polyester structural repair putty

[Dwr0211]

Hunter Legacy 40 structure to hold 40 gal fuel tank.
In the aft cabin, where the cabin meets the galley, there will be a structure built to hold the fuel tank.
One of the challenges is the curvilinear hull shape along with a depth change in the super structure where the floor meets the hull side. My plan is to use Totalboat poly structure repair putty to fill a void on the super structure where the sole plate will sit. If I were to use all polyester structural repair putty to fill the void it would take about 2/3 of a gallon. I am new to this type of resin work. I have heard/read that this resin will be super strong and have longevity. Another solution would be to try and shape a piece of wood to fit this multiple curvy area and then fiberglass it in. Again super strong with longevity.
This sole plate with the mini stud wall type structure will be holding a load of about 280 lbs of fuel when the tank is topped off. Plus the added load of the inertia of a moving boat which could exert somewhat significant forces on the structure. I would rather over design the structure than under design.
Please let me know if you have designed a solution like this?

[Ballsnall]

Polyester putty even if they call it structural is not the way to create a fuel tank support. Shape a piece of hardwood and glass it in, use the structural putty to fine tune the tank supports.

A good method is to shape your hardwood supports and set in position so they hold the tank in the desired location, remove or lift the tank and add the structural putty and apply a film of plastic over the top before lowering the tank back into position.

Once the putty sets up it will perfectly conform to the tank profile allowing even tank support.

[Matt Johnson]

The TotalBoat structural putty has milled fibers (powered fiberglass), but not the large strands necessary for holding together a mass of putty. How thick does this base need to be? Anything thicker than 1/2" would require wood or some other filler.

If it's an aluminum tank, don't set it on raw wood. The moisture from the wood will cause pin hope leaks in aluminum.

[Dwr0211]

This is a plastic tank designed for diesel fuel. There are areas where this will be 1 1/2 inches deep, a narrow strip. Will layer upon layer of chopped strand Matt work for this? Is there another filler that can be mixed with the resin or put into the void to be filled and then pour the poly resin over the top. I need a very strong bond to the fiberglass super structure and a nice even surface to lay a 2x6 sole plate. I am assuming a regular 2x6 can be used and then I encase this with fiberglass. And then build the small stud wall/structure that the 1" plywood deck will rest on. I am not sure if I could do this sole plate in one application. Will the portion of this build that is about 1 1/2 inches cure, and then it tapers to about 3/8 " and this will most likely cure quicker.
To create a shape of wood to conform to the multiple angles and curves of the hull would take a mold first and then have his computer scanned and then cnc created. I am looking for a very strong filler, combination of media, to build up this curvilinear space. The space is 2' long, 5 1/2" wide tapering to 3" at each end and then 3/8" tapering to 1 1/2" deep.
The deck the tank will sit on will have a base and perimeter and straps holding the tank in place. There will be structural foam on bottom and sides of perimeter boards to reduce chafe. Three stringers of 1" plywood will be attached to super structure with fiberglass and also attached to bottom of deck with fiberglass. Everything except for the build up of the sole plate is standard structure and glass work. I need a very strong and lasting solution for the sole plate.

[Spot]

Hello DWR-
If you could post a picture of the tank and space you are refitting that would help to guide people's answers.

Simple wooden supports tabbed properly to the hull and capped in fiberglass cloth and resin should do the trick.

A cardboard template is pretty effective following a hull curve, so is hot gluing scraps or 'ticking' into a shape that captures the geometry. I have taken to a combination method where I rough in with cardboard and use small stickers with hot glue to get an exact curve that is then transferred to the new wood.

Some of my adventures with templating here:
https://www.cruisersforum.com/forums...ml#post3217995