enters the blade.  What's your strategy for preventing that? Cuz one thing about solid wood: when it gets wet, it swells -- and the hydraulic forces involved can split granite boulders. :(

(Our current plan is pour-your-own  foam cores , probably 16lb/cuft urethane, with biaxial glass over that and a scheme of G-Flex epoxy and 5200 at the stock entrance to keep the water out. We molded our own core foam for some cockpit hatches & it worked well, though you need to scuff up the faces to get good epoxy adhesion.)

==========

This is a transom-hung rudder...no post. Ergo, one hopes, no water intrusion, though exactly how I'm going to seal up the bottom, I'm not sure, yet. I'll probably just glom on a bunch of epoxy and smoosh a couple of layers of mat on the bottom.... let it kick of, and sand it.

 

 

 

 

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BTW, thank you to everybody who'se contributed wisdom to this thread. It's really helpful.

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On the home front, I smoothed over the worst of the part that I gouged up pretty badly with the router, when I first started.  This is on my primary rudder.   The leading edge is now acceptable for this stage.  I built up the worst gouges  with epoxy and sawdust...not even wood dough, sawdust. They're back to acceptable now, but for one dollar-sized high spot and a ragged inch on the trailing edge. I'm going to need another box of wood dough.

Tomorrow, back to the router.

 

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There is a simple specific reason that boats or other structural composite objects are not made out of blue/pink construction foam sheet.

core shear

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15 hours ago, CaptainAhab said:

Biaxial cloth is +-45(US)

Double bias cloth is +-45(AU)

Same thing ... different hemisphere

 

 

https://www.jamestowndistributors.com/userportal/show_product.do?pid=1470

Captain Ahab 

It seems that Jamestown distributors may have it wrong in the naming of their cloth. The mat that your link goes to is a combination mat. It’s a double bias +-45 weave and a chop strand mat backing. 

 

So let’s look the basic fibreglass mats you can get to help you out a little and why they are called what they are. Until some one explained the difference between the mats I didn’t get it either and thought that biaxial and double Dias were the same mat. 

 

So how do you explain the different weaves of mat ?

The basic different weaves of mat come from the textile industry and how they explain the mats and the weave. With the cloth laying unrolled from the roll straight and looking at the roll here is how it’s explained. 

 

Unidirectional cloth or Uni - the weave runs at 0 degrees along the cloth and will be as long as you cut the cloth and is great at stopping bend in 1 direction 

Biaxial cloth - when looking at the cloth the weave runs at 0 and 90 degrees along the cloth, think of when you use to do graphs at school and the axis use to run at 90 degrees to each other. 

double bias cloth - the bias of the cloth in the textile industry is when the weave runs at 45 degrees and double bias is 2x the weave . So +45 / -45 degrees when looking at the cloth straight on. Double bias is great for stopping twisting. 

Tri axial cloth - tri axle cloth has the weave running at +45 / -45 and 0 degrees along the cloth. This cloth is great for stopping twisting and bending in one direction along the unrolled cloth. So if I wanted to cut a 8 foot long peace of cloth the uni will be 8 foot long. 

Weft tri axial  cloth - the weft of the cloth is the weave running across the cloth at 90 degrees when looking at it. So weft tri axle is the weave running at +45 / -45 and 90 across the cloth. If I cut a 8 foot long peace of cloth the 90 degrees ( uni ) would be only as long as the roll is wide on average 4 foot long max. 

Quad axial cloth - like the name saids it all  the weave runs in all 4 directions so it’s 0 / 90 and +45 / -45 degrees. This mat is great to use on flat areas like keel floors. It’s a prick at use around corners 

 

This is the basic cloths weaves that you can get in fibreglass, Kevlar and carbon cloths. I hope this has helped 

 

Pulpit 

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21 hours ago, 12 metre said:

Instead of PU foam you might consider expanding epoxy foams.  I believe Sicomen and Pro-Set make these.

