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6 hours ago, Alan H said:

Oh, so those boats for sale that I see, mostly in the Midwest.... all over Yachtworld... that have "bronze bottoms" are using baltoplate?  I dinnae know that.

About the carbon... I decided to use it. There's a 6 inch wide unidirectional carbon strap running up and down about 80% the length of both sides of the rudder, at the thickest part of the chord. They're epoxied to the wood.  I'm also getting a thin coat of epoxy on the whole rudder as it's been suggested by several people that on the E-rudder, the wood soaked up a mess of epoxy and that contributed to making the mix rather epoxy-starved.

Vacuum Bag Day is Saturday afternoon after I finish RC for the Three Bridge Fiasco.

No! That's typically VC-17 for fresh water.  Looks kinda like this:

vc-17+bottom.jpg

Baltoplate is for salt water, and looks like this (kinda a dark gun metal grey)

Image result for burnished Baltoplate

Can be shinier when burnished, but is still a darker grey rather than a bronze/copper color...

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Thanks, Crash. I've seen boats in the yard with that gun-metal grey bottom. Never knew it was Baltoplate.

Anyway this morning the other side of the primary rudder got a coating of "sealer" epoxy. The carbon strip  on that side decided to drink some in, too, so I might have been kinda skimpy with the juice when I bonded it.  Vacuum Bag #2 is tomorrow!  I have a buddy coming over to help so there will be two pairs of hands. MUCH better..

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I also made some progress. Rudder blade is done. The shape came out pretty close to the NACA profile except for the first inch along the leading edge. I had to do some fairing there. Here is the laser-cut template on the blade:

5a6c1758a8153_20180126_224849(Medium).thumb.jpg.186d3ad4f9b1f9ec806567b206bc4170.jpg

 

Now it's time to build the cassette. Carbon or glass???

I'm going to use two of those templates above to set the location and angle of the gudgeons. 

I've made a skeleton of the cassette that was vacuum bagged onto the blade for proper fit. Here is how it should be positioned at the end:

5a6c17bfbac7e_20180126_231232b(Medium).thumb.jpg.e2fd3a1b24e7c3bc8966ec4528140aa5.jpg

 

The plan to build the horizontal strips is something like this:

cassette.JPG.9d928a467f2b493aa240646db178ac79.JPG

Gray is the blade, light blue is filler, black is (many) layers of carbon or glass. White circle is the pin.

So what would you use to laminate these strips? I have both carbon uni and glass uni, glass +/- 45 biax and some carbon twill. Weight doesn't really matter, I just want to make sure the rudder stays on the boat. Carbon is stronger, but glass is tougher, right?

 

 

 

 

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for your forms that will be drilled for the pintle/rod  I'd probably make a shape out of 1/4 inch marine plywood and then laminate 2-3 layers of carbon twill to each side.  You could put a layer of 6-10 oz twill glass on each side between the wood and the carbon, I suppose.  The biaxial would probably be fine, too.   Then you'll have something that's about 1/2   inch thick.  I'd wrap a 1/2 inch wide strip (or two) of linear carbon around the edge of the thing, emphasis on the front so the pintle can't rip out. Then fillet onto the body of the cassette and get a layer of biaxial or carbon twill over the fillets.

Much depends on how you're planning on doing the bearing surface, though. I'm gonna use these...

oilite.jpg

fz21_cusn6zn3pb6_bronze_oil_sintered_bus

 

...bronze, sintered, oil-less bushings. Drill the ply/carbon sandwich, coat the bushing with 5400 on the outside, shove it in there.

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Yesterday the primary rudder got vacuum-bagged. My friend Greg S. came over in the afternoon and between 1:00-5:00 we got it done. We prepped all the fabric before beginning,  had the epoxy immediately at hand,  and with the two of us it was immensely easier than doing it alone. The rudder sat under vacuum and heat for about 2 1/2 hours before I turned stuff off and went to Burns Night. I'll un-bag it this morning. The only downside is that the stock end slipped off the sawhorse while I was adjusting it and fell about 10 inches straight down on my toes. I now have a broken big toe on my right foot. I'm headed to Urgent Care here in Palo Alto later this morning for some x-rays and probably a boot to wear for a month. There goes what remains of any training during the Highland Games off-season. FFffffff----uuuuuucccckkk.

