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Scarfing plywood

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Colombo
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Scarfing plywood

Post by Colombo » Sun Jan 06, 2013 7:34 am

Hi, This is my first post as I am new to the fourm. I have a 1960 23' Sea Skiff and am re-bottoming.I am getting ready to start scarfing boards together and was wondering what type of adhesive is best. Is epoxy ok ? High desity filler or low?
Thanks,
Dave

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evansjw44
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Adhesive

Post by evansjw44 » Sun Jan 06, 2013 7:24 pm

The adhesive used on sea skiff bottoms was thiocol. Thiocol is similar to 3M 5200. Its tougher than BoatLife. Either is flexible and not hard like West system. I wouldn;t use epoxy.
Jim Evans

Colombo
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Post by Colombo » Mon Jan 07, 2013 7:17 am

I am talking about the plywood end to end not the overlapping seams of the lapstrake.

boat_art
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Post by boat_art » Mon Jan 07, 2013 9:36 am

Evansjw44 is right. The scarf should replicate the flexibility of the plank itself as much as possible. If you use epoxy you would have a stiff section in the middle of a flexible plank, not good. 2500 will create a strong, yet somewhat flexible joint which will bend in a very fair curve.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

jfrprops
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Post by jfrprops » Mon Jan 07, 2013 7:34 pm

you are talking about a butt to butt joint not a scarf ?? Jim Evans and other are right on...5200 has some give for the scarf....if that is what in fact you are doing. End to end (butt to butt) you need a butt block behind the joint anyway.
Nice project, good luck.

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)

kleiner
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Post by kleiner » Mon Jan 07, 2013 7:51 pm

I disagree strongly. You don't want any "give" in a scarf joint. Epoxy is the only way to go for a scarf joint in plywood. Use 5200 in the lap between adjoining planks. Use a minimum 8:1 slope in the scarf joint, pre-wet both ends with unthickened epoxy, then batter on epoxy thickened with wood flour or plastic mini-fibers. The scarf joint will be as strong and as flexible as the rest of the plywood plank without any hard spots.

- Kevin

boat_art
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Post by boat_art » Mon Jan 07, 2013 8:11 pm

I guess I'm "other" haha...anyway I dont have a problem with either method, although if the plank is to have a serious bend then I use 5200. In either case the wood will fail long before properly cured epoxy or 5200.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

jfrprops
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Location: Powhatan Courthouse Virginia

Post by jfrprops » Mon Jan 07, 2013 11:14 pm

I respectfully disagree with Kevin. Though clearly the Gougeon goop is better in a scarf than other applications where some "give" might be more welcome.
Sorry I called art the "other" but I can't seem to scroll back to see who said what tonight??
"Go West young man" has never appealed to me.

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)

boat_art
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Post by boat_art » Tue Jan 08, 2013 12:34 am

No problem John.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

kleiner
Posts: 72
Joined: Mon Aug 11, 2008 8:41 pm
Location: Raleigh, NC

Post by kleiner » Tue Jan 08, 2013 5:17 am

I recently reframed my Sea Skiff and replaced a number of bottom planks. You may find this discussion thread on the Danenberg Boatworks Forum useful. I scarfed full-length replacement planks with epoxy, and repaired several plank sections with butt blocks and 5200. 5200 was used in all plank laps.

http://eveforum.danenbergboatworks.com/ ... m/63410169

- Kevin

Colombo
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Post by Colombo » Tue Jan 08, 2013 6:47 am

Thanks for the input. I know that the original planks were not glued with 5200 but the laps were.
Thanks again,
Dave

Jim Bell
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Post by Jim Bell » Tue Jan 08, 2013 11:32 am

I have the starboard side of my 1965 24' Sea Skiff completely stripped and sanded. All the butt joints have a hard black material which I would think is a form of epoxy. Anyone??

jfrprops
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Post by jfrprops » Tue Jan 08, 2013 11:47 am

thiokol most likely, though that is about the exact year they went to early 5200...?

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)

Colombo
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Joined: Fri Jan 04, 2013 6:19 pm
Location: Saratoga Springs N.Y.

Post by Colombo » Tue Jan 08, 2013 4:42 pm

Thiokol would still be soft and flexible. At least mine is from 1960. I think it is some type of plastic resin glue similar to "Weldwood" now. Pre epoxy days?

jfrprops
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Post by jfrprops » Tue Jan 08, 2013 4:56 pm

resorcinol? spelling?
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)

Jim Bell
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Post by Jim Bell » Tue Jan 08, 2013 5:06 pm

jfrprops wrote:thiokol most likely, though that is about the exact year they went to early 5200...?

John in Va.
My boat is hull #5. likely some changes by the last boat on the line.

charlesquimby
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Post by charlesquimby » Wed Jan 09, 2013 1:39 pm

Resourcinal is a two-part mix containing formaldahyde, and when it dries/sets it is hard as duck lips. CQ

Thommyboy
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Post by Thommyboy » Fri Jan 11, 2013 8:32 am

The dark line adhesive is most likely resorcinol or phenol resorcinol.

I certainly would never use 3M5200 for a scarf joint in plywood. Use resorcinol if you are proficient with it or an epoxy appropriate for marine plywood.

Resorcinol today does not contain formaldahyde.

Andreas

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