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I have a whole $7 invested in the carbon.  I'm not married to using it, and the subject of the inadvisability of mixing in carbon into a wood (or foam) and glass strecture, without specifically engineering it, has come up before.

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40 minutes ago, CaptainAhab said:

I am not saying that a hull is a rudder. Simply that it is possible to mix carbon/glass/wood in a very complicated package. In one of the original posts, I gave the link to the Gougeon design for wood composite rudders. They are the ones encouraging the carbon reinforcement. You could use a thick band of uni S-glass instead if it makes you feel better. They do the math & have the experience...

Agreed,

It is one thing to erroneously think that laying a carbon skin over wood gives the combined mechanical properties of the two.  It is another if you make the assumption the carbon will take all the loading (which is what I believe the Gougeons have done), then you should be fine most of the time.

If you haven't done so already, it is probably a good idea to go through the West System link Ahab provided above.

Also, I can't recall if the article mentions it, but the inlaid carbon strip should be at the point of maximum thickness.  Anything outside that is a waste of carbon.

If you want to get real fancy, a  kevlar wrap around the leading edge should help with impact strength.

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I like to route a groove in the leading edge and then strip the cover off of old Kevlar cored line and lay the uni strand core into that groove with some hi density putty. goop it up good and then lay some wide masking tape over the whole mess and massage it into as good an approximation of the hopefully parabolic leading edge. This should let the excess goop squirt ot the ends and save a lot of shaping and sanding, something you don't want to do on kevlar!  A bit of sanding and you will have a near indestructible leading edge. I did this on my cold molded Torado catamaran on the skinny bow stems and  made sure all my competitors knew that I had dreadnought ramming bows!

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Ahab, knowledge has improved since the 80's of that rudder article, it aint bad, but for instance the key:

the carbon will have the same resistance to strain to stress failure as the wood so it will work, forgetting that it will be in an epoxy matrix, which is not of the same resistance.

I do not think a bit of carbon will lead to catastrophic failure or so, and for what Alan is sailing, it would be okay, but when it really get loaded it will deform the glass laminate as one is stiffer then the other. And that is not good.

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I'd be surprised if many people are aware of how far the Gougeon Bros have gone with the wood/epoxy composites and when.

My favorite is  pages 31 & 32. Lead weights for testing Page 82 serious Boeing style testing

http://www.weti.fh-flensburg.de/fileadmin/dokumente/Aktuelle_Meldungen/141216_Hancock_-_Wooden_Blades.pdf

I just fond this online. I already knew a bit about the windmill blades. Goegeon had 95% of the US market until the early 90's. 

This stuff makes our little boats look like toys.

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8 hours ago, LeoV said:

the carbon will have the same resistance to strain to stress failure as the wood

No it won't. Carbon bending modulus is about 5x that of douglas fir (for example). It WILL take the load so if you use it, use enough that can take ALL the load.

Sources:

1) Vectoryply carbon 0 deg uni datasheet:  http://vectorply.com/wp-content/uploads/2015/06/C-L-09002.pdf

Ex, flex =  10.44 MSI (10.44 x 10^6 psi)  71.99 GPa (open mold)

2)  Coast Douglas Fir  http://www.woodworkweb.com/woodwork-topics/wood/146-wood-strengths.html

Ex,flexure = 1.95 x 10^6 psi 

Why you don't mix materials like carbon:

Best analogy I ever heard: picture a flat plate held from above by steel rod and an elastic band, side by side. They have very different modulus of elasticity. The steel is much stiffer than the elastic band (duh). Now add a 15 Ton weight to that flat plate. The steel rod takes the entire weight because it can't stretch enough that the elastic band stretches and takes any load. So mixing materials with wildly different modulus of elasticity means the stiffer material takes most of the load (5x means the wood takes a small % of the load). In about 2nd year engineering you learn how to calculate this sort of thing. Rule of mixtures for modulus

Fastnet Rudder stocks:

They used aluminum rudder stocks with carbon fiber overwrap to "stiffen them up". Don't know the proportions but CF is 2 or 3x the stiffness of aluminum so most of the load went into the carbon, it failed, and then the now weaker alum tube failed not long afterward. Mixing carbon / alum = battery in seawater too unless properly isolated.

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I was surprised too that that was the whole central idea for using carbon in that article.

ps, how you quote it (or how I did write it) looked like it was a statement of mine, its in the article mentioned before that said so. Not me.

I would ditch the carbon. With all respect to Gougeon for their work.

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so if you CF skin your wood structure and the break point of the amount of CF used exceeds the break point of the wood then it seems the CF will fail independently of the wood core, instantly transferring the load to the wood core where it will also fail. Ergo 1. wood cores which do not exceed the CF skin strength are merely overweight plugs to layer the CF on 2. adding CF to a wood core won't add any strength unless it exceeds the core strength and then, see point 1, in which case *foam*

have I got that right?

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About half right.  The core needs to support the compressive and shear loads also.  An I beam works because the vertical web keeps the two plates far apart.  Same with the core.  It has to keep the two skins apart to support the bending moment.  If it''s too soft or not adhered well, the skins will shear the core and fail.  Wood is way better than foam (until it rots)

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cool thanks Kenny! so could it be just air inside if there was a web at max draft? Or does is have to be a more distributed form of support...

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57 minutes ago, Kenny Dumas said:

About half right.  The core needs to support the compressive and shear loads also.  An I beam works because the vertical web keeps the two plates far apart.  Same with the core.  It has to keep the two skins apart to support the bending moment.  If it''s too soft or not adhered well, the skins will shear the core and fail.  Wood is way better than foam (until it rots)

To add to that, the besides being kept apart, the skins cannot move relative to one another.  In an I Beam, the web does this - in cored construction, it is the core and is how those shear stresses arise. 

For example, a member made from veneers will only have stiffness if the veneers are bonded together.  If not, the stiffness decreases drastically.  Same with a telephone book.

Agree too about wood over foam.  Balsa for example has vastly superior mechanical properties compared to typical boatbuilding foams and bonds pretty tenaciously to the skins.  Only caveats are it is a bit heavier - and really hates getting wet.  Foam on the other hand has a nasty affinity for delamination.

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10 minutes ago, overdraft said:

cool thanks Kenny! so could it be just air inside if there was a web at max draft? Or does is have to be a more distributed form of support...

Generally speaking yes.  But it depends on the thickness of the skins and unsupported panel length.  Generally, a member with a slenderness ratio >50 over an unsupported span will be subject to buckling.  Look at an aluminum spreader or an airplane wing.  Or even a boat hull in section subject to forestay and backstay loading.  Think of the deck and hull  bottom  as the skins and the topsides as the web.

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1 hour ago, 12 metre said:

Think of the deck and hull  bottom  as the skins and the topsides as the web.

Exactly. A boat is an oddly shaped box beam.

So use longitudinal unidirectionals on deck and bottom of hull.

Use lots of +/- 45 fibers on hull sides for the shear loads 

(In way of chainplates / main bulkheads use some 90 deg fibers because the rigging /mast/keel loads are trying to squish the boat sides inwards.)

Boat design 101 for fiber boats.

