Centerboard optimization opportunity.

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Centerboard optimization opportunity.

Postby baggywrinkle » Mon Feb 05, 2018 1:30 am

Hello, and thanks for being here and for being helpful.

I own a dinghy that's likely a DS clone rather than a true DS, but I believe this discussion to be applicable to all DS owners. No member replying so far (at my other thread) has seen a DS like it, due to its molded cockpit. The CB trunk has a tackle assisted shortened bronze DS style handle, and no interior cables. Pictures are on page one of that thread, linked below.

A member mentioned that DS CBs are underdimensioned. Hence I welcome the opportunity to enlarge it. As a guinea pig. Or maybe others have already done this, or know of another......?

This boat's CB is problematic. I concluded the CB needs to be modified for seaworthiness. Also it is undersized. So I may as well optimize it while I am at it. Class rules would not be an issue here on Hawaii waters. However the Wednesday Night Races represent a serious concern. A chance for everlasting glory. Beating against the tradewinds matters.

The trunk can accommodate roughly 51 X 14 inches of board. The board in question now is 51" X 12". The position of the square hole causes about two inches of the leading edge to remain protruding when in up position, and about two inches of empty trunk space above CB when in up position. Therefore I will add almost two inches to the trailing edge.

Since I'll be doing surgery anyway, my idea is to add some area to the leading edge of the CB. Hence my request is for suggestions/advice on how much to add. I suppose I could just add a generous slab, and remove some, or raise it a bit, if it costs me too much in weather helm.

Questions include; Parallel to trailing edge ? Other? How much ? If the board's leading edge is not parallel with the trailing edge, I think it should be wider at the top, (to avoid increasing vibration). I heard that vibration may increase with area added forward of the pin.

The added section would be sacrificial, for avoiding damage to the trunk, should the board meet a hefty submerged object.

(apologies to other members if this has been hashed out before I showed up. I did a search and read some before writing this)

Background on my yellow boat is at this thread, with pertinent CB details mostly on page 3.
viewtopic.php?f=2&t=5641

Thanks again, I appreciate this bunch of helpful sailors !
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Re: Centerboard optimization opportunity.

Postby baggywrinkle » Mon Feb 05, 2018 3:54 pm

Well, now someone familiar with foils tells me I may want to reconsider my plan to increase the CB width from 12' to 14' in order to fill the trunk. He said that higher aspect foils can be more effective. I was thinking that adding 2'" to the trailing edge would enhance upwind performance.

That would nix my idea of adding area to the leading edge. Opinions, please ?

The CB I have is 12" X 50". Rudy tells me his new DS boards are 14.5" X 50" . They weigh 55 pounds with the lead.
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Re: Centerboard optimization opportunity.

Postby TIM WEBB » Mon Feb 05, 2018 11:45 pm

Would it be a useful exercise to remove your CB and make a side by side (or stacked?) comparison to a known/stock DS CB? I realize that if there are no DS's nearby it would be an expensive proposition to get a DS CB to compare to, but it might save you a lot of unnecessary headaches and wasted effort?
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: Centerboard optimization opportunity.

Postby Alan » Tue Feb 06, 2018 12:29 am

https://www.drmarine.com/proddetail.asp?prod=DS106

Is the centerboard Rudy mentioned the one in the link above? Class-legal Daysailer centerboards are supposed to be no heavier than 25 pounds, if memory serves. My DSII will never be a competitive racer and it'll sure as heck never be lightweight, so a 55-pound centerboard could be tempting.
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Re: Centerboard optimization opportunity.

Postby baggywrinkle » Tue Feb 06, 2018 1:22 am

TIM WEBB wrote:Would it be a useful exercise to remove your CB and make a side by side (or stacked?) comparison to a known/stock DS CB? I realize that if there are no DS's nearby it would be an expensive proposition to get a DS CB to compare to, but it might save you a lot of unnecessary headaches and wasted effort?


Yes it would be a useful exercise. I dont have dimensions and weight of a legal/stock DS CB, unless Rudy's boards qualify. It was earlier today I called Rudy for DS CB dimensions. He said his are 50" X 14.5", and 55 pounds. Price $545. Or $575 with the bronze square hole fitting. We had a laugh about freight to Hawaii. He sent one to Alaska for $275 freight. He said the CB price has not changed in 6 yrs, crediting the guy who makes them who "does a great job".

