[GoodChance]

As some of you know (thanks Vince!!), I'm in the process of rebuilding a 1988 35 Duffy. I picked this boat up last Ocober from the insurance company after the vessel was involved in a cabin fire. The hull was sound but the main cabin & trunk cabin was destroyed. In addition, I decided to go ahead and replace all the deck beams and deck as well.

Here's my question: As you can see from the attached pictures, I have just finished building the trunk cabin. Instead of using sawn wood beams for the canopy (as is the typical practice), I built a jig and mold in my garage, and bent 2 layers of 1/2" Fir plywood over the jig. To hold the radius, I placed a single layer of epoxied 1708 biaxial in between the layers. FYI - The radius was 4.75" over the course of 10ft. This can be seen in the pictures as well. When the canopy was completed, the overall weight was about 275 - 300lbs of the 8x10ft canopy. After installing, I was able to remove about 75lbs by trimming to fit. But my question is, do any of you have experience in building a canopy with similiar techniques but maybe using slightly different techniques or materials resulting in a stronger or lighter canopy? I am getting ready to build the canopy for the main cabin and looking for improved options (although I am extremely happy with the way the trunk cabin turned out, I main cabing is about 25% larger and thus 25% heavier and the weight sits about 3.5ft higher).

I have thought about using ligher plywood -- maybe using 2 layers of 3/8" fir? Maybe using MDO instead of fir? Or instead of using biaxial and the sandwich layer, maybe using a ligher 6 oz finish cloth? I've enen debated using carbon matting instead of using fiberglass as this stuff is super rigid. Any thoughts?

Chris

This post edited by GoodChance 09:37 AM 03/23/2008

 

[Frigate]

Chris,


I would go with Nidacore to built the house. Take a look at Oneblitzen's Building a New Downeast Design thread on this forum. The pictures you want start on page 8. Also look at the two posts under the pictures on page 8. More on pages 10 and 11.

On my 38 Duffy we used polycore (same as Nidacore but with different core shape) for decking with fiberglass I beams and fiberglass columns. Using these materials we saved 2500lbs. through out the boat decks over using plywood and wood deck supports. There is a good picture on page 23 of the Downeasts thread on this forum showing the decking, glass I beam, and glass column in the engine room.

One last thing using Nidacore you will not have any ROT.

Floyd

 

[oldmil007]

Hi Chris,

Have you considered building the main cabin using a foam cored laminate construction technique? Saves considerable weight and correctly designed nice and strong.

In my fiberglass shop we don't use carbon too often, usually because of cost considerations. But yes, it strength physical properties are substantial. For your purpose, using it to sheath the cabin structure might be minimal strength gain at a substantial cost increase.

Good luck on your project, - Jay

 

[GoodChance]

Thanks guys for the comments thus far and I hope more will come.

I did strongly consider the use of a composite material for the super-structure (trunk and main cabins as well was wash boards). But several factors lead me away from this direction to include 1) cost; 2) special construction techniques which lengthens the construction period and 3) since I would not use composite materials for the deck the overall gains in weight savings would not be as great as if I had used composites throughout the entire boat. I didn't want to use a composite for the deck for durabilty/impact/compression reasons - I use the vessel for commercial tasks beyond recreational fishing -- but I also recreationally fish the boat too.

Floyd -- Yes I did look at Oneblitzens boat. Real nice boat and I did like the composite construction. But I don't think that it's for me.

I'm hoping that someone will have a better or improved way to build the molded canopy using traditional materials. I MAY use Jay and Floyd's advice and decide to use a composite for the canopy if no other options for reducing weight and increasing strength are available.

Chris

 

[oneblitzen]

Chris,

This company makes light weight panels used by many Carolina builders and may be what you are looking for.
Tricel

I have spoken with them regarding their exterior grade panels and many builders are using it with very good results.

John

This post edited by oneblitzen 08:18 AM 03/24/2008

 

[bloodnguts]

i looked at this boat as well. good 2 c it went to a fellow noreater

 

[EdP35]

Try looking into Baltek for the roof structure. My family and I personally built/finished a downeaster from the bare hull up close to 20 years ago and it's still going strong to this day.

We made the cabin sides out of one continuous piece of 1/2 marine plywood and used baltek on the trunk and main cabin roofs. We set 1/8 ply over temporary cambered beams, spanning between the cabin sides, then placed the baltek on top to create a sandwich. Composite construction was in it's infancy back then and if we did it again now, we probably would go 100% composite. Also, I would suggest getting the resin by the 55 gallon drum because it looks like you're going to need it.

You want to keep the weight down of these boats, especially when it's up high, otherwise you will raise the center of gravity too much and you will have a very tender boat. Even though it's only a few hundred pounds as you say, it makes a HUGE difference when it's up high on these boats.

Finally, one thing to remember is to introduce curves into your cabin. Make sure you have at least 3 inches on camber on the roofs and make sure you bevel and camber the sides of the cabin structure as well. Nothing gives an amateur job away more then a SQUARE cabin. Like a fine women, subtle curves in the right places make all the difference in boat building.

Hope this helps and feel free to PM me if you want more detailed info.

This post edited by EdP35 10:33 PM 03/25/2008