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There are also huge twisting loads. The 45 degree fibers take all of those. Another load not typically talked about is when the boat is sticking half way over a wave and has to support itself.  

One of my good friends built a very high end IOR boat in 1982. It was a bit before its time in many regards. Other than the mat(poly resin) to bond the Airex foam, the boat was made entirely of unidirectional S-glass. Bow to stern on the bottom and then at 45 degrees to the waterline. He was a structural engineer back then, then moved on to be the lead composites engineer for one of the major defense contrators.

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I don't want to hijack the thread too much, but I'm also building a rudder for the first time, and I thought I'd join the fun.   My woodworking skills are very limited, so I didn't want to go with the router-shaped wooden core, but I also didn't want to use wire-cut XPS foam for core that seems to be used by many. I came up with an alternative method, will see how it works out at the end.

The general idea is to build the two halves separately starting with a thin flat sheet of already cured glass cloth and bend it to the correct shape, then build up the laminate and core on the inside. Finally glue the two halves together.

I built a "piano" -  flat MDF table with laser-cut ribs on it:

20171202_143942.thumb.jpg.9de95bc54614857e06f9d84b4e56996a.jpg

First I thought the ribs alone would be enough, but the thin layer of fiberglass sagged too much between the ribs, so I glued foam between the ribs and wire-cut them to shape using the ribs as template. This pic was taken after I finished the rudder skins and the foam broke at a few places, because the glass had some pin holes where the epoxy got through.

The fiberglass sheet was clamped to the vertical backboard of the piano with a 6' ruler, and layers of carbon uni and twill were laminated on it:

20171202_144105.thumb.jpg.a53664f4f7a16890c2282f0ab53187b3.jpg

 

Here is the finished skin sanded a little to remove pieces of foam. The layer of glass serves as a sacrificial layer.

20171202_144242.thumb.jpg.fd67a3b11e8885738d8e502b016c603b.jpg

20171202_144253.thumb.jpg.967fcd28fdbf65381f73c2eabb204e29.jpg

It didn't come out perfectly, apparently the foam between the ribs compressed a little, so there is a little bit of waviness in the skin, it will need some fairing at the end.

I thought the advantage of doing it this way is that I could use a relatively thin skin and only build up the layers in the mid-section of the cord where the skins are far apart to do some useful work. I could also taper off the layers going towards the tip of the rudder. Now I will glue western red cedar strips under the mid-chord section and will use expanding polyurethane foam for the rest of the blade for core. Hopefully I'll be able to make a flat surface on both halves and glue the two halves together nicely. This will be a cassette rudder, so I'll have to make sure that the thickness of the rudder is uniform. This is going to be tricky and it's obviously a weakness of this method.

As for the laminate schedule, I looked at a lot of build blogs, articles and books, and was surprised to see the wide range of opinions, just like in this thread, ranging from just slap a few layers of glass on the skin to a whole lot of carbon uni layers. I used the vectorply software and some estimation of potential max forces on the rudder, and I ended up using quite a lot of carbon. However, building up the layers only in that mid section, and tapering off towards the tip saved a lot of money. I got the stuff from Soller Composites, they had by far the best prices and got some nice stuff from them. I think the material was less than $300 for a 6ft blade, and I have enough left to build the cassette, too. I already had epoxy from earlier from Raka.

 

 

 

 

 

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Kurt Hughes uses that method for daggerboards and rudders. Sort of.

Make a bunch of female exterior foil shapes and lay a formica sheet in it for the female mold skin. Don't worry about the leading edge because you glass that freehand when you glue port and stbd pieces together.

Anyway after laminating the skins on the mold skin; glue in foam. Cut the foam off where it stands proud of the center line. Glue port and stbd pieces together/wrap glass on leading edge and fair.

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Work has come to a screeching halt, but will resume tomorrow.  Nothing I will be doing this weekend will be update-worthy, though.

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I didn't read through the whole thread regarding hotwire cut cores but I've done that process many, many times and wanted to point out that doing so with structural foams (such as Rohacell, a high shear strength PMI foam used primarily in the aerospace and wind turbine industry, and C-class catamarans) is a really bad idea, even in a well ventilated area. The fumes are known to cause cancer of the very worst kind, so I would avoid like the plague (had a coworker pass away less than a year after doing this despite recommendations not to). Hot wire cutting the pink and blue XPS foams and couple others are safe, but unless its specifically mentioned as safe, I would pass and go for a wood shaped core or CNC milled core.

Now, blue/pink foam also comes in higher densities, the 60 and 100 psi stuff would make for pretty good cores for boat parts.

If shear strength is a concern, one can always split the core and insert a layer of biaxial carbon, which is vastly stronger than even the best structural foams and can make a nice shear web for a reasonably loaded structure. For highly loaded structures, we use a structural foam (Rohacell IGF71) coupled with the biaxial carbon trick mentioned above. This provides a fully supported foundation for the carbon caps; usually what happens on skinned structures is the spar cap loaded in compression fails by impinging downward into the foundation below it (foam in this example). As a result, its a bit more complicated than your typical steel or aluminum I-beam problem, and more closely approximated by solving a beam on an elastic foundation problem (http://www.uacg.bg/filebank/att_1324.pdf).

Anyway, for a properly balanced rudder that is sufficiently thick, and one where you aren't concerned about weight, 3 layers of 8oz uni carbon 3" wide over a wood core coupled with some 2 layers of 9oz fiberglass skins would likely be nice and strong, though even that is overkill if the wood grain is correctly orientated.

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Sam, I assume the 3 layers of carbon would be on top of each other at the maximum rudder width.  w.r.t. load sharing, the glass would just be a skin, not load bearing to any significant extent?  Would you offset the carbon +/- 1/2 inch or so to taper the edges and avoid a stress riser?

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Kenny, that is a correct assumption. The glass skin would serve to take torsional loads in the rudder (i.e prevent twisting), and should be orientated on the bias relative to the leading edge of the rudder (approximately). It also serves to help waterproof the wood core and provide some impact protection. I wouldn't worry about a stress riser between the carbon and glass skins too much, as the loading makes a stress riser unlikely unless you play with the layup in other ways (i.e mix glass and carbon in the skins). You can transition to 1 layer of uni carbon starting halfway down the rudder blade and save some weight if you want. I should also mention that this layup is rather notional, and intended only to serve as a sort of guideline for what I would use on a 16-24' boat. I haven't run the load cases nor would I necessarily go offshore or foiling with such a layup. I will however say that on lightly loaded rudders (floating A-Cat's for example) the skin and spar is roughly half of what I specified over a weaker foam core. In the A-Cat case, they get away with a single layer of 5.7oz carbon on the inside and outside of a 12mm Nomex honeycomb core for the vast majority of the hull structure, this simply to say that carbon is really strong stuff when separated with a high quality core material (good wood counts as the Gougeon Brothers have shown us for many years).

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On 12/11/2017 at 1:42 PM, samc99us said:

Anyway, for a properly balanced rudder that is sufficiently thick, and one where you aren't concerned about weight, 3 layers of 8oz uni carbon 3" wide over a wood core coupled with some 2 layers of 9oz fiberglass skins would likely be nice and strong, though even that is overkill if the wood grain is correctly orientated.

