Option for light weight Broadbill construction

D

David M

New member
Hi All, I wan to build a Devlin Broadbill this summer (my first attempt). I've read on here that weights of "to-plan" builds are around 150 lbs, although the specs suggested lighter. I would like to get pretty light, although not to the point where I have to really baby it.

I will not be trailering, it needs to ride in the pick-up bed. I hunt central Saskatchewan so most of the lakes lack a developed boat launch, and I expect to have to carry a short distance (probably from 10 up to 100 yds) from truck to water. Fortunately there is not much for rocks in the wetlands and lakes around here, and I'm also planning to use oars or a small 3.5hp, so I don't expect to be traveling at speeds where a collision with a underwater object would be devastating.

Ideas I've pulled from this forum so far

*Use 3-4oz. vs. 6 oz cloth.

*Don't go overboard with expoy (Not sure how obvious this would be to myself as a beginner)

*using plywood lighter than 1/4" (6mm) doesn't seem like its a good option.

*Could just use expoy on inside of boat, instead of using cloth and epoxy.

Can anyone comment on these ideas or others, how much weight they might save vs. how much durability is sacrificed? I want to shave off weight wherever I can without compromising durability too much for my day-to-day use (slow speeds, no rocks). Lastly I do plan to hunt open water with it, so if getting beat up on shallow choppy water could be bad for a light-weight design, I'd have to rethink.



Dave

PS
I got a lot of these ideas from this thread.
http://www.duckboats.net/cgi-bin/forum/gforum.cgi?post=43427;search_string=broadbill%20light%20weight;#43427
 
Hi All, I wan to build a Devlin Broadbill this summer (my first attempt). I've read on here that weights of "to-plan" builds are around 150 lbs, although the specs suggested lighter. I would like to get pretty light, although not to the point where I have to really baby it.

I will not be trailering, it needs to ride in the pick-up bed. I hunt central Saskatchewan so most of the lakes lack a developed boat launch, and I expect to have to carry a short distance (probably from 10 up to 100 yds) from truck to water. Fortunately there is not much for rocks in the wetlands and lakes around here, and I'm also planning to use oars or a small 3.5hp, so I don't expect to be traveling at speeds where a collision with a underwater object would be devastating.

Ideas I've pulled from this forum so far

*Use 3-4oz. vs. 6 oz cloth.

*Don't go overboard with expoy (Not sure how obvious this would be to myself as a beginner)

*using plywood lighter than 1/4" (6mm) doesn't seem like its a good option.

*Could just use expoy on inside of boat, instead of using cloth and epoxy.

Can anyone comment on these ideas or others, how much weight they might save vs. how much durability is sacrificed? I want to shave off weight wherever I can without compromising durability too much for my day-to-day use (slow speeds, no rocks). Lastly I do plan to hunt open water with it, so if getting beat up on shallow choppy water could be bad for a light-weight design, I'd have to rethink.



Dave

PS
I got a lot of these ideas from this thread.
http://www.duckboats.net/cgi-bin/forum/gforum.cgi?post=43427;search_string=broadbill%20light%20weight;#43427
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The boats are designed with weight as a design criteria. I don't think you are going to shave that much off, not enough to make it worth it.

If you haven't read Devlins book read it, he describes thoroughly how he he designs his boats and will help you understand how the modifications you want to make fit with the stitch and glue method. I would suggest reading Devlins's boat building book, and then read Tolman's book, especially the epoxy and wood portions and then read Devlins book again with the Tolman perspective fresh in your mind.
 
I'll certainly get the Devlin book, but Tolman's is a bit expensive in Canada, what are the general differences in philosophy?


And to all, why the discrepancy between reported weights on threads here, and the specs on Devlin's page (and duckboats.net), that suggest weight closer to 100 lbs?
 
look at do it yourself duck boats mine is under 100 pounds

goes good with my 4.5 horse motor

you can use a canoe catty to get it to the water if you dont want to carry.
 
I'll certainly get the Devlin book, but Tolman's is a bit expensive in Canada, what are the general differences in philosophy?