Not sure where you would find Sicomen in North America, but Fisheries Supply carries the Pro-Set, although I imagine you could probably source it through any dealer that sells Pro-Set products.

https://www.fisheriessupply.com/proset-epoxy-pro-set-expanding-foam-resin-m1034-1

https://www.fisheriessupply.com/proset-epoxy-pro-set-expanding-foam-hardener-m2037-1

the Pro-Set expands roughly 3-4x so probably about 16 lb/ft3.  Roughly $150 for 1.5 gal of product.

Kewl.  I'll take a hard look at that ProSet foam.  Its numbers are close to 16# expanding PU, but with over twice the shear.  The main reasons to choose 16# PU over 8# is to get the shear strength high enuf, and because our barny-doory rudder will tend to rise if too light. A few comparables:

 

foams.jpg.5bc73718e645b23ba04f9127c44c6f45.jpg

CC has better shear modulus, as well  (which Ahab notes is important). I casually tested some nominal 8# PU alongside 5# CoreCell and was impressed enuf: a bit less crushing resistance, but also less water absorption for the PU.  Samples lived at the bottom of a 5 gal bucket for a month, and the shop-made PU came out with zero weight gain. :)

 

 

foams.jpg

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8 hours ago, pulpit said:

Captain Ahab 

It seems that Jamestown distributors may have it wrong in the naming of their cloth. The mat that your link goes to is a combination mat. It’s a double bias +-45 weave and a chop strand mat backing. 

 

So let’s look the basic fibreglass mats you can get to help you out a little and why they are called what they are. Until some one explained the difference between the mats I didn’t get it either and thought that biaxial and double Dias were the same mat. 

 

So how do you explain the different weaves of mat ?

The basic different weaves of mat come from the textile industry and how they explain the mats and the weave. With the cloth laying unrolled from the roll straight and looking at the roll here is how it’s explained. 

 

Unidirectional cloth or Uni - the weave runs at 0 degrees along the cloth and will be as long as you cut the cloth and is great at stopping bend in 1 direction 

Biaxial cloth - when looking at the cloth the weave runs at 0 and 90 degrees along the cloth, think of when you use to do graphs at school and the axis use to run at 90 degrees to each other. 

double bias cloth - the bias of the cloth in the textile industry is when the weave runs at 45 degrees and double bias is 2x the weave . So +45 / -45 degrees when looking at the cloth straight on. Double bias is great for stopping twisting. 

Tri axial cloth - tri axle cloth has the weave running at +45 / -45 and 0 degrees along the cloth. This cloth is great for stopping twisting and bending in one direction along the unrolled cloth. So if I wanted to cut a 8 foot long peace of cloth the uni will be 8 foot long. 

Weft tri axial  cloth - the weft of the cloth is the weave running across the cloth at 90 degrees when looking at it. So weft tri axle is the weave running at +45 / -45 and 90 across the cloth. If I cut a 8 foot long peace of cloth the 90 degrees ( uni ) would be only as long as the roll is wide on average 4 foot long max. 

Quad axial cloth - like the name saids it all  the weave runs in all 4 directions so it’s 0 / 90 and +45 / -45 degrees. This mat is great to use on flat areas like keel floors. It’s a prick at use around corners 

 

This is the basic cloths weaves that you can get in fibreglass, Kevlar and carbon cloths. I hope this has helped 

 

Pulpit 

It might help if you read my post. 

The example I gave is real not fake. Its on the label. It has nothing to do with the mat. The mat is simply part of that product.

technically biaxial means opposing 90 degrees. 

In the US the opposing "axial" fibers are unidirectionals are layed on top of another.  

0/90 is a woven cloth. No one calls 0/90 biaxial in the US. They call it cloth.

Its nomenclature.

There is a product of uni fibers in the 0/90 format. Its essentially modern woven roving. Because double bias is so much easier to use its hard to even buy it in the US.

I'm from the US and live in AU. Stop arguing with me.

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https://www.westsystem.com/the-105-system/reinforcing-materials/biaxial-fabrics-tapes/

There you go. Even the Gougeon Brothers at West System made the same mistake.

Next time you are in the States looking for some reinforcing fibers. Ask for Uni, Biax, Triax, or Quad.

Interesting cultural phenomenon. Australian English is based on slang and shortenings. An exception being the highly educated and posh fibreglass tossers use double bias to refer to +-45 fabric.