Thanks, this is interesting. I think one important question is what's sufficiently thick? Obviously core thickness has a huge effect on max bending moment a laminate can handle, but the problem is that for a high aspect rudder with the short cord and the usual NACA0012 profile or similar, thickness is quite limited whereas the bending moment is high.

After seeing all the different variations for building methods and layups, I decided to do a little research on this and get some numbers into all this guestimation (I'm not an engineer). Basically I started out with the worst-case scenario for my boat (23'), surfing down a wave at ~10kt then broach >> max lift on the rudder. I then used the vectorply-vectorlam software, and used a generous safety margin to arrive to a much thicker laminate than what you suggest. The skin is 2 layers of 11oz carbon twill slightly turned at a +/- 10 degree angle and a 6oz glass cloth turned 45 degree on the outside that was used for producing the shape. Inside, at the highest-loaded portion of the blade around the lower gudgeon, there are 4 layers of 6" wide 20oz uni carbon running down at the widest part. The uni layers are tapered down towards the tip. This is for a blade with 12" cord, 65" length, 45" of it immersed. 

I probably way over-engineered it, but that's fine. I'm not that worried about an extra 2-3 lbs, but I'd definitely want to keep the rudder in one piece. One interesting point though is that the original rudder has a ~6-8mm thick glass skin around some pretty heavy and hard filler. So it was definitely built strong, and the 3/8 in SS bolt that was the pin for this kick-up rudder snapped twice already which is why I decided to replace it with a cassette rudder.

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erdb,

  Defining a layup depends on sooo many variables. I've built wings with a single layer of ~1.5 oz/yd^2 carbon on each side of a foam core and 3 layer uni carbon spar cap with a balsa/carbon shear web 1/8" thick inside. The loads are low but the foil is thin as well (<9% thick at the root). I've also designed composite structures with 10 layers of S2 uni-glass over high density foam cores. Every situation is different. My layup schedule above was basically for stiffening up a wooden rudder blade, and wasn't really for a specific boat or load case, nor was it for a pure composite rudder blade.

My F18 rudder blade has approximately 1/4" of carbon on each side of a pretty dense core. This is for an approximately 30 inch blade. I'm guessing the daggerboard layup is twice that through the exit point on the boat, and that board (78" x 7.28", 11% thick) is closer in spec to your rudder. One difference is this board is subject to some pretty high loadings as the max velocity can approach 30 kts. 

I wouldn't necessarily agree that you over-engineered your rudder. One note is the shock loads could be double what you estimated with the 10kt broach case (i.e if you managed to exceed wave speed and have the rudder slam down at some weird angle while operating at max lift). Load prediction is really the hard part here, and without years/decades of data and instrumentation plus experience, often we are just stabbing in the dark for some of the corner cases.What are you using as a shear web? Balsa? Carbon? Why did you place the outer layers of carbon at a slight 10 degree angle, vs the proper placement of the weave on the bias (45 degrees) to take the torsional loads expected on the skin (in any lifting surface)? Why is the uni carbon on the inside, instead of the outside of the blade (inside the two outer layers would be fine), where it is doing the most good? Every bit of thickness counts on a spar, as both the stress in the caps and the deflection of the spar is a function of thickness cubed. Some relatively simple beam bending calculations can help to analyze the situation: https://www.engineersedge.com/beam_bending/beam_bending8.htm.

I say all that but I do realize that construction limitations often dictate where material ends up. My advice to you is to do some load testing on the blade in the cassette at home. Gallon water jugs can make for some useful weights. This is recommended practice for any structure you are trusting life and limb to, especially when that structure is composite (the actual strength of a finished composite can vary by more than 30% depending on resin choice, when/where/how the layup was performed, exact material orientation, batch of material used and a host of other factors).

I would be curious to look at the vectorply-vectorlam software and see how that compares with some in-house tools we have developed for designing structures (which are usually cross checked with ANSYS). I'm confused if Vectroply is giving that away with a simple registration over here? http://vectorlamcirrus.cloudapp.net/#/register

 

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+1 on designing for worst case. If you believe NACA, a 0012 foil has a max Cl of around 1.3. But I've seen data that you can momentary lift transients (just a high angle of attack broach) of closer to Cl = 2.0

Yes, vectorply gives you a copy for free. It's not a FEA, just a laminate stacking program, but I've found it useful. It does assume vectorply's materials of course :) - and properties.

 

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Yep Zonker. A couple plots showing just that here: https://www.nrel.gov/docs/legosti/old/4510.pdf

Different airfoil but similar principal.

One of my notes on materials, often the properties are determined with a relatively thick ply stackup (5 or more layers), so a little caution is needed if dropping below that. Still, having material properties is better than none, as besides loads those are the toughest things to get!

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Hi Samc, the vectorlam software is free to use. It took me some time to figure out how it works, but there are a bunch of fibers, foams and wood you can choose from and you can customize the architecture and weight of the various layers. Select epoxy, poly or vinylester for resin, build up your layers in a list and it gives you all kind of mechanical properties. I mostly relied on ultimate bending moment and flexural stiffness. They have instructions there somewhere, and there is a long youtube webinar as well if you search for vectorlam.

The laminate I ended up with had an ultimate bending moment almost 4 times of what's estimated from the max lift at 10 kts of speed, because I tried to limit deflection to about 1% of length. Somewhere I've read that that's a good safety factor. To get deflection, I used the flexural stiffness given by the vectorlam software and a simple beam bending equation like you suggested. Another safety factor was that in the calculations I used only 6" width  of the laminate instead of the actual 12" width thinking that in bending, only that middle section is really effective where the skins are relatively far apart.

15 hours ago, samc99us said:

Why is the uni carbon on the inside, instead of the outside of the blade (inside the two outer layers would be fine), where it is doing the most good?

Maybe I wasn't clear (plus I realized I left out 2 layers above). All the layers are laminated together, but there are full-width layers that I called skin, these include going from outside to inside:  6oz glass @ 45 deg, then all carbon: 11oz twill @ 10 deg, 8 oz uni @ 0 deg, 11oz  @ -10 deg, 8 oz uni @ 0 deg. Then the layers continue with four 6" wide strips of 20oz uni carbon in the widest segment of the profile, but these are tapered toward the tip, so there's only one layer running full length, the others are cut shorter and shorter. 

15 hours ago, samc99us said:

Why did you place the outer layers of carbon at a slight 10 degree angle, vs the proper placement of the weave on the bias (45 degrees)

I thought the torsional loads would be much smaller compared to the bending forces. The plan is to angle the blade forward a little to balance it out nicely, plus, the rudder cassette will take some of the torsional load, so the blade will work more like a centerboard. I could be wrong though. I do have a 6 oz glass at 45 degree on the outside, does that help? Why is 45 deg the proper placement?

15 hours ago, samc99us said:

What are you using as a shear web?

Western red cedar, but only under this 6"wide strip in the middle, 2lbs polyurethane foam elsewhere, although I may glue in an additional thin strip of cedar running close to the leading edge to help with positioning the two halves when I glue them together.

