Best way to strenghten bottom of 16ft. Don Hill DB

Im in the middle well more towards the begining of a Don Hill build.I drove about two and a half hours to pick up my plywood that they had loaded on my trailer for me 1/4 inch okoume for the sides and what i had thought was 1/2 inch hydrotec for the bottom when i reach home i went to put it away until the weekend so i could start scarfing them together realized that the 1/2 inch was 3/8 seven ply i don't want to drive all that distance again if i don't have to so I'm asking whats the best way to strengthen the bottom (3/8) and do i use anything other than fiberglass or graphite additive to the west system epoxy i will run mainly in the rivers in Michigan 

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Permalink Reply by Mike Thomas on August 12, 2016 at 1:42pm

I`m in Mich myself, I used 3/8 Okume for my bottom, on the outside- cpl coats of epoxy, 12 oz. biax glass and about 4or5 more coats of epoxy and 2 more coats of epoxy/graphite finish coats and just a couple coats of epoxy and varnish on the inside and my bottom has taken some beating this year so far and has held up nice. I used west system too.

Ive been on the Ausable, Manistee, Mo and the PM so far. Ive drug it over railroad ties, across gravel launches, gravel bars, hit some stumps and big rocks.

Permalink Reply by James Prepura on August 12, 2016 at 2:36pm

Thanks Mike

Was actually hoping you would respond to this because I have followed your build and know you had a 3/8 bottom ( beautiful boat by the way ) but wasn't sure on all your steps, I'm in Illinois  but do a lot of fishing on the P.M. maybe I'll run across you on one of the rivers next year I definitely would know your boat if I came across it and you would know mine it will be the Avery Ann named after our first grandchild 

Permalink Reply by Rick Newman on August 13, 2016 at 7:39am

Sounds like your rivers run through some rough conditions. At least the rivers out west don't have any railroad ties in them!:<)

Rick N

Permalink Reply by Phillip Westendorf on August 13, 2016 at 7:01pm

Rick,

Ya gotta read between the lines.  The Ties are used by our illustrious Mi DNR to shore up the river banks at launch and take out sites.  The canoe rental jocks use them to bounce their canoes into the rivers.  

You'd really have to be haulin to make it up far enough to hit them, even in the spring.  :)

Dorf

Permalink Reply by David Witton on August 13, 2016 at 6:42am

I used a technique borrowed from Mike Baker that adds a layer of honeycomb material (nidacore) to the bottom. Details are in my build story. 

http://westcoastwoodenboats.ning.com/forum/topics/16-double-ender-w...

Permalink Reply by James Prepura on August 13, 2016 at 8:03am

thanks for the tip I'll look into that what about the difference in expansion rates between the wood and nidacore have you had problems with that, this boat will see some extreme weather especially when it steelhead season here and theres snow on the ground

Permalink Reply by David Witton on August 14, 2016 at 6:47am

Cored fiberglass construction is used pretty much everywhere in larger boats - hulls, transoms, bulkheads, so I figure it'll hold up well. Temps here in eastern Idaho range from well below zero to 90 or so, and based on my research and the recommendations I've gotten I'm confident in the product. 

On the other hand, a layer of 17 oz biaxial cloth should do pretty well - if it gets chewed up after a couple of years you could add more. 

Permalink Reply by tungsten on August 14, 2016 at 4:32pm

One thing you don't see in cored boats is large pieces of plywood epoxied to it so yes there would be different expatiation rates.In this case its more of a shoe so its not structural,made to take the bumps and scrapes.One thing to watch out is that its 100% sealed between the plywood hull and the cored shoe.As once water gets in...

And I'll second the extra layers of biax its strong stuff.

Permalink Reply by James Prepura on August 14, 2016 at 5:51pm

thanks for the input much appreciated 

Permalink Reply by tungsten on August 14, 2016 at 9:21pm

In your case James 2 layers of 12 oz or one 18oz over 3/8 ply is pretty durable.Extra glass with just enough epoxy to wet it out is much more durable then several layers of neat epoxy/graphite.

Permalink Reply by AJ DeRosa on August 15, 2016 at 4:36pm
We've got 7 years on an "experimental" bottom of 1/4" marine fir ply, 1/2" plasticore honeycomb and 20oz.triaxial fiberglass/epoxy.
This bottom is on ur hardest working 20'boat. This boat usually carries 1000+ lbs of passengers every day all summer. We drag over cobble and gravel.

Jackson Hole has an annual temperature swing of 100 degrees+ and so far all is working well. We are thinking that we will remove the experimental tag if it hits 10 years and still solid.

Banged a similar bottom on a smaller boat down the middle fork with excellent results this spring. The pros were using uhmw bottoms. I had plenty of water but managed to hit a few good ones.
Permalink Reply by James Prepura on August 15, 2016 at 6:00pm

ok couple of questions were can I research the plasticore, did you cover the whole bottom and how did you attach it

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