Thoughts on how to straighten a bent strut?

[Jammer]

If it were my boat I would affix wet rags around the portion closest to the fiberglass, and around the cutlass, then heat the portion in between with an acetylene torch and a large rosebud tip, and bend it back by hand with a few gentle taps with a 16 pound sledge or maybe with the slide lever mentioned upthread.

Bending it back cold would weaken the strut.

[Suijin]

I think you're going to run into two problems trying to straighten it on the boat:

1) If it's bronze, the force required to bend it back may loosen it in the bedding/glass, or may weaken it significantly, if both of those have not already happened.

2) Getting it properly aligned is going to be extremely difficult. You're going to have to continually re-insert the shaft and check, and it has to be near perfect or your cutless bearing will need replacement every few months. And then there is the coupling...

As mentioned, you should have the shaft checked. And rolling it on a concrete floor is not going to cut it. Send it to a machine shop.

That said, you could try bending it back. Worst that would happen is you break the strut and need to replace it, which is the next step anyway.

My strut was bent last year. Ended up pulling it down, grinding out the bed and rebedding it to align it properly instead of trying to bend it. Given what it took to get it aligned properly, I can't imagine doing it by bending it and continually checking it on any boat, but I suppose it can be done with the right tool and enough patience.

[teneicm]

Lots of great ideas and food for thought so far! I've been struggling with the best way to stabilize the top end of the strut while getting enough force to bend the bottom part back. The slide bar approach seems pretty good.

Guess I'll need to figure out the "to hear or not to heat" issue. I won't know until I pull the boat out but I think the bend is closer to the top of the strut. Applying heat that close to the hull could be problematic.

I'll also try contacting some of the folks mentioned. I'll report back if I make any headway there.

Cheers- Matt

[teneicm]

Originally Posted by puffcard

Following, There's a guy at Elizabeth City Shipyard, who's now a surveyor and travels all over the world. I'm not saying that he comes there to fix it. But the guy is amazing. His yard is at the end of the Dismal Swamp ditch and he has straighten more things than anyone. I know a boater who hit a log in the ditch, had a huge vibration, went into his yard. Lloyd lifted the boat, got this big old mallet and starting beating away. Dropped the boat back in the water. Friend said the boat, never ran smoother. I would ask him, about the approach you're thinking. I known Lloyd for years and would trust his opinion, as he knows more about boats than most I know.
Contact:Lloyd Griffin
Phone:+1 (252) 335-0171
Fax:+1 (252) 338-5188
722 Riverside Avenue
Elizabeth City, NC 27909
AICW, Pasquotank River 51.2 mile marker

You wouldn't happen to have an email address for Lloyd, would you?

[Tetepare]

You're going to have to remove the shaft and strut.

Check with the locals they are typically adept at fixing things. In Fiji my local friends converted a turbo Mitsubishi engine to caburated at night under an 18 watt fluorescent with nothing but hand tools. If I'd not watched it I'd not have believed it.

[BlackHeron]

Bronze sounds like it might be a bit tricky to re-bend successfully even in the best of shop conditions. I bet it depends on the exact type of the alloy and how it was originally cast. I am no expert, but I would imagine that it would work harden fairly easily and crack or be weakened substantially like aluminum castings and extrusions often do. In my previous life in the bicycle world we could bend back steel frames, or spread the rear Over-Locknut Distance to use a different size hub on the rear wheel with no problems. With aluminum frames this is a no-go. Bronze? I'm interested in what can be gotten away with here.

I think that a call to an expert and perhaps getting a local bronze expert tell you exactly what kind of bronze you are dealing with here, or maybe find out from an expert on your type of boat what this shaft strut was originally formulated.

[Cheechako]

Get the shaft out. It may be bent anyway.
It's metal, metal bends a lot before breakage. It's probably cast bronze, so has some malleability. I'd use a 2-3 lb maul and a chunk of wood 2 x 4 etc between the maul and the strut. You may get lucky. Start at the lower end of the strut if you need to refine the bending move the 2 x 4 closer to the hull.
A picture of the bend would help, but assuming it's a gradual bend, not a sharp radius the hull should support the load right? It dis when it bent originally.
But then I'm an ex metal worker, so I'm pretty optimistic about bending metal. I've seen amazing things done.
DO NOT heat it. Too much copper and too good a heat sink. You'll just start melting resin before you have any effect on the bronze.

[teneicm]

Originally Posted by BlackHeron

In my previous life in the bicycle world we could bend back steel frames, or spread the rear Over-Locknut Distance to use a different size hub on the rear wheel with no problems. With aluminum frames this is a no-go.

Totally off topic, but an odd coincidence... We're from Chicago and I too worked for a number of years in the bike industry (worked at the Pony Shop in Evanston back in the late 80's). Bent plenty of cro-mol frames back in the day.....

[iancoombe]

A lazer pointer Centred in the cuttlass bearing is a good check on alignment.just get the dot dead center of the coupling.

[Paul L]

Originally Posted by iancoombe

A lazer pointer Centred in the cuttlass bearing is a good check on alignment.just get the dot dead center of the coupling.

Definitely the way to do the alignment, but I don't think the fine sledge hammer pounding or bending pivot is going to get to a reasonable alignment. I think the strut is going to need to be removed, straightened and reglassed at the correct alignment. Maybe Mineret will chime in with some wisdom.

[puffcard]

Originally Posted by teneicm

You wouldn't happen to have an email address for Lloyd, would you?

Here is contact page
Frigate Marine Surveyors, Lloyd E. Griffin, III, SAMS® AMS®, NAMS CMS, Elizabeth City, North Carolina, USA - Index Page

[Rich60]

My thought would be to place a piece of thick enough steel along side of the strut in such a way that using a clamp over the steel and strut would bend the strut back into a straight shape. In other words the clamp would be placed over the most convex part of the bend in the strut. Good luck.

[svHyLyte]

Christopher on a Crutch. We're talking about bending a 7"-8" long, 1/4" thick bronze plate all of about 20º. Speaking as a registered structural engineer for 40+ years, such a limited cold bend most assuredly isn't going to "work harden" the plate, even remotely and can be done manually in about 10 minutes with hand tools and patience. Using a laser pointer through the center of the cutlass bearing is a fine idea. So is simply using a string, tied to a "cross-hair" made of bamboo chop-sticks or skewers taped on the outboard end of the cutlass bearing and matching "cross-hairs" on the transmission flange. It "ain't" that hard or complicated and was how things used to be done before all this computer/laser BS existed (which doesn't seem to have improved much of anything anyway).

Good grief!

[BlackHeron]

Ricardo on a Ritz cracker. We all just talkin' here.

[Squanderbucks]

Remove and fix/replace. Alignment of shaft and engine and sgtrut is measured in thousands. No way you are going to bed it back to those tolerances. Even if you get it what appears to be close by eye it will still be way off to required specs.
Even if by miricle you could get i close you will still have to straighten shat (or get new) and realign the engine with the strut.

Good luck but I think you are wasting time trying to straighten it while still attached to the boat.