And to all, why the discrepancy between reported weights on threads here, and the specs on Devlin's page (and duckboats.net), that suggest weight closer to 100 lbs?
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Tolman's narrative on how stitch and glue works and needs to be maintained is very good and his building perspective is very different than Devlin's. I didn't read Tolman until after I built my snowgoose and sure wish I had. Can you get it used - I haven't bought a new book in a while now that I found that Amazon and half.com offer used? Tolman's perspective is from a work boat and Devlin's is more from a pleasure boat designing background.

I can't comment on the weights, I haven't payed all that much attention to weights for the boats, especially the broadbill. I will say that some of Devlin's other figures tend towards the optimistic, if you catch what I mean.

My feeling is that Devlin's glass recommendations are on the light side already. There are a lot of guys here that don't have a problem with them, though. I've talked to Eric and he is happy with the glass that Devlin suggests, but I woudl liek heavier and woudl use heavier if I built again. Your use as you describe is in a pretty forgiving as far as rocks and such, but I would not go less than Devlin's spec. I don't know if there is anyone who owns one of his designs and woudl say to use less, especially on a powered boat. Not a ton of guys have the smaller boats and use them hard. Dragging the boat is very hard on them, harder than most anything else, so you are goign to want protection.
 
I used 6 oz on a strip built boat. I wish I would have put two layers of the 6 oz. over everything instead of worrying about a little extra weight.
 
OK, well I think I will stick to specs. Perhaps the canoe caddy with some oversized wheels is the way to get it to the water.

Thanks for the advice.
 
OK, well I think I will stick to specs. Perhaps the canoe caddy with some oversized wheels is the way to get it to the water.

Thanks for the advice.
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Built it with the caddy or attachment points for the caddy as integral and have it balanced like a wheel barrow. One trip to the water with everything in there.

If money isn't an object, consider building with one of the synthetic composites like Coosa. You coudl save a ton of weight because you wouldn't need to put epoxy on the inside, and you coudl probably get away with just taping the seams on the outside (not fully glassed) and wouldn't need epoxy on the outside either. Material cost would be more than wood by a good bit, but epoxy savings woudl be there. Depending on the material, the weight is 3/4 that of wood and that doesnt' include the epoxy weight savings.
 
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If money isn't an object, consider building with one of the synthetic composites like Coosa. You coudl save a ton of weight because you wouldn't need to put epoxy on the inside, and you coudl probably get away with just taping the seams on the outside (not fully glassed) and wouldn't need epoxy on the outside either. Material cost would be more than wood by a good bit, but epoxy savings woudl be there. Depending on the material, the weight is 3/4 that of wood and that doesnt' include the epoxy weight savings.
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You sir like typing your "D"s before "L"s ;)
 
David, I did a build of sorts a couple years ago. Purchased the raw hull off Craig's List and then went from there. It was before I knew of this forum so I didn't have any plans other than in my head as to what I wanted the boat to look like when I finished. That said, I believe the hull to be dimensions of a Zach Taylor Widgeon. My point...I use a canoe carrier to get my boat where I need, as I too don't always have nice ramps to launch from, and it works great. The tires are simply 14" bicycle tires. Good luck with your build. The hull is 1/4" plywood too.

Troy

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Thanks for the reply Troy. Nice looking rebuild. Your canoe carrier looks interesting, in that each wheel has its own axle. Home build? have any pictures of the carrier by itself?
 
Having used 4mm plywood for a project I don't recommend going with it for a work boat. Anything less than 1/4" needs additional glass and you will loose the weight savings.

One of the best ways to drop weight in a small boat build is to use light weight solid wood like cedar where you can. Devlins boats don't have a lot of solid wood in them, but some of the frames and knees could be replaced with solid wood rather than plywood resulting in a few pounds of weight savings. however you will need to have some wood working skills in order to do this. I don't recommend it on your first boat if you don't have some high end skills already.

When people talk about weight savings during the epoxy work they are usually considering the amount of epoxy used to fill the weave of the cloth or the volume of thickened epoxy used in the fillets on the joints. Attention to detail is the only way to overcome these issues. That and experience building a couple of boats.

In the end with materials selection and careful epoxy installation you can only save a few pounds of overall weight.

