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View Full Version : Is this bracing okay to support the boat?



chuckt
02-04-2010, 09:27 AM
If anything, I suspect I have over-engineered here but I am paranoid about removing the keel blocks so I can drop the keel and repair it. I have visions of the floor timbers collapsing and the whole boat coming down. Or of somehow deforming the timbers or frames. All but one or two of the floor timbers are solid. I'm just being paranoid right?

BTW, the cross pieces on the bottom of each triangle support aren't attached on the other side yet--I'll do that when I jack up the boat to remove the keel blocking. The idea is to jack up, then pull the legs in on each support to make them tight against the bottom, then secure the cross-brace.

Oh--and I hereby release and hold harmless anyone giving an opinion on this -- lol

http://i571.photobucket.com/albums/ss151/cmeke0870/work%20begins/100_0131.jpg

seo
02-04-2010, 09:46 AM
The stands look like they're vertical. Normally they tip in a little bit, and are chained together with a chain leg under the keel to keep them from kicking out. I have also used lag bolts through the plywood pad to keep it from moving against the hull, and have bolted the base to the floor. But that was pretty extreme.
The chains do a good job of preventing kick-out, and the pairs of stands can still be moved easily to improve access.

Ian McColgin
02-04-2010, 10:00 AM
Looks terrific. The stringer spreading the stress across the frames and floors is smart. The outward spreading thrust on the supports should be modest enough that your planned cross memebers ought to do the trick but two things I would do differently:

Slope the foot of the supports so they land more broadly on the ground thus spreading the load more fairly there; and

Make the side to side tie lay on the ground so you can have everything fully supported as you lower the keel. If you go to move the keel out from under after it's dropped, this will involve more jacking to move one roller back every few feet till the center has cleared but it'll be a lot safer.

Oh yeah - I don't think you need that many supports, especially with those stringers spreading the load. Maybe one every other or even every three frames.

G'luck

KAIROS
02-04-2010, 10:01 AM
Like this, as in most boatyards. Note the chains and the angles. The aft chain runs under the keel.

http://www.yachtflyers.com/ABLE/images/festival2009_12.JPG

Ian McColgin
02-04-2010, 10:04 AM
The pic in #4 is for when the weight of the boat is taken on the keel balks. In this project, the balks must be removed to drop the keel.

Thad
02-04-2010, 10:04 AM
different shape boat

KAIROS
02-04-2010, 10:24 AM
The pic in #4 is for when the weight of the boat is taken on the keel balks. In this project, the balks must be removed to drop the keel.

I only meant to tell the thread starter that the jack stands in the photo showed how they should be more perpendicular to the hull, and my photo shows the chains running between jack stands. Even if a chain has to be moved to drop (or work on a portion of) the keel, it can be reattached right afterward so the stands are prevented from kicking out as much as possible.

wizbang 13
02-04-2010, 10:29 AM
post #1 is an un ballasted hard chine ?

Ian McColgin
02-04-2010, 10:37 AM
I'd NOT rest more than balancing weight on poppetts. Such a localized stress will distort the hull rather horridly.

Chuckt has the right idea. Once the keel is off, the total weight is much more manageable. I'm sure that he'll only be dropping it a 1/16 " or less at a time so that the keel bolts won't bind and all that. It's my opinion that getting the bolts to slide out in one go is too fraught with peril and you don't want to reuse them anyway, so I'd drop the keel barely enough to guide the saw kerf between keel and ballast and then have at with the most violent SawsAll I could borrow. Once they are cut away, it's really safe to lower the ballast onto pipe rollers and come-along it out of the way.

Brian Palmer
02-04-2010, 10:47 AM
I think that is just a timber keel, not ballast. Looks to be a powerboat.

Brian

nedL
02-04-2010, 12:42 PM
Yep, looks like a hard chine, plank on edge keel, powerboat form (similar to std 1950's C.C. form - except it is not a double planked bottom, so it's not C.C.) I'm thinking you will need to be able to drop the keel maybe 12"-16" for the bolts to clear the floors & keel batten (?).
Your blocking looks good enough to bare the weight, what I do NOT see is a way to keep everthing from skewing sideways & coming down. You will need either LOTS of BIG gussetts (diagonals) between your uprights & your cross supports (preferably extending past the cross supports & bearing on the floor), or something that acts in a similar way. It looks like you may have the fore-aft movement addressed with your diagonal 2x4, though I'd suggest a couple more doing the same thing. Also, what looks like that horizontal 2x6 fastened along the uprights isn't really going to do anything for you (unless the compressional load on the uprights is so much that they start bowing.-- I hope not!) Keep in mind that there will be a lot of climbing on & off her, moving around, & driving the keel bolts out when she is up like this, and there is a lot of mass in that boat, so any little movement or jostling of the boat will require good strong bracing to keep it in check. Will you have the ability to add four points of tradional cribbing for safety (one stack under each transom corner, and a stack up forward on each side)? I guess I'm thinking my concern with her up on stilts like that, is that if things start to shift there is no real 'safety net' so to speak, it can all come tumbling down.

chuckt
02-04-2010, 01:49 PM
Thanks gentlemen. I'm sorry--should have describded the boat more. She is a 1950 30' CC Cruiser. She is doubleplanked. Doesn't look that way because I ran a saw along the seam of the second plank deep enough to cut through the inside layer. This so as to facilitate frame repairs after I get the keel repaired. I think this bracing will work but Ned's suggestion to add stacks wouldn't hurt. The 2x6s on the middle supports are just in case I bang into one of them so I dont knock an individual support loose. I figured the other diagonals plus the stands will limit fore and aft movement. Those stands, btw, are keel stands and therefore can, aand are, takng some weight. There are heavy building posts set in concrete on either side of the boat. I can fashion some supports tied into them to elminate risk of sideways movement although I think this unlikely. This boat is supposed to weigh about 7500 pounds w/o fuel or water so its not a monster.

The keel/skeg is in three pieces so that will make the drop(s) more manageable. Haven't figure out yet how to drop it in a controlled fashion. Probably will put stacks underneath so it can't fall far although my guess is that its not really going to want to just drop and I will be prying it off by fractions

Ian McColgin
02-04-2010, 01:56 PM
Don't be surprised if it give a huge argument due to the keel bolts freezing into the wood. Since it's not ballast, it won't drop by itself and the power of prying will do much damage to the inner keel member.

I'd not waste time trying to pry it out. SawsAll to get if free then sledge and drift from above to get the remaining studs out.

It'll be faster and easier.

G'luck

chuckt
02-04-2010, 02:05 PM
Thanks again--I'll experiment. Yes, she is a champion debater--she likes to argue and has been reluctant to give up everything I've tried to take off so far. It took me 16 hours to get the garboards and the next plank up off. I dont expect her to give me the keel without similar protests.

chuckt
02-04-2010, 08:42 PM
Dang Feaz--you are right about the stand locations--glad you noticed that. And Ian said something similar I just didn't pick up on that there shouldnt be much weight held up by the stands. The planking is pretty strong but I could see how it would be better on the chine and make sure I dont have significant weight on the stands.

John Meachen
02-05-2010, 11:31 AM
It would be worth ensuring that you are supporting the hull where the bulkheads are located and not just on a single plank thickness.The junction of chines and bulkheads would be even better.

chuckt
02-06-2010, 10:04 AM
Just an update--the boat is now resting on my bracing. I heard no creaking or cracking as the weight settled on them and she seems very secure. No deflection of the frames or planking that I can see. Started taking the keel off last night and, to my great surprise, it is dropping fairly easily. Probably will be harder to get back on after repairs. Still a possibility I may laminate a fir replacement.