Jammed C/B

[Mrleft8]

OK, OK, I know I should have made the centerboard looser to begin with. Being a furniture maker for the last 25 or so years is a hard thing to put aside though. I built the centerboard so that it moved beautifully and slicky-slick in the C/B trunk...... Until it got in the water and swelled up. So I drilled a hole in the C/B trunk cap, and used a piece of dowel to push the board down, and the rope still pulled the board up just fine. Then we had a week of bad tides and rainy weather. I tried to push the C/B down yesterday, and couldn't. I finally had to remove the C/B trunk cap and push it down with a bigger stick. Then I broke the rope trying to pull it back up (1/4" parachute cord). So now I need to haul the boat (catspaw dinghy) up on a beach and re thread the pull cord. While I have it out of the water..... Is there any slippery goo I can slather in the C/B trunk to keep me sailing this summer without having to pull the C/B and plane it down and repaint it? (please say "yes")

[Bob Smalser]

Sorry. No.

I've had similar problems getting back to boat building after decades of general woodwork...tootightitis and noroomferpaintitis.

If it don't fit now...how's it ever gonna be repainted?

Reduce the width of the board.

[Klaus]

Whatever you do now to your CB to make it move is like throwing coins into a wishing well ;) .
No, you did not make the CB too tight a fit if it originally moved easily.
What you did was obviously to neglect to coat it thoroughly with epoxy :( , letting the board absorb water :mad: and stick inside the trunk.

Do yourself a vavour and take the board out, redoing it properly this time. Valuable sailing time lost is part of the lesson learned tongue.gif

After you dried the board thoroughly reduce the thickness a little for the following: epoxy coat the whole board then it give it some additional coats with some graphite powder mixed into the epoxy. This makes a slippery, hard wearing surface.
Ideally you had (or should have) lined the trunk's inside also with graphite reinforced epoxy epoxy.

I just removed the board of my NIS 26 after 5 years of use, for inspection, there is minimal rubbing wear on the board's cheeks and the trunk's inside due the graphite/epoxy mix.

Klaus

[N. Scheuer]

In a related mechanism, my old Dovekie had a mahogany rudder blade bolted between two fiberglass cheeks of a rudder/tiller assembly. A 1/2" stainless bolt with a Nylock nut were used to adjust the cheek friction so that it was sufficient to keep the blade immersed, without making the up-lanyard fast to a cleat, or tying it around the tiller.

I sailed that boat twelve years, and the last was no different from the first in respect to rudder friction; I'd have to readjust the Nylock nut, depending wheather we were daysailing, or cruising for a weekend or longer. The mahgany blade would swell up significantly after a day in the water.

I kept a pair of open-ended wrenches handy for rudder adjustments.

Moby Nick

[N. Scheuer]

Opps! Make that DOWN-Lanyard, not "UP-"

MN

[bainbridgeisland]

Centerboards need reasonable clearance due to the possibility of debris or sand that can sometimes get into the trunk. The centerboard can jamb when its foil shape wedges the sand or debris against the sides of the trunk. How much clearance? Depends on the size of the boat, the centerboard and trunk materials, and the anticipated use. I would use at least 1/8" clearance on a Catspaw dinghy. It is also helpful if part of the centerboard cap can be easily removed so that debris or sand can be hosed out of the trunk from above.


Originally posted by Klaus:
...epoxy coat the whole board then it give it some additional coats with some graphite powder mixed into the epoxy. This makes a slippery, hard wearing surface.

Ideally you had (or should have) lined the trunk's inside also with graphite reinforced epoxy.

KlausI would not use graphite if you ever plan to keep the boat in salt water any significant time. It creates a battery with any metal it touches, accelerating galvanic corrosion.

[ 07-18-2004, 05:37 PM: Message edited by: bainbridgeisland ]

[J. Dillon]

This seems to be a common error designers make . NOT ENOUGH CLEARANCE FOR THE BOARD TO FUNCTION.

Just last week blundered into a launching where the whole sail had to be aborted due to a stuck board. The plan called for 1/8" clearance. That's 1/16th on each side. Not much IMHO.

Doug, as been said above . Just take out the board and re do.... it less thick.
I made mine loose when it wobles under sail I have two easily removeable wedges. When placed in the right spot the looseness is gone and the board NEVER jambs.