 

 

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Hey erdb,

  You did the right thing by designing your laminate based on stiffness, rather than strength. That is usually the defining factor for composite structures. Your more clear laminate schedule makes sense, though I stand by my recommendation that the twill layers should be on the 45/45 bias. You have the uni carbon layers there for bending stiffness. The reason for the bias layers are that airfoils tend to have a negative pitching moment about the quarter chord line. When this is looked at in 3 dimensions and applied to a structure, you get a twisting force that starts at the tip of the rudder and works its way to the root. Grab a sheet of paper at both ends and twist it and you'll see what I mean. Another good example is taking a straw, twisting it, then cutting it down the middle and doing the same. Anyway, the best way to stop this twisting is with fibers on the 45/45. Glass certainly works, but carbon is ~4x stiffer, so does a much better job (and if you have 2 layers of the same in the same orientation, the carbon is going to do all the work; glass is often used outside of carbon in layups as finer glass is available which means less pinholes to fill when painting).

If you can, I would glue in the cedar in the LE simply for the damage protection it offers. Overall you have a sound build, I'd like to see more torsional stiffness but many production rudders forgo this and work well enough.

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  I'm in the middle of the really boring part....mix up spooge (epoxy and wood dough), and slather it on.  Wait overnight. Sand. Repeat. Repeat again. I'm one repeat of "mix-slather-wait-sand"  away from moving on to the second side.

However, I have belt sanded, surform-planed, and sanded the second side of the rudder now, so the basic shape is there. Amazingly, the trailing edge is ramrod straight and pretty exactly 1/4 inch thick over the entire length of the blade. Wooo.  It's not PERFECT but it's pretty darned good. I was worried that I'd built some twist into the thing, but nope. Nope.   Now I have to decide if I'm going to stick on a bit of fiberglass batten to the trailing edge, as suggested above..

Today I  used the belt sander to work in some of the tapers, like where the foil shape transitions to the part of the rudder that's out of the water. I also smoothed up the upper part of the blade, the part that's out of the water.    I  made some decisions last week about what to do with the bottom, aft corner of the blade.  Upshot, I cut it in a semi- circle since "elliptical" is probably beyond my abilities. This made for a  lot of sanding but *Hey*. whuddever.

The thing is actually starting to look pretty good. It looks like the best of about 1988 technology.  Works for me.

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I've read through everything above about the pluses and minuses of adding a 6-inch wide strip of unidirectional carbon to each side of the rudder. The "No" arguments make sense, in how the carbon will take all the load until it fails, then transferring the load to the wood and glass.  I've also had comments from two guys whom I know personally who build boat-stuff all the time who both basically said..."It'll be stronger with the carbon than without it. I'd add it".

So I guess I'll decide when I get there.  I have a very generous offer of the use of a vacuum pump from solosailor, which I'll take him up on when I get there.

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On 12/29/2017 at 9:45 PM, Alan H said:

  I'm in the middle of the really boring part....mix up spooge (epoxy and wood dough), and slather it on.  Wait overnight. Sand. Repeat. Repeat again. I'm one repeat of "mix-slather-wait-sand"  away from moving on to the second side.

However, I have belt sanded, surform-planed, and sanded the second side of the rudder now, so the basic shape is there. Amazingly, the trailing edge is ramrod straight and pretty exactly 1/4 inch thick over the entire length of the blade. Wooo.  It's not PERFECT but it's pretty darned good. I was worried that I'd built some twist into the thing, but nope. Nope.   Now I have to decide if I'm going to stick on a bit of fiberglass batten to the trailing edge, as suggested above..

Today I  used the belt sander to work in some of the tapers, like where the foil shape transitions to the part of the rudder that's out of the water. I also smoothed up the upper part of the blade, the part that's out of the water.    I  made some decisions last week about what to do with the bottom, aft corner of the blade.  Upshot, I cut it in a semi- circle since "elliptical" is probably beyond my abilities. This made for a  lot of sanding but *Hey*. whuddever.

The thing is actually starting to look pretty good. It looks like the best of about 1988 technology.  Works for me.

Good luck... Are you using some kind of template to get the right foil shape?

I'm also in the fairing phase, which is the part of every project I hate the most. Luckily, I don't have to do too much thanks to using the female template. I was hoping I could get a perfect shape without any fairing, but the leading edge of the blade somehow flattened out a bit either when I glued the two halves together or  when the epoxy cured.

Here is one of the halves with cedar stripes glued in and the polyurethane foam shaved down flat. 

5a4d4e9740189_20171227_151256(Medium)2.thumb.jpg.6832c807b6f24c200021a7d9610f8223.jpg

The blade as of this morning. The two halves glued together and the pic rotated to show the approximate final position on the boat - angled forward to balance the forces.

5a4d4e9d790b6_20180103_085007(Medium)3.thumb.jpg.816f8869f01c599887fb7828bf5d2447.jpg

A little more fairing, then I'll have to start working on the cassette using the rudder blade as template. 

 

 

 

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The shape is pretty good, and the join on the leading edge, where I glued two pieces together is undetectable. However, on close inspection, on the top half of the rudder, one side is a bit "fatter" than the other, in the 20% right behind the leading edge. So I'll lay in one or two inch-wide strips of core mat and then sand it down. That should take care of it.

As always,  it's when you finish the job that you figure out how you SHOULD have done it in the first place, right?

All things considered, this is taking a long time but I think it's going to be a good rudder.

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TAP Plastics was out of core mat so I improvised with a mix of wood dough, tiny wood shavings and microballoons.  The coremat would have been an awful lot easier but oh well.  It's just more sanding.

After layering that spooge on, I *Finally* starting routing some shape into the redwood emergency rudder. So I spent about two and a half hours today, doing this..

 

E-rudder005.JPG

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Here's the end result. Notice that I only did the aft face/edge of the rudder. I tried one pass at the leading edge and the bit dug way too deep. After looking at it closely, I finally figured out why. If anybody is interested, I can take some photos and explain, but take it from this guy. If you do this, make your two template foil plates exactly the radius of the middle of the flat riding surface of your router. Any time you're routing over a strongly curved part of the foil, and the template slips off the inside of the riding surface of the router, your bit will dig too deep. When the shape of the foil is relatively flat, that's not an issue.

 

E-rudder004.JPG

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I'll use the circular saw, surform plane and belt sander to make some sort of reasonable leading edge. It's an EMERGENCY rudder, to keep me sailing at a reasonable clip....not win the Volvo. also, I will practice vacuum-bagging on this rudder before I do the primary rudder.

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On 1/6/2018 at 11:06 PM, Alan H said:

I'll use the circular saw, surform plane and belt sander to make some sort of reasonable leading edge. It's an EMERGENCY rudder, to keep me sailing at a reasonable clip....not win the Volvo. also, I will practice vacuum-bagging on this rudder before I do the primary rudder.

So are you building two rudders then? Will you make the emergency rudder a one-piece rudder as well with the same attachment points as your primary rudder or will you make it a cassette rudder? 

I'm almost done with fairing the rudder blade that and will soon start working on the cassette. I haven't made up my mind on what gasket to use between the cassette and the rudder and how to glue that in place. I'd be interested in how you're planning to do it if you're also planning to use a cassette for the emergency rudder.

