Wooden Boat People
By McKenzieDriftBoat.com
A few questions about wood vs. foam
I am in the process of building a modified Briggs dory from Roger Fletcher's book. It will be about 15'9" at the centerline and a double-ender. The hull is marine grade plywood and is all scarfed together and the frames are built. (Boy, I sure hope this works...)
I am new at building dories, but I have rowed one fairly extensively that my ex owned... The River Gypsy. The Gypsy had a honey-comb kevlar bottom (and partway up the sides) and was stitch and glue construction. I like the idea of a lightweight, durable material for the bottom of the boat, but after putting three large holes in the chine, I'm not sold on this particular material. I also have no idea how to properly fix it... we were on the Middle Fork at the time and just stuffed a bunch of epoxy and wood filler in there and called it good. It was ugly but held out about 90% of the water and as far as I know he has not done anything else to it. The relationship ended at the end of the trip but I was bit by the wooden boat bug, so here I am, and here are a few questions:
-What kind of foam works best for a durable bottom?
-How do you fix it (on and off the river?)
-I don't have much money... can I even afford to consider anything other than wood?
-Is there a cheaper polyurethane alternative?
-Do I even need to bother with chine logs if I use foam?
-Should I use it for the decking and bulkheads to keep the weight of the boat down?
Here's a few pictures: (the first are of my 1" to 1' scale model, and the last is of one of the larger chine holes in the Gypsy)
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Replies to This Discussion
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Permalink Reply by River Gypsy on
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And I just figured out how to get the photos up...
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Permalink Reply by tungsten on
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My guess is the holes in the chines happened because there wasn't enough glass there,probably the wrong kind also.You'll have to add more to repair and use stitched 45/45 glass not woven glass.
If money is tight then plywood all the way,foam needs a lot of glass so its going to be costly.
nice models by the way.
Curious why double ender?
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I've always wondered why you wouldn't want a double ender. The only place I can think that I might want a transom would be on Cataract Canyon where you would want a motor. Seems like a double ender will handle waves much better and faster when you have to pull away from big scary objects. I also am reading The Emerald Mile (amazing book by the way) and when Grua rebuilt his boat, he made it a double-ender, which was good enough confirmation for me.
It took me a few tries to get the model right; I did a few with cardboard until I got what I wanted. I changed the last four frames (five, really, since I took one away completely). The chine line I kept it the same, the sheer line went from a slight curve in the book to completely straight which enables the back end to bend up for the double-ender and gives it just a couple more inches of freeboard. I hope it works out! I like the way the model looks at least.
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Yes of course.No big scary objects to row away from where I'm from.
Good luck with your boat.
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Permalink Reply by lhedrick on
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I have seen lots of holes in boats at the chine. Framed/stitch-glue a big hit can get through.
The builder of this boat is now using evolved materials and vacuum process in continue the quest for lighter and stronger. We keep trying but, we will not be able to prevent all damage. The good part is that with wood or composite we can make repairs and keep the boats going for years.
Over the years I have been building up the chine much more. I am up to about 8 layers of glass and kevlar to make them stronger. 17 ounce biaxial glass tape is strong stuff. The more layers the stronger the end result but, with each layer it gets heavier.
A comment was made about strength of framed boats V stitch and glue. I won't even comment because they are both up to the task. Compound angle cuts on a table saw for the frames are a lot more complex then stitch an glue which has no frames. Then again stitch and glue takes longer and the process of working with epoxy and fiberglass takes some time but, it's not difficult.
I would advise people who are looking at the hole in the Chine of the Gypsy to not jump to any conclusions about it's construction. I once saw a totally destroyed wood, framed boat on the bank on day 1 of a MF trip. I saw another all wood framed boat with holes all over and a split stem on a Yampa/Green trip. It was being towed by the time it got tot the take out ramp. Nothing wrong with the boat, it just got smashed into everything. I have seen wood framed boats up in camp being repaired in the Grand Canyon. I have helped pull wood stitch and glue boat up into camp and get those repaired after rocks went through the bottom and chine. The photos of the rear floor of Kelly's with the delaminated plywood show what can happen to a plywood bottom and the fact that it can be made as good as new. Wood and composite both have a proven history and a river can destroy both. I will say that having built from wood and composite, the composites are more expensive. As for wood, the quality of marine plywood gets worse every year.
The Gypsy is a Rogue style boat with the gunwale edge cut down at the transom for motor use. It was built from the plans in Rogers book.
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Permalink Reply by Kelly Neu on
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Psyched to hear about your project. I built my dory w/ plywood so I am pro wood:)
-What kind of foam works best for a durable bottom? I don't know but 1/2 inch plywood works darn well.