Off the subject, when it comes to doors, one that sticks gets noticed, not one that is hung too loose. ;)

JD

[Andrew Craig-Bennett]

Are you sure that grit or gravel has not got trapped between board and case? It's horribly easy to do, espescially landing on a beach or hard. That's why a couple of dinghies I've done have the centreboard offset and working through a garboard - keeps stones out of the case better.

[John B]

vaseline, Lefty. You won't know until you give it a go.
what have you got to lose. It might pick up some sand ( or not)but your other option is to plane down and refinish the thing anyway.

[Scott Rosen]

Pull it. Plane and sand it. Slop on some paint for now. Go sailing.

This winter, you can pretty it up when you have the boat out of the water.

[Mrleft8]

The boat has been known to hit bottom fairly hard at low tide, but I don't think it's grit in the case.... I was thinking Boeshield, or WD40..... I have a hand hauling it onto the beach tomorrow if it's not raining ( :rolleyes: ) I'll assess the pull the C/B at that time..... Pulling it, planing it, and replacing it requires 1 week, and 2 days of finding a willing helper at high tide.....

[Klaus]

Originally posted by bainbridgeisland:
</font><blockquote>quote:</font><hr />Originally posted by Klaus:
...epoxy coat the whole board then it give it some additional coats with some graphite powder mixed into the epoxy. This makes a slippery, hard wearing surface.

Ideally you had (or should have) lined the trunk's inside also with graphite reinforced epoxy.

KlausI would not use graphite if you ever plan to keep the boat in salt water any significant time. It creates a battery with any metal it touches, accelerating galvanic corrosion.</font>[/QUOTE]Well, I beg to differ! I have sailed my boat exclusively in salt water and the entire bottom of the 26' boat, its largeish centreboard and its rudder blade are epoxy graphite coated.
The centreboard has a 'flap' which closes the slot and this is held in place by long ss strips which in turn are fastened by ss screws.
Nether this strip nor the screws show the slightest galvanic corrosion damage! The boat has been sailed for up to 8 weeks at a time in salt water, though it is dry stored on a trailer.

Theoretically there 'should' be a large potentional difference between the ss and the graphite coating.
There is no potential there. Why? I measured the resistance of the graphite reinforced epoxy and it was not measurable, even when using a 600V megger tester.
Consider this, each and every particle of the very fine graphite dust is completely encapsulated by epoxy, isolating it from forming a galvanic 'battery'. This apparently even occurs at the surface which was wet & dry sanded to a very smooth finish.

I will test this even further soon as I just completed applying a 'copper poxy' antifouling coating to the bottom. The sections above the chine up to the boot stripe had been copper coated (on top of the graphite loaded epoxy!) last year for testing purposes and no detrimental effects were observed. Again, the very fine copper particles are isolated from each other and from the graphite particle below them by epoxy.

Now, if anybody wants to shoot that method down in flames, please back it up with pictorial evidence of actual cases.

I should emphasize that my boat's hull is of plywood/glass/epoxy construction.
Klaus

[Frank Wentzel]

Klaus

I think you covered the graphite/electrolysis myth quite well. I have used conductive epoxies. They were filled with silver powder. But in order for them to be conductive the epoxy was filled until it was almost as thick as peanut butter. Graphite filled epoxies are not loaded at a high enough level to promote contact between the graphite particles and they are therefore non-conductive.

/// Frank ///

[ 07-20-2004, 08:52 PM: Message edited by: Frank Wentzel ]

[Keith Wilson]

There is absolutely no reason that a centerboard should fit tightly in the case. Furniture-maker tolerances be damned; it works just as well when sailing with a good 1/4" or more of clearance on either side. Graphite and epoxy is nice, but the main problem is that the thing is just too tight. Close fits are wonderful when you need them, but if the board swells or twists at all, well, you already know what happens. Haul it out, let it dry, pull it out, plane it down. Think LOOSE. If you don't, it'll just jam again.

One minor point - Pete Culler's designs almost always show a small round hole in the top of the case and a belaying pin or something similar nearby to bash the board loose when a rock gets stuck in there. Good idea, IMHO.

[ 07-19-2004, 03:17 PM: Message edited by: Keith Wilson ]

[bainbridgeisland]

Klaus

You are probably right about the galvanic potential on your boat, it is entirely possible you have no problem. The graphite has to be electrically connected to metal for the corrosion cell to develop. Further, the amount of corrosion depends on the relative area of the anode to the cathode. Also, each epoxy compound is a little different and even within one installation, you will find variation in conductivity and electrolytic potential. Because your boat is OK does not mean combining graphite and epoxy cannot accelerate corrosion on other boats.

