Thanks to everyone for their tips on what's wrong with the hull of my 1961 Thompson Offshore, in a thread back in September. It was hogged, and several folks suggested ideas on how to correct it: brace it against the shop ceiling, while keeping it wet, for several months. Unfortunately I don't have a shop ceiling I can dedicate to this for several months, so instead I jacked it while floating. I wrapped two, 2" nylon webbing straps under the hull, each attached to braces resting across the gunwales near the stern. Each brace was made of two 2x6's nailed together. I jacked against these down on the inside of the hull, in the areas of worst hog. To prevent the hull from collapsing in at the chine, I put 2x4's lengthwise along the chine, around which the nylon webbing wrapped. Photos of the whole works are here:
http://www.cablelan.net/wstrong
I set all this up on Sept 20, and it's been under pressure ever since. The boat had been in the water for 2 months already, ribs and inner keel soaking up water, and it's been wetter ever since. Each Sunday I crank up the jacks another 16" or so, like tightening up dental braces. It's all pretty tight; the 2x6 braces have bowed up a bit but the hull has noticeably pressed out. The chines haven't caved in at all. It leaks faster and faster the more I press on it... with luck it won't open right up and sink! It's been 6 weeks now; I'll leave it another couple weeks, then trailer it with jacks intact, supported with blocks on the trailer so the weight is only on the transom and front keel. Then I'll dry it completely for another 2 months with jacks still pressing. It's overcorrected now; hopefully when I pull the jacks out the hull will rebound just the right amount!
This message is cross-posted to the Wooden Boat forum.
--Ward.
Jacking out a hogged hull!
Moderators: a j r, TDockside, Miles, Moderators
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Ward Strong
- Posts: 9
- Joined: Sat Sep 09, 2006 12:32 pm
- Location: Vernon, BC Canada
As ajr said, WOW!. This is truly a heroic effort. Seems to be doing the job though. It will be interesting to see how much spring back you end up with. Keep us posted.
My biggest fear would have been that the downward pressure would tear open up the joints at the transom or along the keel.
Ward, now that you have had this experience, would you (and other expierenced folks) care to comment on the practically of the "thru - hull " clamping method I proposed in the pervious post. I think it would be benificial to the group to explore these and other creative solutions to the hogging problem.
Thanks for sharing your experence. (great pics too!)
Joe
My biggest fear would have been that the downward pressure would tear open up the joints at the transom or along the keel.
Ward, now that you have had this experience, would you (and other expierenced folks) care to comment on the practically of the "thru - hull " clamping method I proposed in the pervious post. I think it would be benificial to the group to explore these and other creative solutions to the hogging problem.
Thanks for sharing your experence. (great pics too!)
Joe
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Ward Strong
- Posts: 9
- Joined: Sat Sep 09, 2006 12:32 pm
- Location: Vernon, BC Canada
Hah! Imagine being called "experienced"! Just a backyard hacker flubbing around. I figured it's either throw the boat out or try this, and this has, if nothing else, been a great conversation starter!
I was worried about the planks/stringers popping right off, but I had it down to bare wood last winter and everything seemed surprisingly tight. Really, my main worry is losing the motor, which is worth something even if the boat isn't!
Regarding your through-hull technique, JoeCB, I think it's a great idea, except I'm not sure how pressure will be applied to the hull. I think it's important to be able to slowly crank up the pressure: jacking up to the final position right off the bat will probably crack or sproing things (like my technical terminology?).
I will *probably* end up bolting angle iron on the keelson to stabilize it flat. I don't think I'll actually luck out and have it work out right after the jacks are removed. I'm planning to leave the angle iron in... i.e. I'd better make sure it doesn't leak too bad or the steel will rust like crazy!
--Ward.
I was worried about the planks/stringers popping right off, but I had it down to bare wood last winter and everything seemed surprisingly tight. Really, my main worry is losing the motor, which is worth something even if the boat isn't!
Regarding your through-hull technique, JoeCB, I think it's a great idea, except I'm not sure how pressure will be applied to the hull. I think it's important to be able to slowly crank up the pressure: jacking up to the final position right off the bat will probably crack or sproing things (like my technical terminology?).
I will *probably* end up bolting angle iron on the keelson to stabilize it flat. I don't think I'll actually luck out and have it work out right after the jacks are removed. I'm planning to leave the angle iron in... i.e. I'd better make sure it doesn't leak too bad or the steel will rust like crazy!
--Ward.
Ward, thanks for responding, hope we can get some more discussion going on this topic. As for the "thru- bolt" proposed method, what I had envisioned was to have a steel beam ( say 3X3 tube about 5ft lg.) under the hull and another similiar piece inside with bolts thru the hull. The bolts could be drawn up perodically to maintain the stress to flatten the hook. The beams could be prebent into a slight bow to provide compensation for hull spring back. Alternatively arch shaped wood spacers could be sandwiched between a straight beam and the hull to provide the same compensation.
With a paired bolt arrangement straddling the stringer or keel the steel beams would be bearing directly on the member most resistant to straightening. This arrangement would impose no stress on adjacent joints, concentrating balanced forces directly where they are most needed. I suppose this could even be done with a boat afloat ( I like your idea of keeping the hull wet) , assuming the holes and hardware were installed on shore and the bolt holes caulked.
I'm hopeing we can get some folks to chime in on this ... or maybe even try it out.
Joe
With a paired bolt arrangement straddling the stringer or keel the steel beams would be bearing directly on the member most resistant to straightening. This arrangement would impose no stress on adjacent joints, concentrating balanced forces directly where they are most needed. I suppose this could even be done with a boat afloat ( I like your idea of keeping the hull wet) , assuming the holes and hardware were installed on shore and the bolt holes caulked.
I'm hopeing we can get some folks to chime in on this ... or maybe even try it out.
Joe