Best fabrication method for one off kayak catch bin

[fallguy]

Both the plastic sheet and tape methods sound workable. I'm not sure how well the kayak surface will stand up to tape being pulled off? The outer surface is acrylic so perhaps it will tear? It certainly scratches easily.

I can test an inconspicuous area and see. I guess I could wax the well and then tape it?

I wouldn’t wax personally. The stuff to take off the wax will be the worst of all. I’d probably tape. If you are worried; you could buy some clean release masking tape and then put the gorilla tape above it. If you don’t use the shipping tape; the masking tape will be a part of your cooler in my experience.

 

[IronPrice]

I like the idea of using masking tape first. I have a few rolls of low adhesion masking tape in my workshop.

So...
Layer 1 is masking tape and Layer 2 is a more adhesive tape like packing tape.

Do I lay the glass straight over the packing tape?

Or do I wax the packing tape before laying glass?

 

[fallguy]

You don’t need wax. Epoxy won’t stick to the tape. If you use ve or pe; it might perform better for you as the mat would breakdown if you wetout in the boat. I have little experience with those resins; so you need to hear from others. I would probably use a lighter fabric as it would be easier for a rookie. Like 1208 a couple layers? But take the advice of the old salts who have made lots of plugs. I add what I can when I can. But disqualify when appropriate.

 

[fallguy]

Put a string or piece of braided line under one edge of the part as it will be hard to start and you don’t want to drive anything sharp against the boat

When cured up; you pull the string from both ends and get the part to start to release. The string can go under the shipping tape.

But the part might be a little tough to remove; even though not stuck.

And be careful of reverse curves or lips on the boat that might lock the part on and make it unremovable.

 

[IronPrice]

Thanks I've been looking material again and decided to go with building a foam box and then glassing it. Although I'm confident I could use the kayak as a mold, I would the have the issue of getting foam sheet conform to the shape of the moulded piece. Pour-able two part foam is an obvious solution, but then it is difficult to get a nice internal shape to the foam which the inner glass lining can be applied to.

Building foam sheet containers and glassing both sides solves these problems. I can then cut out the hatch and join the two halves. For ease I'm going to make the hatch out of two layers of fabric with closed cell foam in between and secured by a zip.

Next question - how to you create areas of solid material for screwing fastenings into?

I was thinking about using thickened epoxy to glue some marine plywood into the foam at those points. I'll have offcuts from a shelf I'm fitting to the boat in the next couple of weeks.

 

[rwatson]

Thanks I've been looking material again and decided to go with building a foam box and then glassing it. Although I'm confident I could use the kayak as a mold, I would the have the issue of getting foam sheet conform to the shape of the moulded piece. Pour-able two part foam is an obvious solution, but then it is difficult to get a nice internal shape to the foam which the inner glass lining can be applied to......

I told you how to use foam to conform to the deck shape. Cut small blocks ( say 50mm x 50 mm x 20mm and smaller as needed ) , sit them on the deck with ( over the top of the decking, with a bit of gladwrap or similar to protect the kayak from any splashes). This will form a pretty close contoured block, then glue them on the upper surface temporarily with say hot glue, or even a bit of expandable foam.

Once glued, take this "base" off the hull, and fill in gaps and imperfections on the deck ( underside) side, with thickened epoxy, and sand to a smooth and attractive shape.

Build the upper part on top of this base, then sand the foam "box" to a nice shape, filling with thickened epoxy, then epoxy and paint the final shape.

 

[upchurchmr]

Trying things yourself is worth a lot more than just asking questions.
Then you actually see why thing work or don't.

 

[IronPrice]

Trying things yourself is worth a lot more than just asking questions.
Then you actually see why thing work or don't.

You are right I will learn a lot more by doing than asking. But doing involves purchasing materials. In New Zealand materials are very expensive.

