Another wanna-be boat builder

[Oysterbreath]

Hello all, this is actually only my second post here but I noticed that there are a lot of boat builders here. So I wanted to ask a few questions. I am building a small 18'-0" long by 66" wide, cold-molded flats boat. I'm currently planking. I have the first of two layers on and I'm getting ready to start the second layer.

My first question is, what thickening agent, if any, should be used for layer to layer adhesion? I currently plan to pre-coat the first layer and the inside of the second layer with un-thickened epoxy just prior to bonding, then quickly add a thin slurry of epoxy thickened with microfiber/ wood flour/cabosil in a 33/33/33 mix ratio by volume to catchup consistency. Then bond. Is that a good ration for plank to plank bonding?

My second question is my lamination schedule. The designer calls for 8oz glass on the outside and epoxy coat only on the inside. The two layers of ply are 4mm each. I think I want a wee bit more abrasion resistance than what 8oz can offer me. Because he says the fiberglass is not included in the structural calcs. I think this gives me the opportunity to even try something like Xynole which as little structral strength to offer but has a ton of abrasion resistance. But I'm not sure. While I like the "poor mans kevlar" part of the sales pitch, they never tell you that you'll have to use a lot more of that darn expensive epoxy. So my thought it, maybe I should just source some REAL kevlar or some other Aramid fiber. Sure the fiber is more expensive but I'd be using less glass.
Bottom line is, I'm lost.
I like the idea of xynole but the epoxy soaking worries me!
I like kevlar but it's material cost scare me and I hear that it can get really fuzzy if it gets worn into
I like what I hear about syntex but can't find it.
I'm curious about vectorply too.
Once again, bottom line is...I'm lost!
Any advice from a real boat builder would be greatly appreciated.
I'm the mean time, here are a few pics of my build. This is my first build. Actually...my first real wood working project too:

[billschwabe]

Hello all, this is actually only my second post here but I noticed that there are a lot of boat builders here. So I wanted to ask a few questions. I am building a small 18'-0" long by 66" wide, cold-molded flats boat. I'm currently planking. I have the first of two layers on and I'm getting ready to start the second layer.

My first question is, what thickening agent, if any, should be used for layer to layer adhesion? I currently plan to pre-coat the first layer and the inside of the second layer with un-thickened epoxy just prior to bonding, then quickly add a thin slurry of epoxy thickened with microfiber/ wood flour/cabosil in a 33/33/33 mix ratio by volume to catchup consistency. Then bond. Is that a good ration for plank to plank bonding?

My second question is my lamination schedule. The designer calls for 8oz glass on the outside and epoxy coat only on the inside. The two layers of ply are 4mm each. I think I want a wee bit more abrasion resistance than what 8oz can offer me. Because he says the fiberglass is not included in the structural calcs. I think this gives me the opportunity to even try something like Xynole which as little structral strength to offer but has a ton of abrasion resistance. But I'm not sure. While I like the "poor mans kevlar" part of the sales pitch, they never tell you that you'll have to use a lot more of that darn expensive epoxy. So my thought it, maybe I should just source some REAL kevlar or some other Aramid fiber. Sure the fiber is more expensive but I'd be using less glass.
Bottom line is, I'm lost.
I like the idea of xynole but the epoxy soaking worries me!
I like kevlar but it's material cost scare me and I hear that it can get really fuzzy if it gets worn into
I like what I hear about syntex but can't find it.
I'm curious about vectorply too.
Once again, bottom line is...I'm lost!
Any advice from a real boat builder would be greatly appreciated.
I'm the mean time, here are a few pics of my build. This is my first build. Actually...my first real wood working project too:

Welcome and nice work, especially for a first timer! There are no "right" ways to do things but here's my take on your questions;

For thickening between layers we use a mix of about 30% cotton fibers and 70% cabosil troweled on with a 1/4" grooved trowel. The cotton fibers will soak up and absorb the epoxy keeping it in the joint between the layers and the cabosil thickens the mix to make it spreadable. No need to prewet either side of the planks, in fact it is a bad idea as the thickened mix will not penetrate as well and secondary bonding can be compromised if open time windows are not strictly followed.

8oz finish cloth is useless and I wouldn't use it on anything but small parts if that, in fact I don't have any in the shop and haven't for years. With epoxy construction chopped strand mat is a needless waste of resin and we did away with it years ago as well. You can put two layers of 1700 biaixal cloth (Vectorply, Knytex, JBM or whatever brand is available) and get double the strength for the same weight as a single layer of 1708 and offset seams much better. For your intended use I would do two layers of 1700 outside and one inside. Just coating with epoxy is ok but why take a chance, spend the little bit extra to make your creation truly immortal!