While we were at it, I cut off the extra flash on one edge of the E rudder stock and Greg got some 6 oz. glass and epoxy on it. I got two layers of 6 oz glass on the bottom of the e-rudder, so that can banged around a bit now and none the worse for wear.   It's getting very close to being done.  With the cassette in mind, yesterday I looked at the E rudder and realized that the cassette is really going to be quite small. Yes!

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On 1/26/2018 at 10:38 PM, erdb said:

I also made some progress. Rudder blade is done. The shape came out pretty close to the NACA profile except for the first inch along the leading edge. I had to do some fairing there. Here is the laser-cut template on the blade:

5a6c1758a8153_20180126_224849(Medium).thumb.jpg.186d3ad4f9b1f9ec806567b206bc4170.jpg

[/quote]

Wow... that's sweet.  While I think my rudder is pretty fair, I doubt that I got this close to perfect with my template.

Quote

Now it's time to build the cassette. Carbon or glass???



Personally, I think a biaxial glass cassette with a couple wraps of unidirectional carbon at the top and bottom, at the high stress points, would do the job well.  I'd probably wrap the blade twice with the biaxial glass.  You could use carbon twill for the body of the thing, but not sure if this part is worth the expense.

Quote

I'm going to use two of those templates above to set the location and angle of the gudgeons. 

I've made a skeleton of the cassette that was vacuum bagged onto the blade for proper fit. Here is how it should be positioned at the end:

5a6c17bfbac7e_20180126_231232b(Medium).thumb.jpg.e2fd3a1b24e7c3bc8966ec4528140aa5.jpg

 

The plan to build the horizontal strips is something like this:

cassette.JPG.9d928a467f2b493aa240646db178ac79.JPG

Gray is the blade, light blue is filler, black is (many) layers of carbon or glass. White circle is the pin.

So what would you use to laminate these strips? I have both carbon uni and glass uni, glass +/- 45 biax and some carbon twill. Weight doesn't really matter, I just want to make sure the rudder stays on the boat. Carbon is stronger, but glass is tougher, right?

 

 

 

 

 

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I de-bagged the primary rudder today. This time the bleeder has pulled a significant amount of epoxy out of the mixture.  93% of the rudder is absolutely pristine. The bonding is tight, the weave is filled, the peel-ply finish is smooth.  The center of the rudder where the loads will be highest is rock-solid.  The ends aren't so great, and a bunch of glass will need to be cut off and patched in. The lower, aft corner of the trailing edge , well the glass got folded over somehow in the bag on one side, so there's about 4 inches of the trailing edge of that curve that will have to be patched in.  However, this is a low-load zone so it's no biggie.   There's one sort-of  medium-sized bubble in the aft part of the transition from "boxy" to "foil" that I'm attempting to heat up and mash down.  I've slit it with a razor,  got some epoxy under it and a bigass Highland Games weight, which is round, is sitting on it overnight.    Yeah  there are some bits here and there that will need cutting out and patching in.  But all in all, this rudder is a *Significant* improvement over the E-rudder.  It will be plenty strong.  Wherever the loads are high, the glasswork is really solid.  I'm pleased.

After an uncomfortable night, I went to Urgent Care this morning. The PA melted a hole in my toenail, which soon was very messy. However, that relieved a lot of pressure. X Rays, to my surprise, reveal that there is no break. Considering the pain and spectacular colors I figured it broke for sure. I've spent the day in an open toe'd orthotic shoe, and managed to walk several blocks around Berkeley to go to a concert and meet Mrs. Alan H's nephew for dinner.  No surgery. No titanium pin in the toe.....things could be worse.

I'll put up some pics tomorrow.

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Blood trapped under a nail can be very painful!  Once the hole is thru and pressure off, make sure to keep hole moist with ointment so it doesn’t scab over and build the pressure back up...don’t ask how I learned that lesson:blink:

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I'm walking just fine. I changed the bandage, got some antibiotic ointment in there and am sporting the very fashionable orthotic shoe for a few days.

OK, here are some close-ups of the laminate, taken in the middle of the rudder where the stresses are highest. I'm stoked!

