H36 Rudder "Flaps"

[chichiflys]

Looking back at older threads I saw some talk about the rudder flaps on 36 & 37 model Hunters. Looks like a few folks decided to remove them. Any adverse effects? Mine are old and warped. I had replaced them with some plexiglass versions but they keep falling off, I guess plexiglass isn't flexible enough. So while I have the boat on the hard I was going to put the old nasty plastic flaps back on, but then happened upon some of the older discussions here about them and I am re-evaluating that decision.

So now I thought about removing them for good and filling in the holes with epoxy. Anyone else try this with success or at least a neutral effect on sailing, handling, rudder vibration, etc?

Thanks,
Marc

 

[rardiH36]

Hi Marc:

I removed mine two years ago. Their condition was the same as you described. Warped into a permanent flare (20 degrees or so) away from the rudder when the rudder was straight midships. And the hardened plastic was very rigid. My impression after their removal was better feel at the helm. But that was compared to the flared flap condition before.

John Cherubini must have had a reason to put them on his boats. Reduced turbulence? Better fluid dynamics around the area?

Unfortunately I discarded my bad flaps. In retrospect I should have restored the concept using the old flaps for a template. And I might just eyeball and cut new ones at my next haul-out. The original flaps were 1980 chemistry plastic. Today, there must be some plastic sheet product about 1/8" thick that will flex as the rudder is turned, but then return straight for the next decade or two. For example, the plastic used for ski boots would be perfect. The plastic constantly flexes. It's relatively rigid (or soft depending on where on the boot it is) but always returns to its original molded shape. This is in contrast to ski boots made in the 70's and early 80's. The plastic chemistry worked fine for several years, but then became hard and brittle. About 1990, when I was skiing down a mogul field, the sole of my 1980 era ski boot completely separated from the rest of my boot . My first thought was that I prematurely released from the binding. The sole was still attached to the ski when I climbed back up the hill to get it. That was pretty neat. Boots nowadays are still pliable after many many years.

Gotta find that type of plastic for new flaps.

 

[JimBr]

I thought the purpose was to keep lines from fouling the rudder. I bought some plastic a few years back and heated it to the original shape

 

[Redbeard33]

doesn't apply to me just curious, but any pictures of said "flaps" would be interesting.......dont go out of your way but if its only a click and drag file then I'd fancy a look

 

[rardiH36]

The below url from several years ago contains a picture of Ed's replacement "flaps". Also some commentary from Blaise, who is undoubtedly the most knowledgeable speed successful Cherubini owner.

http://forums.hunter.sailboatowners.com/showthread.php?p=709018&highlight=flaps

 

[chichiflys]

Hi Marc:

John Cherubini must have had a reason to put them on his boats. Reduced turbulence? Better fluid dynamics around the area?

Yeah - that's what I was thinking - they must have had a fairly good reason to go to the trouble of installnig these things. I sailed for what I assume is quite a long time with one missing - not sure if I could tell a difference. I suppose I'll look for a better material and re-install them....

 

[SailH37]

What about cavitation?

I thought of taking mine off too, and someone said, 'hey, what about those flaps preventing cavitation helping with keeping proper flow so rudder stays balanced'? I thought that they would also help to keep lines (crab trap floaties) from getting into a really really bad place. I don't think the flaps being warped outwards takes any appriciatable speed. That's based upon racing against a J24 in perfect conditions many times in different wind conditions. They both rate the same (the shoal draft keel gets a few additional seconds on the PHRF scale) and we were really close, he did better in lighter air and I did better in heavier weather.
s/v Renasci