I'm leary of the "gee whiz" fibers and stick with proven materials. I do use Kevlar on all our hulls but you absolutely do not want to use only Kevlar! Kevlar fibers have a tendancy to stretch within the epoxy matrix and break the bond eventually causing delamination. What most builders do is use a hybrid weave of Kevlar and E-glass, in our case a 1200 weight available from all the major suppliers as well. Kevlar also fuzzes up horribly when sanded and it opens up a path for moisture to enter the matrix so you want to bury the first layer with Kevlar under an outer layer of plain e-glass that you can sand and fair without fuzzing. I use the 1200 Kevlar/E-glass hybrid and an outer layer of 1700 biax on all our hulls, even the 60+' ones and have had absolutely zero problems, knock wood! Several have had extreme impacts with floating logs or hard bottom at high speeds and none have resulted in any hull damage whatsoever. A couple extra staggered layers of 1700 on the keel and chines is also a good idea for abrasion. Do that to yours and it won't be bulletproof but you will not have to worry and any "encounters" with docks, rocks or other boats will leave them more damaged than you!

Good luck and keep the pics coming!

[Agitated88]

I cannot get enough of these build threads and the outpouring of information from folks like Bill and Bo. As Bill said, nice work for your first and please keep the pictures coming!

[brokensheer]

Following Bills very sound and proven advise, I would add and suggest you get your hand on a book called the Gougoun brothers on boat construction, this publication is as close to a boat builders bible as you will find, you may recognize the name as the w.e.s.t. system people

[Oysterbreath]

billschwabe, thanks for the info. The more I read, the more I think that maybe I should stick with fiberglass too. I do have a concern about the heavier glass though. What I'm building is a shallow water boat. It's gotta be light. So then my delima is how do I balance light weight for high strength? How much MORE weight would two layers of 1700 be than the single layer of 8oz. Sure, it'll be way stronger but no one ever claims that their corvette can take the abuse that their Hummer H2 can. lol
How much strength is enough for a microskiff? Well, I guess I just have a LOT to think about...and I'll be reading your post again! Hey, so what do you think about 10oz or 12oz?

[billschwabe]

billschwabe, thanks for the info. The more I read, the more I think that maybe I should stick with fiberglass too. I do have a concern about the heavier glass though. What I'm building is a shallow water boat. It's gotta be light. So then my delima is how do I balance light weight for high strength? How much MORE weight would two layers of 1700 be than the single layer of 8oz. Sure, it'll be way stronger but no one ever claims that their corvette can take the abuse that their Hummer H2 can. lol
How much strength is enough for a microskiff? Well, I guess I just have a LOT to think about...and I'll be reading your post again! Hey, so what do you think about 10oz or 12oz?

You are preaching to the choir on lightweight construction! As you will find, everything in boat construction is a compromise, from the hull design to the paint you will be faced with choices only you can make and you will find examples covering every extreme.

Two or even a single layer of 1700 will definitely be heavier than a layer of finish cloth but you said you wanted a little more protection and I agreed it would be most helpful. I personally don't use finish cloth because it has very little structural strength or abrasion resistance because it is just a thin layer of glass. Does your hull "need" it, no. Will it give you a lot more protection from damage, yes. Your choice. If ultralightweight was your intended goal, you are working from a handicapped position since you have a "traditional" cold-molded hull. Granted it is built on the lightweight side of that method and will definitely be lighter than a well-built single skin glass hull but composite (foam cored) would have been another 30% lighter right from the start. It is more expensive to be sure but again, it's all a matter of personal choice.

[Oysterbreath]

Thanks again Bill. Soooooo, I guess it's NORMAL to flip flop ever few MINUTES about this whole fiberglassing issue? I'm gonna drive myself bananas! Biax or woven, fiberglass or xynole, 8oz, 10oz, 12oz, or 17oz, laying fiber port to starboard vs bow to stern, overlap seams or center cut....ugggg! I freaking dreamed last night about glassing! lol
I guess after the first time it gets a lil better huh? lol
Well off to bed I go. I'll prolly dream about glassing the boat again! lol

[Oysterbreath]

oh yeah, one more thing. Where do you guys get that hybrid fiberglass with kevlar in it? I checked boatbuilder, fiberglast, raka, and fiberglasssupply comp. I can't find it...

[Tarbaby]

Don't sweat it too bad. If you think you are pulling your hair out with the glass choice wait till you flip her over and start thinking of how you will lay it out. You will change your mind 20 times..... All glass is 50 inches wide so you can stagger the keel and chine. My method is to cut the cloth that is used on the bottom flush with the chine . Then glass the hullsides and go over the chine so that the lap is on the bottom. Easier to fair the bump on the bottom than on the hullside. I would do a single layer of 1208 and be done with it. It is easy to get. Lay it out front to back so there are no bumps on the sides and bottom.
Then the fun part starts!! More pictures please.

[billschwabe]

Dreaming about boats at night? That's one of the first signs of dementia, better quit now while you still have a chance!!! The rest of us didn't and look where we are now.

In your general area Merritt Marine supply in Pompano is probably your best bet for getting cloth of any description and I know they keep the hybrids on hand since they use it on their hulls. I have to differ from our esteemed Tarbaby though, a single layer of 1208, while easy to get, is the same thickness and weight when wet out as two layers of 1200 or 1700 would be. If you go with the hybrid, you really should use another layer of eglass over it or the fuzzies will drive you nuts. For weight considerations, a single layer of 1200 or 1700 is not much difference at all. Overlap the chines and keel like Shay said and you will be golden. You don't "need" to but I would at least do a single layer inside up to the waterline belowdecks where you will never get back to again unless it has problems, and it won't with the glass.