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My supplier says that "biax" is properly termed "uncrimped" fabric as it is stitched unidirectional layers, not woven.

The fabric with mat attached used to be called Fabmat.

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Today I finished off routing one side of the blade, flipped it over and did the leading edge of the other side. It's not turning out as thick as I'd wanted, so I'm scabbing on some"cheater" 3/16ths inch fir strips, which I will rout and belt sand.  I also got the first "fairing" coat of epoxy and sawdust on the leading edge side that I did today.

Tomorrow I'll use the surform plane to even out the leading edge on that side, and then fair some more with epoxy and wood dough. If I can, I'll route out the trailing edge.  If that's the case, then the basic forming of the overall shape will be done.

About the pink and blue home insulation foam.  Capn Ahab, you said "core shear".  That sounds reasonable except that in the case of using the blue or pink stuff, it would just be for a form, over which you create a laminate which carries all the load. If the laminate provides the strength, then the shear resistance of the core is irrelevant.  It could bend during layup....absolutely. So if it were me, I'd put one or two little carbon  struts in the foil before laying on the glass.

Now, I'm making a transom-hung rudder....no rudder post. Things might be very different for a rudder with a stainless steel or carbon post in it.

 

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Apparently poly resin dissolves some of that "House" foam - the pink IIRC.

Just an FYI - epoxy isn't a problem AFAIK.

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Polyester almost instantly dissolves EPS and XPS foam (the pink or blue stuff)

For the terminologies, perhaps look at one of the major North American manufacturers of fibreglass - Vectorply http://vectorply.com/database-search/

Under architecture they list the +45/-45 as double bias - although it seems very common to refer to it  as +45/-45 biax in North America.

Interestingly, they list a 0/60/60 triax as well as 0/45/45 and 90/45/45. 

A 0/60/60 orientation seems odd to me -  a 0/30/30 makes more sense in my mind as that would seem to almost provide the properties of a UD/biax layup (used in compression members where any load asymmetry can induce torsional loading).  A person with more knowledge on the subject than I suggested a rough lam schedule of 4 UD/1 Biax in compression members

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8 hours ago, Alan H said:

Today I finished off routing one side of the blade, flipped it over and did the leading edge of the other side. It's not turning out as thick as I'd wanted, so I'm scabbing on some"cheater" 3/16ths inch fir strips, which I will rout and belt sand.  I also got the first "fairing" coat of epoxy and sawdust on the leading edge side that I did today.

Tomorrow I'll use the surform plane to even out the leading edge on that side, and then fair some more with epoxy and wood dough. If I can, I'll route out the trailing edge.  If that's the case, then the basic forming of the overall shape will be done.

About the pink and blue home insulation foam.  Capn Ahab, you said "core shear".  That sounds reasonable except that in the case of using the blue or pink stuff, it would just be for a form, over which you create a laminate which carries all the load. If the laminate provides the strength, then the shear resistance of the core is irrelevant.  It could bend during layup....absolutely. So if it were me, I'd put one or two little carbon  struts in the foil before laying on the glass.

Now, I'm making a transom-hung rudder....no rudder post. Things might be very different for a rudder with a stainless steel or carbon post in it.

 

Its fine to use the non structural foams as a form. As long as you honestly know how much glass/carbon to put on the outside. There is a much higher safety factor using a structural foam because it creates a reliable composite panel. The stiffness goes up by orders of magnitude. The money you save on inexpensive foam is spent on more fibre & resin. I prefer cedar cores myself. Beautiful material to work with and it kills a couple of birds with one stone(core and fiber)

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4 hours ago, CaptainAhab said:

Its fine to use the non structural foams as a form. As long as you honestly know how much glass/carbon to put on the outside. There is a much higher safety factor using a structural foam because it creates a reliable composite panel. The stiffness goes up by orders of magnitude. The money you save on inexpensive foam is spent on more fibre & resin. I prefer cedar cores myself. Beautiful material to work with and it kills a couple of birds with one stone(core and fiber)

Makes sense.  After buying a core from Flying Foam back in 2007, and putting on 3 layers of 23 ounce knytex (linear glass stitched to mat) , which wasn't really a pleasant job, I thought I'd prefer shaping a wood rudder and doing less epoxy work this time. So far, it's a lot more pleasant.   It's also my first time using a router since 8th grade shop class.

