Covering plywood seat box with fiberglass and epoxy

[bobmaes]

I am building a plywood console and a five sided sided box (the box which measures 19" by 28" by 19" high, will be a seat and a storage box and will be mounted to the cockpit sole behind the console) All edges of the console and box will be rounded over with a 1/2 inch radius rounding over router bit.

My questions are:

1. What weight and type of cloth should I cover the outside surfaces with and where should the material be overlapped? Is one layer enough? and will fairing be able to smooth out overlaps and not show up under high gloss paint?

2. The plywood panels will be glued together with thickened epoxy and filleted then tabbed with fiberglass cloth. What tabbing material and how many layers should I use?

3. Finally, the area of most concern to me, is to know if there is a technique to use to get the glass to cover the sharp corners. By sharp corners I mean the four 90 degree corners formed at the top of the seat and the top of the console. It seems that it will be difficult to cover these "points" with fiberglass.

Any suggestions would be greatly appreciated. Thank you to all.

[fallguy1000]

I am building a plywood console and a five sided sided box (the box which measures 19" by 28" by 19" high, will be a seat and a storage box and will be mounted to the cockpit sole behind the console) All edges of the console and box will be rounded over with a 1/2 inch radius rounding over router bit.

My questions are:

1. What weight and type of cloth should I cover the outside surfaces with and where should the material be overlapped? Is one layer enough? and will fairing be able to smooth out overlaps and not show up under high gloss paint?
10 oz woven to 12oz biax, 6oz might be okay with good joins
Overlap into reliefs. Use an electric planer or planer or hand plane. The only fill is the relief done right.
2. The plywood panels will be glued together with thickened epoxy and filleted then tabbed with fiberglass cloth. What tabbing material and how many layers should I use?
One layer, 1-2" on each panel so 4" tape, tape with 12-18 oz tapes. Tape the inside only. Finish the outside monocoque.

3. Finally, the area of most concern to me, is to know if there is a technique to use to get the glass to cover the sharp corners. By sharp corners I mean the four 90 degree corners formed at the top of the seat and the top of the console. It seems that it will be difficult to cover these "points" with fiberglass.
Build all with good radius and build edges back to sharp using backer boards with shipping tape using thickrned epoxy. I like adding a bit of glass on the first fill pass, but you can also just use a cab/balloon mix for a console and keep it light.

Any suggestions would be greatly appreciated. Thank you to all.

[Fuzz]

Do like Fallguy says and there is no reason it can not come out perfect.
I do think I would leave the 1/2 inch radius on all the corners. It will look better but more important is sharp corners always find a way to hurt you sooner or later.

[Capt UB]

Do what Fuzz said...

On all my Fiberglass boats with CC, the corners were not sharp at all. Too sharp, the paint will chip.

Will you be adding hand rails and/or windshield with frame? If so, think about glassing in backing before you put it to gether.

Finish the interior nicely, no sharp cloth edges and SEAL it and paint it. One thing about my Scout boats I liked was they were finished inside and under, places you would most likely never see. This did help when installing new equipment.

Have a way water can drain out on the bottom.

[bobmaes]

Thank you for your responses so far, however it seems I did not make myself clear.

"I do think I would leave the 1/2 inch radius on all the corners. It will look better but more important is sharp corners always find a way to hurt you sooner or later"

When I say sharp corners, I don't mean hurt yourself on them sharp. Rather sharp the the the tip of a finger as everything will be rounded with the 1/2 inch rounding bit. I still think it will be difficult to cover these corners. So please reconsider my question if I have made myself clearer.

"Do like Fallguy says and there is no reason it can not come out perfect"

I looked at the fallguy thread and it is huge. Can someone please direct me to the relevant parts.

[fallguy1000]

I answered all your questions in this thread embedded in your quote.

Let me know if I was unclear and i'll reply again tomorrow.

My thread would be useless for you.

[piperdown]

Edited the post with Fallguy's answers.

1. What weight and type of cloth should I cover the outside surfaces with and where should the material be overlapped? Is one layer enough? and will fairing be able to smooth out overlaps and not show up under high gloss paint?

Fallguy -> 10 oz woven to 12oz biax, 6oz might be okay with good joins
Overlap into reliefs. Use an electric planer or planer or hand plane. The only fill is the relief done right.

2. The plywood panels will be glued together with thickened epoxy and filleted then tabbed with fiberglass cloth. What tabbing material and how many layers should I use?

Fallguy -> One layer, 1-2" on each panel so 4" tape, tape with 12-18 oz tapes. Tape the inside only. Finish the outside monocoque.

3. Finally, the area of most concern to me, is to know if there is a technique to use to get the glass to cover the sharp corners. By sharp corners I mean the four 90 degree corners formed at the top of the seat and the top of the console. It seems that it will be difficult to cover these "points" with fiberglass.

Fallguy -> Build all with good radius and build edges back to sharp using backer boards with shipping tape using thickrned epoxy. I like adding a bit of glass on the first fill pass, but you can also just use a cab/balloon mix for a console and keep it light.


From me, if you leave the corners with a 1/2 inch radius that's perfect for laying glass. That's what the designer JM typically has in the plans. You can get away with 3/8" if you're careful.

[fallguy1000]

btw, the lighter the ply the heavier the cloth, but it will be hard to radius the really thin ply

Thanks for the reprint piperdown.

[Evan_Gatehouse]

- Don't try to cover it all with 1 piece of cloth. 6 oz cloth is very forgiving. 1 layer is sufficient for cosmetic protection of the wood.

- do radius the edges with 3/8" minimum
- with 1st piece of cloth cover the left side, lap on to the top, and then down the right side
- with 2nd piece cover the front, and overlap onto the top a few inches
- with 3rd piece cover the back, and overlap onto the top a few inches
- if you are going to create sharp edges then do with thickened epoxy putty after covering with cloth and cloth has hardened.

The only tricky bit is the corner where 3 edges meet.

Use a couple of layers of light cloth (4-6 oz). Cut into a small circle (say 2" max). Cut little triangular notches in from the edge. Like this:

bobo.jpg (6.04 KiB) Viewed 12995 times

Put center of circle right on corner and wet it out onto the 3 faces. Repeat with 2nd piece of cloth.

Then fair overlaps with a lightweight fairing mixture.

Sharp edges won't hold paint that well but you can create one with a very small radius or angled chamfer if you desire. Technique for creating sharp edges:

- Get a piece of smooth (finished) wood and cover 1 face with brown mylar packing tape. Make it as smooth as possible with no bubbles or wrinkles.
- This is going to be your dam. Apply the dam to the side of the box using a few dabs of hot melt glue
- put some masking tape on the box where the hot melt glue will be applied to prevent getting glue into the fiberglass weave
- fill the gap between dam and box edge with thickened epoxy putty. Don't worry about getting the top edge perfect. Use a bit of excess
- when putty hardens give a gentle whack to the dam and it will pop off. Remove masking tape
- sand the top edge of the epoxy putty edge flush with the top of the box
- repeat for all 4 sides. (you can do this with 4 dams at the same time)
- give each edge a very small radius (hand sand) or chamfer with a file held at 45 degrees to break the edge.

Like this:

bobo.jpg (6.04 KiB) Viewed 12995 times