Boat Builder Central - Builder Forums

Hi all,

I’m starting a GV13 shortly and I have a couple questions about plywood.

1. I have access to doug fir marine ply in 1/4 and 1/2 inch from my local Menards. The 1/4 is 3 ply, is that acceptable for the hull panels?

2. Is substituting 1/2 for 3/8 a problem, aside from about a 30lb penalty? The 1/2 that I’ve used seemed pretty light for bulkheads as it was. Also, do you encapsulate the bulkeads in glass?

I built a Redwing 18 a few years ago out of this same doug fir ply, stitch and glue and it worked very well but I’m curious about these two above mentioned circumstances. I’m off the beaten path and shipped marine ply is kinda pricy.

Thanks,
Bill

Also, I’m looking at doing an open center console with sole instead of the benches. I have incorporated the existing bulkheads into this design. Hopefully I’m not throwing the balance of the boat too far out of whack.

My motor choice is a 20 hp Honda remote short shaft that I have sitting around.

Bill

About the plywood, I might be saying stuff you already know but here goes. The three ply 1/4 just have to hope it has no voids. It will be both heavier and stiffer than what is sold here. Also I would want to put at least a light layer of glass over everything to keep it from checking.
About the power there was a real nice GV13 built not long ago that had a 40 hp on it I believe. Everyone who has built a GV and posted about it has been pleased as far as I know.

Fuzz wrote: ↑Wed Sep 22, 2021 12:06 am About the plywood, I might be saying stuff you already know but here goes. The three ply 1/4 just have to hope it has no voids. It will be both heavier and stiffer than what is sold here. Also I would want to put at least a light layer of glass over everything to keep it from checking.
About the power there was a real nice GV13 built not long ago that had a 40 hp on it I believe. Everyone who has built a GV and posted about it has been pleased as far as I know.

There's a lot of really nice GV13 builds, which encourages me to choose it. I know from experience that the doug fir stuff isn't very bendy, it's really not very nice to work with, routes poorly, usually warped, but is basically fine when covered with glass. I would enjoy the opportunity to work with a higher grade of plywood.

Bill

Assuming you have, but compare pricing from your hosts. At the peak of the wood market here. I had real marine wood delivered from BBC for about $15 a sheet more than I could get “probably work OK” wood from a big box store in town. That made it an easy call for me.

Jbo

jbo_c wrote: ↑Wed Sep 22, 2021 11:06 am Assuming you have, but compare pricing from your hosts. At the peak of the wood market here. I had real marine wood delivered from BBC for about $15 a sheet more than I could get “probably work OK” wood from a big box store in town. That made it an easy call for me.

Jbo

You are exactly right, the price for my local junk is really high, and not ideal anyway, so I just placed an order with our hosts.

Thanks!
Bill

You are going to be really happy you got the good stuff! It is so nice I always hate to cover it up with paint.

Yes you can but:

- you should probably cover doug fir plywood with a light layer of glass. This costs extra money, weight, and epoxy.
- 1/4" 3 ply is OK
- 3/8" is adequate. That's why it was designed that way to keep it cheaper and lighter.
- bulkheads are not glassed just epoxy coated. But again in doug fir, light glass will keep it from checking

Fuzz wrote: ↑Wed Sep 22, 2021 1:24 pm You are going to be really happy you got the good stuff! It is so nice I always hate to cover it up with paint.

Ha! Good life lesson, I’ve rarely regretted getting the good stuff. Especially tools.
Bill

Evan_Gatehouse wrote: ↑Wed Sep 22, 2021 1:30 pm Yes you can but:

- you should probably cover doug fir plywood with a light layer of glass. This costs extra money, weight, and epoxy.
- 1/4" 3 ply is OK
- 3/8" is adequate. That's why it was designed that way to keep it cheaper and lighter.
- bulkheads are not glassed just epoxy coated. But again in doug fir, light glass will keep it from checking

Thanks for this, and now I’ve decided to go with the good stuff.

Does my center console idea above look ok? It’s basically the same console as in the OD16. Best case scenario I integrate it into customized C and D bulkheads. I wouldn’t mind moving bulkhead C forward 5 inches. It doesn’t look like that would interfere with the stringers or the bottom but I haven’t studied very closely.

Bill

Hi all,

iI also have a bulkhead C and D question. Could I cut them down as illustrated below once they were installed?
Thanks,
Bill

No, all bulk heads must be 3" thick at all points. A 1/2-3/4" drainage hole at the bottom would be okay. The small area you leave in that bulk head is a stress point and is just waiting to fail on the first wave you hit hard. Also never use sharp inside angles in a boat as they can cause stress cracks, round them. Sorry I just re-read this and it sounds pretty harsh, please don't take it that way. Just trying to keep you from having problems.

Tom

TomW1 wrote: ↑Wed Sep 22, 2021 8:30 pm No, all bulk heads must be 3" thick at all points. A 1/2-3/4" drainage hole at the bottom would be okay. The small area you leave in that bulk head is a stress point and is just waiting to fail on the first wave you hit hard. Also never use sharp inside angles in a boat as they can cause stress cracks, round them. Sorry I just re-read this and it sounds pretty harsh, please don't take it that way. Just trying to keep you from having problems.

Tom

Ahh, of course. Good point, not harsh. I was hoping to position the aft face of the center console in front of frame C about 5 inches, hence the severely cut back frame. But I could also integrate frame C as the aft face of the console, as illustrated here, potentially with a sole, as noted:
Bill

The upside down V cut is because the GV13 has some stringers that are made up 2 pieces of plywood in an inverted V shape. Naturally the bulkhead must be notched to suit.

I am concerned about the position of your console. On such a small boat a single person is a big weight. So if you are going to operate the boat with just 1 person, having a console further back will put too much weight aft, sorry. There is a reason the steering position is where it is on the plans. It works with 1 person. With a 2nd person they can sit beside the operator or forward depending on their weight.

How about building your console so you are still sitting on the middle seat position, but make your console centered and taller so you're standing at it. As long as you keep framing depth shown on the plans you're OK.

Since you are putting in a sole, you could change the upside down V stringers to 2 laminated together pieces of plywood that do not penetrate the frames (stopping and starting at each frame). This would allow you to keep frames at a minimum depth

Hey Evan,

Thanks for all that insight. I think I can make it work. This drawing is pretty close to the captain’s dimensions on my Redwing, more or less: Best case scenario I’d like to preserve the center console with fore seat, my wife likes that. I’m glad I can use this alternative stringer. How tall should they be? Like 3” also?

Thanks,
Bill

Yes, 2 x 3/8" plywood stringers, 3" high will be similar enough to the inverse V shaped one in strength.

Good idea on the fwd seat in front of the console.

Make sure the angle of the seatback is about 12-15 degrees. Make sure you have enough depth in the upper part of the console for throttle/shift mechanism and steering mechanism too.

On a side note, I’d like to see some pics of your Redwing. I love that boat.

Jbo

Here’s the Redwing. A little too big for towing with our camper van.

Evan_Gatehouse wrote: ↑Mon Sep 27, 2021 2:56 pm Good idea on the fwd seat in front of the console.

Make sure the angle of the seatback is about 12-15 degrees. Make sure you have enough depth in the upper part of the console for throttle/shift mechanism and steering mechanism too.

Thanks for this!

Do you know of a compact mechanical steering helm? I installed the Seastar NFB 4.2 in my Redwing and it is huge. It looks like the Safe-T II is smaller, but, wow, those things are bulky.

Bill

Good execution on the Redwing. Looks really nice.

I o