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So if I'm planning on putting on one layer of glass, why shouldn't I use triaxial, assuming it's available?   One layer would go straight up and down the rudder, the other two layers are 45 deg off that axis?

 

http://www.fiberglasssupply.com/Product_Catalog/Reinforcements/Knitted_Fabrics/knitted_fabrics.html

Fiberglass Supply dot com has both biaxial and triaxial cloth.  The triaxial  is 19 oz per yard at basically $9 US  per yard.  They say...

 

Knitted Triaxial Bias (+45°/-45°/0°) Fabric, use where strength and stiffness in length (0°) direction is required.  Good wet out, excellent resin/reinforcement ratio and provides smooth laminate with minimal shrinkage.

------To do both this rudder and my emergency rudder I'll need 5 yards.

The Biaxial stuff is 12 or 17 ounces per yard at  $7.30  or $7.50 / yard.  They say....

 

Knitted Double Bias (+45/-45 Deg.) Fabrics, use where equal strength and stiffness in both directions is required.  Good wet out, excellent resin/reinforcement ratio and provides smooth laminate with minimal shrinkage.

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Quote

That sounds reasonable except that in the case of using the blue or pink stuff, it would just be for a form, over which you create a laminate which carries all the load.

As mentioned... to carry the load on ONLY the outer skins requires what 5x? 10x? the layers of a properly cored rudder.   The proper core costs less than the additional cloth and resin.

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3 hours ago, solosailor said:

As mentioned... to carry the load on ONLY the outer skins requires what 5x? 10x? the layers of a properly cored rudder.   The proper core costs less than the additional cloth and resin.

Lets not confuse panel stiffness with member stiffness.  You can have a hull/deck with thick core and thin skins that has large panel stiffness but the boat will still bend like a banana under forestay and backstay tension.

In bending, rudders are designed with the assumption that ONLY the skins provide resistance. so only 1x required no matter the foam - provided the skins are properly supported, which is where the choice of core does come in to play. 

If the skin separates from the core (delam in the case of foam or rotting to the point of soup in the case of balsa ) then you are effectively down to a single thin skin with regards to panel stiffness - so you can feel the skin moving underfoot on a deck or push the sides in on a hull.  Yet there are many successful club racers that are found to have substantial rot or delam upon survey.  I'm sure the separation of core from skin has some impact on the overall fore and aft stiffness of the boat - but its main impact is on panel stiffness.

Having said this, I do agree that cheap Home Depot type foam is not the way to go in a structural member.  For most structural members, my personal preference is balsa.  The exception being rudders where it is next to impossible to eliminate the ingress of water. For a rudder, I would lean towards a SAN foam (Corecell) - but any decent structural foam will do the job just fine

 

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OK, then!  Nix the blue and pink stuff!   The things you learn....

OK, today I spent another two hours, adding up to probably about 5-6 hours total now, with the router.  I've finished routing out the basic shape. There's more to do...I'm adding some material at the thickest part of the chord, as somehow I'm about 1/8 - 1/4 inch too thin overall, but the shape is there.

Here's my setup in my fancy-pants workshop, aka the driveway.


 

IMG_2059.JPG

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I'll add some closeups to show the degree of smoothness (bleeccch, lots of sanding here!) and accuracy. *meh*... that I've achieved, later.

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1 hour ago, Alan H said:

OK, then!  Nix the blue and pink stuff!   The things you learn....

OK, today I spent another two hours, adding up to probably about 5-6 hours total now, with the router.  I've finished routing out the basic shape. There's more to do...I'm adding some material at the thickest part of the chord, as somehow I'm about 1/8 - 1/4 inch too thin overall, but the shape is there.

Here's my setup in my fancy-pants workshop, aka the driveway.


 

IMG_2059.JPG

Your neighbours must love you - the dental drill from hell running all day in your driveway.

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I have been thinking of doing this to my exsisting rudder - its the wrong shape.   I could either hand sand it into shape using templates then long boarding in between the templates.  Or build a jig like you did.  My problem would be to get the jigs centered on the midlines of rudder correctly (1/2 point).  Maybe glue them in place???