-How do you fix it (on and off the river?) Ideally duct tape. Next, marine putty. Basically you want to make a repair that will get you to the takeout but be easy to remove once you get home. That way you can dry out the boat, remove the other damage and do a permanent repair. As you know, make sure you figure out the compatibility of your hull material/glass, etc.. with your epoxy vs poly patch material.
-I don't have much money... can I even afford to consider anything other than wood? Foam is double the cost due to the fact that you need close to double the epoxy and glass layers.
-Is there a cheaper polyurethane alternative? I used Raka epoxy which was cheap and good. Poly gets you in trouble with compatibility issues if you ever have to repair or rebuild. I'm not a fan of poly but mostly because I don't have much experience with it. Would like to know what you find out!
-Do I even need to bother with chine logs if I use foam? If you are talking internal chine log... You don't need 'em if you are building stitch and glue style. Fillets are amazingly strong!
-Should I use it for the decking and bulkheads to keep the weight of the boat down? In my experience, Foam does not keep weight down as you need so many epoxy/glass layers to make it stiff. The bonus of foam is that it absorbs impacts better than wood and potentially does not rot. ...But remember I am a plywood enthusiast.
Cheers to your project. Can't wait to hear about what you decide.
-Kelly
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Thanks for the great info, Kelly! We are building a framed boat and I think we'll probably stick with plywood after seeing your advice, but any other input on the matter will be much appreciated... we have a long way to go before we even get to that point!
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Just in case its any use to you ... here is the address for my blog. The recent posts are of a boat I made from driftwood which is not of much use but if you go into the history there are pics of my Grand Canyon dory build. -It has a transom though. -Kelly
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Permalink Reply by chris towles on
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I'm guessing this is Anika? It's Chris, used to live with Jason at the pawn shop. U may remember the first boat I built in the parking lot.
Anyways I am mid build on a corecell a foam dory with a honeycomb interior. I'm right in town in jackson if u want to come by and check out the boat, check out materials, ask any questions. I'm working on it most days. I am about to do my big exterior layups too if u wanna come watch, gawk, learn about vacuum bagging or help out.
If u are looking for local cheap wood for a floor I do have 2 sheets of 1/2" marine fir I could be convinced to get rid of. I've been holding onto them to build another boat but is take reasonable offers.
As to your questions, you want corecell foam 1/2" minimum. It's really expensive, and you'll need to add alot of glass. Wood with one layer of 18oz biax will get you there cheap as possible. That being said foam translates impact better, is lighter, is more easily repairable and doesn't absorb water.. If you break a hole. patch over it with 5 min epoxy and glass fillers, duct tape it and get on your way. no need to worry about water intrusion. It can arguably be engineered to be much stronger than wood but that depends on your layup. they wont build jets and space ships out of wood...thats all ill say.If you are gonna do a foam floor id go stitch and glue. Building a foam floor in a framed boat just seems like a bad mix of modern and classic. Brad dimock makes hybrid ribbed dories with a filleted and taped floor often with foam. They are sweet, but brad is the guru.. that guy can make artwork boats out of scrap wood in a few days. If u go stich and glue if just go stitch and glue period and skip the ribs u don't need them in a dory.. Nor the chine log either. All that said plywood works and has worked for a long time. And is the cheapest and easiest method. A framed Briggs can be built out of the book from the plans as is. That's sweet. Lofting can be a bitch. I've spent the better part of the summer refining actual full scale dimensions after making something like 20 cardboard models.
As to the interior you can save a ton of weight with a foam or honeycomb interior. I think this is the place for the honeycomb. It's light stuff and strong and is not gonna take damage inside like a floor will. It's also about 1/3 the cost of foam and available in the us. And u will save weight. I've been building with the foam and honeycomb daily for months now. After coming from working with plywood, I can tell u there is a significant weight savings with the synthetic cores. Larry Hedrick has skinned honeycomb successfully with 1 layer of 10 oz for interior panels. That's a super stiff light panel for its weight and I don't believe plywood could match it. Don't believe it, do the math. Glass and resin is not that heavy. A layer of 10 oz big enough to do my entire floor on my 17x55 weighed in at about 4 lbs. heck my entire inside floor layup was just under 28 lbs for glass and resin.. That's 10oz, 5 oz Kevlar with 30" overlap in the center, 18oz biax chine reinforcements , biax/kevlar tip and tail reinforcements, and a layer of 12 oz biax. That's alot of protection for its weight. Glass is not that heavy but Plywood is.