 

IMG_0238-sm.jpg

IMG_0242-sm.jpg

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This layup is miles ahead of the E-rudder but t's not perfect. In the interests of honesty and helping the poor sucker who comes along next month or next year and reads this thread as preparation for making their own rudder...here goes. This first one is likely a result of deciding to slam the upper edge of the rudder into my big toe, and then put it back.   While it's bagged, under vacuum and taking heat from some space heaters, the rudder is suspended by two bolts, one at each end, driven into the ends of the rudder. Each bolt sticks out 3-4 inches and the structure rests on that, on the sawhorses. After it went *crash* and I screamed a lot, my friend Greg S. and I pushed it back up on the sawhorse but probably caused this displacement. It's not a big deal, as it's not in a high-load area. I'll cut it off, grind it flat and wrap the top 5-inches of the rudder with another layer of triaxial, anyway.

Also, the bottom is nasty. We got layers of breather in between the glass and the wood, so that messed it up. Also, one side of the cloth got turned over in the bag, but we couldn't see that through the breather. Ah, well... I'll have to grind out and fix that trailing edge, but again, not a super high-load area. "Smooth" is what's important here and I can make it smooth.

IMG_0240-sm.jpg

IMG_0243-sm.jpg

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I'm showing you all the ugly stuff, but one side of the rudder was essentially perfect. There's some minimal fairing to do. The bottom, you've seen. There's only one flaw on the other side, and the weight you see in the above picture is how I tried to fix it.

After I unbagged it,  there was a bubble in the area where the "boxy" stock area transitions into the smooth foil.  I cut the semi-hard laminate in this area with a razor in the longitudinal direction in a couple of places. Basically I "popped the bubble".   Then I warmed it up pretty good with a heat gun until it was really flexible. I smooshed some fresh epoxy underneath it. Then I added some weight and came back the next morning.  Incredibly, it worked! Now, the whole bubble is not "perfect" some of it will have to be ground down and faired, but the part I smooshed with the weight and chain actually conformed to the wood pretty well. It just needs to be faired, now.

I've shown you all the flaws. The other side is essentially ~perfect~. Seriously, 95% of this job is perfect. The parts that aren't are easily fixable/fair-able and mostly in low-load areas. This is SO much better than the emergency rudder. I'm stoked.

Here's a view of the table and layout. You can see my trucks rear-view mirror on the right. The truck wasn't there when we did the layup on this table.

 
 

IMG_0237-sm.jpg

IMG_0245-sm.jpg

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21 hours ago, Alan H said:
 

IMG_0245-sm.jpg

 

Looks good. This pic shows really well why construction methods and laminate schedules vary so widely when you do a search on the net. That's a massive piece of wood! You must have some strong bones if it didn't break your toe. I hope it heals up quickly!

In your case, it doesn't really matter what you use to laminate the rudder, because the wood itself is strong enough to carry all the loads. My rudder is probably half as thick and I only have wood core in the middle of the blade, so I needed lot more fiber to make it strong and stiff. It becomes a problem when people use a layup schedule from someone else's build on a completely different rudder. It would be nice if someone did a write-up or made a simple enough calculator to help home-builders with laminate schedules. I searched a lot for something like that, and there's basically nothing on the subject. The vectorlam software is a good start, but it's not that simple to use and how you use the output is not trivial either.

I'm quite confident I made my blade strong enough, but the cassette is lot more complicated in terms of figuring out the loads and how many layers of what should be laminated. I'll probably just pile up as many layers as I can before it becomes an ugly piece of mess :D.

This is how I wish it looked at the end:

seascape-cr.jpg.c2eb2612e37a6492489556cfea4af670.jpg

 

...but it will probably end up being much bulkier with a lot of filler and fairing needed to look relatively decent.

 

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2 hours ago, erdb said:

 

Looks good. This pic shows really well why construction methods and laminate schedules vary so widely when you do a search on the net. That's a massive piece of wood! You must have some strong bones if it didn't break your toe. I hope it heals up quickly!

In your case, it doesn't really matter what you use to laminate the rudder, because the wood itself is strong enough to carry all the loads.

The un-glassed rudder was 46 pounds. It's now well into the 50-pound range. The One Design rudder has to be 61 pounds + according to the class rules.  Of course, this isn't a 1-D rudder, but I figured Nor Cal PHRF would be nicer to me if I could say that the rudder weighs the same as the 1-D rudder.

Turns out I didn't break the toe.  I was in Urgent Care on Sunday morning and x-rays showed no break. It hurt like a mo-fo though.  I'm actually back in a regular shoe, today, though I won't be jogging for a while, or doing squats or deadlifts in the gym.

