Cocktail Class transom bowed out

We're in the early assembly stages of building a Cocktail Class Racer, will soon be at the point where we stitch in the transom.  We have previously laminated the transom as in the instructions, and as far as I could tell at that time, the panels were flat.

Since then, the transom seems to have bowed out in the center about 1/4 inch.  It's enough that I'm concerned about the fit.  It's been sitting crosswise on a board for about three weeks with four bricks on each end, bending the ends down in the desired direction, effectively bowed in the opposite direction, but when I take the weights off, not much has happened.  It's still bowed outward in the center.

At this point, I see two choices:

1. Try to work with it as-is, although I'm not sure the transom bracket would fit properly when it gets to that point, nor am I sure about the rest of the fit.

2. Use a temporary rigid bar (such as steel angle) screwed in from the outside/back to force it flat, complete the installation, and remove the angle later when everything is expoxied and hope that it doesn't pull itself apart or distort.

Does anyone have any advice for this?


7 replies:

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RE: Cocktail Class transom bowed out

marty, 

my advice is if the transom is supposed to be flat....you want to execute it flat or nearly so...a 1/4 inch out sounds a like a lot to me...so i think you are correct to try to address it.

your option 2 has some potential....but you may need to get more bend out first...

here are three ideas:

1)  if you have laminated the pieces (glued them together on the mating side) but never completely coated the non-mated sides with epoxy, differential moisture absorption from the air may have played a role in warping the piece.   when working with pieces that start flat and that you want to keep flat, you should always coat both sides as soon as possible.  if you have not coated a side, consider bracing the pieces flat, heating them, and then coating the non-coated side with epoxy while braced and let sit for a couple days.

2) if you have already laminated the piece and it is not true....trying to simply bend it into submission will probably not work.  i would suggest the application of heat from a heat gun to make the boards very hot (don't burn them) and which will soften the epoxy....and then immediately transfering to a flat surface with appropriate bracing to cool. 

3) another option is to cut fresh pieces that are flat or to order replacement pieces.

i am sure some other clever forum members will also have some suggestions.  i have deal with warped pieces before and usually got it done with my suggestion 1 or 2 above married with your option 2.

all the best

h

 

 

 

 

RE: Cocktail Class transom bowed out

   I'd contact CLC via the "Contact Us" link above. A quarter inch may not matter a bit if you can successfully stitch the boat together. In this case the transom's function is to hold the boat together and hold an outboard motor properly. If it can do those two things well, why should 1/4" matter? John can give you an answer, I bet.

RE: Cocktail Class transom bowed out

Thanks for the advice.

Birch2, if the transom can be made to fit successfully, it's probably not a problem, especially as it's bowed out nicely in the center. We haven't got to the point where we can evaluate the fit with the hull and other parts that need to attach to it, but we will soon.

Hspira, your explanation makes sense.  Those pieces were assembled and expoxied on a flat work surface, and each piece was flat when we started with it.  Much of the "inside" of the transom is now covered with epoxy and the reinforcing piece, while the "outside" has nothing on it, leaving a large area to absorb moisture and expand.  This would explain why it bowed neatly in the center.  In addition, we've had some very humid weather here in Central Maryland recently.

I'll take the transom for a site visit to CLC and see what they suggest.  I'll continue reporting back on this thread.

Marty C.

RE: Cocktail Class transom bowed out

   You may be able to use heat lamps or something like that to try to remove the moisture from the raw side.  If so it should pull back to straight.  Long duration gently applied heat would be best.  I had a kayak that the hull was together and glassed inside. then it sat for 1 year and the sides drew in.  A few days in the sun and it came most of the way back, a few sticks to hold it and glassed the outside and its fine.  The same heat might loosen the epoxy enough to allow the pieces to slide a bit which will help uncurve it.  

Good luck.

 

RE: Cocktail Class transom bowed out

   Here is how the transom has been for the last six weeks:


Yesterday, after a day or two of drier, colder weather, and six weeks after the weights went on, we took off the bricks and the piece now looks relatively straight from end to end.  There is some slight back and forth curvature in the center, but the overall appearance is straight.

I'm not sure if it's the effect of the weights or of the drier air, probably both.

We bought the transom into Jack's house, and he is going to coat the other side and outer edges with epoxy to seal it and hopefully prevent future warpage.  We'll see how that works out.

I'll report back after we see if the transom stays straight, maybe in a few weeks.

Next step is to stitch it to the rear of the boat, and check and adjust the alignment of everything before expoxying continues, probably in the spring.

RE: Cocktail Class transom bowed out

I see that we have the well-known Photobucket issue with the picture I posted in the last reply.  Sorry about that.

In any case, we are farther along with the project now, and the slight bowing in the transom, which I was not able to straighten, does not seem to be a problem at all.

We currently have an assembled and fiberglassed hull with keel.  The next step, when the weather cooperates, is to install the outside rails (page 81 of the manual.  In the meantime, we'll shape the bow end of the keel and keep on sanding.

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