Again, I'm a bit out of place arguing this on a wood boat forum but there are some great modern materials out there for boat building and they can be incorpororated into wooden boats in a lot of ways. Floors, bulkheads, decks, etc. all I have to say is don't knock it til u try it. If u look at the modern sailboat builders, those guys are utilizing these materials to make amazing light and fast boats. I'd hate to miss out on all that fun because I was stuck in a time vacuum of boatbuilding. Wood is great, we all know that. Has worked for a long time and will continue to well in the future. All that said, just because they figured out how to build drift boats in the forties and that method has withstood the test of time, doesn't mean its the only way
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Hi Chris, yes this is Anneka. I just moved to Bozeman about a month ago but I might be coming through Jackson in a couple weeks and I'll let you know because I would love to see your boat. You must have built that first boat later because I have never seen it. I will also take that 1/2" marine fir off your hands.
I think a corecell floor is out of the question for me. At $250 per sheet for 4x8' 1/2"... I think I'll have to wait a few years after we get sick of fixing the wood. Plascore, on the other hand, is relatively cheap at about $45 for 4x8' 3/4", so that may be a good way to lighten up the bulkheads. Is it as strong as 1/4" plywood though? Stronger?
Another question I have is: how is stitch and glue so much stronger than a framed boat? I already have the frames built (and spent a lot of money on the nice douglas fir that they are made out of).
I am certainly convinced that foam is lighter and stronger, but I simply don't have the money to build with it right now. Luckily, my boyfriend and his family own a big wooden sailboat and they have rebuilt and repaired it many times so they are no stranger to the amount of work a wooden boat takes. The boat is being built in his folks' shop in Spokane and we will make a few weekend trips there over the next several months.
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Anneka,
Feel free to drop by if you make it to town. Four 1 three- four 2 seven- zero 7 fo nine. Guessing your done guiding for the season?
As to foam vs wood, wood is cheap and easy. Working with glass is really not that sweet. Im itchy every night. Miss making good smelling dust in the shop. This boat is tyvek suit, respirator, goggles all day and it kinda sucks. If you still are considering foam You can get corecell a little cheaper thru noahs in canada. About $145 for 1/2 sheet and $190 for 5/8. Shipping will get you to $250 a sheet i bet tho so kind of a moot point. Its really good stuff tho. There are also some cheaper options. You can get divynicell cheaper and in the us thru fiberglass supply in washington. Its a x link pvc foam so not as sweet overall as corecell in some aspects, but is a strong structural foam core used heavily in making sailboats, powerboats and the like. I bet you could do a foam floor with divynicell for a few hundred bucks less. There is also the option of doing a double floor...plywood inside, and a thin plascore, foam, or even coremat layer over that with the glass layup on top. Idea is the crushing blow crushes your layup and core top layer, but dont bust thru the plywood floor and into the boat. You could even run core up the sides as additional protection like joshes dory had. There are also various way to make the plywood stronger too...heavier outer layup, heavier inner layup, polyester fabric to toughen, kevlar as a last inside layer in the impact area for stiffness andstrength in tension. coremat or similar bulker ply to add thickness and stiffness to the laminate. Just some other options to think about.
For interior stuff i think plascore is a good option. Its cheap, no more $ than plywood. You need to glass it, but i would glass all ply both sides anyways if it were my boat so not a whole lotta differance in glass or resin weight. I might add another layer of glass on places like deck top that see foot traffic, but it seems 10oz of glass will get you there with plascore. Im using 8oz/6oz at 45 degrees for blukheads and deck bottom 8oz/9oz for deck tops for my boat but thats just personal preferance. You will save weight tho. No question.
As to framed vs stitch and glue...sounds like you already made your decision. I hate moving backwards ever, so if you spent time energy and money making all those frames out of nice looking doug fir i would just roll with it heck id even finish em clear for effect. Youll have plenty more battles to fight before the boat is ready for water so i wouldent waste energy fighting that one. If you havent notched the ribs for chine logs there is still the option of skipping the chine log and having a ribbed stitch and glue hull, or hybrid such as brad dimock makes. These are popular because you get the advantages of both construction method...bomber frames, bomber stitch and glue chine joint, and a radiused chine with no chine batten. Most ww Dory guys dont like chine battens cause they are prone to chine dip in squirrelly water and Eddylines. Why is stitch and glue stronger, theres many who will debate that notion, all i will say is a 1/2" thick epoxy fillet and to layers of 12 oz biaxial tape is pretty darn tough.
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Well, I know that boat. I've been on few trips with that rig. I remember waiting around below Joe Hutch on the green while it's first hole in the chine was fixed.
Been on many trips with the builder.
I too build with the same honeycomb. Sound like you figured out how to fix it. On the river just fill it in with thickened resin and a cover it with a piece of glass cloth. When you get it home grind it out a bit and built it back up. The good part is the stuff can't develop rot.
The foam products cost a lot more then the plascore honeycomb.
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