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Plywood construction boats

Framing, planking and fairing. Repair, or reconstruction. If it's hull related, you'll find it here.

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kmjohnson
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Plywood construction boats

Post by kmjohnson » Fri Feb 26, 2016 9:28 am

I am rebuilding a plywood boat (1962 Compact Skier). I have completed the frame and am now working on the plywood sides and transum. I have the original pieces for templates so that is no problem. My confusion lies with the fastening of the plywood to the frame. I have decided with advice to use screws and i realize you need to only drill deep enough to fill the countersink with putty so you avoid drilling past the top veneer of the (3/8") plywood. The next question is glue or not? The frame work on this boat is marginal so the plywood is very structural on this boat. Some people have told me to use a very good strong glue (adhesive) such as 5200, others have told me that is to permanent and suggest using bedding compound. Any suggestions would be appreciated. I have considered using 4200 which is a good adhesive but can be taken apart if needed. Also is it suggested that the matting surfaces, that is outside of the frames and inside of the plywood be bare wood or is it OK to seal with something like a sealer or CPES?

Having fun with this one

Ken
Ken from Maine

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Bilge Rat
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Re: Plywood construction boats

Post by Bilge Rat » Fri Feb 26, 2016 2:54 pm

You are correct that the plywood "fabric" is an integral part of the structural members of the framework. Different boat manufacturers used different adhesives such as resorcinol glue. Properly applied resorcinol required high camping pressure and inserting the hull in an autoclave oven to bond (cook) the wood and glue.

If the hull is to be painted, I would do the following: seal all surfaces with CPES (two coats), use 3M5200 for all frame and plywood to plywood joints, use bronze flat head screws countersunk only as deep as needed to be covered with a marine putty/fairing compound. While 5200 can be tough to separate for future repairs, it can be done. West epoxy, while strong usually causes the wood fibers to tear out from the glue line when stressed. It is extremely inflexible as compared to 5200 which leads to the stressing of the wood fibers. It isn't the glue that fails, it it the wood in this case. It also does not penetrate into the wood grain very deep at all.

I'm not all that familiar with the Correct Craft Compact Skier, but Correct Craft does have an owner's website. The Chris Craft Cavalier series was similar in construction.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

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Re: Plywood construction boats

Post by jim g » Sat Feb 27, 2016 8:19 am

If it helps you in making a decision. Chris Craft used 3m5200 in the construction of both the Cavalier Sea Skiff line.

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Re: Plywood construction boats

Post by jfrprops » Sat Feb 27, 2016 1:33 pm

I agree with both of the above posted comments.......I would only add the 4200 is not much different than 5200....just a faster cure....which is an issue in itself.....take you time and use the 5200 IMHO

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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Re: Plywood construction boats

Post by jim g » Sat Feb 27, 2016 1:56 pm

4200 is half the strength on 5200. Its more for bedding hardware and other things that you want to take back apart later. 3m does make a fast cure 5200. See link to 4200 description.

http://www.jamestowndistributors.com/us ... o?pid=2004

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kmjohnson
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Re: Plywood construction boats

Post by kmjohnson » Sat Feb 27, 2016 2:14 pm

Thank you all for your suggestions!

The hull (plywood) will not be painted it is all Mahogany and will be stained and varnished on the outside and inside above the floor boards. Bilge paint below.
I am using bronze flat head screws and will putty the holes.

Will 5200 adhere to plywood that is stained and sealed with CPES? If that is not recommended I will use 5200 they stain and seal after.

I also have a 15" 1956 Cavalier that I restored about 5 years ago. I did not have to remove any of the plywood on that boat as it was all in great shape.

Ken in Maine
Ken from Maine

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Re: Plywood construction boats

Post by jim g » Sat Feb 27, 2016 4:46 pm

Use mahogany colored 5200. Put all your panels on the boat with 5200. Then seal the inside with the CPES. You can also use it as the sealer coat with stain. The 5200 won't adhere as good to the wood with CPES on it. 5200 adheres better to raw wood.

You can use a cheap pump up weed sprayer to seal the bilge with CPES. When your done just throw the sprayer away.

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Re: Plywood construction boats

Post by jfrprops » Sat Feb 27, 2016 9:17 pm

Agree with all the jim says...but IMHO that mahogany color 5200 is more like purple...

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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Re: Plywood construction boats

Post by jim g » Sun Feb 28, 2016 12:59 am

jfrprops wrote:but IMHO that mahogany color 5200 is more like purple...

John in Va.
I agree with you on the color. I swear when I started restoring these boats in the early 90's the mahogany color was darker. But its better then white showing through the stain.

On a side note. Tan works really well on the blonde stain wood if you bleach and use the Sandusky Cordova stain.

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Re: Plywood construction boats

Post by Bilge Rat » Mon Feb 29, 2016 8:27 am

I second on the weed sprayer to apply CPES. I applied CPES on the hull bottom of my 25 footer right side up because it was too big to flip in the shop I was using at the time. I wore a Tyvek suit, nitrile gloves, old eyeglasses and a cheap full face mask as I brushed it on the new bottom planks. WHAT A MESS, and it still found its way to bare skin (it burns but is only an "irritant"). Years later Don Dannenberg stated to use a weed sprayer to avoid this upside down hassle. I guess that's why he's the expert and I am the amateur. I will definitely use a sprayer when I do the interior of the Sportsman I'm about to start work on. CPES is like painting with water, it gets everywhere.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

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kmjohnson
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Re: Plywood construction boats

Post by kmjohnson » Mon Feb 29, 2016 4:11 pm

Great advise, thanks all.

I installed the plywood on the transom today, used Mahogany 5200.
The boat is right side up now and i will be flipping it over to do the plywood on the hull sides next. I have already scarfed the plywood and rough fit from patterns.

I will take your advise and mount plywood bare so the 5200 adheres better then stain and seal the inside. I will use CPES on the inside and outside of the bottom which will be painted with bilge paint inside and bottom paint outside.

Ken
Ken from Maine

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