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Old 11-12-2017, 21:10   #1
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Thoughts on how to straighten a bent strut?

Hello all-

We recently bent our port side shaft strut when hitting a log in Indonesia. The strut (which supports the prop shaft about 30 inches after the shaft exits the boat, and is only a couple of inches in front of the prop) has been bent sideways at an angle of about 20 degrees. The strut is glassed in to the hull of the boat. There appears to be no structural damage to the hull. By all accounts, getting the strut out is a very intensive and destructive endeavor, so we'd like to first try to straighten it in place.

The "thin" part of the strut is about 7 inches long (dimension running perpendicular to the hull) and 4 inches wide (dimension running fore/aft) and 3/4 inch thick. The "thin" part then flares out into the casing that holds the cutlass bearing (bearing is 45 mm x 120mm, sized for a 30mm prop shaft). The strut is solid bronze.

Anyone have any thoughts or tactics on straightening the strut out? We will be out of the water when we try and do this. My thoughts have included pushing with a hydraulic jack or perhaps attaching a line and pulling it with a pulley or windlass system. But I'm not an engineer or a metallurgist, so they may be a heap of concerns of which I'm not aware....

Cheers- Matt
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Old 11-12-2017, 23:09   #2
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Re: Thoughts on how to straighten a bent strut?

I wish you luck but I don't think you could ever bend it back to a point where it would be on center sufficiently to allow for normal shaft alignment methods to have your shaft spin true.
I think you're looking at a replacement project.
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Old 12-12-2017, 00:36   #3
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Re: Thoughts on how to straighten a bent strut?

Are you sure that the strut is only glassed and not also bolted?
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Old 12-12-2017, 00:54   #4
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Re: Thoughts on how to straighten a bent strut?

I have a friend who strightened his ,he said it was not as difficult as he first thought, apparently he tapped it over and the used a bar to a just alignment. I've not looked but utube is a gold mine for such things.
best of luck
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Old 12-12-2017, 00:59   #5
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Re: Thoughts on how to straighten a bent strut?

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Originally Posted by Paul L View Post
Are you sure that the strut is only glassed and not also bolted?
Yes, glassed in. I've talked to some other Privilege owners who've had to work on theirs. Some models do have thru-bolts, but not mine, unfortunately.
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Old 12-12-2017, 01:33   #6
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Re: Thoughts on how to straighten a bent strut?

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Originally Posted by teneicm View Post
Yes, glassed in. I've talked to some other Privilege owners who've had to work on theirs. Some models do have thru-bolts, but not mine, unfortunately.
In that case I'd take the First do no harm approach. No point in tearing up the glass base if it is not damaged now.
Could you build a steel jig that clamps to the strut base and then comes down below the strut and across the bottom, connecting back at the base. Then drill and tap a hole at the level you want to push the strut back into line. Thread a large bolt through and try straightening. This would only put pressure on the metal strut, not the glass base.
I'm sure any welding shop could create one.
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Old 12-12-2017, 05:12   #7
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Re: Thoughts on how to straighten a bent strut?

In addition to the strut being bent, I suspect your shaft is bent as well. Hopefully you're in a locale where you have have that straightened if not replaced.

As for the strut, if the locale has someone that can weld, and some pipe available, you can make a Slide lever pretty easily. Essentially nothing more than a pry-bar with a T-Top that bares against the side of the strut at the hull and an L shaped bracket, also with a T-top that bears against the off-side of the strut, welded to a collar--a short length of somewhat larger pipe that can slide over the lever are and engage the strut. (NTS sketch follows I hope!). With this, you can "gently" coax the strut back into alignment without stressing the hull.

Good Luck!
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Old 12-12-2017, 05:19   #8
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Re: Thoughts on how to straighten a bent strut?

I would contact a guy who specializes in marine shaft straightening: Keith Fenner.

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Old 12-12-2017, 05:46   #9
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Re: Thoughts on how to straighten a bent strut?

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I would contact a guy who specializes in marine shaft straightening: Keith Fenner.

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Ah... I think you missed the part about the OP being in Indonesia, eh?
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Old 12-12-2017, 06:36   #10
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Re: Thoughts on how to straighten a bent strut?

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Ah... I think you missed the part about the OP being in Indonesia, eh?
No. Getting a real expert's advice via phone or email can save a lot of headaches ...
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Old 12-12-2017, 09:06   #11
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Re: Thoughts on how to straighten a bent strut?

You are getting some good ideas here, I think it would be worth a try, you have nothing to lose. The main thing is to bend the strut without putting strain on the attachment area. (Hull) A hydraulic jack should provide all the force you need, you just need to create a fixture that will concentrate the forces on the strut itself. Good luck.
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Old 12-12-2017, 09:36   #12
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Re: Thoughts on how to straighten a bent strut?

Just a caution... a friend had a slightly bent strut straightened on his monohull. Looked good until it sheared off at the hull several hundred miles later. Fortunately his stuffing box held up.
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Old 12-12-2017, 10:12   #13
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Re: Thoughts on how to straighten a bent strut?

Some Greek guy once boasted that if someone gave him a lever he could move the world.
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Old 12-12-2017, 10:26   #14
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Re: Thoughts on how to straighten a bent strut?

With most metals, it's a good idea to apply heat while straightening (to help avoid the type of brittle failure described above). Then again, too much heat could damage the fiberglass if not done by someone knowledgable. Good luck.
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Old 12-12-2017, 11:25   #15
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Re: Thoughts on how to straighten a bent strut?

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.
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