Zuma rudder blade on a sunfish?

hospadar

tiny boat fiend
The rudder that came with my fish needs enough love (many significant cracks to fill, very badly needs refinishing) that I was planning on just getting a new one to spend more time sailing and less time sanding and varnishing.

BUT it just so happens that I have a zuma rudder laying round and was thinking that maybe I'd just go ahead and use that instead? It's much larger (rough estimate 2x the area) and is more or less vertical (like the aerosouth rudder) instead of the swept-back sunfish style. My understanding is that the rudder brackets are the same so if I switch out the tiller handle (or put the zuma rudder on into the sunfish bracket) I should be all good?

Any particular concerns with the bigger rudder? It's not going to do something insane to the helm balance will it? (I guess that the CLR might go aft a bit because of the bigger blade but maybe not change all that much since it's vertical vs. swept?).
 
The rudder that came with my fish needs enough love (many significant cracks to fill, very badly needs refinishing) that I was planning on just getting a new one to spend more time sailing and less time sanding and varnishing.

BUT it just so happens that I have a zuma rudder laying round and was thinking that maybe I'd just go ahead and use that instead? It's much larger (rough estimate 2x the area) and is more or less vertical (like the aerosouth rudder) instead of the swept-back sunfish style. My understanding is that the rudder brackets are the same so if I switch out the tiller handle (or put the zuma rudder on into the sunfish bracket) I should be all good?

Any particular concerns with the bigger rudder? It's not going to do something insane to the helm balance will it? (I guess that the CLR might go aft a bit because of the bigger blade but maybe not change all that much since it's vertical vs. swept?).

I haven't visited the forum much and just saw your post. I have a Zuma, but had a Sunfish many decades ago... anyhow, my guess is that the Zuma rudder will improve the weather helm of the Sunfish. I bet it works better. Let us know!
 
THE PLOT THICKENS: (or at least, the rudder thickens)

I can't use the whole zuma rudder cheek assembly on the sunfish because the pintle on the zuma is 1/2" instead of the sunfish's 3/8" and doesn't fit in the sunfish's gudgeons.

I can't just put the zuma rudder into the sunfish's bracket because it turns out that a zuma rudder, while having basically the same bracket design is slightly thicker (or at least mine is). My sunfish rudder measures .75" thick on the nose and the zuma rudder measures about .85" thick (mystery!). The plastic spacers/bushings that go around the pivot bolt are about .025" thick each, so the sunfish's rudder cheeks end up being too narrow even if were to just leave out the plastic spacers.

Thinning out the top of the zuma rudder to fit, while probably practical and not too hard, didn't sound very fun to me, so instead (due to a surplus of scrap metal/free time and a deficit of trailer tires that hold air/good sailing weather) I've decided to embark on the insane plan of fabricating a new stainless steel rudder cheek assembly for the sunfish that's slightly wider than the stock bracket which can accomodate the zuma rudder _or_ a stock sunfish rudder (in case I ever splurge on an aerosouth rudder maybe?). Pending more measurements, I'm going to shoot for a cheek assembly with .86" - .87" between the cheeks. I think that should accommodate the zuma rudder with no (or very thin) spacer bushings, and accommodate a stock sunfish rudder with thicker (or just 2 stacked up) spacers. Probably would make the new spacers out of appropriately-thick PTFE film/sheet from mcmaster or ebay (or other tough slippery plastic - acetal, uhmw, hdpe, etc, etc).

Sunfish rudder:
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Zuma rudder:
2022-06-07 12.01.27.jpg

I used masking tape to copy the outline of the zuma's rudder bracket and transferred that to stainless plate for cutting:
2022-06-07 10.22.21.jpg

Cut & rounded off rudder cheek pieces. Transferred the shape to cardstock to locate the pivot bolt's position for drilling:
2022-06-07 11.49.56.jpg


Haven't started welding yet, will post more pics when I get there!
 
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The different thicknesses is frustrating. I encountered the same thing when I thought about trying a Sunfish daggerboard in my Zuma. The Sunny's board is thicker than the Zuma's. Plus, it has a much shorter chord (fore and aft length) than the Zuma's so it's pretty much a no-go unless I make some sort spacers for the daggerboard slot etc.
 
Preparing the rudder cheeks for welding. A bolt is being used to keep the pivot holes in alignment. The cheeks are clamped around a piece of oak shimmed out with aluminum tape to .87". The hole drilled in the oak block (visible in the pic on the right) is to permit back-purge gas to keep the inside of the weld clean.
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The welding setup - the red hose is providing the aforementioned back-purge gas.


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The brackets which will be welded to the rudder cheek assembly to hold the pintle are cut from a piece of thick rectangular stainless tube. A 3/8" threaded rod is being used to maintain the correct alignment and spacing of the brackets.
2022-06-07 17.43.54.jpg
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Welding the brackets in place. Also welded on some gussets to support the brackets (probably unnecessary) and add a little extra strength to the whole thing. A 1/4-20 nut also welded on which will be used to anchor the kick-up springs. I welded the upper gusset on upside-down so ended up having to trim most of it off (whoopsies).

2022-06-08 09.15.46.jpg
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Aaaaaaand: the rudder bracket doesn't fit around the zuma rudder . The bracket warped a bit during welding (I'm not exactly a _great_ welder if we're being honest). I ended up grinding down the zuma rudder a bit with a sanding disc on an angle grinder like I should have done in the first place :). In these pics the oxidation from welding has been wire brushed off.

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The finished product! 1/4-20 machine screws are holding in the springs (hopefully between blue loc-tite and bottoming them out they'll stay in place). The pintle is a 3/8x6" stainless bolt with the threads chopped off and a hole drilled for a hitch pin. I put a small hole in the lower bracket for a little cord to tie to the hitch pin so I don't loose it. Rudder blade has wet polyurethane on that so haven't mounted it all up yet.
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Update:
Took the zuma rudder + stainless bracket out for the first time (which custom hockey-stick-turned-tiller and golf-club+ronstan-joint-extension) and it worked like a charm! Only sailed the classic rudder once under slightly different conditions, but the zuma rudder works great (and isn't falling apart like the sunfish rudder that I have ☺)
2022-06-09 17.31.47.jpg
 
Really cool! Excellent pics and explanation, though I have no welding skills and wouldn’t imagine doing this little DIY! Nice work!
 
Update:
Took the zuma rudder + stainless bracket out for the first time (which custom hockey-stick-turned-tiller and golf-club+ronstan-joint-extension) and it worked like a charm! Only sailed the classic rudder once under slightly different conditions, but the zuma rudder works great (and isn't falling apart like the sunfish rudder that I have ☺)
View attachment 51741
When I made a vertical rudder for my Sunfish, I also used a hockey stick for the tiller. :cool:
See details here.

- Andy
 

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