Though I have seen this problem from time to time, I do not have photos. Here is an epoxy experiment you can try though. Epoxy glue multiple pieces of conductive metal to conductive metal. Check the conductivity between the smaller pieces and the large piece. You will find variable conductivity. This shows you cannot count on the epoxy isolating the potential corrosion cell.

Why take the risk of creating a corrosion cell? Other products also produce very low friction without the risk.

[BillyBudd]

Too loose a fit of the CB in the trunk and you stand the chance of the rattles. Not too tight, not too sloppy.

[Mrleft8]

Weather and work got in the way today..... Tomorrow High tide is at 2... I can somehow see tying this job in with a beer at 5..... I hope.... First try will be a generous coat of wax. If that doesn't work, I'll pull it out next week and do it right.

[Scott Rosen]

If it expands too much, it may damage the trunk and the trunk fastenings.

Be careful. I would only use the kind of shortcut you describe in the case of a dire emergency, like if you were stuck in the mud and the only tools you had handy were a pair of pliers and a can of WD-40; and only until I could get a proper fix.

Trouble with any lubricant, is that it can interfere with paint adhesion later on.

Another option would be to leave the board down and avoid shallow water. If you need to, you can slop a coat of anti-fouling paint on the exposed portion of the board.

Why will it take you a week? Remove the board. Lay it on a pair of saw horses. Give it a few passes on each side with a power planer. Slop on some paint and go. It's a days work it you're slow like me. For a pro like you, it's a couple of hours. You can pretty it up in the winter.

[paul oman]

It gets worse. Wait until the board warps a bit!

Just a few thoughts - generally folks use a thin stainless wire and not rope for the CB penant.

On my most recent daysailer similar problems only board was a steel plate and CB all fiberglass (I guess the fiberglass 'squeezed in' after years on the trailer. Anyway the fix was a drill / drill bit back and forth to ream out the trunk a bit....

epoxy coating the wood should keep it from absorbing water and swelling (hopefully)

paul

www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)

[Mrleft8]

Pulled the board yesterday.... I tried slathering it with butcher's wax first... But it was still too tight. One pass through the planer brought it from .75" to .665". I'll prime it this morning, top coat it this evening, and wax it tomorrow..... Next trick is to find a willing helper to help haul out the boat on Friday.....OK OK.... Sunday?

[Wooden Boat Fittings]

Originally posted by Keith Wilson:
There is absolutely no reason that a centerboard should fit tightly in the case.... it works just as well when sailing with a good 1/4" or more of clearance on either side. I quite agree, Keith. Sloppy is good, and 1/4" each side isn't too much. Moreover, there's a solution for the slap than could otherwise develop with a sloppy fit; and a way to stop the case getting jammed up with stones too. (No good to Lefty though unfortunately, unless he wants to rebuild the c/b and/or case.)

It's to firstly make sure that when the board's fully up a small portion of it stays protruding through the bottom slot (1/4" is plenty.) Then cover most of the bottom slot with removable strips overlapping from each side of the case, protruding far enough to stop just a whisker clear of the board (1/16" or less. The strips could be timber or stiff rubber. Rubber might be better, because if the board's ever pulled up too high it can be forced back down between rubber strips but not between wooden ones, but this should only ever happen at maintenance time anyhow.) Run the strips from the forward end of the slot to within about 2" of the after end, leaving that last 2" open on each side.

The narrow gap between strips and board for almost the full length means the board doesn't rattle; and it also means that stones and gravel are largely kept out of the case. The 1/4" gap above the strips means that any stones that do get in somehow don't jam between board and case. And the 2" gap at the after end means that sand and any other junk that gets in will mostly wash through and out again.

(Having said that, a removable top to the c/b case, or an inspection opening in it through which something can be used to push the board down is still a good idea. A spot of redundancy never hurts.)

Mike

[RodB]

What could be used to mix in the epoxy in lieu of the graphite to get the tough, slick finish?

I like the idea of mixing something like graphite in the final coatings on the centerboard and centerboard trunk, those surfaces can never be too tough.

RB

[Andrew Craig-Bennett]

I've always believed in readily removeable (eg screwed, and not dowelled over) tops to C/B cases, and enough space either side to get a metal slat (a bit of flat bar) down either side.

You need a top to the c/b case if you ever tow the boat, and I daresay it adds a little strength.