 

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Yes, I'm making two rudders at the same time.  I started out with one, then realized that if I'm gonna do what I plan to do in the next few years, I'm going to need an E rudder. I knew of some wood, free, down the street so I went and grabbed it. I kind of got lucky, it's almost knot-free redwood.

Anyway, cassette.

I'm a big proponent of KISS.  For me to venture into vacuum bagging is *Seriously* outside my comfort zone!  So the top of the E rudder is rectangular. The top is cut back about 3 inches from the leading edge of the blade. The back of the top half of the rudder is directly in line with the trailing edge of the blade. I haven't shaped the top of the rudder at all, except to round the corners off some, and fill in where one piece of redwood was about 1/16th of an inch skinnier than the other pieces.

The top half of the rudder, the part that sits in the cassette is NOT foil-shaped. Only the part that's in the water is foil shaped.  That means I can build a "boxy" cassette. It just has to be big enough for the bottom of the rudder to slide through it.  Since the top of the rudder is smaller in chord than the bottom, by 3 inches, when the rudder is all the way down, it's going to wobble fore-and aft, yes?  OK, so I will make a "Jammer" out of a piece of the same redwood that the rudder is make out of.

Here's the process.

main rudder go boom. skipper cusses and cries.  Then he goes below and fetches e-rudder setup.

1. drop cassette onto hopefully intact already-existing transom gudgeons.


2. drop rudder into cassette. It wobbles/swings fore and-aft but is pretty tight from side-to-side

3. Drop "Jammer" piece in the cassette behind the rudder. This shoves the rudder forward up into the front edge of the cassette and holds it-= "jams it"  in place.

4. Use magic thingamabob (which I haven't developed  yet) to hold "jammer" and rudder down in the cassette

5. attach tiller

6 sail away.

Why the "jammer?" Because my previous rudder sat in a much fancier cassette,  as the whole blade was foil-shaped. Ergo, the cassette was foil shaped as well.  I actually made it from a couple of layers of doorskins, just bent the shit out of 'em and glued 'em together.   However,  when the s.s. pintles were attached, it worked out that the leading edge  of the rudder blade was almost 2 1/2 inches behind the axis of rotation. Man-o-man did that tiller load up. It was a bitch and a half to steer the boat. It steered it, but I'm sure it'd burn out any autopilot I attached it to, pretty fast.

So I got to thinking, how could I make an E rudder in a cassette where I could get the rudder a lot closer to the axis of rotation? It took about 30 seconds for the light to come on.....cut back the part that sits in the cassette, and when it's deployed, jam it forward.

I actually didn't cut it back, I just didn't laminate another piece of redwood to the top half of the rudder blank. My pieces of redwood are 3 inches wide, and they're glued edge-to-edge.

What will my cassette be like? Remember, I'm a KISS retard. It will be 3/8th plywood, mostly, probably with 1-inch thick doug fir ends, and wrapped in linear carbon at the top and bottom. I'll run a couple of 1/4 inch bolts through it for good measure.

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If in fact the transom-mounted gudgeons are damaged...or most likely, the bottom one ripped out, I will have a piece of 2 x 6 on board with gudgeons pre-mounted  It'll have holes drilled in it for bolts to go into what still exists of the transom.

So I put this board up on the transom----  ram a pencil into the mounting holes and mark up the transom where I need new  holes. Take the board away, fire up my drill, and pound some holes in there. Now, put the board back in place, shove the bolts through, and tape the heads over so they don't fall out while I'm messin' around under the cockpit sole.

I reach through the cockpit lockers and put double fender washers and two nuts on each mounting bolt.  Tighten. The proceed as above.

Also, use a bunch of the underwater epoxy/glass to patch the hole caused by the original transom gudgeon ripping out so that the ocean stays on the outside of the boat.

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Having tried to mount a rudder on my Cal 20, many years ago, bobbing around on a pretty nice day in the Gulf of the Farallones, I'm going to have my e-rudder in a cassette.

Now, I've seen some chill solutions where the gudgeons are mounted on this stainless steel framework which rotates up over the cockpit.  Then you mount the rudder, horizontally while standing in the cockpit.

 

(This is an autoclaved carbon mammoth-fossil-epoxy  vacuum-infused, spectra-obtused  miracle rudder made by little elves that live in the Carbon Forest, it weighs 4.3 ounces, which is a good thing because you have to hoist the damn rudder over your head to mount it...)

and you see, part of the s.s.framework is pre-mounted to beefy mounts on deck, and after everything is ready, it just swings down onto your transom, neat as a pin. You put in two more bolts and you're off and running again.

Nah. KISS. Cassette for me.  I just want to get the submerged part of the blade forward and closer to the axis of rotation.

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I have also seen one solution where a rather trick shaped saloon table gets turned into the e-rudder. There's actually a carbon sleeve worked into the laminated  saloon table. A long carbon shaft goes into that sleeve and is pinned in place. That gets mounted into some bearings that are built onto a strong wood upright support, and the whole thing gets mounted on brackets on the transom.

It's not the fastest e-rudder in the world, I mean...it's a freaking table, but it works and beats all hell out of not having one. Also, you usually sail with the table in place, this way you don't have to carry something else.

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Yes, raking the blade forward is fine as long as the blade is stiff enough (flutter is otherwise a problem).

Maybe make your cassette and slightly tapered and same as top of the rudder. Like a tapered wedge in 3D. You could shim the upper part of the rudder by gluing on some thing wood wedges to make the shape, then form the cassette around it. Nice tapered wedgey plug.

Our cat had daggerboards. Upper part was rectangular, lower part was foil shaped in a rectangular trunk. They always "thunked" sideways a bit in a seaway but not a huge issue. Tapered wood wedges about the side of somewhat skinny doorstops worked well to diminsh/stop the thunk but the tiny amount of give would eventually pop them out. So if you have a wedge, tie a piece of string to it, and tie the other end to the back of the cassette. The daggerboards were about 5' long x 2' chord when fully down.

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Zonker, the blade isn't raked. The whole blade stays upright...straight up and down, and the jammer just shoves the whole thing forward into the front end of the cassette.  My transom is perfectly vertical....the front of the cassette is vertical, the leading edge of the rudder will be vertical.    By my measurements, and if I can do what I plan to do, this will put the leading edge of the blade about half an inch forward of the axis of rotation. The axis will be completely vertical.

It would be nice to have a balanced E-rudder, but this is going to be so much of an improvement over my old one that I'm happy.

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22 hours ago, Alan H said:

Zonker, the blade isn't raked. The whole blade stays upright...straight up and down, and the jammer just shoves the whole thing forward into the front end of the cassette.  My transom is perfectly vertical....the front of the cassette is vertical, the leading edge of the rudder will be vertical.    By my measurements, and if I can do what I plan to do, this will put the leading edge of the blade about half an inch forward of the axis of rotation. The axis will be completely vertical.

It would be nice to have a balanced E-rudder, but this is going to be so much of an improvement over my old one that I'm happy.