As it not really far off maybe hand sanding is all I need to do.

What you are doing is very cool - I realize this is much too late - you might get better results using a milling bit.  I got a 1/2 inch fiberglass cutting bit and it cuts wood/ext very nicly.

keep posting - love the workshop :)

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39 minutes ago, Lucky Dog said:

I have been thinking of doing this to my exsisting rudder - its the wrong shape.   I could either hand sand it into shape using templates then long boarding in between the templates.  Or build a jig like you did.  My problem would be to get the jigs centered on the midlines of rudder correctly (1/2 point).  Maybe glue them in place???

As it not really far off maybe hand sanding is all I need to do.

What you are doing is very cool - I realize this is much too late - you might get better results using a milling bit.  I got a 1/2 inch fiberglass cutting bit and it cuts wood/ext very nicly.

keep posting - love the workshop :)

39 minutes ago, Lucky Dog said:

I have been thinking of doing this to my exsisting rudder - its the wrong shape.   I could either hand sand it into shape using templates then long boarding in between the templates.  Or build a jig like you did.  My problem would be to get the jigs centered on the midlines of rudder correctly (1/2 point).  Maybe glue them in place???

As it not really far off maybe hand sanding is all I need to do.

What you are doing is very cool - I realize this is much too late - you might get better results using a milling bit.  I got a 1/2 inch fiberglass cutting bit and it cuts wood/ext very nicly.

keep posting - love the workshop :)

On 11/25/2017 at 3:09 PM, Alan H said:

Today I finished off routing one side of the blade, flipped it over and did the leading edge of the other side. It's not turning out as thick as I'd wanted, so I'm scabbing on some"cheater" 3/16ths inch fir strips, which I will rout and belt sand.  I also got the first "fairing" coat of epoxy and sawdust on the leading edge side that I did today.

Tomorrow I'll use the surform plane to even out the leading edge on that side, and then fair some more with epoxy and wood dough. If I can, I'll route out the trailing edge.  If that's the case, then the basic forming of the overall shape will be done.

About the pink and blue home insulation foam.  Capn Ahab, you said "core shear".  That sounds reasonable except that in the case of using the blue or pink stuff, it would just be for a form, over which you create a laminate which carries all the load. If the laminate provides the strength, then the shear resistance of the core is irrelevant.  It could bend during layup....absolutely. So if it were me, I'd put one or two little carbon  struts in the foil before laying on the glass.

Now, I'm making a transom-hung rudder....no rudder post. Things might be very different for a rudder with a stainless steel or carbon post in it.

 

Its fine to use the non structural foams as a form. As long as you honestly know how much glass/carbon to put on the outside. There is a much higher safety factor using a structural foam because it creates a reliable composite panel. The stiffness goes up by orders of magnitude. The money you save on inexpensive foam is spent on more fibre & resin. I prefer cedar cores myself. Beautiful material to work with and it kills a couple of birds with one stone(core and fiber)

 

39 minutes ago, Lucky Dog said:

I have been thinking of doing this to my exsisting rudder - its the wrong shape.   I could either hand sand it into shape using templates then long boarding in between the templates.  Or build a jig like you did.  My problem would be to get the jigs centered on the midlines of rudder correctly (1/2 point).  Maybe glue them in place???

As it not really far off maybe hand sanding is all I need to do.

What you are doing is very cool - I realize this is much too late - you might get better results using a milling bit.  I got a 1/2 inch fiberglass cutting bit and it cuts wood/ext very nicly.

keep posting - love the workshop :)

He's cutting across the grain. Whatever bit he is using its not the appropriate one. Milling bits are designed for metal and will cut fiberglass as well.  Personally I would have tried a planer router bit or a 3/4" wide mortising bit. There is a fair amount of sanding after a rough router job

The last rudder I did was a Naca 0012  profile. vertical grain western red cedar core. epoxy/ glass.  I used a power plane and a straight edge. fastened my templates to the end of the blank. I took light licks from one end to the other. I was done in an 1-1.5 hrs ready for glass. I'm a true craftsman with a power plane. Not for newbies.