Regarding looks...it's always nice to have sleek-looking sexy blade or cassette. However, the only part that matters is what the water sees, right?

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For the cassette - decide on the one material and stick with it. I'd pick glass myself for this boat and this job.

Here's a good instructional page - but don't mix the carbon and s-glass like he did:  http://www.single-handedskiffs.com/images/MakingyourRudderCassette.pdf

Also you need some big horizontal external stiffening flanges at top and bottom for anything bigger than a skiff. Look at some F-27 tri rudders to see some nice examples.

IMG_0823.jpg

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Thanks Zonker. So yes, this is interesting, most builds posted on the net use carbon uni for those horizontal strips, but I agree with you, it seems to make much more sense to build it from glass. The distances are short, so flex is not a problem, but fatigue from repeated stresses certainly is. Glass should be better for that unless I'm missing something.

I already had that pdf, and while it's very helpful for the general building method, that's for a much lighter boat, and without knowing the exact dimensions of the cassette, just simply taking the layup schedule would be dangerous.

This is how I'm trying to estimate the loads - tell me if you notice something seriously wrong with it. I can estimate the max sideways force on the pintles from max speed, max CL and dimensions of the blade, then use a simplified geometry like this (looking at the cassette from above):

Forces.JPG.fd48661ebf8c56a0d697dc679fc65624.JPG

I'm only calculating with tension on one side. I guess compression from the other side would help as well, but decided to ignore that as a safety measure.

Using 1.5" wide horizontal strips, a 3x safety factor (is that reasonable?) and 30 deg for the alpha, it seems  I'll need a ~ 7mm-thick laminate (little less than 5/16") going around the pin. I have 6oz glass uni and 17 oz +/-45 biax, and according to vectorlam, I can make up the 7mm thickness with 18 layers of the uni and 3 layers of the biax. Does this seem believable?

If I used carbon uni, I could get the same numbers with about half the thickness, but the weight difference is negligible for my boat.

Instead of having those horizontal flanges, I plan to just bulk up the horizontal strips. I'm not sure what's the best way to do that, I could use wood as Alan suggested or just build up thickness with thickened epoxy. This would act as core within those strips so there would be layers of glass inside then the thickened epoxy ~3/8" thick, then more layers of glass on the outside like this:

cassette.JPG.07b2ab5b45e97149d1e0b96452790b7c.JPG

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Use something greater than published Cl for foils - if you go down a wave sideways in a broach and rudder is hard over, you might get transients where Cl ~ 1.9

3x safety factor is OK if you are reasonably good with your glass work. It's a bad place to have a failure so a little more doesn't hurt!

I find 1.5" tape pretty fussy to work with but are you matching to existing gudgeons? By the time you sand off overlaps you might end up with 1.3" wide net strips because it's hard to make them all line up. I'd use 3" but if you have 1.5" existing uni tapes that are only that wide, just keep it tidy. Do it in a few layups to stop it sliding all over the place.

Thickness sounds right for 1.5" wide strips.

The top and bottom flanges are more to keep the cassette from flexing. They are for stiffness, not strength. So depth (sideways width) is your friend. I'd just cut out a piece of wood like the F-27 flanges and glass over them with 3 layers of biaxial. If you use thickened epoxy as a core, also use some wood fiber or milled fiber. Straight resin+cabosil is brittle.

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1 hour ago, erdb said:

Thanks Zonker. So yes, this is interesting, most builds posted on the net use carbon uni for those horizontal strips, but I agree with you, it seems to make much more sense to build it from glass. The distances are short, so flex is not a problem, but fatigue from repeated stresses certainly is. Glass should be better for that unless I'm missing something.

I already had that pdf, and while it's very helpful for the general building method, that's for a much lighter boat, and without knowing the exact dimensions of the cassette, just simply taking the layup schedule would be dangerous.

This is how I'm trying to estimate the loads - tell me if you notice something seriously wrong with it. I can estimate the max sideways force on the pintles from max speed, max CL and dimensions of the blade, then use a simplified geometry like this (looking at the cassette from above):

Forces.JPG.fd48661ebf8c56a0d697dc679fc65624.JPG

I'm only calculating with tension on one side. I guess compression from the other side would help as well, but decided to ignore that as a safety measure.

