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CS17 #375


Tgabe

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Plastic is like poor mans peel ply.  But kind of acts similar.  Every wrinkle in the plastic fills up with epoxy and is a mirror image of itself.  The bubbles can usually be worked out if enough resin is available to fill them.  You could run the bubble out with a plastic spreader, but they often return.  A bubble usually forms along the edges.  Your ok there.  Just sand them smooth and feather the edges of the tape.  An orbital sander works well here with about 80 grit.  The white ish spots you have may be resin starved.  Always check as you go and add a little more resin to the white spots until transparent.  It is to late now to add more resin.  It must be done before curing.

 

Peel ply works better as you can roll out the air with a ribbed metal or plastic roller.  Your seam looks ok.  Nothing some sanding wont fix.  Just make sure the cloth is wet out properly next time.  After wetting out the glass, give it a roll with the ribbed roller to release small air bubbles.  I posted this before I saw Howards post, so what he said to.

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Howard, Thanks for the reponse. So if I do it your way, I don't clamp the joint between two boards while it dries, correct?

When you lay down the tape on top of the epoxy, do you add more epoxy? Do you put plastic over it and roll it out?

 

I need to go to epoxy school.

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Plastic sheet under the joint to keep what seeps out below from sticking to anything. But on top, no need for plastic if you do one joint at a time. You will be doing this out in the open where you can see everything and gravity is working for you. This then becomes the basic tape job.......the same as you will do for taping joints over fillets. Just enough epoxy to wet out the tape until it goes clear.......no white spots. Once it does that, you can squeegee off or brush out the surplus epoxy. You don't want the tape to be dry and starved, but not floating either. The surface should be clear, but still able to see the weave the the glass tape. That will leave you a clean surface and if you snip the edges off, about as flat and level a joint as you can get using a butt joint.

 

Once you turn the panel over, you will no longer need the finish nails to hold the panels in place. You may need to slightly sand the bottom joint flush if epoxy dripped through and puddled on the plastic sheet below. That goes pretty fast with a random orbital sander. Just sand it down flush, lay down the epoxy and then the tape.

 

Again, do make sure the first side is cured enough to survive the rollover.

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Chick- the CS 17 kit. doesn't have finger joints between front and back panels....those are scarfed joints. There are finger joints near bow between top and bottom panels, and the plans call for FRP tape. Both sides That is a high stress area going 3D. So, no apples to apples comparison but I believe you would need tape like you would for a butt joint in that area because the surface area is relatively small.

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To avoid the wrinkles caused with plastic sheeting, use packaging tape on a scrap of plywood, under the joint or applied directly to the bench or table your doing the bond on. It doesn't wrinkle and is easy to remove. I also have scrap pieces of plywood (usually 1/4" off cuts) that have plastic sheeting spray mounted or firmly taped to it. This also prevents wrinkles.

 

All joints, regardless of type will  have this basic procedure: any raw wood is wetted out with unthickened epoxy - any previously coated (cured) surfaces are toothed (sanded) with 80 - 100 grit, after having amine blush washed off - the joint area is coated with a slightly to heavily thickened mixture (depending on application) so it will be gap filling and doesn't run out of the joint - next the joint is brought into alignment (screws, wedges, jig, whatever) and weighted down, just enough so you have good goo contact and some ooze out all around. At this point you can just wait, but most of us will remove the excess ooze out, to save work later.

 

If the joint is on the work bench, the mix only needs to be about the consistency of ketchup. If the joint is vertical or overhead, then it needs to be thick enough (peanut butter) so it doesn't run out of the joint from gravity. Also, if you need a fair bit of clamping pressure to align things (not uncommon), place a length of very fine cotton string or 10 pound fishing line (monofiliment) around the perimeter of the joint, say a 1/4" inside the edge, so it's not seen. This will hold the joint open, so you don't starve it with too much clamping pressure. I have a bale of cotton kite string I use for this, which works well and the cotton swells up as the goo saturates it, further helping the seal and bond. Monofiliment can be left in place or removed after the cure. If you want to remove it, leave a tail hanging out and just pull it out when the goo is good and cured. I usually don't bother, just leaving it in place.  Of course, a cotton (or polyester) string isn't coming out, unless you take a chain saw to the joint afterward.

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Lennie, I guess it was a bad guess on the CS-17 kit. Actually, I'm joining the pieces on the hull panels that Graham cut for me for my Sport Boat (See thread on it.) I assumed that since it has finger joints, that the other boats did too. This boat is a "one off" and has no plans, and the only parts in the kit are the hull panels.

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Gabe:

 

If you have not glanced over the "Epoxy Tricks" thread, you might want to. Rather than cluttering up your thread with general stuff, I have swerved that thread into the topic of butt blocks, scarfs, etc. Had meant to do that all along and it got lost in the shuffle. I suspect that topic will flare up and continue for a while.

 

Good luck with today's effort. Let us know how it turned out.

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  • 3 weeks later...

The CS 17 plans have two options for the aft configuration.  It can be built with an aft deck or left open.  Is there any advantage to one over the other, or is it just personal preference.  Obviously, the open cockpit would have more room, but are there other things to consider?

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Flex would be a problem my way, but I also made the transom curved, which employed a big ass (technical term) horizontal brace, across the transom about mid way up (just below seat height, so it could act as the aft support for the removable seat. If I was to do it again on a straight transom, I'd still use the brace, if only to add athwart stiffness, replacing the lose of the bulkhead.

 

post-304-0-11553100-1405821034_thumb.jpg

 

Horizontal brace. It's dirty after a sail and I've yet to finish up the paint in this photo, as I've just installed twin transom drains, so water can't pool on either side of the keel batten.

 

post-304-0-90413800-1405821079_thumb.jpg

 

With seat in place, it seat lands on two lengths of aluminum angle stock, which are screwed to the seat box risers, so it (the removable seat) is resting on the brace and the angle stock on each side. A curved (laminated) beam on the front of the seat stiffens this area. There's no lose of floatation chamber dimensions, in fact there's more, because the seats are wider aft than on the plans, because I curved the seat faces (risers) to mimic the sheer and offer more butt room (another technical term).

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