DS1 Centerboard shims

[kokko]

I need to shim my cb to reduce the wobble. As many DS1 owners know, the CB is about 1" thick and the trunk is about 2". The pivot point is a square rod through a square slot in the cb.
I have reviewed all the old posts on this topic and wondered if any consensus has developed on tackling this problemm, other than the cb should be shimmed.

Some have added shims to the cb itself. I don't hink this is ideal since the shims would be parallel to the direction of travel only when the board is fully down. If partially down it might act as a brake.

Others shim the cb trunk opening. Some seem to have shimmed what seems to be the entire opening, but I wonder if that is necessary. I have thought the best solution is to glue/bond/screw plastic shims that are about 1/2 x 1 x 12 to the opening.
Some have used formica strips, and others use either PVC or polyethylene. Formica and pvc are fine for bonding with 3M 4200 or epoxy, but adhesives don't work well on Polyethylene.

Anyways, I solicit the thoughts of this group.

[itsermam]

I am tackling the same issue this winter - I'll be curious to see what those in the know say.

I was considering two circular shims around the pivot point (one on each side) with a radius small enough that it would not protrude below the CB trunk. I am not sure if that will provide enough area to stop the CB from flopping around, but it seems to me that shimming on the CB itself will be easier than working in the CB trunk.

If you happen to get any suggestions "off line" please let me know - I hope not to repeat this project in the near future.

[kokko]

Online I see that Home Depot sells pvc moulding. Some of the profiles might work. PVC will bond well with either epoxy or 3M 4200. Polyethylene and polypropylene are very hard to bond, so avoid them.

I plan to stop by HD sometime this week. I will let you know whether it is suitable.

[Geronimo]

A fellow DS-1 owner builds custom cabinets. He made a jig to cut perfect circles of laminate to match the radius of the top of the board. The center hole matched the diameter of the handle shaft. As I recall, we may have used a spot of hot glue here and there to help with the placement of the board. We've been using this arrangement for years now with essentially no adhesive. It goes without saying to split the number of discs required evenly, port and starboard.

[K.C. Walker]

Last summer I re-faired my centerboard and shimmed it. I used a high density polyethylene for the shims and secured them in place with countersunk stainless screws.

I fit the top shims first which were 2 inch wide strips. If you fit these first you can really get an excellent fit. I started out a little too thick and kept thinning them down until they were perfect. Then I did the same thing with the shims at the bottom. I did radius the front of the bottom shim so that it does not project past the opening in the trunk when the board is tipped up.

I wanted to get the shims at the maximum distance apart and the maximum bearing surface (the full width of the board) for maximum strength and rigidity. I also reinforced my centerboard trunk to make it extra rigid.

The high density polyethylene is self lubricating so the board now feels like it is greased all the time. However, the fit is snug so the board stays wherever I put it without slipping, unless I hit bottom.

KC

[jdoorly]

Polyethylene can be made adequately bondable to epoxy by treating the surface to be bonded with a flame. Do NOT heat to discoloration or melting. The plastic's molecular structure will be changed and epoxy will adhere to it.

I repaired a hole in one of those cheap plastic kayaks with a fiberglass patch and epoxy after I learned the technique on a kayak forum.

[Anstigmat]

Re engaging in this old thread to see if anyone picked a specific method for their shims?

I am thinking of cutting some PVC sheeting into large washers, and using JB Weld to stick them around the square hole. I'm hoping this reduces the play/wobble in my board significantly. I do worry a bit about the wear that might be caused in the contact point between the PVC and the CB hump wall...

Anyway I'd love to hear some other solutions.

[GreenLake]

HDPE is more slippery than any of the alternatives. But it doesn't bond well, therefore as KC writes, the method is to screw it on, but to countersink the holes, so the screw heads are well below the surface. Or you can heat treat it as @jdoorly writes.

I'm with @kokko in thinking that shims are most effective if added to the CB trunk walls.

[Anstigmat]

Well this is likely to impress just about nobody, but I think it just may work!

My handle pin extended into the trunk with the 'square part' going into the CB. If you will recall the remainder of the handle has a curved dome end to it. This was not extending all the way to the other size of my trunk for whatever reason and the board was wobbling a lot. My concern was that it would slide from off the square part on to the dome a bit, or back and forth and further wear out the square hole. Also creating a lot of knocking around.

I think the HDPE is a better choice in general, but I already had PCV sheeting, so that's what I used. I simply eyeballed a 'washer' shape over the square hole, and cut it out of the sheet. I then drilled a hole so the dome part can stick through the washer. I attached the washer to the CB with a screws. I also rounded the edges a bit with a sander.

So now the board fits much better with no risk of it moving back and forth. It still has some capacity to wobble I think, but I hopefully just won't lose the ability to raise and lower it as needed.

If I could lift the boat high enough to full lower the CB down, I could trouble shoot this more. However I used ratchet straps and a jack to get it off the trailer enough to the point where I could pull the trailer out from under it. The challenge I had was that of course ratchet straps don't let you slowly loosen the boat down, they just let go. I could only raise it high enough to the point where I could get the trailer out, and back in, with enough space for my smallish jack to take over and slowly let it go down on to the trailer.

The folks at O'Day were quite clever with this CB design but I do wonder if a simpler design isn't better. It would be nice if I could just insert the board like I remember doing on Sunfish sailers. I don't have a bunch of buddies to come help with this so everything is a lot harder to accomplish by myself.

Anyway, job's done. Now I get to cut holes in my seats for re-foaming.

[GreenLake]

Looks good. Let us know how it's working out.

What the Sunfish and other boats have is a "daggerboard". Its main difference is that it isn't as forgiving in hitting underwater obstacles. You can sail in shallow waters, but must raise the daggerboard in advance. Also, a partially raised daggerboard is still at the same fore/aft location while a centerboard swing backwards, allowing you to adjust the balance of your sailplan.

So there are some advantages.

I'm sure we've mentioned that before, but you can easily drop the boat onto level ground from the trailer (and if you've raised the mast first), you can use the jib halyard or spinnaker halyard to pull it on its side where all this becomes quite accessible. (Apologies if this repeats something we've discussed, it's difficult to remember what threads touched which issues). I've done this several times both with helpers and alone.

If you are set on doing the work in a garage where you have good overhead room: instead of a ratchet strap you might use a simple rope sling that you run through a block. You can then tie another rope to that block and connect it to some kind of purchase that you run sideways to a wall, where you can belay it. I built a system like that using sailing parts, which made it perhaps more expensive than necessary, but you can sometimes find a pre-rigged purchase in hardware stores or other non-marine settings.

If the purchase isn't quite powerful enough, add a cascade to double it.