I think I'm now past the stage of headaches and wasted effort on the CB. Hopefully, that is. As you suggest, I just need to decide on what the finished dimensions shall be.

Mine is 51" X 12", with the square hole positioned so the board protrudes when it is up. The lower end is cut straight across, not rounded like Rudy's. I dont need a new one. I just need to modify the one I have. Some of the leading edge will be cut off so it no longer protrudes when up. I thought I should add some to the trailing edge so it fills the 2" empty space in trunk above CB when in up position. I was thinking 51" X 14". Now I need to decide whether or not to do that since today I heard that a high aspect foil is more effective than a low aspect foil. There I was simply thinking bigger is better, especially since I heard that DS boards are underdimensioned.

According to Alan's info below, it sounds like Rudy's boards are overweight per class rules.


Alan wrote:https://www.drmarine.com/proddetail.asp?prod=DS106

Is the centerboard Rudy mentioned the one in the link above? Class-legal Daysailer centerboards are supposed to be no heavier than 25 pounds, if memory serves. My DSII will never be a competitive racer and it'll sure as heck never be lightweight, so a 55-pound centerboard could be tempting.


Apparently so, as he referred to that page, saying all his DS boards are the same size. He said he has to crate them for shipping because "...the clowns at UPS always damage them. I guess they throw them around and drop them...".

OK I just weighed mine.....16.6 pounds, 51" X 12". It has some lead shot in resin, in the bottom end. Weighed after grinding off a fair amount of its foil fat, which prevented it from going all the way into the trunk. The other issue of course being the location of the square hole causing a couple inches to protrude when CB is 'up'..


Thanks Guys !
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Re: Centerboard optimization opportunity.

Postby TIM WEBB » Tue Feb 06, 2018 1:48 pm

This may or may not be an obvious question, but is it possible that the CB is simply installed the wrong way? If you have room at the top, and it protrudes at the bottom, could you simply flip it around? Or fill the existing pivot hole and put a new one where it needs to be to have the board fit the trunk correctly?
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: Centerboard optimization opportunity.

Postby GreenLake » Tue Feb 06, 2018 10:30 pm

Excellent point. Usually, a straight edge is a the rear of a board (and should be up, when retracted).

The difference of quoted 55lbs to 25lbs might be a slip, or, if real, it' just going to be good - you don't need to follow class rules if your hull isn't a true DS (as we suspect, but can't prove) and an extra 30 lbs might just well make the boat a bit nicer to handle when it starts to heel.
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Re: Centerboard optimization opportunity.

Postby baggywrinkle » Wed Feb 07, 2018 4:09 am

Pic below of the CB in question.

Pic taken after its beautiful foil shape was mercilessly ground off. It was too fat to fit in the trunk. Hence I deemed it unseaworthy in the event it is struck by a submerged log. It could have fractured the trunk if it got forced up in there. Somebody put a lot of time into making a really nice laminated CB with a great foil, and I ground off the foil in minutes with a monstrous grinder. Tsk, tsk. A shame, really. Now with the slimmer CB up in the trunk, there is about 1/4" clearance on each side. I will add some conciliatory new foil to it, after it comes out of surgery. Remind me to leave room for a couple coats of bottom paint.

The black/gray is lead shot. Next to the lead, you see the corner is rounded. It was straight across, as I mentioned earlier. Thinking that the 90* corner was causing it to jam and protrude (It wasn't) I mistakenly rounded off the square corner. That was before I discovered that measuring things can be really helpful sometimes. I just never dreamed the board was too fat, the cause of the tail end protruding 3.5".

I guess the straight across bottom edge shape with 90* corners was no accident, ie for performance...? Anyone know about that?

Thats an old FGlass Thistle between the yellow mystery ship and the ancient dugout.

Last nights rain flooded the yard. They pump it out. Mudville.

The trailing edge is the white edge (right side of CB in pic)

Centerboard, ancient dugout.jpg
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Last edited by baggywrinkle on Wed Feb 07, 2018 4:30 am, edited 3 times in total.
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Re: Centerboard optimization opportunity.

