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resin research

Posted by Trapperbob 
resin research
June 14, 2020 02:35AM
I have been looking through old posts and articles on this site to find a series of tests done with a certain type of surfboard epoxy , I think it was called resin research. I am pretty sure it was on this site but maybe not. the article and tests showed it to be much more resilient than what we normally use. that is it was much more flexible and held together better under severe impacts. I think they tested it with sledge hammers ect. Anyone remember this? any idea where i could find those vids? Thanks
Re: resin research
June 15, 2020 07:35PM
The report was provided by Brad Dimock on Wooden Boat People some time ago. He even soaked a roll of toilet paper which became almost unbreakable! Fretwater Boatworks is his home in Flagstaff when he isn't floating rivers.

Here are a few words concerning what I have learned about composite structures for drift boats. Hope it helps.

Panel strength is also dependent not only upon the "core" material but also the thickness of the "core" material. What I am saying that a composite structure comprised of a lamination of epoxy and fiberglass on both sides of a core material will increase in exponentially. So an example would be a 1/2" core with laminations will be four times more resistant to specific forces, than a 1/4" core.

With that being said the most frequent drift boat repair that I am aware of be it fiberglass or wood/composite is damage to the chine area when a boat hits a rock or similar item. That is one of the reasons for chine caps that are easily removable. If broken, unscrew them and replace them.

It has been my experience in both drift boats and rafts that if I travel over a rock I either get a scratch in the graphite/epoxy mixture or a rub mark or at worst case in older style non-self-bailing rafts a tear can occur. When I stuck a raft on rocks in the Grand Canyon last year there was no damage as the floor flexed. My drift boat has both been run over rocks and run into rocks. So I have either scratches or beat up White Oak chine caps.

When I build my drift boat my primary concern was to build it so that I could withstand reasonable impacts to the floor and sides. In order to do so I laminated S-Glass to the interior of the sides prior to assembling the boat. The floor was constructed of 1/2" Meranti I believe. I laminated 18 ounce triaxial weave fiberglass to the inside of the floor before I installed it. It made it quite difficult to bend but it also made it much tougher. As fiberglass resists being bent when it is stretched it provides the most strength on the inside of the boat where it can resist intrusion from a rock or something similar. After I finally got the floor to bend to the shape of the boat I added an additional layer of 18 oz triaxial weave fiberglass and then several coats of epoxy then epoxy and graphite powder to the outside bottom of the boat.

The result has been an exceedingly stiff floor that should resist and has so far resisted any damage other than scratches and has withstood some very loud, potentially hard impacts from rocks during low water floats. My aim was to build a boat that would withstand reasonably hard hits and would be field repairable to get to the takeout. So far so good.

The "bottom" line is you can indeed build a very strong boat bottom, but at what cost and at what difficulty during the assembly of the boat. Also since most damage occurs from the chine cap on up that is where more strength is seemingly needed. A

Dorf, (Phil Westendorf) is the engineer around here, I'm sure he can provide further elucidation on the mathematics of strength. I am simply sharing what a few thousand miles of floating has taught me in the riverine environment. Your mileage may vary.

I have never experienced any drift boat with a cold molded panel, Dorf's boat is essentially a cold molded panel of sorts as he laminated strips of wood in several directions on the bottom of his boat. I don't know if he has done a cost comparison on materials. You might ask him about that and also inquire how much time it took to assemble the bottom of his boat.

A consideration about the synthetic materials, foams and honeycomb cells materials is they will initially weigh less than wooden products so you can increase your strength by increasing the thickness without a large weight penalty. The tradeoff is cost of the materials and potentially the cost of freight.

Another thing to consider is that rot and improper storage and care is probably the most common bottom repair issue that is brought up on these pages. Another thing that damages bottoms is intrusion of water into the plywood and then not being promptly repaired.

Rick Newman
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