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Old 18-07-2014, 03:35   #1
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Rudder Rebuild

Hi all,


Need to tap a few brain cells on how to repair our rudder off a Bowman 40.

Story is: we opened up the old rudder as the foam core was sopping wet. Cut a window in the non-web side of the rudder, removed old foam. In Turkey, all we could get was spray foam (insulation foam). Turkish repair sprayed the new foam into the cavity, but then glassed up the rudder before allowing the foam to fully cure. Result was that the rudder expanded and stretched itself out of shape. The turkish yard repaired the rudder, but they did not re-fair the shape. Consequently, the boat now pulls hard to port. The rudder is visibly asymmetrical.

I need to have a new rudder built. The shaft and webbing are fine. The construction is that one side of the rudder is glassed to the webbing, and foam fills the remainder of the cavity.

I'm unclear about the best way to rebuilt the rudder. Make a mould of the one good side, then try to reduplicate the other side? Make a foam male mould over the webbing, lay up a mould? Not sure how to proceed. Would love recommendations of the best way to rebuild the rudder.

I will try to do this in Lefkas, Greece. If anyone has recommendations for a good glass guy in Lefkada, I'd appreciate the referral.

Thanks,

Steve
S/V Pavlov
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Old 18-07-2014, 03:58   #2
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Re: Rudder rebuild

The only thing I can think of requires being a bit of a craftsman and artisan.

- Make the female mold from the good side.
- Make a new Male form for the good side.
- Make profiling templates out of plywood - these are the same kind of templates used to profile racing keels - think fancy french curves. How many you need will depend on how much taper and profile change there is couple with your skill as an artisan.
- Blow foam into the good side - If you have access to a packing foam machine that would be ideal - build up the foam enough soe you can cane carve the opposite shape

Then the hard part - carve the opposite shape by hand using the profiling templates to guide the final form.

If you've succeeded this far you now have a male plug from which to make a female form.

I can't think of an easy way.

Idea 2
If you have access to a CNC shop they may be able to map the good side and then "machine" a wooden mirror male form - Might be expensive but lots of specialty auto and motorcycle shops have CNC machines these days (in the US) maybe not so much in Turkey...

OK

Idea 3

- Make two good "left" sides
- section 1 of the left sides laterally into say 1 inch slices
- Flip over and lay these "slices" into suitable base - say heavy sand covered in thick plastic
- You now have a very "Choppy" female mold for the opposite side
- pour a plaster mold - male
- build up the plaster mold with bondo
- fair, sand and shape using aforementioned profiling templates
- Make another female mold from this from which to make the final fiberglass half
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Old 18-07-2014, 04:13   #3
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Re: Rudder rebuild

This may sound weird but take a look at this thread from a hobbyist website.

Scroll down to where he is making "buck" molds filled with foam. This is sort of what I was talking about in idea 1.

You can see that you an do a good job foam carving a mirror shape although this is on a pretty small scale.

Fiberglass How to: Plug to Mold to Parts
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Old 18-07-2014, 07:36   #4
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Re: Rudder rebuild

I have seen identical "repair" read damage done by a "boatyard" in Chroatia.

I think save yourselves any Greek adventures and ship a lamination specialist fro some more technically aware location.

You can draw the foil from the undamaged part and then the rudder can be build in one piece over shaft and grid.

You can build a full size model of the foil from an inexpensive material and then create a female mold. Then build the new thing in two halves.

But I believe for a one off item the single piece round a foam core is fastest and least expensive.

Hire a skilled lamination specialist in a good (UK, NDL, SWE, etc.) boatyard, ship the shaft to them, wait some and get a 100% reliable new rudder.

b.
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Old 18-07-2014, 08:32   #5
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Re: Rudder rebuild

Care to recommend a 'skilled lamination specialist'.

Half the problem of doing repairs while cruising is knowing how to evaluate the skills of unknown tradespeople. I've been ripped off blind by both British and Greek mechanics, so I'm not sure if skill is ethnocentric!
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Old 18-07-2014, 08:41   #6
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Re: Rudder Rebuild

WEST SYSTEM | Projects | Fiberglass Boat Repair and Restoration - Rebuilding a rudder
Rudder repair

Here are a couple of articles that may or may not help you out. Do a search on "how to build a rudder" and you get lots of hits.
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Old 18-07-2014, 08:45   #7
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Re: Rudder Rebuild

http://www.google.ca/url?sa=t&rct=j&...71198958,d.aWw
Here is something you might like to download and print.
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Old 18-07-2014, 08:48   #8
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Re: Rudder rebuild

Holy Crap...