Using 1.5" wide horizontal strips, a 3x safety factor (is that reasonable?) and 30 deg for the alpha, it seems  I'll need a ~ 7mm-thick laminate (little less than 5/16") going around the pin. I have 6oz glass uni and 17 oz +/-45 biax, and according to vectorlam, I can make up the 7mm thickness with 18 layers of the uni and 3 layers of the biax. Does this seem believable?

If I used carbon uni, I could get the same numbers with about half the thickness, but the weight difference is negligible for my boat.

Instead of having those horizontal flanges, I plan to just bulk up the horizontal strips. I'm not sure what's the best way to do that, I could use wood as Alan suggested or just build up thickness with thickened epoxy. This would act as core within those strips so there would be layers of glass inside then the thickened epoxy ~3/8" thick, then more layers of glass on the outside like this:

cassette.JPG.07b2ab5b45e97149d1e0b96452790b7c.JPG

For calculating the rudder loads, you may try Sec 9.13 of ABS 1994, a rough copy of which is here: http://assets.system.tamus.edu/files/communications/cynthiawoods/Appendix-F-American-Bureau-Guide-Yachts.pdf 

I'm sure there are better copies available on the net, but this is the first example I stumbled across.

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After all this back and forth, I still think the West Epoxy guys had it right. Western red cedar core. epoxy/high density filler leading & trailing edges. A couple of layers of uni carbon in a rebate at max camber. Do all those first. Fair it and then laminate in one drape, (1-2)layers of 12oz of biax and (1) layer of 10oz cloth. Cover it with peel ply and squeegee the hell out of it. Yes I'm saying bagging it is a waste of time. 

The all the load will go to the carbon and the whole thing will blow up is bs. The carbon will simply increase the overall stiffness. The glass and cedar will do their jobs and the world will be finally at peace. 

Make sure you are drinking a nice beer the entire project when you aren't using power tools. Also belt sanders are for destroying things, not for making things.

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20 hours ago, Zonker said:

Use something greater than published Cl for foils - if you go down a wave sideways in a broach and rudder is hard over, you might get transients where Cl ~ 1.9

3x safety factor is OK if you are reasonably good with your glass work. It's a bad place to have a failure so a little more doesn't hurt!

I find 1.5" tape pretty fussy to work with but are you matching to existing gudgeons? By the time you sand off overlaps you might end up with 1.3" wide net strips because it's hard to make them all line up. I'd use 3" but if you have 1.5" existing uni tapes that are only that wide, just keep it tidy. Do it in a few layups to stop it sliding all over the place.

Thickness sounds right for 1.5" wide strips.

The top and bottom flanges are more to keep the cassette from flexing. They are for stiffness, not strength. So depth (sideways width) is your friend. I'd just cut out a piece of wood like the F-27 flanges and glass over them with 3 layers of biaxial. If you use thickened epoxy as a core, also use some wood fiber or milled fiber. Straight resin+cabosil is brittle.

Thanks, the 1.5" width is the final minimum width, I may end up a little wider. I'm planning to cut 2" strips of glass from a wide roll then clean up the edges as needed. I don't really have to match the original gudgeons, but I figured unless everything is lined up perfectly (I'll try but there's a limit), increasing the width of the strips much further won't help, because it's unlikely that the forces will be spread equally among the fibers anyway. 

As for creating a core to increase the width of the strips, I'm thinking maybe I could use small pieces of end grain cut cedar and glue them on in a row with thickened epoxy then sand the outside smooth. It seems easier than trying to carve out a bigger piece to match the shape of the cassette. Also, this way the grain will be perpendicular to the laminate.

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20 hours ago, 12 metre said:

For calculating the rudder loads, you may try Sec 9.13 of ABS 1994, a rough copy of which is here: http://assets.system.tamus.edu/files/communications/cynthiawoods/Appendix-F-American-Bureau-Guide-Yachts.pdf 

I'm sure there are better copies available on the net, but this is the first example I stumbled across.

That's a great source, thanks. I've been using "Principles of Yacht Design" as a source for load calculations, but when it comes to cassette rudders, there isn't really anything to use other than the various build blogs that usually lack explanation on how the layup schedule was designed. I think in most cases the design process is something like - let's put x layers of carbon, glass and kevlar on - that should do it! :D I try to use some numbers, but I'm a neuroscientist, not an engineer....

