Centerboard pivot setup or modification.

[persephone]

I have the centerboard out of my DS 1. The square section of the handle is worn to a slight taper (this allows the board to move a bit in two axis). I also noticed that the pilot of the handle doesn't reach the other side, and there does not appear to be a bushing in the trunk for the pilot to pivot in.
Is the handle supposed to pivot on one side only? Has anybody modified the trunk and handle to use two bushings (one on either side of the trunk) to better support the centerboard and keep it from moving around?

I have the ability to engineer a solution, as well as make the modifications to the handle and trunk to allow for a two bushing setup. Is it worth doing?

[kokko]

I can't answer yor question, but can you tell me how difficult it was to remove the cb? Did you do it while the boat was on the trailer?

[djd]

I had a centerboard problem in my DS 1 a couple of years ago. Like you I found the square piece was worn and wondered why there was no support on the port side. When I got into it, I found there was a metal (brass?) plate glassed into the inside of the trunk with a small dimple or divot in it. I reasoned this dimple was there to support a pin or boss that extended from the square end of the center board actuator. My actuator had nothing sticking out and I assumed it had just broken off over the years.

I drilled and tapped the square end of the actuator with a 1/4-20 thread, then screwed in a stainless bolt (about 1-1/2" long?) with a round head. Before threading in the bolt I put several nuts on the bolt to use as jam nuts and to help stiffen the 1/4" thread. I put the actuator in place temporarily without the centerboard and adjusted the projecting length of the screw so the head fit up snugly into the dimple, then locked it there with the jam nuts. Then took it back out and re-installed with the centerboard in place as normal. The screw head acted as a support on the port side.

This worked OK, but I found my center board trunk was considerably wider then the center board. This allowed the centerboard to slide from side to side. So much so that at the extreme port side it almost disengaged from the square part of the actuator. I was going to make up a thick plastic washer to take up the space, but decided to make up a whole new actuator instead, with a longer square section. I did install a spacer washer along with the new actuator to keep the board from sliding side to side.

My original actuator did not have the projection or the locking pawl that is supposed to be on the DS 1, so I assumed it was not original. Maybe it was?

Hope this helps...
Dennis

[persephone]

Thanks for the info. That clears up what the original design was. The pivot handle of mine does have a small pin at the end of the square section.
Not really much of a pilot to keep a side loaded centerboard in place though.

Were you able to discern any improvement in the boat handling or performance after you modified it?

[djd]

I don't use the boat that much - no racing - so can't say I noticed much of a performance difference. However, raising and lowering the centerboard felt more stable and secure.

Also I added the locking pawl feature and this comes in handy. When I got the boat, the PO and drilled a hole thru the upper part of the trunk and the centerboard. We had to put a pin thru the hole and board to lock it in the raised position. The hole let water into the CB and the board was cracked probably as a result of ice expansion.

Did your mechanism have the locking pawl feature?
Dennis

[ssawyer]

I am interested in this as well. For my 1985 Spindrift Daysailer 1, my basic question is: Is the centerboard handle pivot supposed to go all the way through the centerboard and rest or lodge in the opposite side of the centerboard trunk?

When looking in the centerboard slot (from the bottom), I also have what looks like a small bronze bushing on the opposite side of the centerboard trunk. However, when I insert the handle through the centerboard, it doesnt quite reach across to insert into that bushing.

Is this normal? Or is the handle only supposed to mount (and be secured) on only one side of the centerboard trunk?

Thanks!

[persephone]

Sounds like the spindrift is similar to the Can-Am (I think that's who made my boat although she carries proper O'Day ID in the HID#). My original handle didn't reach the far wall of the trunk although there is the bronze plate with a divot in it for the nose of the handle to pilot in,
What I have decided to do is replace the part of the handle that goes through the cb with two pieces, a thru-bolt and large disc spacers on either side of the cb to eliminate the excess play. It's hard to describe what I'm doing. I'm having a machinist remove the old cb shaft from the handle and make the two new parts. I drilled a small hole through the far wall of the cb trunk, the bolt will pass from that side and thread into the handle. I'm also making a brass bushing for the handle side to ride in rather that wearing away the fiberglass.

[persephone]

Forgot to mention to Dennis, my locking pawl is missing. I'm hoping the tension from the thru-bolt will eliminate the need for it.

[K.C. Walker]

Okay, it's a little OT but you guys brought it up first (Phill & GreenLake). My centerboard trunk was showing some problems anyway. However, I had not noticed the thin walls of the centerboard trunk flexing, that is until I went out there and pushed on them and grabbed the handle and flexed it and watched the centerboard walls flex.

However, I had noticed that my centerboard trunk was a bit canted. I did some measuring and found that the thwarts were different in length by 1 inch. I also noticed that the front of the centerboard trunk did not line up with the keelson and in the same direction. I got poking in there with a chisel and found that the original glassing work between the keelson and centerboard trunk was not adhered very well. So, I decided to go at it. Apparently, they had not sanded the gelcoat before glassing those parts together. Also, I think it must've been Friday and already beer time.

Once I cut the fiberglassed tabbing out the centerboard trunk lined up with ease. I cut the long thwart and taped the piece to the short one as a shim. Everything lined up so I started to glass it all back together. I figured while I was there I would go ahead and reinforce the centerboard trunk walls around the pivot point. I had some extra corecell so I decided to use that. I put a little carbon fiber cloth down and then glued the corecell to that. I'll do carbon fiber cloth on the outside and then cover that with glass.

