I searched thebeachcats for winglets and came up with little to nothing. It's an intriguing thought to add mini-foils to our older cats for fore/aft stabilizing. Adds a vertical load component to the gudgeons that they were not designed for. Seems like an easy thing to 3D print and bolt to the side of the rudder. Has anyone done research on them?

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FYC, Nacra 5.2 "Chris's Flyer" & Nacra Playcat & Farrier Tramp
Previously owned: Trac 14, H14, H16, H18, N5.0, G-cat 5.0
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Is the idea to give some lift to the aft end of the boat while underway? I'm not sure it would stabilize the ride at speed. My Nacra seems to cut through the water and responds to shifting weight fore or aft to control how much bow-dive I get. I tend to move forward at slower speeds and back as things get faster and the rudders start to lift clear, especially with a beam or full reach under high wind conditions. My concern is introducing stress and fasteners to rudders that are really hard to find replacements.

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Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
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They certainly would "fix" the pitch of the boat underway. I usually keep bows down upwind and ride them with the bow chine kissing the water downwind.
The theory is when the boat pitches forward the winglets will pull down the stern and when the weight (or wave) kicks up the bows they lift the stern. While they may not benefit the ride on my 5.2 they would definitely calm down hobby horsing on asym hulls.
check the 9:00 minute mark
https://www.youtube.com/watch?v=8nrCYTxQDtQ&t=6s

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FYC, Nacra 5.2 "Chris's Flyer" & Nacra Playcat & Farrier Tramp
Previously owned: Trac 14, H14, H16, H18, N5.0, G-cat 5.0
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It reduces the hobby-horsing in chop, and significantly reduces the tendency to pitch pole at high speed.

You will need to beef up the transom, the gudgeons, and rudder case/bracket/etc.

There are significant loads generated by adding winglets. I've broken all of the parts listed above (and numerous winglets) until the entire assembly was bulletproofed.

Thanks Mike. Now at least we have this subject somewhat covered on this site. I was thinking it would require a full custom rudder setup. I have definitely found the limit on my 5.2 solo going downwind where the winglets would have saved my tail.
Have any pictures of a reinforced setup?

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FYC, Nacra 5.2 "Chris's Flyer" & Nacra Playcat & Farrier Tramp
Previously owned: Trac 14, H14, H16, H18, N5.0, G-cat 5.0
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I've added a set to a Tornado and installed at zero degrees angle of attack. Used small a-cat winglets and estimated that at 15 kts and 5 degrees down angle they would add ~65 lbs of downforce to the stern of the boat.

The most noticeable improvement was the reduction in pitching. We were certainly able to drive it harder in chop.

I agree with Mike, most boats are going to need some stiffening and upgrades to the rudder system to go this route though.

If you are looking for some, I have a mold and can make them.