Hey all - when sailing on my Nacra 5.5 the boat loves to sing a harmonious whale song above about 10knts. After reading around on this forum and others the consensus was dirty water off daggerboards and rudders causing the noise. I looked over mine and they were truly showing their age. Both the daggerboards and rudders had areas on the perimeter where all gelcoat had ben sanded away and either UV or impact had caused the core to crack or become exposed. Documenting my overhaul process here for anyone in the future.

First I sanded the boards down completely using 220 grit to remove minor gelcoat imperfections and to fair out the very rough epoxy/graphite that had been brushpainted on the bottom sections by the previous owner (never sanded smooth). Next I block sanded the leading and trailing edges to smooth out previous repairs and sanded back some considerable damage on the trailing bottom corner. The previous owner had also done some pretty rough repairs to the trailing edge likely from running aground at speed. I took this opportunity to block sand them down and see where new epoxy was needed.

Unfortunately I didn't take good pictures at this step but you can see the worst damage to the trailing corner by zooming in on the first picture, the second picture is the better of the two boards.







Edited by carbonc on Jan 16, 2022 - 11:59 PM.

Next I used West System epoxy with colloidal silica to rebuild the corners and fill in all the open cracks or knicks on the trailing edge. Where needed painters tape was used to dam up or shape the edge of the boards to hold the epoxy in shape while curing.

After a week of epoxy cure block sanded again using 220 to shape the new epoxy and smooth out all edges. By this point I had decided I was going to finish the bottom section in epoxy+graphite (as covered elsewhere on this forum and Youtube for EPO repair). Since that finish required additional sanding between coats I didn't shoot for perfection at this stage. I masked off a line that corresponds exactly to where the boards are flush with the bottom of the hull when pulled up. This will help me know they are high enough when coming back to shore.

Example of the shaped corner following repair.


Ready for first epoxy + graphite coat following this video http://www.youtube.com/watch?v=jNwMgX48uwQ


First coat applied and sanded down. I didn't thicken this coat as as you see it was hard to get it to stick to the corners.




After several thickened coats. I block sanded quite a bit but also used my orbital sander to speed things up.




Edited by carbonc on Jan 17, 2022 - 12:10 AM.

Finally I decided to gelcoat the top of the boards. I know brushing on they won't be mirror smooth but these are daggerboards, most of this section is above the waterline, and I don't mind sanding a bunch with my orbital to smooth things out. Just to make everyone go crazy I tinted my gelcoat to hot orange because why not.

On the line ready to get coated


Coated




There were a few spots I had to thicken the gelcoat layer due to the existing expoxy repair showing through. I'll sand this smooth once cured




Edited by carbonc on Jan 17, 2022 - 12:10 AM.

Very nice job, but the resonance can as well be the result when the carpet tape at the daggerboard slot is missing. As you are on the go, change them!


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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

https://www.facebook.com/groups/1192604934176635
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Thanks for the heads up Lars. Both slots are dogs breakfast of different carpets right now. I can probably track down scrap carpet somewhere, do you have a preferred adhesive method?

As I couldn´t fine the correct ones in Europe, I actually bought a pile weatherstrip of the same type as is used on the 29er. Bought a roll of 3M on eBay. Works like a charm .
https://ovingtonboats.com…-new-style-2016-onwards/



Edited by revintage on Jan 17, 2022 - 05:56 PM.

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Brgds
Lars

Frankentri 5.8/5.5/Inter20
Aerow trimaran foiler

https://www.facebook.com/groups/1192604934176635
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I found that Shoe Goo is probably the best adhesive out there for my NACRA. holds great when wet, and can still be scraped off if needed. keep a tube in your cat box!

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Central Iowa


2017 Hobie Getaway

Memento Mori...
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