Because I have not worked with this material before I thought it might be a good small project for a shakedown. Here are some pictures from today http://www.walkerguitars.com/photos/daysailer/CB/

KC

[GreenLake]

K.C.,
some thoughts/comments: First, as always, thanks for sharing this. Next, I note that your trunk has this cute 'cap'. Something mine doesn't have - it's all laminated in one piece.

I think your corecell is going to be effective in distributing the load over a wider area - but I doubt that you will get any benefits of having used carbon fiber other than perhaps a bit of weight. The reason is that the carbon sits on what will be the inside of the skin for your sandwhich. Because of geometry, it would seem that most of the tensile load will simply go to the existing laminate. I also wonder whether that layer was even necessary at all (except if you had evidence that the laminate of the CB trunk walls had already failed).

What could make a bigger difference might be whether and how well you round the corners and fair the edges of your reinforcement. Right now, it looks like you are going for all right angles and abrupt transitions in strength. I'm afraid that sets you up for stress cracking if you're not lucky.

For the outside laminate, I think you are into overkill territory, but I know I won't be able to talk you out of your carbon fiber

I bet that a single layer of glass, even ordinary fabric, not biaxial, would probably be sufficient for the expected tensile loads, and as your corecell sounds like it supports out-of-plane loads really well, there's less need for providing impact protection via a thick skin.

[K.C. Walker]

Well, not only OT but totally in the wrong thread. I meant to post this in the core project. I will move it there.

Greenlake, thanks for your comments.

[Phill]

Back On Topic... (reverse OT is To ??) Topic On. ??? now i'm cornfused.

My solution for the 'not quite long enough' CB handle axle;

Brass tube that fit over the round end of the CB handle spindle. From hobby shop, thin wall, good fit.
Placed it over the round end. Cut to just reach across the gap to the reciever.
Drilled the center of the round end of the spindle, and put in a small longish self tapping screw, long enough to reach accross the gap to the "reciever' on the opposite side from the handle. A brass rod that fits the drilled hole would do the same thing.
Filled the brass tube, rebar (screw) reinforced, with "Marine Tex" (white, no reason, just trying to be accurate)
After the Marine Tex cured, shaped it to more 'comfortably' sit in the reciever. (please dont ask me about all the uses I have found and successfully used Marine Tex) We would need another thread catagory)
problem solved.

now back to your favorite OT'ers !

[persephone]

So I thought I would post some thoughts on my modifications to the centerboard pivot after this season and some racing.
Overall the mods worked well. I ended up nixing the bronze bushing on the handle side if the cb trunk. Too difficult to get the bushing epoxied in in exactly the right orientation. With no sealant or gasket the handle leaked more than I liked, but no more than 1 gal/hour.
Tension was excellent and adjustment is possible. I eliminated the need for the outer plate and locking pawl.
Although my spacer discs are too thick (requires lube, long bar and hammer to install cb and discs to say nothing of flipping or careening the boat... lots of fun in the mud flats in Chatham harbor at 6 pm the night before race one after a 12 hour day chasing down the needed replacement parts for my illegal stays...) the board does not have any motion outside of the intended pivoting motion. The downside to this (I should have expected rom KC's comments about the trunk walls) was the trunk cracked open right underneath the factory installed reinforcing during race 3 on Sat of the NACR ending my first major regatta.
My father who was my crew for the NACR and helmsman for our last race (our best finish I might add), who has 35 years experience said it was one of the best handling boats he has ever sailed, and much better than his old DS1 (a #3k boat).
If I have the cb out this winter I will try to remember to snap some pictures of the parts. It wasn't cheap and it isn't a fix that anyone could do (at least not exactly as I did it), but I think there were some good simpler solutions posted here to this problem. It's well worth taking the time to do as a floppy board will act much like the control surface of an airplane pointing and shifting the boat in unintended directions.

[K.C. Walker]

So, I've been thinking about this since I read your solution to the problem.

I approached it differently, however. I decided that the axle had not as much to do with the stability of the board as the "board to the trunk fit". It seemed to me that I was not going to be able to get a good enough fit between the axle and the board to make it do much of anything for stability. So I shimmed the board carefully with high-density polyethylene. I made it just a slip fit. With a little bit of use it started working great. The high density polyethylene acts as self lubricating so the board, though stays in place well, moves fairly easily. I just used shims at the very top of the board and just at the opening to get the most stability. This also made fitting pretty straightforward. Each shim is a 2 inch wide strip. Along with the reinforced centerboard trunk it feels very solid.

I also did a fairing job on the centerboard while I was at it (it's a stock one). I still think I'd like to make a new centerboard that is a better foil shape, though.

KC

[persephone]

K.C. Walker said:

I decided that the axle had not as much to do with the stability of the board as the "board to the trunk fit"

I think you are 100% right on that. As I had access to a machinist at a reduced cost I decided to take on both issues, but if you have to pick one the board to trunk fit is the one to do.
I also like the use of self lubricating materials. The material I used, while not high in friction is not slick. The upside to that is the board stays where I put it under most conditions without any external device to hold it there.