Postby baggywrinkle » Wed Feb 07, 2018 4:14 am

TIM WEBB wrote:This may or may not be an obvious question, but is it possible that the CB is simply installed the wrong way? If you have room at the top, and it protrudes at the bottom, could you simply flip it around? Or fill the existing pivot hole and put a new one where it needs to be to have the board fit the trunk correctly?


Thanks Tim,
Alas, if only it were so. 'Twould be simple a solution. However, 'tis not the case. I considered relocating the hole. I instead decided surgery on the board was the way to go, considering I had to operate anyway due to dat fat foil.



GreenLake wrote:Excellent point. Usually, a straight edge is a the rear of a board (and should be up, when retracted).

The difference of quoted 55lbs to 25lbs might be a slip, or, if real, it' just going to be good - you don't need to follow class rules if your hull isn't a true DS (as we suspect, but can't prove) and an extra 30 lbs might just well make the boat a bit nicer to handle when it starts to heel.



Thanks GreenLake,
I thought so too....So I called Saint Rudy of Assonet again today to confirm the weight of his boards. Yep, 55 lbs. He said they vary from 51-55 pounds since each one is individually made by hand. Yep, he (aww shucks) knows the class rule re CB weight. He said lotsa people like 'em heavier.

I'll be shopping for some lead this week. May as well shoot for a 50+ pound CB while I'm at it.
.
Last edited by baggywrinkle on Wed Feb 07, 2018 1:04 pm, edited 5 times in total.
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Re: Centerboard optimization opportunity.

Postby baggywrinkle » Wed Feb 07, 2018 4:17 am

Here (pics) is the slimmer CB now in retracted position for marking cut line. Due to the pin hole's location, it protrudes when retracted. I'm not thrilled. My friend thinks I'm nuts (he's right) because I worry about submerged logs and protruding centerboards teaming up to ruin a sailor's day.

So I marked the leading edge for cutting off and reshaping. May as well get it right before re-launch.

Because it is under-wide, the after end now can tuck up out of sight, but I will cut parallel to leading edge for correct re-shaping. The wooden board is also shaped in a foil. After thusly 'fixing' the leading edge, the CB will be about 10" wide. So I think I must add some area to the trailing edge. There are a few inches of vacant trunk space available up there.

Thats the other "discussion" with my friend ie whether or not a (high aspect) foil needs to be wider. Well, it cant have much of a foil since the thickness cannot increase more than about 1/2" due to trunk width. This makes me think I should make the board wider. Thoughts?

By the way, when it was too fat, the after end protruded about 3.5 inches.

Two pics: fwd end and aft end. Poor lighting I think maybe.

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Centerboard frwrd end.jpg
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Centerboard  after end.jpg
Centerboard after end.jpg (95.2 KiB) Viewed 2586 times

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It really was a nice professionally made CB. They won lotsa races, I'm told. I hope to do it some degree of justice.
But I also want to go sailing. This year.
.

Here is that other pic again. May help see what's what in the two pics above. By the way I just got contact info for prior owners that won races and probably built the nice CB I am "fixing". Maybe they will know more about the yellow sloop's heritage and pedigree. Or maybe they will shoot me if they've seen this thread.
.
Centerboard, ancient dugout.jpg
Centerboard, ancient dugout.jpg (118.54 KiB) Viewed 2586 times

.

.
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Re: Centerboard optimization opportunity.

Postby TIM WEBB » Thu Feb 08, 2018 1:34 pm

I'm curious about what appears to be a "notch" in the trailing edge (?) of that CB? Seems to me that would weaken it substantially?
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: Centerboard optimization opportunity.

Postby GreenLake » Thu Feb 08, 2018 11:17 pm

Been wondering the same.
~ green ~ lake ~ ~
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Re: Centerboard optimization opportunity.

Postby baggywrinkle » Fri Feb 09, 2018 2:37 am

TIM WEBB wrote:I'm curious about what appears to be a "notch" in the trailing edge (?) of that CB? Seems to me that would weaken it substantially?



GreenLake wrote:Been wondering the same.


Work in progress.

That prior post's pic shows rough results of grinding off the fat foil. It was such a lovely foil. before I got my hands on it. Oh well. Safety first.

The notch(es) you see are dings in the white,now nearly paper thin remnant of the thickened epoxy trailing edge, (after grinding off more epoxy, FG, and paint). The edge is history anyway. Up to 4.5 inches width can/will/may be added.