What a disaster... Insulating foam...

Do you have any pics of the construction? Frame glassed to "ONLY" one side??? Obviously you've got to get the "ballooned foam" out and restore the bad profile... How big a window did they cut? Can you remove the foam and get back to the original shape? If so... glass in some struts to maintain the shape???

Ex-Calif has a lot of great ideas, but these are solely dependent on the skill of the "rudder profiler" The series of templates is the normal way... You need a good glass guy who's done this before... If no competent boatyard glasser, are there surf shops in Turkey? A board shaper could do this...


Maybe the Foss Foam NewRudders.com ยป About Us guys could recommend somebody near you...

Honestly... It may be simpler to add glass to the good side, get out of Dodge, and get to a real yard... AFTER MAKING TEMPLATES OF THE GOOD SIDE...
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Old 18-07-2014, 09:25   #9
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Re: Rudder Rebuild

Is Bowman still alive? If so I recommend you get in touch with them. The may have the rudder measurements and would know who built the rudder for them, if they didn't do it in house.
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Old 18-07-2014, 09:37   #10
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Re: Rudder rebuild

Quote:
Originally Posted by steve.garlick View Post

(...)

so I'm not sure if skill is ethnocentric!
It is one thing to be PC, another to be realistic.

Why have a Bowman fixed up by people who cannot build one.

I live in the Med.

b.
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Old 18-07-2014, 22:12   #11
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Re: Rudder Rebuild

Simplify. Make a series of marks along the axis of the rudder shaft. Transpose a fair copy of water line along the top section of the rudder. (This on the good side first). Then draw a series of lines from your marks to define a number of sections you will copy with light ply or foamboard. Make up the profile templates and give each a number.get out the disk sander with 80 or 120 grit disks. Using the profiles as a guide remove the "extra" material till profiles are roughly correct. Evaluate what you've got. If the uncured foam is bad dig it out. Use west sys or other with fairing filler. When almost even to profile...using a fine cloth laminate a couple of gradually increasing patches to cover the fill. Fair it out again.check profile. At some point here shict to random orbital sander and do not be heavy handed....When patches reach intact areas of rudder laminate one good sized patch to entirely overlap good territory. Fair out and using a fairly large plastic squegee fair with thickened resin till all sections are fair. Wet sand with 220 till it looks and feels right. Prime it with epoxy primer and paint the damn thing
If you choose enough sections intellgently it should be a very good copy of the other side.... and plenty strong...
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Old 18-07-2014, 22:27   #12
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Re: Rudder Rebuild

I have seen one rudder repair where the glass/epoxy went on without regard to the gap between the skeg and rudder. Much of the glass had to be sanded off and the profile sanded smooth again.
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Old 19-07-2014, 07:16   #13
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Re: Rudder Rebuild

Quote:
Originally Posted by Seacod View Post
Simplify. Make a series of marks along the axis of the rudder shaft. Transpose a fair copy of water line along the top section of the rudder. (This on the good side first). Then draw a series of lines from your marks to define a number of sections you will copy with light ply or foamboard. Make up the profile templates and give each a number.get out the disk sander with 80 or 120 grit disks. Using the profiles as a guide remove the "extra" material till profiles are roughly correct. Evaluate what you've got. If the uncured foam is bad dig it out. Use west sys or other with fairing filler. When almost even to profile...using a fine cloth laminate a couple of gradually increasing patches to cover the fill. Fair it out again.check profile. At some point here shict to random orbital sander and do not be heavy handed....When patches reach intact areas of rudder laminate one good sized patch to entirely overlap good territory. Fair out and using a fairly large plastic squegee fair with thickened resin till all sections are fair. Wet sand with 220 till it looks and feels right. Prime it with epoxy primer and paint the damn thing
If you choose enough sections intellgently it should be a very good copy of the other side.... and plenty strong...
Holy Crap!

All these years, and I've never wet sanded with 220 before antifouling....

I was wondering why my boat(s) don't plane!

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