If you want a light weight, simple to build, truck bed carried, and drag it to the shore kind of boat you should look at the Hybrid NL. They are ugly boats compared to Devlin's. However, they function extremely well in small protected waters using small motors or oars/paddles. Think of them as just a larger pond box that you can strap a motor on if needed. If you use a dog you have to make the boat bigger. Again not a boat for rough water.

http://www.hybridduckboat.com/files/index.php?id=1

This thread on the Refuge should keep you busy researching for a few weeks.
http://refugeforums.com/refuge/showthread.php?t=602498
 
Coosa? wrong stuff for the job. Coosa makes two grades of fiberglass reinforced foam. One is 15 lbs per cu. ft. the other is 26 lbs per cu.ft. Coosa is used for its resistance to compression where cleats,struts, misc. hardware, etc. are thru bolted in foam core boats. A lot of boat companies used it for transoms in outboard boats and found that since it is a polyester foam and not a cross linked polyurethane like corecell or divinycell, it was very brittle and turned to little particles and powder under stress. H 80 Divinycell which is the average density foam for most hull construction is 5 lbs. per cu ft. I dont think Coosa would recommend their product for a no glass construction project. Plus the boat would weigh a ton either way, with or without glass. Rich
 
Coosa? wrong stuff for the job. Coosa makes two grades of fiberglass reinforced foam. One is 15 lbs per cu. ft. the other is 26 lbs per cu.ft. Coosa is used for its resistance to compression where cleats,struts, misc. hardware, etc. are thru bolted in foam core boats. A lot of boat companies used it for transoms in outboard boats and found that since it is a polyester foam and not a cross linked polyurethane like corecell or divinycell, it was very brittle and turned to little particles and powder under stress. H 80 Divinycell which is the average density foam for most hull construction is 5 lbs. per cu ft. I dont think Coosa would recommend their product for a no glass construction project. Plus the boat would weigh a ton either way, with or without glass. Rich
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I followed your thread on structural composite panels with Mark W very closely and learned a lot.

The heaviest Coosa is about the same weight as Okoume (yes, it is spelled that way).
 
Coosa? wrong stuff for the job. Coosa makes two grades of fiberglass reinforced foam. One is 15 lbs per cu. ft. the other is 26 lbs per cu.ft. Coosa is used for its resistance to compression where cleats,struts, misc. hardware, etc. are thru bolted in foam core boats. A lot of boat companies used it for transoms in outboard boats and found that since it is a polyester foam and not a cross linked polyurethane like corecell or divinycell, it was very brittle and turned to little particles and powder under stress. H 80 Divinycell which is the average density foam for most hull construction is 5 lbs. per cu ft. I dont think Coosa would recommend their product for a no glass construction project. Plus the boat would weigh a ton either way, with or without glass. Rich
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Rich I'd really like to hear you detail how you would build a stitch and glue Devlin Broadbill out of Divinycell foam core. Remember you are talking to amatures, so we need lots of guidance.

I think it would be instructive if you specify what Divinycell you would use as well as the glass you would specify, since I have no idea.

Also I'd be appreciative if you would explain how the building sequence would be altered to accomodate the foam sandwich that would result rather than the structural panel the plywood supplies.

Tod
 
Look at the do it yourself duck boat sight.
it is a foam boat with wood box and glass over it.
mine with the layout style blind with marsh grass is very light under 100 pounds.
goes good with a small gas motor on it.
 
I know I was just throwing out some ideas

stitch and glue take alot of time and the all wood boats can get heavy in a hurry

Also they take alot of time.

I have a lap stitch canoe I made that took 3 times as long as the duck boat I built.

fun to do but lots of work.
 
There is a lot of knowledge, advice and information on this site:

http://www.bateau.com/

I've been a member there for a while.

As is the case on this site, you have to register to get 100% out of their site.

I would like to build an ultra-lite sneakbox myself. maybe in the 8'-9' range. Myself, dog, gun, decoys, gear, and of course lunch, and be able to slide in the back of a pick-up and carried to the water's edge easily.

I too, was wondering about the composites and weight saving-vs-strength and puncture reistance.

Interesting read...

Jon
 
What about using Nid-a-Core (Hope I speleld it right) A fiberglass Honey comb product. Very lite and very strong. It's what I'm going to replace the cockpit deck in the Windy with in a couple of weeks. When I had ideas about building a Devlin Scaup I spoke to Sam and he though it was a good option
 
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