 

[IronPrice]

I told you how to use foam to conform to the deck shape. Cut small blocks ( say 50mm x 50 mm x 20mm and smaller as needed ) , sit them on the deck with ( over the top of the decking, with a bit of gladwrap or similar to protect the kayak from any splashes). This will form a pretty close contoured block, then glue them on the upper surface temporarily with say hot glue, or even a bit of expandable foam.

Once glued, take this "base" off the hull, and fill in gaps and imperfections on the deck ( underside) side, with thickened epoxy, and sand to a smooth and attractive shape.

Build the upper part on top of this base, then sand the foam "box" to a nice shape, filling with thickened epoxy, then epoxy and paint the final shape.

Wouldn't that be quite heavy due to the thickened epoxy? Or are you referring to epoxy thickened with micro-balloons or similar?

 

[fallguy]

For your purpose; plywood would be fine and far better/cheaper than foam for fastenings. You could overbore and refill and redrill, but then you must really bolt; not screw. Ironically, The screws in most coolers fail and the lids break. I repair them with old safety belt / gunwhale strapping.

 

[IronPrice]

I told you how to use foam to conform to the deck shape. Cut small blocks ( say 50mm x 50 mm x 20mm and smaller as needed ) , sit them on the deck with ( over the top of the decking, with a bit of gladwrap or similar to protect the kayak from any splashes). This will form a pretty close contoured block, then glue them on the upper surface temporarily with say hot glue, or even a bit of expandable foam.

Once glued, take this "base" off the hull, and fill in gaps and imperfections on the deck ( underside) side, with thickened epoxy, and sand to a smooth and attractive shape.

Build the upper part on top of this base, then sand the foam "box" to a nice shape, filling with thickened epoxy, then epoxy and paint the final shape.

I've .... decided to go with building a foam box and then glassing it.

I should clarify that I had been thinking of forming the outer shell of fibreglass first using the kayak as a mold first (as suggested by another member).

What I am now talking is forming a foam base and sides within in the well by gluing together sheets of foam that conform to the shape of the well, then glassing over this structure. That is on reflection quite similar to what you are suggesting but won't conform quite as closely.

The well is actually a reasonably simple shape if I truncate the ends. I don't need to conform exactly to the indents etc in the bottom of the well - it's better to bridge across them and leave space underneath for drainage.

Foam sheeting is cheap enough so I can have a play with that first and see if I can build the base as simply as I think.

I'm still not sure how to make stronger areas for screwing in fastenings.

 

[fallguy]

See my post. Overbore and epoxy with filler and rebore for bolts. Plywood inserts for screws. Make your lid hinges from safety strapping.

 

[IronPrice]

For your purpose; plywood would be fine and far better/cheaper than foam for fastenings. You could overbore and refill and redrill, but then you must really bolt; not screw. Ironically, The screws in most coolers fail and the lids break. I repair them with old safety belt / gunwhale strapping.

Are you suggesting building the whole structure from play instead of foam, or are you suggesting gluing in blocks of ply where fastenings will be located?

I thought I would be able to cut slots into the foam and glue blocks of ply with thickened epoxy, before glassing the whole lot. I have some marine ply offcuts from another project.

As you suggest I would overbore the ply and backfill with epoxy before re-drilling. Then I should be able to use screws?

 

[fallguy]

Just glue ply blocks in where you need to screw; not the whole thing. Build it out of polystyrene n epoxy! I said long ago you don’t need to mould based on that picture.

Overbore, refill with cabosil n epoxy, redrill right size for bolts; bolts only. The overbore won’t crush if you ise some washers on each side.

Use safety strap or buy hinges. You can bolt the hinges if you want; or you can use a ply insert and screw. Use longer screws with all thread. I’d 3/4 ply backer; type of ply is optional, but more veneers is better.

It’ll be great; build it!

 

[rwatson]

Wouldn't that be quite heavy due to the thickened epoxy? Or are you referring to epoxy thickened with micro-balloons or similar?

Of course micro-balloons.

You will probably find that a couple of areas can be made of up quite large flat sections of foam. It doesn't all have to be small bits.