I made up some 10mm G10 like flat stock on a sheet of melamine and bonded them to the top and bottom of the blade. I used high density filler for the leading 1/2 inch and 1 inch for the trailing edge. carbon inlay at max chord . 1st coat of resin soaked in for a couple of hours. Then 12 oz double bias. Followed by 4 oz cloth to get a smoother finish and less print thru. I'm not concerned about water intrusion unless its damaged. At least the cedar won't rot. 

I like making foils. They are time consuming and finicky. If done right they rewards justify the efforts.

People also try using plywood cores. I find them brutal to shape compared to solid wood. apparently thye have found some of the older plywood rudders on bigger boats that suffered core sheer. The veneers kind of roll over and disturb the whole laminate.

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Regarding the router bit... the guy in the video I referenced at the beginning used a round-bottom bit to "avoid tear-out" as he put it. Thinking about that, it seemed logical to me so I bought round-bottom bits. Were I to do it again, I'd stick with the round-bottom, but I'd use a "bigger"...3/8 instead of 3/16th bit, with cutting surfaces that run higher up the shaft. It would go a lot faster.  Also, once again, I have  never touched a router since 8th grade shop, when we used one to make a street sign for our houses as a class project. This is the first project I have done with a router since I was 13 years old.  So if I don't screw it up beyond all recognition, it's a WIN as far as I'm concerned.

The other trick I discovered is DO NOT MAKE THE TEMPLATE WIDER THAN THE FLAT PLASTIC SURFACES OF YOUR ROUTER. It's too easy to "slip off the edge".  Ah well, if I were to do this again I could probably do it in 2/3rds the time.  Since I'll be shaping an e-rudder which will be about 75% of the size of this one, and starting that in a week or two, I'll have a chance to test those theories -- different bit, narrower template.

About my neighbors...the guy on my left loaned me the taller sawhorses and came over 3x to check out what I was doing, so he's OK with it. The guy on the right is off on another bicycling trip. The house across the street, and the two flanking them, though. Well...nobody said anything. I'm always out there, shaping cabers, working on the skerry, or something. I think they're used to it.  Mrs. Alan H however, was ready to kill Friday afternoon.

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2 hours ago, Lucky Dog said:

I have been thinking of doing this to my exsisting rudder - its the wrong shape.   I could either hand sand it into shape using templates then long boarding in between the templates.  Or build a jig like you did.  My problem would be to get the jigs centered on the midlines of rudder correctly (1/2 point).  Maybe glue them in place???

As it not really far off maybe hand sanding is all I need to do.

What you are doing is very cool - I realize this is much too late - you might get better results using a milling bit.  I got a 1/2 inch fiberglass cutting bit and it cuts wood/ext very nicly.

keep posting - love the workshop :)

If you look closely at my routing table picture, you'll see a gray block resting up against the far edge of the rudder. That's a 28 pound lead brick. I'm serious...it's a brick shaped  hunk of lead that weighs 28 pounds. I have two of them, and braced the template between them. The bricks were always on the "other" side of the rudder, the side opposite where I was standing.

You could probably make some 6 x 6 x 18  concrete blocks to do the same thing, or just buy some concrete blocks from the landscaping store.

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6 minutes ago, daddle said:

Next time find a table saw. Ten minute job, max.

Having made "foils" that way....did one for my Cal 20 with a table saw and a surform plane 20 years ago, I can say that this time I wanted something a bit more accurate. The table saw work took more than ten minutes, but maybe only half an hour. There was a lot of sanding, however, and the foil was still slab-sided. 

Oh, wait...you're mister "goofy trailing edge" comment  from 25 posts ago. Right.... got it.

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11 minutes ago, Alan H said:

Having made "foils" that way....did one for my Cal 20 with a table saw and a surform plane 20 years ago, I can say that this time I wanted something a bit more accurate. The table saw work took more than ten minutes, but maybe only half an hour. There was a lot of sanding, however, and the foil was still slab-sided. 

Oh, wait...you're mister "goofy trailing edge" comment  from 25 posts ago. Right.... got it.