Zonker may have been talking about how I'm planning to rake forward the rudder for balance. I toyed with your idea, too, but then decided to go with foiled shape blade all the way with a foil-shaped cassette, because I'd like to be able to pull up the rudder and maintain steering in shallow water with raised centerboard (around boat ramps or in shallow bays/rivers). However,  I still haven't completely figured out how to secure the blade in the cassette. I'm afraid that if I make the cassette very tight, it will be hard to move the blade up and down. On the other hand, if I make it loose enough to move the blade easily, the blade may move a little under sail. Side-to-side a degree wouldn't be a huge issue, but if it tilts just a little bit aft, it would mess up the balance of the rudder.

So I thought I could make an insert incorporated at the aft edge of the cassette that could be tightened by a knob/bolt, but your wedge idea is interesting as well. I'd just have to make the inside of the wedge foil-shaped to correspond with the aft edge of the rudder. Then push it down and lock in place somehow.

Maybe I'm just overthinking it. For me, the KISS approach would be just to laminate the cassette around the blade and hope I can get the tightness, material and friction of the gaskets right.

Also, a question about your rudders. If I understand correctly, you're planning to use one cassette for both rudders and the main rudder will have to be inserted from below since it's thicker than the cassette, whereas the E rudder can be lowered from the top, right? How are you planning to build the cassette? You'll have to make it stronger than your rudder to make sure you'll have an intact cassette to drop your E rudder in ;).

 

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22 hours ago, Alan H said:

Rudder dimensions

 

rudder comparison.jpg

No comment on the rudders.  I like your fonts though.  what is the left one called?

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10 hours ago, erdb said:

Zonker may have been talking about........... inside of the wedge foil-shaped to correspond with the aft edge of the rudder. Then push it down and lock in place somehow.

Maybe I'm just overthinking it. For me, the KISS approach would be just to laminate the cassette around the blade and hope I can get the tightness, material and friction of the gaskets right.
 

Also, a question about your rudders. If I understand correctly, you're planning to use one cassette for both rudders and the main rudder will have to be inserted from below since it's thicker than the cassette, whereas the E rudder can be lowered from the top, right? How are you planning to build the cassette? You'll have to make it stronger than your rudder to make sure you'll have an intact cassette to drop your E rudder in ;).

 

If I were making a rudder like yours that's exactly what I'd do. I'd wrap a layer of plastic...maybe TWO layers of painters-tarp plastic around the rudder and mold a cassette in place.  I'f I'd thought of that back in 2007, I would have done it back then, but I had "doorskins on the brain" from making a hard cockpit-hatch cover from doorskins.

You could also make the whole thing 1/8th of an inch too big and line it with neoprene, maybe?  To hold the rudder in, do a Michael Storer trick. --- https://www.storerboatplans.com/design/the-standard-storer-boat-plans-kick-back-dagger-rudder/

6876775598_bc1c2ba49e.jpg

 

379091135_dac1a798cd_z.jpg?zz=1

 

8682704912_0d59efbe1e_b.jpg

....except that if I were you, I'd make the cassette completely enclose the rudder at the top and bottom. Just leave a 2or 3-inch gap in the middle, at the back and use a bigass bungee cord to hold it in there.

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In my case, the primary rudder will hang off of the pintles on the transom. No cassette.  I only use the cassette for the E rudder.

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9 hours ago, MR.CLEAN said:

No comment on the rudders.  I like your fonts though.  what is the left one called?

Hell if I know. LOL....a mess of weird fonts came with the Mac free app "Paintbrush" which is basically Microsoft Paint for OSX.

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Hey laminate cognoscenti, the E-rudder goes in the vacuum- bag tomorrow, if today goes the way it should.  I'm pretty sure I have enough 19 oz triaxial cloth to do two layers, as the cloth is 60 inches wide.  The rudder has a chord of 13.5 inches...doubled-over makes 27 inches...add a bit for the front and back / curve of the foil and it's going to be close..    I expect that two layers will make it absolutely bombproof, but it will also add a bunch of weight.

Suggestions?

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VACUUM BAG DAY!!

...what a shi*tsh0w!!. I'm so glad I did the E-rudder first. Now I've made all my mistakes and know what to do differently for the primary rudder.

Mistakes...#1 I thought I cut the triaxial glass wide enough to cover the blade with an inch overlap for "flash". Nope. There might be some overlap at the trailing edge. Might not. It's that close. Lesson - cut 4 inches more than you think you need. #2.. well, mistake #1 took so much time to readjust that by the time we got the rudder in the bag, the epoxy was starting to gel. So I doubt that the breather pulled anything out. I certainly can't see any resin in the breather. The cloth and the peel ply are well soaked, though, so there will be a good bond.

BIG 3-cut all the cloth out FIRST, BEFORE coating the rudder. Don't "cut as you go". Oh, well. This is why I did this rudder, first.

Here's what my garage looked like, cutting out breather while the rudder was on the table with peel ply on it. Me=Dummy! I won't do that again.

vacuum-bag-garagemess.JPG

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Mrs. Alan H  helped me get the rudder in the bag I had for it, after doing all the layup, finding out that I hadn't cut enough triaxial to quite get to the trailing edge on both sides, removing it and laying it all in, again. Here it is, hanging from a line between two sawhorses.

vacuum-bag-hang1.JPG

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Then, on with the pump, loaned to me by my laminates/carbon/composites whiz friend, solosailor. Another lesson...get the butyl tape on the bag BEFORE hanging it. Sealing the bag took 45 minutes and a lot of cussing. LOTS............of cussing, seriously. Oy, ve.

 

 

vacuum-bag-pump1.JPG

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Finally, "tented up" (there's more plastic on it now, down to ground level everywhere but one end)... and two space heaters running.

 

Solosailor says that the orange pump pulls air pretty fast, so I ran it for about two hours. He loaned me another, smaller one, which I set up in the other end (the end closest to you in this photo.. The "big" pump ran for about two hours. The little one ran for about an hour and a half. I never got a really excellent seal, so needed one or the other to be running to keep the bag down on the rudder. By the time I turned off the one pump and started the other, I'm sure  the epoxy has started to seriously set up, so I doubt anything is going to get pulled into the breather. If it was going to flow, it would have done so in the first hour.

I'm going to be moving the space heaters around under the "tent" until about 9:00 PM, tonight.. That means they'll have been under heat for about five hours. Incidentally, there's more plastic over the "tent" now, so it's more or less touching the ground everywhere but one end. I estimate it's about 85 degrees at the "top" of the tent and 70 nearer the ground.  It's open at one end 'cause I ran out of plastic.

vacuum-bag-tent2.JPG

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This has been a high-stress day. Hopefully what I've learned will make the next one lower stress, and with better results! Also, very curious to see this rudder when it comes out. I'm concerned that I was a bit skimpy with the epoxy, since absolutely nothing that I can see, has migrated into the breather.  Then again. that might be because it took so long to get the rudder into the bag and under vacuum, and by then the epoxy was gelling.

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It's the next morning. Well, OK, it's noon now but it was 8:30 AM when I started what I'm going to write about, here.    I un-tented the rudder and turned off the heat at about 10:00 PM last night. I strung it up in my 50-deg. garage overnight and went to bed. This morning I went out and pulled the peel-ply off. It did not want to come off all that easily. The laminate was very sticky. It was very tightly adhered to the wood, but sticky.

