PDA

View Full Version : Daggerboard/Case clearance



Lewisboats
06-30-2008, 08:03 AM
What are we looking at for clearance min/max between daggerboard and case sides? I laminated up 4 layers of 6mm plus I am going to coat it a couple of times plus paint...so say 25.4 mm or 1 in total. What kind of clearance should I use between the DB and the case walls...1/16"...1/8"...friction fit?

Oh...and it is 20 plys thick on a 10 ft boat so it should stand up.

Thorne
06-30-2008, 11:07 AM
I'd give it 1/8" at least. You may not get much swelling with ply, but you need to allow for some increase in size.

Also remember water weeds, sand and pea gravel -- all which magically seem to attach themselves to centerboards.

If you make the fit very tight and the CB case has a closed top (which I prefer), make sure you drill a hole in the top so you can shove the boathook handle into the case and force the CB down. Plug it with the traditional large cork...

Lewisboats
06-30-2008, 11:09 AM
Actually it is a Daggerboard (gets pulled out more :) )not a Centerboard but the consensus on the various boards I asked at is 1/8" for either. Thanks for the info

ChrisBen
06-30-2008, 11:24 AM
I like to leave a little extra room inside the case. If a bit of debris does get into the slot, there's less chance of it jamming the board in the case.
http://i143.photobucket.com/albums/r133/loki59/board.jpg

Canoeyawl
06-30-2008, 01:34 PM
I would leave 1/4"

johngsandusky
06-30-2008, 08:02 PM
Mine was binding, at the worst times. I sprayed it and the inside of the case with silicon lubricant. Slips fine now.

Phil's Foils
07-03-2008, 01:57 PM
For performance, the closer the fit the better. And you're LESS likely to pull in junk that's going to jam the board.

Even 1/8" slop at the trunk will lead to a fairly large deflection from vertical by the time you get to the tip of the DB.

A good compromise is to built the trunk (or the board, whichever comes first) to allow a loose fit, and then tighten it at the top and bottom of the trunk with shim tape.

Besides, who wants to hear their daggerboard rattling back and forth in the case every time you hit a wave?

Carlsboats
07-03-2008, 03:02 PM
I agree with the sloppy-fit crowd : give the board 1/4" or more of clearance, and if it slops around in the case, tack on some shims on the part that stays in the case. These can be sacrificial -- if the bottom paint wears off of them, no damage done to the board and minimum rob off on the case sides.

MiddleAgesMan
07-03-2008, 03:33 PM
For his Goat Island Skiff, Boatmik told me to allow 1 or 2mm for clearance. I really don't see any need for more than that. You would be fine with 1/2mm but making the board and case to such tight tolerances is really where the problem lies.

TerryLL
07-03-2008, 05:56 PM
If you really want a snug fit on the board, either to reduce turbulence or to reduce knocking, you might consider aluminum plate for the daggerboard. 3/16 would probably do, 1/4 for sure. Aluminum is simple to cut and shape, nearly maintenance free, and will never swell. Be sure to put a lanyard on it in case you take a spill and the board slips out of the slot when you go turtle. If the case is already built, you can pad out the part of the plate that stays in the case with sacrificial shims. UHMW works great for shims, as it will not absorb water and is very slippery. Simply through-bolt the UHMW to either side of the plate with countersunk SS machine screws, washers and nylocks.

Lewisboats
07-04-2008, 07:50 AM
If you really want a snug fit on the board, either to reduce turbulence or to reduce knocking, you might consider aluminum plate for the daggerboard. 3/16 would probably do, 1/4 for sure. Aluminum is simple to cut and shape, nearly maintenance free, and will never swell. Be sure to put a lanyard on it in case you take a spill and the board slips out of the slot when you go turtle. If the case is already built, you can pad out the part of the plate that stays in the case with sacrificial shims. UHMW works great for shims, as it will not absorb water and is very slippery. Simply through-bolt the UHMW to either side of the plate with countersunk SS machine screws, washers and nylocks.

Thanks...that gives me a great idea on how to do this. I have access to 3/4" UHMW by the ton...along with the SS hardware. I'll get some scraps tonight.

Steve Lansdowne
07-04-2008, 01:02 PM
What is UHMW?

TerryLL
07-04-2008, 01:57 PM
UHMW. Ultra High Molecular Weight polyethylene. Also known as "monkey wood". This stuff has high impact resistance and low friction and is easy to machine. Something akin to a plastic cutting board, but denser and very slippery. Used for hull guards, rail caps, false bottoms on drift boats, etc. Available in sheets, rods, tubes, blocks, planks, in practically any thickness or length. Great stuff.