Yeah, I asked an honest question about your template shape and got a good answer...I've never made a rudder before.

My comment about the table saw is honest too. I would cut it to a template as well. A table saw is certainly more accurate than a hand-held router. Plus the horsepower advantage. Yeah maybe more than ten minutes as I would shim the extension table to be perfectly co-planar with the saw table. And another five minutes to mount the Dado blade. There would be no work with a planer afterward. I would expect perfection. I would think a nice taper could be cut as well, however I'd have to think about exactly how. My main concern would be accommodating the changing bow, cup and twist that would develop as the material is removed.

However I do realize that table saws are rarely found on-board a yacht...as handy as they are. There are many in Fiji. I found one a hundred yards from the anchorage at Pohnpei, Micronesia.

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1 hour ago, Alan H said:

Regarding the router bit... the guy in the video I referenced at the beginning used a round-bottom bit to "avoid tear-out" as he put it. Thinking about that, it seemed logical to me so I bought round-bottom bits. Were I to do it again, I'd stick with the round-bottom, but I'd use a "bigger"...3/8 instead of 3/16th bit, with cutting surfaces that run higher up the shaft. 

There's a family of cutter called bowl&tray routing bits that would be pretty good for this task: they have the softer corners of a round nose ('core box')  bit but leave a flat bottom.  The better versions include a modest upshear.

45981-LI.jpg

They'll plunge cut, but they aren't happy about it.  The  radiused parts of the bit tend to gum up and need periodic cleaning.

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Those bowl cutters wear out fast. you just need a good sharp 3/4" dado bit. It exactly what they are design for. The wider the bit, less lines and it's more stable.

Table saw would not be accurate. It would need a ton of clean up. Expecting perfection is a false expectation in this case. Too much glue too many joints. clamping it together is a pain in the ass. Hard to keep it perfectly straight. Which in all honestly is the most important part. Bow or twist ruins rudders.

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8 hours ago, daddle said:

Yeah, I asked an honest question about your template shape and got a good answer...I've never made a rudder before.

My comment about the table saw is honest too. I would cut it to a template as well. A table saw is certainly more accurate than a hand-held router. Plus the horsepower advantage. Yeah maybe more than ten minutes as I would shim the extension table to be perfectly co-planar with the saw table. And another five minutes to mount the Dado blade. There would be no work with a planer afterward. I would expect perfection. I would think a nice taper could be cut as well, however I'd have to think about exactly how. My main concern would be accommodating the changing bow, cup and twist that would develop as the material is removed.

However I do realize that table saws are rarely found on-board a yacht...as handy as they are. There are many in Fiji. I found one a hundred yards from the anchorage at Pohnpei, Micronesia.

OK, good to know.  I'm not grokking how you'd do this with the dado blade, though.   Want to elaborate?  I actually have a table saw, though I mostly use it on the floor of my garage!

 

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The dado just to make a wider cut...save some time. But the character of the wood might need to be accomodated. I think most of the material would be removed by ripping along the long rudder axis. The template used to adjust the blade in depth and angle. I suppose I would leave guide strips uncut at the max thickness point and at the trailing edge. Some initial cuts...or a big planer...might be needed to make true reference surfaces on the laminated mess...same as any other technique. With about twenty adjacent cuts the surface would be quite true...better than a layup...not more than a little sanding away from perfect. 

There are other ways too. It is the accuracy of the table and the HP that make the job easier. Could be cut crosswise like was done with the router, too. On a convex part like a rudder the circular saw blade is just as handy as any router bit. It this case some kind of jig, maybe like you had, maybe full length, would be needed to follow the templates.

Maybe more than ten minutes...heh...nothing marine happens in ten minutes.

Might do a rough pass leaving a few mm proud then re-true the guide surfaces for warp.0

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There's video on you tube of people doing basically what I'm doing, but running the router longitudinally...presumably along the grain of the wood. I could see doing pretty much exactly this with a circular saw to put a mess of grooves in the board and then use a power planer to cut down until the grooves "disappear". If you could put a dado blade on your circular saw...I don't know of a way to do this, but if you could.... you could align the blade both in depth with your foil template and tangent to it, and then do what they're doing in the video.
 

 

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