 

vacuum-bag-post-cure1.JPG

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Good news, I have contact/coverage all along the trailing edge of the blade.
Bad, but not unexpected...The impossible "inside angle" of the leading edge where the stock is set back 3 inches from the blade is ugly...big surprise. I'll have to grind out about 5 inches of stuff. No biggie.

However, the worst news is that now I know why the breather cloth didn't absorb any excess epoxy. There wasn't any. The mixture is rather epoxy-starved, darnit. There's a lot of bonding to the wood, but also areas that need more. I only found two very small "silvery" areas, in non-structurally important places, where the glass didn't wet out at all. However, this *meh* bonding is not good.

Upper half of rudder close-up...  The blade area looked about the same.  NOT happy about this.

vacuum-bag-post-cure-closeup-stock.JPG

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Well, the rudder was still very tacky, so there were still chemical bonds forming. I quick-like got the rudder outside and hung it on some sawhorses. Then I mixed up some epoxy and wiped it on there. It took a surprising amount to fill in the weave, but it did wet out really well. Lesson Learned!...more epoxy in the layup.

So this rudder is less than optimal. There is now probably too much epoxy in the epoxy/glass mixture for optimal strength. It'll be really strong, no question about that, but not optimal.

vacuum-bag-post-cure-fillin-hang.JPG

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Close-up shows that the stuff I wiped on there, is working its way in...

vacuum-bag-post-cure-fillin-closeup-blade.JPG

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The fact that I did this while the overnight-coat was still pretty tacky is good. It will probably bond really well, and from the appearance of the rudder, it SEEMS like there's a lot more wood/glass/epoxy filling-in-the-gaps going on. Still, it's frustrating. However, this is why I did the E-rudder first, before the primary rudder. I'm glad I'm making my mistakes here..... Next time...MOAR EPOXY in the layup!!.

i really want to finish this rudder off, but I need to return the vacuum pumps as soon as I can, so weekend after next, the  primary rudder goes in the bag.

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Alan, after your experience, so you think you need to bag the main rudder? Wet out and the peel ply to squeegee stage getting some epoxy out will make sure it’s wet and the peelply will keep the fibers in place till it kicks. Yeah, you might save a bit of weight, but as you now know, bagging can be painful...

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I'm really enjoying reading about your project, thanks for taking the time to take all the photos and post it here. I know how hard that can be when you're actually trying to get things done!

How did you wet out the glass? For something like this I think you'd find it easiest to drape the glass over the rudder (1 side first), then wet it out by pouring on a bunch of epoxy and spreading it around with a squeegee. Once the first side is done, flip the rudder, careful to avoid messing with the cloth, and do the otherside. At this point you should have a nice quality hand-lamination. You can then use the peelply and bag it, but I wonder if you're really getting much benefit with the vacuum bag for this kind of application. You can use the peelply regardless to save finishing time. 

One other thing to consider is that the wood will absorb some epoxy, and you might want to give it a sealing coat before doing the laminating. Less of an issue at low temperatures, but something to keep in mind.

I built a much smaller rudder and centerboard using a hand plane and some templates and found the shapes came out nicely without too much effort. For a larger wood core one I'd consider the same kind of technique but with a power planer. And if you think you've had any problems... my rudder #1 was coming together really nicely until I realized I'd shaped the foil backwards!Sooty_Tern_145.jpg

 

Sooty_Tern_151.jpg

Sooty_Tern_165.jpg

 

 

 

 

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Alan, prepare your glass, get the weight of it, prepare same amount of epoxy.

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1 hour ago, Raz'r said:

Alan, after your experience, so you think you need to bag the main rudder? Wet out and the peel ply to squeegee stage getting some epoxy out will make sure it’s wet and the peelply will keep the fibers in place till it kicks. Yeah, you might save a bit of weight, but as you now know, bagging can be painful...

That's a really good question.  I'm vacuum-bagging because someone who really knows their stuff suggested that I'd get a better rudder if I did.  Also, honestly....I've never done it before and I thought it would be a good experience to learn how to do it.  Now I have the peel ply and breather, and a bag, so it only seems right...you know?

Now, I have to say that except for the ugly "fold over a hard edge" areas, the contact between glass and wood is amazingly smooth. This is by far the most fair layup I've ever done.  That's not saying a lot, I mean, I laid up my E rudder in 2007 and glassed a Cal 20 rudder back around 2002, so I'm no expert. Still, I think if I am just more generous with the epoxy next time, I'll get a good result.

But that's a valid question...

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59 minutes ago, andykane said:

I'm really enjoying reading about your project, thanks for taking the time to take all the photos and post it here. I know how hard that can be when you're actually trying to get things done!

How did you wet out the glass? For something like this I think you'd find it easiest to drape the glass over the rudder (1 side first), then wet it out by pouring on a bunch of epoxy and spreading it around with a squeegee. Once the first side is done, flip the rudder, careful to avoid messing with the cloth, and do the otherside. At this point you should have a nice quality hand-lamination. You can then use the peelply and bag it, but I wonder if you're really getting much benefit with the vacuum bag for this kind of application. You can use the peelply regardless to save finishing time. 

One other thing to consider is that the wood will absorb some epoxy, and you might want to give it a sealing coat before doing the laminating. Less of an issue at low temperatures, but something to keep in mind.

I built a much smaller rudder and centerboard using a hand plane and some templates and found the shapes came out nicely without too much effort. For a larger wood core one I'd consider the same kind of technique but with a power planer. And if you think you've had any problems... my rudder #1 was coming together really nicely until I realized I'd shaped the foil backwards!

 

 

 

 

 

 

 

In fact that's what I did.  I'd get photos, but you know....gloves with epoxy on them and digital cameras are a bad combination!

My "workbench" is a slapdash table set on sawhorses, covered with plastic. You can see my setup, such as it is, in the photos.  So I brushed off the plastic very thoroughly, and laid the bare rudder on it. Side #1 got a substantial coat of epoxy. Then I went and cut out the triaxial cloth.  (stupid....have the cloth ready to go BEFORE coating...) So the epoxy had ten minutes to penetrate the wood. I laid the cloth on that side, squeegeeing it on pretty tightly.

Then I went and cut out the peel ply.  (again, stupid....have the peel ply ready to go BEFORE coating...). That went on by hand, spreading out everything nice and flat.  Then I flipped the rudder and brushed on a mess of epoxy to the prepped wood/epoxy/wood-dough surface.  That was followed by laying the triaxial cloth on the second rudder surface, only to find out that it was about 3/8ths of an inch too short to meet up with the first layer at the trailing edge of the rudder.

That set off about 90 seconds of screaming four letter words. My wife came out of the house into the garage, took one look and went right back inside. Lesson : cut more cloth than you think you will need, dumbass...


So I flipped it all over to the first side again, pulled the cloth and peel ply off the first side, and placed it back on, again, pulled slightly up so as to give me a chance at overlapping on the trailing edge. That's when the peel ply slipped off and one corner of it fell in the dirt. More cussing.  Anyway, I finally got it all back on, hand-smoothed out pretty well, but it took a long time. The epoxy was starting to set up.

