Centerboard problems

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Re: Centerboard problems

Postby mark48 on Wed Sep 06, 2017 7:56 pm

This isn't a problem yet, but I'm posting to ask advice about the centerboard pivot installation to prevent one:

Page 26 of the PS manual advises leaving the "epoxy-filled" (pivot) holes in the forward end of the developing centerboard trunk "until much later." Page 223 notes that we've "located and drilled out the pivot hole" for impending installation of the centerboard. At this point of course, the centerboard trunk is a completed, integral part of the hull - and it seems that the "port" and "starboard" pivot holes must be at right angles to the keel and perfectly lined up with each other to allow installation of the pivot rod and appropriate CB pivoting. Also, as we drill the pivot holes on each side of the trunk, we must avoid penetrating the thickened epoxy in the holes which would defeat the protection of the trunk from future water damage.

#1 - I'm wishing I'd drilled those holes before I'd built the trunk when I could position the two trunk sides exactly together, one over the other. (See #2 below for why.) I also wish I'd drilled the holes a bit oversized so I'd have more diameter through which to now drill the two holes for the pivot rod. (And in fact, were I to build another PS, I'd make a number of the "drill-fill-drill" holes a bit bigger. John Harris has endorsed that with respect to the companionway hood drain holes and the holes draining the footwell through the transom.) But penetrating the hardened epoxy and inadvertently touching centerboard trunk wood is a disaster to be avoided; if it were to happen, it's critical to recognize it at the time and re-seal the spot with epoxy, even if it means re-filling the hole with thickened epoxy, without leaving slag on the inner trunk surfaces.

But #2 - How are builders ensuring the pivot, when installed, is indeed at right angles to the keel (so the CB is free to drop)? It seems that some filing of one or the other hole will be required to get the pin to fit through the CB trunk opening.

And #3 - Don't I want the 3/8" stainless steel pivot rod itself to be motionless once it's sealed into the trunk with thickened epoxy, while the pivot hole in the CB is just slightly over 3/8" in diameter to allow the CB to swing freely on the pivot? It seems I wouldn't want the rod to "work" at all as the CB was lowered and raised over time. Maybe I'm worrying too much, but other PS Forum posts about water damage in the CB trunk have made me properly scared.

Thanks for any advice,
Mark

ps - Maybe "Were I to build another Pocketship..." deserves its own subject line in the PS Forum.
mark48
 
Posts: 67
Joined: Fri Jun 28, 2013 9:55 pm

Re: Centerboard problems

Postby Bflat on Thu Sep 07, 2017 10:31 am

I followed the manual for installing the CB pivot and had no problems although, like you, at the time I wondered why I couldn't have drilled and filled the holes earlier (one could, it seems). Anyway, It was quite easy. Although care should be taken, extreme precision isn't necessary since a tiny bit of slop in the fit is desirable for the board to pivot freely. To fill the large holes I wrapped waxed paper around a 1" thick scrap wood and inserted it in the CB slot. Then I easily filled the holes with thickened epoxy. When that cured I removed the scrap. The next step was of great importance - locating precisely where the final hole should be drilled. I made a "fake" centerboard from cardboard that matched the profile of my actual board including its pivot hole. When inserted in the slot this greatly aided locating the best spot to drill the hole. Another aid was to start with a small pilot hole first. With that hole in place I could check that the fake CB had proper clearance. A small round file made short work of "creeping up" on the final hole location. It turned out really well.

Getting the hole to be at a right angle to the trunk was not difficult. Drilling the small pilot hole first and using a round file to get it to final fit was the key on that point. After the pilot hole is "tuned" a bit with a file I used increasingly larger drill bits to bring it to it's final size. Also, since the pivot hole of the CB itself is slightly bigger than the pivot rod (it shouldn't be a really tight fit) aerospace precision isn't needed.

Once the pin is finally inserted, the thickened epoxy used to cover it up will keep it from moving.

Before permanently installing the pin, I checked the final fit with the actual centerboard to be sure it could move freely.

I agree with you about filling holes. I gradually learned to make filled holes generous in size to avoid problems. I can't remember, but I don't think I deviated much in that regard when it came to the CB pin.

I've finally launched my boat. Raising and dropping the board has been problem free (so far).

I hope this helps.

The photo won't be of much help, but just shows the CB being held temporarily with a screwdriver as pivot pin. I wish I'd taken some photos of the hole filling and drilling process (much before the attached photo was taken).
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Bflat
 
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Re: Centerboard problems

Postby mark48 on Fri Sep 08, 2017 6:15 am

Bflat, thanks for your advice and suggestions.

My biggest concern is that I'll inadvertently penetrate the hardened epoxy somehow, during drilling or filing the hole to allow the pivot to fit, and not recognize it - allowing water penetration to a "hidden" part of the hull which will ultimately cause a disaster. Most of the rest of the hull I'm able to inspect for adequacy of epoxy coverage; the CB trunk assembly is another issue. And if I'm not sure, I'll re-drill the hole to a larger diameter and refill the holes with thickened epoxy. I just wish I'd done that in the beginning.

All the best,
Mark
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Posts: 67
Joined: Fri Jun 28, 2013 9:55 pm

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