How Big a Gap for Keel Slot?

[Mist]

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I'm sticking with the traditional method of installing the keel box (no shims like the pdx folks). I've got the keel faired to the point I can build the sleeve around it. But, I don't know how big of a gap to have between the keel and the box. Any suggestions out there? I don't want the keel to slop around (too big of a gap) or get stuck (too small of a gap).

tf, thanks for the help refreshing my mind how upload picture to this forum.

[micah202]

,,,beautiful blade!

the 'issue' with having a form-fitting keeltrunk is that the keel-blade MUST stay perfectly in column with the trunk while raising/lowering.Even with a 1/8'' gap built allround the blade,and resulting slop while sailing,,it'll still jam when it's not perfectly in column.

...a VERY good reason to have a bigger keel- box,with some sort of shims,,,is the possibility (or eventuality)of hitting bottom sometime.--with a tight fitting trunk,there's (much) more chance of causing nasty damage to the trunk/boat.

...wedging doesn't have to be for the intent of adjustment,,,it can be as simple as 2x3/8'' peices of PVA sheet plastic bolted to the keelsides inside the box,,with slots in the trunk-sides for these to lock into,,,and have the trunk go ~2'' back behind the blade,,with foam filling that void.
...if you use ~1/4 bolts for the PVA 'wedges',,,these will give-way rather than the trunk or boat

[Chad]

I don't like the keel-shaped sleeves, either. But if you insist...

I'd taper the sleeve, so it's tightest at the bottom and opens up maybe 1/8" at the top -using increasing layers of masking tape is the method I'd try first. Also, add a piece of split tubing to the aft edge of the keel to give that fragile edge plenty of clearance. Then wrap in plastic and proceed with the sleeve layup.

Then how to fill the gap? Pourable urethane (like spartite- there's much cheaper versions available from McMaster, needs at least 1/8"+ annular space to pour into) is one option (I'd only pour the bottom 2" or so), or (and) use tapered strips of delrin adhered to the keel head. Or a +/- 1/8" horizontal delrin strip at the top of the keel, that you shave to get the fit as tight as you need.

Edit: oh, and nice looking foil, too!

[jray]

Tim, I rapped the blade with thin plastic, if I remember it was 2 mil, then covered that with thee layers of 6 mil. The trick for me was to get the plastic to slide between the layers. It took me two tries to get what I thought was an acceptable sleeve. The cloth I used had a tendency to loosen when I wet it out with epoxy. That was because I was working to many cloth layers at one time, the second attempt I worked one layer at a time and the results were better. I would also suggest pulling the sleeve off your strut while it is still green and a little flexible.

[micah202]

Tim, I rapped the blade with thin plastic, if I remember it was 2 mil, then covered that with thee layers of 6 mil. The trick for me was to get the plastic to slide between the layers. It took me two tries to get what I thought was an acceptable sleeve. The cloth I used had a tendency to loosen when I wet it out with epoxy. That was because I was working to many cloth layers at one time, the second attempt I worked one layer at a time and the results were better. I would also suggest pulling the sleeve off your strut while it is still green and a little flexible.

..sounds like your dealing with both a tight/tricky up/down,,AND some shiming,,AND being vulnerable to a hit all at once

[Mist]

Wow! Certainly a lot of options to consider. I need to think this out before I jump. I was hoping to fabricate the sleeve this weekend. I'll surf a few more blog sites and consider the replies above. Thank you and I'll keep you informed.

[jray]

..sounds like your dealing with both a tight/tricky up/down,,AND some shiming,,AND being vulnerable to a hit all at once[/quote]


Actually no shiming, no problems raising or lowering the strut. The clearance is around .030 each side which makes .060 all directions. I'm only dealing with less then 9" of sleeve/cassette not 19" and the strut tapers quickly after leaving the hull. I tie down solid and haven't had any vibration problems yet. When I was building the only example I could find was Andrews from his build pictures, which I copied for the most part. In fairness I'm unaware of what Eric is doing with the Portland builds. My plan is not to run aground, If it happens I'll fix it. No problem I know every inch of the boat.

[admin]

I posted a reply last night but I musta did it wrong and it isn't on here, but in essence, it agrees about 100% with what Jray is saying above. I think there's a tendency to over-think and over-engineer these things.