I then went and cut the breather cloth.  That went on pretty easily. Then the Mrs. came out and helped me get the thing in the bag. I hung the rudder, now bagged from the rope I had over the sawhorses....then tried to seal it with butyl tape.   I won't make that mistake again, next time I seal the bag on the bench.

Finally the pump hose went in, and I turned it on and it did pull down a vacuum, if not a super-tight one.

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I'm documenting this like crazy so that someday, when some other idjit with no common sense decides that they want to build a rudder like this, they'll have a reference for it.  I have almost the exact same thread going at the Wooden Boat Forum.

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Good point up above. Sealing coat needs to get to at least a green cure stage. That way, epoxy can’t get sucked into the wood starving the laminate

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Did you apply any extra epoxy after the cloth was on? Your way sounds good to me as far as letting it soak into the wood but I wouldn't expect to be able to apply enough epoxy to fully wet out the cloth. 

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If my experience is anything to go by, your ratio of mistakes made to experience learned is better (lower) than average - keep up the good work!

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36 minutes ago, andykane said:

Did you apply any extra epoxy after the cloth was on? Your way sounds good to me as far as letting it soak into the wood but I wouldn't expect to be able to apply enough epoxy to fully wet out the cloth. 

A little bit, not much. The peel ply was soaked, so I figured that was enough.  Now I know otherwise!

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4 minutes ago, Fleetwood said:

If my experience is anything to go by, your ratio of mistakes made to experience learned is better (lower) than average - keep up the good work!

HA!....thanks for the kind words.  I am definitely learning, here.  I'm glad I didn't muck up the primary rudder. I'm not so worried about this emergency blade. It'll still be strong, just not "optimized" in terms of glass/epoxy ratio.

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Leo, the most accurate scale I've got is for our cat. --seriously!   My wife will kill me if I get epoxy on it, it's a $60 scale! LOL

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Alan, 

I build up the trailing edge (no bag) before doing the entire skin of the rudder. I do a layup of 4" uni tape and biax down the trailing edge on one side, sticking out 1/4" past the core, as soon as it's cured enough to flip, fill the 1/4" overhang with thicken and repeat the same layup on the opposite side. Cut and clean up before bagging the main skin on the rudder. This ensures a clean and strong trailing edge, and allows you to taper your main skin layers. I  would do a seal coat on the wood (using peel ply), then do you laminate over it. More resin when wetting your glass, get a catch pot. Ditch the breather cloth, the peel ply functions as a breather cloth. I run my spiral vacuum tube draped over the leading edge with it reaching from end to end.

It looks to me like your resin:hardener ratio was off and this caused all the air in your laminate, because it wasn't;t fully cured before you shut the vac off. 

Good luck! 

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1 hour ago, Alan H said:

A little bit, not much. The peel ply was soaked, so I figured that was enough.  Now I know otherwise!

If the peel ply was saturated, the only place for it to go was into the wood....

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So, one thing I've learned from this thread is that there are lots of ways to do this.

carbon - no carbon.  There are arguments for both.
Four different ways to treat the trailing edge have been outlined in this thread, plus how Phils Foils/Custom Composites does their trailing edges.
Three specific ways to vacuum bag have been in this thread, plus another variation that I've seen on the WBF.  I happened to watch Phils Foils video on YouTube and decided to do it that way.

There are principles but lots of "right" ways to do it.  One thing I might change is the pre-coat step.  I hear that if you don't pre-coat, you get bubbles.  Well, is "pre-coat"...."paint on epoxy and wait for it to kick off"?  Is it.. "Put on epoxy, wait fifteen minutes then lay on the cloth? I dunno.... but what I did didn't work so good so I think I'm going to pre-coat, lightly and wait an hour or 90 minutes before laying on some more epoxy, and cloth.

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10 hours ago, LeoV said:

Alan, prepare your glass, get the weight of it, prepare same amount of epoxy

No, you will need more, especially if you are not experienced in bigger layups.

- always some waste on stir sticks, containers, and application tools and gloves
- drips
- some for peel ply/breather

I'd add 20% for just this. Have your epoxy + hardener premeasured before hand in multiple mixing cups. Then you can keep going but only mix a smaller batch at a time so it won't get too hot and gel. Have bag, peel ply, breather all ready and pre-cut but you know that now.

Yes, pre-coating the core and waiting is fine. Otherwise you risk resin starved cloth as the wood drinks it in. 100 gm/m2 is about right for softwood coating. Uh about 3 oz/sq yd for you 'mericans

Wrap scale in cellophane / ziploc bag to protect from drips

Also wrap cat too just to be sure

 

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Preparation is king, as always...

Zonker good post, Alan knows me, and would have prepared more. If I said your amount he would have prepared 40 % more, lol.

Scale, for a cat ? Okay, I picture now a to fat a cat on a diet... place scale on table, strokes of clingfilm over it, criscros, ductape it on the edges to table. Keeps it clean.

 

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Good point... Saran wrap over the scale. I'll have to do it while she's not there.

Zonker: " Have your epoxy + hardener premeasured beforehand in multiple mixing cups. Then you can keep going but only mix a smaller batch at a time so it won't get too hot and gel."

 

REALLY good idea!  Gonna do this. It's the simple things...

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The epoxy fill-in I put on yesterday morning kicked off all day yesterday and last night in the garage. Rudder finish looks really good, tight to the wood and smooth, yay!  OK, there's a bit too much epoxy in the epoxy/glass ratio but I can live with it.   On to the primary rudder!

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Hey, this is premature, but....I have a can of white Gel Coat and hardener, was going to coat both rudders in that.  However, maybe a 2-part epoxy paint...white... would be better?  Thoughts?

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2 hours ago, Alan H said:

Hey, this is premature, but....I have a can of white Gel Coat and hardener, was going to coat both rudders in that.  However, maybe a 2-part epoxy paint...white... would be better?  Thoughts?

uh oh, you just started the "anchor" debate version of poly over epoxy.

You'll hear about Barely Careful's gel coat popping off grand-prix boats

and how Poly CANT be used over epoxy, never, never!

 

Reality it, IF the epoxy is fully cured, it's inert. Follow the instructions on the gel coat container.  Paint can be easier to deal with however.

 

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Raz'r, I bought the gel coat  literally because the sales guy told me to. That's dumb because he clearly didn't know a damn thing. However, both the can and the MEK are unopened, I can return them easily enough. Two-part epoxy paint should be relatively easy to deal with, I'd think.

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Just now, Alan H said:

Raz'r, I bought the gel coat  literally because the sales guy told me to. That's dumb because he clearly didn't know a damn thing. However, both the can and the MEK are unopened, I can return them easily enough. Two-part epoxy paint should be relatively easy to deal with, I'd think.

i personally love 2 part epoxy paint. But it ain't inexpensive...

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2 part Epoxy paint (if it’s truly epoxy-based) won’t like UV. I would recommend a polyurethane for above water portions of the rudder. IP2000 the whole thing then mask the waterline. 

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