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Spindrift 10N - how remove twist?


Rdubs

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Hi all,

Have been stuck on my Spindrift 10N for some time now because I am at the stage where everything is wired, the breastplate and knees are epoxy'd in and the next step is to make the seams permanent by fiberglassing it in.  However the directions say "be sure to check for twist at this point" and I read a forum that showed a fellow using a level to check the front and rear angles to see if they were the same.  On mine if I set the stern level, the level shows that the bow is tilted, one side seems to be higher than the other.  Problem is, I don't know how to make any adjustments to try to get it back to level.  So two questions:

1) What's a good way to remove this twist?  I imagine some of it has to do with loosening the copper ties, but not sure how to adjust it from there.

2) Is there a good way to mount or hold the hull while you try to adjust it?

 

Many thanks, I've been stuck for a while trying to figure this out.

'Dubs

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It is good that you are on top of this, but you do not need to sweat it. It is the best time while the boat is very malleable to get it true because as the boat gets stronger and stronger as the structure comes together, it will get ever harder the straighten out.

 

You should be able to wrack the boat easily at this point. If the stern cradle is solid and level you can twist the forward cradle to bring the boat back to true. If you do not have a forward cradle you can use a piece of wood , say 1 x 2 or whatever as a prop down on the floor on the low side forward and a clamp to the side of the boat near the sheer. You can lift up on the boat and clamp, then check the twist, adjust until it is true.

 

I have used gravity by hanging a C clamp on the high side forward to untwist. If a C clamp is not heavy enough I have hung several more off of the first one. I have twisted the boat the other way for a while hoping that when it springs back it will come back to true.

 

Sometimes it is difficult to find the root cause of the twist. If your panels were true and it is neat and evenly tied together, just carry on but keep an eye on it until you are done. Once the decks are on you will own any twist that you have built into the boat.

 

One of my favorite ways to check for twist is to have a vertical center line on the transom. Stand back about ten feet if you have the room and sight down the centerline on the transom lining up the center of the stem. Keeping that alignment, I lower my eye until the transom crown kisses the top of the forward bulkhead. If the centers are aligned and the edges of the forward bulkhead are hitting the transom top at the same time, the boat is twist free. If one side of the bulkhead is higher, you have a twist. It may sound convoluted but once you master it you can check your boat in seconds without having to use tools. Of course it depends on whether the forward bulkhead is in its proper place. If I am checking a new boat and observe a twist. I check if the forward bulkhead is in its place by measuring back from the center of the bow to each side to make sure that the bulkhead is in square to the boat, if the bulkhead is set below the sheer, I measure down from the sheer on each side to make sure that they are the same. When overseeing large boat building groups I can wander around the classroom and monitor the entire group in minutes every day. 

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  • 2 weeks later...

Check my thread, Rdubs.  I used plastic shims between the cradles and the hull to raise the low sides so that both bow and stern were level.  I'm building in a backyard and don't have the advantage of a nice level surface to work on.  Devlin suggests measuring from the bow to each corner of the stern and pulling down on the shorter side: 

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