fiberglass splices (scarfing plywood)

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TW28RJ
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fiberglass splices (scarfing plywood)

Post by TW28RJ » Wed Feb 20, 2008 10:46 am

Question regarding the fiberglass splices when making long panels..

The how to file say that the plans specify the fiberglass splices. I don't see anywhere on the plans that specifically say what the fiberglass splices are. Are they the same schedule as the taped seams?

Also should the plywood panels be butted tightly together or should there be a gap between the panels like there is in the seams.



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Post by Spokaloo » Wed Feb 20, 2008 11:00 am

The splices need to be as strong as a butt block of wood in the same application.

Use the tape you will be doing the chines with (generally a 12 or 17oz biax). There is no need to indicate the locations of the splices as you will be splicing at every 8' (or 8'-1 1/2" on metric plywood). The splices fall where they want to fall due to the length of the plywood. Where they land matters very little, as you are making a single sheet of wood with each splice.

Butts need to be tight in this application, but make sure they are coated with unthickened epoxy first, then filler applied before butting them together.

E

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Post by jacquesmm » Wed Feb 20, 2008 11:01 am

No gap required.
The splice plays only a small role in the structure.
If you make the splice strong enough to keep the panle in shape during the planking, it will be just right.
For boats with 6mm panels, one layer of biaxial tape 12 oz. 6" wide is sufficient.
For 3/8 (10 mm), 2 layers each side, offset edges is more than enough.
For 12 mm: 2 or 3 layers.
You can use more layers on the inside than the outside, like 3 and 1.

In all cases, use those tips:
- grind the panels a little bit, 1/16 to 1/8" (1 to 3 mm) depending on the thickness
- always offset edges
- use more layers on the inside than on the outside to avoid bumps.

PS: please update your personal info to show your location. I don't know if you use metric or inches.
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Post by jacquesmm » Wed Feb 20, 2008 11:15 am

Spokaloo wrote:The splices need to be as strong as a butt block of wood in the same application.

In the same application is important.

In a plain stitch and glue application, that is correct but in many cases, the splice is covered with several layers of glass and in that case, we can consider it a core.
Compare to large foam cored boats: the foam parts are never spliced together.
Our method is an hybrid: we still count somewhat on the properties of the plywood and the splice plays a role but not much.
As a rule, if the splice is an alternative to a butt block ( = small boats) it must be as strong as the butt block but if the boat has thick skins ( = large boats), the splice is less important.
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TW28RJ
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Post by TW28RJ » Wed Feb 20, 2008 11:51 am

I just checked my profile infomation and my location (Boston, Ma.) is listed there.. Is there something else I need to do to make it visible?

Thanks for the information very helpful.

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Post by jacquesmm » Wed Feb 20, 2008 12:34 pm

Sorry, it did not show up.

That's weird, maybe a database glitch.
Anyway, you know about the splices now.
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Post by davidtx » Wed Feb 20, 2008 12:57 pm

This is good information - I'm adding this to my notes for the next build. If this keeps up, I won't have to fair at all :lol: 8) :roll:

Jacques - can you also grind down a bit at the hull-transom joint to help with the bump there?

-david
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Post by jacquesmm » Wed Feb 20, 2008 1:58 pm

davidtx wrote: Jacques - can you also grind down a bit at the hull-transom joint to help with the bump there?

-david
Yes.
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Re: fiberglass splices (scarfing plywood)

Post by Bluefish2 » Sat Jan 02, 2010 7:32 pm

TW28RJ,
Are you north of Boston or south?
If you need a hand I am north of boston. At some point I would like to see one of the TW's close up so let me know when the weather improves.
BF2

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Re: fiberglass splices (scarfing plywood)

Post by TW28RJ » Sun Jan 03, 2010 3:40 pm

I'm north of boston.. haven't started bulding yet, have the kit and just about everything else less the engine. I'll let you know when I start building. Where are you from Bluefish?

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