CB pin - fixed to case, bushing in CB head for pin?

[Thorne]

I noticed that Bob S's excellent pages on building a trad centerboard for a Gunning dory, he shows the bronze pin being set into a bushing in the centerboard head (I think).

I was going to use a SS bolt and a number of SS washers, the washers both on the inside and outside of the case to hold the CB centered.

The question is, should I fix the bolt in the case sides to eliminate leakage? This means that the CB has to pivot on the pin/bolt, eventually causing wear on the hole through the expoxied plywood.

If I go with a fixed pin, do I need to install some sort of bushing or SS pipe into the head of the CB to line the hole and eliminate wear? The potential downside seems to be that if any corrosion or sand gets into the bolt/bushing, the CB could stop rotating -- not good.

Alternately, I could let the bolt rotate in the holes in the CB case, and epoxy it into the head of the CB. But this option can cause more leakage and eventual wear on the CB case.

As usual, thanks in advance.

[Carlsboats]

I would vote for the tried and true: a bronze bolt with a bronze bushing in the centerboard.
My guess is that it will outlast the boat and both of us.
The problem is to keep the bushing in the board, and my solution to that has been to recess a plate --say 1/16" or 1/8" bronze -- into each side of the board, screwed in place, bored out so the bolt will pass through but not the bushing. In effect, these are just big washers.
I suppose you could do the whole job with stainless, but I am uncomfortable about SS underwater, especially when metal is rubbing on metal from time to time.

[Thorne]

Carl -

Thanks for the suggestions. I'll admit that I'm weary of having to order ALL the hardware from RI, Maine or Mass -- the timelag (not to mention the shipping fee) is killin' me!

;-0

I looked for bronze pins locally but came up empty-handed.

The boat will be drysailed, so I don't anticipate any issues with the stainless. And I am using silicon bronze fasteners everywhere else.

From what I've read, as long as stainless is exposed and not underwater constantly, it should decay at the minimum rate. But if sealed and submerged all the time then it will fail much sooner.

[ 11-14-2005, 06:17 PM: Message edited by: Thorne ]

[Bob Smalser]

What's important is the board rotate on the pin and not the pin on the bed logs, and corrosion or goo won't end those relationships over time.

You don't find any bronze pin stock available because builders buy common-as-mud bronze rod and cut it to length. Cheaper and better than even the SS bolts you have in mind. Cut to length, run thru a bronze bushing inletted into the board (I like Carl's capture plates.)...insure a relatively sloppy fit....the pin ends run thru the bedlogs into wooden caps sealed by a neoprene gasket and fastened with screws.

If you have to use a bolt, use a galvanized bolt. Place neoprene gaskets beneath galvanized fender washers on either side of the bedlogs and it'll last the life of any drysailed boat without worry of crevice corrosion.

The advantage of rod and large pin caps is that if the boat is neglected for decades and the board eventually binds in the bushing, the pin can rotate and wear the hole in the bedlogs forever before causing a leak.

Bronze is nice and adds value, but functionally, if your boat lives in real cold water, it's a waste of dough. Especially on a work boat. Galvanized lasts the life of the boat around here...and in cold fresh water, longer than the life of the boat. The first work boat I built for my main pond has oarlocks salvaged from the original homesteader's work boat circa 1940.....I had to dive to get them. Makes for continuity of spirit.

[ 11-14-2005, 06:56 PM: Message edited by: Bob Smalser ]

[Frank E. Price]

Or, for fellow Luddites:

1" oak pin 3" or so above waterline, snug friction fit in the trunk logs, well soaked in creosote and tarred ("bear s---"); through a sloppy hole (say 1 1/8") in the board. No caps and no leaks. The boat is an 18' sharpie skiff and the board is about 2'x5'x1 3/4". It's only about 4 1/2 years old, but lives in the water year 'round and no sign of trouble. No metal, no worries; spend the money on fishing gear, a new chain for the saw, whiskey, whatever.

Frank

[DougWilde]

I used a 1/2" silicon bronze bolt, cut off head and threads. I embedded bronze bushings (purchased at Lowes) in the centerboard case logs, flush with the inside surface of the case and then another bushing in the center board. The pin/bolt is inserted and free to rotate both in the logs and the centerboard. I used 1/2" PVC caps the seal the case.

Take a look at

Centerboard and case for Williwaw (http://dbwilde.home.comcast.net/Williwaw/ctrboard.htm)

near the bottom of the page.

[Thorne]

Thanks, everyone.

I got the case built and the centerboard fitted -- needed to trim off the teensiest bit of the aft corner to ensure free motion if the wood case or board swells or shifts. This will also allow me to glass the leading/bottom edge of the board.

Does anyone use a second pin to hold the CB in place when up? On larger boats with swing keels, there is often a pin that goes through the case into the board/keel in three positions: Fully up (transport), halfway down, and fully down (to keep it from slamming back into the case in a knockdown). The CB/swing keel has these three holes drilled in an arc so they all match the single hole in the case.

I was thinking of just one hole to hold the board up during storage and transport to avoid undue strain on the pennon and its attachment point on the aft head of the CB.

[ 11-20-2005, 11:06 AM: Message edited by: Thorne ]

[Carlsboats]

Thorne, I don't know how much of a hurry you are in, but I am sure I have some scrap bronze rod and plate stock around my shop. I could send you wnat you need to make a pin and a couple of end plates. Trouble is, I won't be going back to my shop, which is on Block Island, for a couple of weeks. Too late to be of help?

[Thorne]

Carlsboats -

I'm zooming right along and have gone for a SS bolt through a SS bushing in the CB, but thanks for the offer.

The weather is brutally beautiful here right now, with highs in the 70's and 80's -- so all my painting and epoxy schedules have gotten pushed ahead to take advantage of the warm weather.

I'll install the CB case in the next few days, then move on to the false bottom, rudder and mast partners.

[DougWilde]

Yes, I installed a pin to hold the centerboard in the up position. A lot of folks put some sort or wear plate or material on top of the centerboard case in way of the pin. I installed a couple of fairleads that this pin fits through to prevent the board from slamming into the top of the centerboard case as I trailer the boat about.

Doug Wilde

[Frank E. Price]

Thorne, the trunk in my skiff is open at the top and the board projects through it. There is a hole near the top corner of the board and another about a foot down. There is a short lanyard made fast to board's trailing edge about eight inches down and hitched to a small locust belaying pin at the other end. The pin goes through the lower hole and rests on the top of the trunk to support the board when it is up, and the other hole supports the board at about a foot down. Top of the trunk is a small strip of oak. Lowered all the way, the pin goes into a hole in the main thwart (in way of the after trunk ledger). Dead simple, cheap and easy to put together, nearly foolproof.

Frank