What type fiberglass to use?

[First class repairs]

Getting ready to purchase some exopy and silica compound and make my fillets then sanding and priming. I am wondering what yall think would be best for this application. I plan on glassing the interior and exterior but want to keep it light so not too many layers but want my kids to be able to give it to their kids one day.

 

[gonzo]

First question is if the design calls for a certain weight of fiberglass. Otherwise, if it is only for waterproofing, you don't need fiberglass on the inside. On the outside 4oz if fine for waterproofing.

 

[First class repairs]

There were no plans for this boat. Its just a small pirogue. I made it out of 1/4 marine grade plywood. I made it very light and flimsy. I planned on glassing the entire thing for some added structural integrity and waterproofing.

 

[gonzo]

How much does it weigh now, and what is the finished weight target?

 

[Milehog]

I suspect you will want rub and maybe cap rails to stiffen the structure.
I'd put light glass fabric on the outside, add rub rails then determine how sturdy it felt. From there determine if the interior needs glass.

 

[First class repairs]

Thank you

 

[Tops]

My current project has 6oz cloth on the bottom and about 3" up onto the sides covering the bottom outer seam tape. There is no other glass on the outside sides or inside.
Outside seams are 4" stitched biax 12oz tape, more weight than needed but the right fiber orientation to prevent cracking along outside corners.
Inside seams are 6oz x 2" tape over the fillets. Tapes were wetted out off the boat on a board covered in plastic film and then applied and smoothed.
For fillets: 1 part mixed epoxy, 2 parts glass spheres (lightweight filler), 1 part fumed silica (so prevent slumping). Pipe the material in with a small plastic bag and smooth/radius with a 1" wide tongue depressor/stir stick. I do not go back with a finger and alcohol to attempt to smooth them.
All bare woods, ply and lumber, are coated with epoxy (2 coats, 2nd applied while 1st coat was still tacky) and will be ready for sanding and paint this coming week.

 

[fallguy]

The most common approach is 2 layers of 6 ounce on bottom and footwells and a single layer on sides.

Gonna echo @Milehog ; you need something on the inwhale/outwhale to stiffen the sides or someone or something will break it. A lite piece of ash would be ideal, but cedar can work. Ash, as a hardwood is less prone to massive denting. I’d take a piece of ash, say 1x2 and router all four edges with 1/4” to 3/8” and the rip it to 1/2” to 5/8” wide and get two pieces and then dryfit them with some ss screws and then go back and epoxy putty bond and rescrew them together. Then after cure, cleanup and put a sanded edge back on them. If you want to be fancier; you can hide the plywood with a lap joint.

Those edges are really handy then for setting the boat on horses, for example, or foam blocks to cartop. The foam blocks actually have reliefs for them.

 

[Tops]

Mine has steam-bent pine as a gunnel. I was going to do white oak but got talked out of it.
Hiding the plywood edge would be a nice touch.