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You can figure the load for your rudder as if it was a spade rudder and determine the rudder stock diameter using the ABS rule and then divide that diameter by .5 to get your pintle size. At least that is what my rudder engineer has been telling me. We are waiting to see how that goes over with the Coast Guard...

    We are also using the GL rule to compare. Way bigger pintle that I would have ever thought on our design.

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15 hours ago, CaptainAhab said:

After all this back and forth, I still think the West Epoxy guys had it right. Western red cedar core. epoxy/high density filler leading & trailing edges. A couple of layers of uni carbon in a rebate at max camber. Do all those first. Fair it and then laminate in one drape, (1-2)layers of 12oz of biax and (1) layer of 10oz cloth. Cover it with peel ply and squeegee the hell out of it. Yes I'm saying bagging it is a waste of time. 

The all the load will go to the carbon and the whole thing will blow up is bs. The carbon will simply increase the overall stiffness. The glass and cedar will do their jobs and the world will be finally at peace. 

Make sure you are drinking a nice beer the entire project when you aren't using power tools. Also belt sanders are for destroying things, not for making things.

It's certainly a good and easy method, and if the wood is thick enough, the wood and the carbon will be strong enough to handle the loads. I think the glass is only there to seal the wood in this case. However, if the aspect ratio of the foil is high, and you don't really want to go higher than 12% on thickness, the wood core will not give enough strength and the skin will have to be much thicker to take the load. 

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Sometimes we engineers have to use:

EST = estimated

WAG = wild assed guess

TLAR = that looks about right

and other sophisticated analysis tools. In my work we actually use WAG to make sure other readers of a calculation know that there is a lot of uncertainty with a number.

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I figure that if I make ~"it"~ so damn strong that any contact with any body part will result in destruction if not death, then my SWAG is that it's about right. Maybe 75% right. Better add one more layer.

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Also, my premise when crossing oceans goes like this......"If the mast doesn't fall down, the keel doesn't fall off, and the rudder doesn't fall off, you'll probably get there".

I suppose you could add something about concussions, broken bones and heart attacks but that's the skipper, not the boat.  Anyway, so I tend to err on the heavy-duty side on those three things. 

Also, must have water to drink and food to eat.  It would be good to have some sort of fucking clue where you are and where you're going though obviously Dimas ... Rimas...whatever his name is, and those two chicks and their dogs  have proved that even those aren't mandatory. Other than that, it's all optional.

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21 hours ago, Rasputin22 said:

I like that Zonk but we have the upgrade to SWAG.

Scientific Wild Ass Guess

Clients are so much more impressed.

Image result for Scientific Wild Ass Guess

Yes, that's my preferred method as well!

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14 hours ago, Alan H said:

I figure that if I make ~"it"~ so damn strong that any contact with any body part will result in destruction if not death, then my SWAG is that it's about right. Maybe 75% right. Better add one more layer.

Oh, so you were just conducting tests using your toe.. I see.:)

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This weekend I cut off the "flash", the excess fiberlass, with a cutoff wheel on a Dremel rotary tool.  Well, OK, I have the Craftsman version of that tool.   man, that thing is the ticket for that job.   I ground out the worst of the "bubbles", not that they're bad, with an attachment on that tool as well.

What remains is the following...

1.) fill in the cut-out "bubbles" space and the "folded over" part at the bottom with a mixture of glass fibers in epoxy, and build them up to more-or-less flush with the rest of the rudder.
2.) get a layer or two of 6 ounce cloth on the bottom...sand and fair
3.) the trailing edge is a little thick, it's pretty darned straight, just thick.  So I'm going to buy a 4 foot long strip of pultruded fiberglass rod, square in cross section rather than round. It'll be 1/4 inch on a side. I'll epoxy it in there on the trailing edge and fair it. That should give a nice, squared-off edge.
4.) once over the whole rudder with epoxy/microballoons to fill any little divots or places where the peel ply didn't quite stick
5.) paint - probably a two-part epoxy below the waterline and Interlux enamel above the waterline.  Below the waterline will get two coats of black Petit Hydrocoat antifouling
6.) Install the custom pintles that I'm having made at my local welders
7.) Install and sail

All of this is pretty obvious to anybody else coming along in the future who is thinking about making their own rudder, so I think I'll leave this thread until the rudder is done.  That's why I did the thread in the first place, for the next poor slob that thinks they want to build their own transom-hung rudder.   There's no point in belabouring it.  I'll post one last pic of the rudder before I mount it on the boat and call it good.

