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John Kinnane

Catspaw 8 A Question Help Needed

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I have now 'tack welded' the dingy together and have ended up with a twist.

 

Should I just make sure it is level again before I do the fillets and tape or should I put a bit of opposite twist in and then the fillets and tape ?

 

Hoping someone has been through this before and can share their experience.post-148-0-79575100-1366508131_thumb.jpgpost-148-0-39812600-1366508167_thumb.jpgpost-148-0-66961600-1366508197_thumb.jpgpost-148-0-84168600-1366508223_thumb.jpg

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Wow, those are serious tack welds. If I was caught in a similar situation I would ask meself, "How bad is the twist?" Now if my lady sez "That boat doesn't look right." Big clue, I screwed up. But if it's one of those "eye of the builder" deals were you're squinting down the winding sticks and stressing out because they're a rat hair off, it might be a no call.

Can't tell from the picture but she looks fairly sweet. I have jigged up a hull by lashing it down with line and a few clamps to remove a slight twist before doing the fillet and tape drill. It worked. I did not "reverse twist" it.

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Ouch. I would fix a 12mm twist for aesthetic reasons, but in actual operation it probably would not affect performance. It appears you own a rotary grinder/multi-tool, maybe a Fein? What I would try is lash down the stern level, then back twist the bow, even over back twist, and see if I could identify tack welds that seem stressed. Then I would cut the welds with the grinder, back twist again, cut a few more welds until the hull was loose enough to retie with wire straight, and tack weld again. Might want to wire it loosely before cutting tack welds if you decide to try that.

But Wait! Before embarking on what is a PITA repair you should contact Graham (Designer) and see what his thoughts are, and maybe one of our forumites with more experience than my 7 S&G builds will toss in an opinion.

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You can easily get a 12mm/1/2" twist out of the boat in its present condition. Once you put in decking/ seating you will own what you have. You need to set up your cradle support so that it encourages it to untwist. It may not want to relax into an untwisted state. You can ballast the diagonal corners until the boat is straight while you add more strength to the boat as you continue to build.

 

When I have this situation in my boat building class, I over twist the boat in the other direction between classes to help it to straighten out. Ballast can be, epoxy jugs,paint cans or anything that you can find. To get more force in the bow which is not that wide, I clamp on a C clamp and hang ballast off of the clamp.

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Thanks Graham & hokeyhydro,

 

Yesterday I taped the inside seams with a few mm of opposite twist. Following your advice I will set up a bit more negative twist then instal the seats and the panels for and aft to make bouyancy with a bit more neg twist. I will see how it sits tomorrow first.

 

Catspaw With A Twist.pdf

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Well, It must be the drugs but when I checked the 'twist' his morning It's Gone. So now the inside seams have been taped and the outside sanded smooth  and holes and voids are filled. Tomorrow I will tape the outside and then start on the bulkheads and seats.post-148-0-41952800-1367044567_thumb.jpgpost-148-0-24873000-1367044627_thumb.jpg

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Graham's instructions for the nesting Spindrift say to install the nesting bulkheads as part of the wiring process which is before any interior fillets.  This is what I did (when in doubt, follow the directions).  Was curious why you used a template to shape the hull for the fillet process instead of the bulkheads themselves?  The plans had me install the breasthook, knees and gunwales before fillets as well.  It is all of these things that assure a true and fair hull for the fillets.

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G-day, 

 

I'm Nick I am new on here and I have been looking at a catspaw or spindrift 10 to build for a project and teach the kids to sail on.  How is your build progressing have you finished it yet?

 

I noticed you are in Sydney, I am in outer west Sydney I would like to see your boat at some stage if possible.  Do you have any recent photo's?  

 

All the best,

 

Nick.

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