Any thoughts on importance of making it max width ( 14.5" ) vs the 'high aspect foil is better' assertion?
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Re: Centerboard optimization opportunity.

Postby GreenLake » Fri Feb 09, 2018 1:43 pm

I think the most important thing would be to make sure there's a remnant of a reasonable foil shape, not just some flat half-profile like this: \____/

By thinning the board, you've also reduced its strength a bit; more than you realize perhaps. Maybe you should hold off increasing the area.

I'm still concerned why a reasonable foil shape didn't fit your trunk opening, but that's not something we can diagnose remotely and you are done.

Incidentally, the same things with grinding a shallow channel and embedding several layers of unidirectional roving applies to the CB as well, should you be concerned with strength.
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Re: Centerboard optimization opportunity.

Postby baggywrinkle » Sat Feb 10, 2018 6:00 am

Thanks GreenLake !

GreenLake wrote:I think the most important thing would be to make sure there's a remnant of a reasonable foil shape, not just some flat half-profile like this: \____/


By thinning the board, you've also reduced its strength a bit; more than you realize perhaps. Maybe you should hold off increasing the area.

I'm still concerned why a reasonable foil shape didn't fit your trunk opening, but that's not something we can diagnose remotely and you are done.

Incidentally, the same things with grinding a shallow channel and embedding several layers of unidirectional roving applies to the CB as well, should you be concerned with strength.


a) The latest plan was to add as much foil as the trunk can accommodate. That means the board can be about 15/16" at most. Maybe one inch. Including paint.

b) Well, the lovely original foil (now dust) was simply too fat to fit. Fatter than the trunk's interior could swallow. It was fat. Apparently foil value was deemed more important than CB retracting all the way.

c) Yes I hear ya re strength loss. Especially with more of the wood CB core cut out for lead slabs to fit in. Hence, actually, seizing the opportunity further now, a new CB is on the drawing board, as follows.....roughly, mind you. Final details (and feasibility) are yet to be determined.

* Finished thickness shall be 15/16". Maybe 1" if more precise measuring of trunk interior allows it.

* Width to be determined. Preferably more than the 12" wide it was. Trunk allows approx 14.5" CB width.

* CB innards shall be 2 or 3 Rows of roughly 3" X 4" slabs of lead, encapsulated in epoxy, in the cavities between 1/2" thick foil shaped bones. The bones will be skinned both sides with plywood or fiberglass sheet, 1/8" thick. That brings the thickness to 3/4". Covering that with glass/epoxy, and paint should bring it up to the 15/16" or 1" inch target.

The foil bones will be drilled to allow 5/16" or 3/8" SS threaded rods to pass thru from top to bottom, between the rows of lead slabs. Thinking the tightened nuts at bottom end will stiffen/strengthen the product.

Configuration of the foil bones, slabs, and rods yet to be determined. Whatever fits. The lead slabs can be cut, to get it right.

The following part is theoretical only, ...at this point. It addresses the top end. Hopefully it can work.

Roughly 16" of the old CB (now a stub) containing the pin hole may be saved. The stub gets widened to match the new build which gets grafted on to it. The SS rods would be epoxied into holes drilled into the stub.

The grafting is partly to re-use the bronze hole fitting in situ, rather than have to new build an entire CB. But if necessary, I will.

Meanwhile, the friend I got the boat from says: "Baggywrinkle, just cut your new board out of the (his) Thistle's FGlass CB, put a square hole in it, and go sailing asap." He is right. Again. Nobody is buying the Thistle. It has to go.

You see, I had told him I decided to turn my CB into a coffee table and only sail downwind from now on. He is very knowledgeable, generous and helpful. He also came up with the SS rods part of plan A, above. Actually, that is more like plan B or C or J or Q, at this point)

I will take him up on the Thistle's CB. Clock is ticking. Build dream board later.... ....Yeah, right, I might wind up just living happily with the Thistle's CB and never build the new one. (Worse things have happened).

For the lead you need, Mr Okuda's shop is the place to go. He has a big pile of it, recently removed from a warship in Pearl Harbor shipyard....

Mr. Okuda's shop.jpg
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Last edited by baggywrinkle on Sat Feb 10, 2018 12:45 pm, edited 1 time in total.
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