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All the ABS guides can be found at eagle.org  at no cost.

 

Rasper, did you really mean divide by 0.5?  Or divide in half?  The end results will be quite different depending on which one you really meant ;)

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Sam

 

That is much like what the engineer keeps saying. You never know what he means and it is hard to get a concise answer.  I think he meant take half the spade rudder diameter for pintle size. Seems a bit simplified to me as the two loading scenarios have little in common other than being on a rudder. Number of gudgeons would surely come into the load estimate on a pintle. 

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plus i’d imagine the strength would be related to the amount of material... half the material would equate to half the area wouldn’t it? not half the diameter... that would be a quarter of the area if my 45 year old algebra skills are still working...

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On 2/10/2018 at 12:37 PM, Rasputin22 said:

Sam

 

That is much like what the engineer keeps saying. You never know what he means and it is hard to get a concise answer.  I think he meant take half the spade rudder diameter for pintle size. Seems a bit simplified to me as the two loading scenarios have little in common other than being on a rudder. Number of gudgeons would surely come into the load estimate on a pintle. 

Not sure what the engineer means by rudder diameter.  But  my previous boat was a 27 footer with OB rudder.  The rudder was 2 inches thick IIRC and the pintles were 0.5 inches in diameter

Number of gudgeons may come into play with an attached rudder.  But for a spade rudder, even if there were multiple gudgeons, the upper and lower two would take most if not all the loading.  Really no different than a regular spade rudder where you  typically only have an upper and lower bearing/bushing.

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I've been filling and sanding, filling and sanding...ugh.  I've given up on the part of the rudder that's above the waterline. All any little imperfections will do is offend onlookers eyes. I've been really focusing on what the water will see, and that is one-sand-away-from-done. This last round has all been on the trailing edge.

Anyway, last night was welding night at my buddy Len's house. I bought him a new tank of argon and two boxes of s.s. welding rod, and he did all the work.

 

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All cleaned up nice  'an pretty. Actually, now that I look closer, they need one more session with the wheel. I'm impressed by the fact that the post-weld shrinkage of the diagonal bracers actually bent the 3/8 'ths steel of the "backbone" piece that everything is welded  to.

 

IMG_0280.JPG

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Maybe see if there is a local facility that will electropolish them. Gives a nicer corrosion resistant finish, and is usually pretty cheap.

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On 2/21/2018 at 3:27 PM, Alan H said:

All cleaned up nice  'an pretty. Actually, now that I look closer, they need one more session with the wheel. I'm impressed by the fact that the post-weld shrinkage of the diagonal bracers actually bent the 3/8 'ths steel of the "backbone" piece that everything is welded  to.
 

Progress has been a little slow here, but finally the cassette is taking shape. 1st I made tubes by wrapping fiberglass around the SS rod I'm using for the pins, then glued these tubes to the cassette using my templates as guides and an arrow shaft making sure they're in the center-line and had the proper angle to the rudder blade. The laser-cut templates sat on the blade as I've shown it above. They had the proper NACA profile, I just had to make sure the blade was also faired properly...

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Wrapped a few layers of glass around the tubes, and filled the void between the cassette and the tubes with a mix of thickened epoxy and chopped glass.

Then glued on pieces of cedar as core to increase the thickness of the lower and upper straps and shape the rudder head:

5a99ab0c00e04_20180301_181201b(Medium).jpg.5ef60e6d9665b3885efc2369283c6ed6.jpg

The rod is only there to check alignment, it will be cut into shorter upper and lower pins. Now I'll wrap a scientifically guestimated number of glass uni and 45 deg biax layers around the cassette. Then, I'll clean up the edges and do some fairing to have a smooth surface. The tiller will be fixed,  glued to the cassette, I just wanted to do it in two steps to have better access to the cassette while I laminate and and fair it.

I'm using glass everywhere except at the trailing edge where I have a few layers of carbon uni running down inside and outside of a couple of layer of glass biax creating basically U channel-shaped sandwich to resist against torsion of the cassette. The part of the cassette covering the leading edge of the blade is made mostly of 45 deg biax glass. It already feels very sturdy, but I'm planning to build up around another 1/4" thickness of glass on the outside of the straps (mostly uni, with a few layers of 45 deg biax and maybe 1-2 layers of 0 - 90 in between).

