525 under construction

The place to discuss SCAMP (Small Craft Advisor Magazine Project), our 11' 11" micro minicruiser.

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Jennifer J Harold
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Re: 525 under construction

Post by Jennifer J Harold »

Hi Marc,
While I'm certainly not an expert, my centerboard seems to have turned out okay, so I'm happy to share what I've learned.

I glassed one side at a time. I cut the fiberglass (2 layers) big enough to hang over on all sides about 2". I cut darts (v shaped notches) in the corners so the glass could fold around the corners. I also cut slits where the flat/foil parts of the centerboard meet because the glass won't really wrap well over those 90deg angles at the top, and I don't think it's really necessary to glass those edges anyway. I like a clean line where the glass wraps to the other side, so I put masking tape around the opposite side where the glass would lay down. (After doing the whole board, I'm unconvinced that the trailing edge needs to be wrapped in glass while glassing the side of the cb, and its a kind of significant PITA to get the glass to wrap properly there.) I taped the edge of the glass to the masking on the opposite side and wetted it out. After the epoxy was green, I trimmed around the 90degree edges at the top of the board and along the masking tape on the back side. I repeated the process for the other side (probably after sanding and faring some spots with microballoon thickened epoxy).
For the edges, I used 12oz tape. I think I'd do that again. Thats why I dont think wrapping it earlier was necessary. I stood the cb in a vice and cut darts in the tape at the corners and wetted the tape out. It mostly worked, but needed some babysitting to prevent bubbles from forming, especially on the trailing edge of the cb.
I used epoxy thickened with microballoons to fair the cb, then painted with 2 coats of epoxy mixed with graphite. I cant remember if I also used a bit of fumed silica in the mixture. I think about 70%graphite/30% silica mixed to about 3T total per 8oz of epoxy, give or take.

I did inadvertently fill the cb pin hole with epoxy, but it cleared easily with a dremel tool. I’ve heard there are ways to prevent that though, like stuffing the hole with gloves or ear plugs or something.

I hope this helps. Good luck!
Jenn
Marc
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Re: 525 under construction

Post by Marc »

Hi Jennifer
Thanks a lot. I'll let all that info sink in. I also went to see Jason Talbot's videos ( Argo) and that is informative too.
I have a couple of questions: 1- I constantly read "green" with epoxy and don t understand...
2- The manual refers to bronze into the cb hole for the pin to slide in. It tells us the length but not the width and the plans dont state the hole's diameter. So what is the diameter ( outside and inside ) of the bronze part? It also says 4 bronze sections and I can't see why only one from side to side would not do..
Jennifer J Harold
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Joined: Mon Aug 03, 2020 10:17 pm

Re: 525 under construction

Post by Jennifer J Harold »

Hello!
Green: hardened but not fully cured. My favorite time to cut off excess glass is when the epoxy in the glass is still sort of pliable, but soft enough to run a razor knife through.
The bronze is for the bushings in the walls of the centerboard trunk and in the centerboard. When you source the bronze tubing, it'll usually be too long for the wall of the trunk, but too short for the centerboard. Therefore, its necessary to cut them to size for the centerboard trunk, and put two into the centerboard. With two in the centerboard, the total length is too long, so you need to trim them.
Dimensions: ID is the same as the cb pin (1/2"); OD is 3/4". If you're building a kit, the precut holes in the cb trunk are slightly undersized on purpose.

For the cb pin, I bought a 1/2" bolt that was long enough for the unthreaded part to go through the entire trunk so I could cut off the threads. I think it was 6" long total, but double-check that.

I found th Argo blog helpful too. Good luck!
Jennifer J Harold
Regular Contributor
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Joined: Mon Aug 03, 2020 10:17 pm

Re: 525 under construction

Post by Jennifer J Harold »

I re-read your question and understand better.
The bronze bushings are built in to the cb and trunk walls to prevent chafing when the cb pivots around the pin, to they must be separate pieces since the cb moves but the walls don't.
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simeoniii
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Re: 525 under construction

Post by simeoniii »

Marc, I think Jenn answered your questions. Here's a link to an old post from 2012that may be helpful.
viewtopic.php?p=1681#p1681
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Simeon
Voyaging with Noddy, #11
Marc
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Joined: Thu Feb 04, 2021 5:18 pm

Re: 525 under construction

Post by Marc »

Hi JenniferThanks for the answer. Ai was on another post (mast substitue) and
Asked the sme question there.where i was told you had answered! Hadn t seen it. I bought a3/4 OD iron tube just to see and there is soooo much space lest It convinced me 3/4 od was too wide. Also the manual does not say to drill the board hole. Maybe the iron tube walss are thinner than bronze...will measure.
Marc
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Re: 525 under construction

Post by Marc »

I went to see another post on the centerboard pin. And a 7/8 bushing is used..
More confusion for me. I guess I will just have to try and fit what I feel is the best.
The picture above shows a tight fit, apparently.
Sorry for all the spelling errors above. I wrote real fast.
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