Most of the load from the keel goes to the beefed up woody bits and the sleeve is more or less just a barrier that keeps water on the outside of the hull from becoming water on the inside of the hull. At least, that's the way my ride is going to roll. The foil slides up in down in it. If it gets tight, I'll sand it a little and bang on it with a mallet. If it's sloppy I'll bang some delrin sleeve down into it.

Where Tim K and I sail, the bottom is pretty forgiving, but even so I do not plan on running aground.

[admin]

Also: I forgot to compliment you, Mr Mist, but that is one gorgeous foil pictured above!
And: not sure I can find the link, but if you want to see a really slick way of seating a keel in a sportboat, google Brian Jones'es "Problem Child" build. I'll see if I can find the link and or pix...he sent me some a couple years ago and I squirreled them away somewhere, but lord only knows where-at!

[Tim Ford]

Yukon see the inverted prism shape in his CAD drawing here: http://bcboatworks.com/default.htm
That would be "Problem Child."

[Chad]

I think there's a tendency to over-think and over-engineer these things.

I resemble that remark!

[admin]

HAH! yeah, you do , but the stuff you do is so amazing and the level of craftmanship is so fine, we can only step back in awe. Keep doing what you are doing and let us aspire to those heights!

Besides, it ain't over-engineered when yours don't break and ours does! Could've used you on PUMA Overpowered by BERG a year or so ago.

[Mist]

tf and Chad, I did find myself over engineering the keel sleeve. I wrapped the keel in three different arrangements only to scrap all of them. Finally, I just wrapped the keel with four layers of 3mil plastic, add a few extra layers 3" inches from the top and bottom, and three strips along the aft edge. The extra layers provide room for the glass tape when I glass the cockpit floor and hull bottom to the keel box. I used two layers (one 6oz and one 10 oz) for the sleeve. Once it was cured I reinforced the top front and lower aft corners with another layer of 10 oz cloth. Lastly I epoxied cedar strips to the sides. Hopefully I can measure, align, and glue the keel box in this week. The sleeve easily slides along the full length of the keel. Thanks for the assistance.

[Mist]

I meant thanks for the assistance to everyone not just tf and Chad. Another useful tip provided above was to remove the sleeve while the epoxy was still green. That works slick!

[jray]

Looking good Tim! Another step done.

[Kevin]

Tim K, Nice looking foil and sleeve !!!

Sorry for the late chime in.

I can assure everyone that a too tight keel box really sucks. Especially when it's an hour driver to the lift you are using and you have to come home with your keel not in the boat. Been there and there was no stinkin' t-shirt. My foil was not fully finished when I made my sleeve and that was a big mistake. I wrapped with plastic to allow for finishing, but it wasn't enough. I now have no sleeve in by keel box after cutting it out with a dremel. There is a little too much play in the keel box and little bearing surface at the hull (1/2" all the way around) for the keel to hull interface. The box is coated with epoxy on the inside so now real worries, but it's pretty fugly at this point and the keel looks like crap and only get's worse. Dream solution is a new foil and a replaced keel box, but that's not happening right now.

My thought on potential impact issues is that they will happen. Count on it. When it happens your very strong keel strut will stop moving and your boat will want to continue moving. That force will go somewhere. With a tight joint the load should be disbursed across most of the keel box. But if you have slop you will get point loading at the leading edge at the top and at the trailing edge at the bottom. The more slop you have in the box the more point loading will result. Either the box or the keel will give in the end. Andrew reported after running aground at 15 knots that he needed to repair his keel box (which was too tight). Beyond that, no one else has had any major issues.

Good luck placing that keel box and keep the pictures coming.

Kevin.

[Mist]

Mist's keel box is installed. Now I need to add the glass cloth and finish the the lower bunk support. Notice the small wooden pads (aft lower and top forward). Hopefully, they'll support a slow speed grounding. I'll have floatation bags in the boat for the high speed grounds, a different problem all-together.

[jray]

Looking good Tim! The sleeve looks like you used some carbon, maybe its just the light and camera angle. Mist is getting there, good job!!

[Chad]

I like the way these guys reinforced their hull bottom for grounding loads, using 3 tapered layers of biax (last pic, can't link to it directly):
http://thegt6.blogspot.com/2010/08/fitt ... l-box.html