What do you guys think?

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I want to know what you've done at the point where the laminate wraps around the pin.  Are there a few layers of unidirectional carbon, there?

 

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On 2/21/2018 at 1:40 PM, Zonker said:

Maybe see if there is a local facility that will electropolish them. Gives a nicer corrosion resistant finish, and is usually pretty cheap.

Tempting.  It was suggested that I soak the jewelry for about half an hour in somewhats concentrated citric acid, which would "passivate" it...I think that's the term that was used.

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20 hours ago, Alan H said:

I want to know what you've done at the point where the laminate wraps around the pin.  Are there a few layers of unidirectional carbon, there?

 

I decided to use fiberglass instead. I was originally planning to use carbon, as it seems a lot of people use that, but then though that glass is supposed to be more forgiving, flex is not a problem here, and I don't mind a couple of extra grams. I really don't know, I guess carbon would have been fine, too. 

I laminated the final layers and did the first rough clean-up of the edges. This is how the cassette looks like now:

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Here is a close look at the lower gudgeon:

 

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First I wrapped the SS rod with packing tape, then 2-3 wraps of 6oz glass cloth to make the tube. Once that cured, I removed the SS rod, and used my jig to position the tube accurately relative to the rudder blade. I made that inside "A" seen above by putting a glob of thickened epoxy with chopped glass between the tube and the cassette and covered it with a few layers of glass. Later I built up a few more layers of glass on that, then glued the cedar on for core, faired it and then laminated a bunch of layers of glass on the outside. For both the inside "A" and the outside layers, I mostly used glass uni with a few layers of 45deg biax mixed between them.  The glass uni I had was 6oz, so it took a lot of layers and a lot of time. It would have been better to have fewer layers of heavier glass I guess. The thickness of that outside wrap is about 1/4". 

Hope it answers your question. The whole cassette is very sturdy, in fact it feels a little overkill, but that's fine. I want the rudder to stay on the boat. The only issue now is that the gap between the cassette and the blade is not as tight and uniform as I wanted. I'm planning to use the fuzzy side of a velcro tape for gasket, and now I'm thinking of ways to put some thickened epoxy or some gasket glue under the velcro tape to make the gap tighter. It should be tight, but at the same time, I may need to replace that velcro in the future, so I don't want to glue it on too permanently either.

 

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I figured I'd post pics of the finished rudder. Everything seems to work fine, boat sails great and so far nothing has broken.

Have you finished your rudders Alan?

1601538766_20180523_203518(Medium).thumb.jpg.531cff57a12d9ab05f9ac3d06b7946dc.jpg

 

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On 2/11/2018 at 10:17 PM, 12 metre said:

Not sure what the engineer means by rudder diameter.  But  my previous boat was a 27 footer with OB rudder.  The rudder was 2 inches thick IIRC and the pintles were 0.5 inches in diameter

Number of gudgeons may come into play with an attached rudder.  But for a spade rudder, even if there were multiple gudgeons, the upper and lower two would take most if not all the loading.  Really no different than a regular spade rudder where you  typically only have an upper and lower bearing/bushing.

Isn't this meant to be 1/2 D shaft?, therefore 2" shaft = 1" pintle, sounds right, load is all at the bottom bearing.

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On 5/29/2018 at 8:13 AM, erdb said:

I figured I'd post pics of the finished rudder. Everything seems to work fine, boat sails great and so far nothing has broken.

Have you finished your rudders Alan?

1601538766_20180523_203518(Medium).thumb.jpg.531cff57a12d9ab05f9ac3d06b7946dc.jpg

 

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SWEET!  I am impressed.  That is sure pretty.

I had rotator cuff surgery on May 4th and have been told that I can't pick up anything heavier than a laptop or a cup of coffee since then, so NOTHING has happened until this past weekend.  I'm still not supposed to  pick up any thing but it's been over two months and I just said FFFFF'it and the Mr's helped me tote the rudder down to the boat and toss it on the pintles.  It's all good.  Well, I need to come up with some different bushings but everything else fits great. If I were to do it all over again I might add in another 5% balance, but it's no big deal.

 

Hopefully I can actually SAIL with the thing sometime in August and see if the boat goes in a straight line and turns when I wiggle the tiller.

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