Rudder tube construction for glass fibre hull

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Petel
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Rudder tube construction for glass fibre hull

Post by Petel » Sat Jul 21, 2018 9:07 pm

The re-fit continues...I'm now wondering about moving the rudder from the transom to an internal tube to (1) allow me to hook up a wheel with ease and (2) clean up the look of the transom. I've noticed some pulleys already installed in the area so I'm not the first to think about this.

What is the best way to make / install a rudder tube that sits below the waterline?

My current idea is to fit a fibreglass tube to the hull with epoxy / fillets / cloth, fit top and bottom bushes made from Acetal and support the tube with a few vertical ply webs. There is a shelf already fitted above the waterline at the back of the boat, so if I run through that as well, that the tube will be well supported top and bottom.

If I leave the tube long enough to be above waterline inside the boat I'll have no need to look at sealing it with a gland.

Am I on the right lines? Can anyone advise if this is the best way to do this before I start drilling holes in the hull!

Thanks

Pete
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DetroiTug
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Re: Rudder tube construction for glass fibre hull

Post by DetroiTug » Sat Jul 21, 2018 9:31 pm

Sitting still it might not be an issue without a gland, most displacement hulls like we use build a bow and stern wave and the latter can become quite high under way. I would install a packing gland.

Everything else sounds fine. Although there is a lot to be said for a dependable and reliable easy to get along with rudder on pintles on the transom.

-Ron
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fredrosse
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Re: Rudder tube construction for glass fibre hull

Post by fredrosse » Sun Jul 22, 2018 1:52 pm

Transom mounted rudder shafts of the Margaret S. They have tiller arms piercing the transom at the top, with steering connections all inside the hull. This gives 90 degrees of rudder turning, with only 3/8 inch x 3 inch holes at the top of the transom.

These rudder shafts are made from pipe, with a common hinge joint near the waterline, so the rudders can fold up and then I can back onto a beach. When underway, wood dowels are inserted straight thru the the pipe shafts, to keep the rudders well submerged. If I hit something in shallow water, the dowels break, and the rudders fold up, no harm done. When exploring shallow inlets, I usually break a couple of dowels. This is a handy feature when the rudder(s) are the deepest appendage under water.
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barts
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Re: Rudder tube construction for glass fibre hull

Post by barts » Sun Jul 22, 2018 7:14 pm

Petel wrote: My current idea is to fit a fibreglass tube to the hull with epoxy / fillets / cloth, fit top and bottom bushes made from Acetal and support the tube with a few vertical ply webs. There is a shelf already fitted above the waterline at the back of the boat, so if I run through that as well, that the tube will be well supported top and bottom.

If I leave the tube long enough to be above waterline inside the boat I'll have no need to look at sealing it with a gland.
This would work just fine. If you can find some G10 tubing (strong epoxy fiberglass) that's ideal for this sort of thing. And evidently the preferred bearing material for this sort of service is UHMW polyethylene, available as tube from mcmaster.com: https://www.mcmaster.com/#uhmw-polyethy ... s/=1dts5wb.

See David Gerr's book 'Boat Mechanical Systems Handbook' for lots of excellent details and engineering how to:

https://www.gerrmarine.com/BOAT_MECHANI ... NDBOO.html

- Bart
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Bart Smaalders http://smaalders.net/barts Menlo Park, CA
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