Centerboard pivot

[mwybo]

I am at the centerboard fabrication stage of my Pooduck and am looking for instructions on how to make the pivot. The seacrh function as you know does not work and the instructions for using Google do not work either (the keyword "boat" returns no hits).

Thanks

Mike

[Bob Smalser]

http://www.woodenboat-ubb.com/c gi-bin/UBB/ultimatebb.cgi?ubb=get_topic;f=1;t=010983 (http://www.woodenboat-ubb.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic;f=1;t=010983)

http://pic3.picturetrail.com/VOL12/1104763/6791366/85168918.jpg

http://pic3.picturetrail.com/VOL12/1104763/6791366/87637951.jpg

http://pic3.picturetrail.com/VOL12/1104763/6791366/87638107.jpg

http://pic3.picturetrail.com/VOL12/1104763/7309305/95249642.jpg

[ 07-07-2005, 11:32 PM: Message edited by: Bob Smalser ]

[mwybo]

Thanks Bob

Mike

[Mrleft8]

Perhaps the most valuable information that Bob just gave you is: Drill the pivot holes in the C/B case before you install it in the boat! On my Catspaw dinghy I used a stainless steel 5/16" bolt with fender washers and neoprene rubber washers as gaskets, the nut is one of those "Nylock" jobbies that won't back off on you as you use it.

[StevenBauer]

Perhaps the most valuable information that Bob just gave you is: Drill the pivot holes in the C/B case before you install it in the boat! Man, I wish I had done that! :eek:

Steven

[Dave Gray]

I followed the directions in the monograph, "Building the Shellback Dinghy", and used a 3/8" bronze nipple screwed and epoxied into the centerboard, then cut flush. The pivot is bronze bolt through the centerboard logs with rubber washers to keep out leaks.

Must admit, if I had seen Bob's method during that construction stage I would have used it. I like the covering wood rounds over the pivot ends and may still use them, seeing as how the project has somewhat stalled due to too many other demands on my time.

[John Meachen]

As ever,Bob has done a fine job of illustrating his way of doing the job.The advice about drilling the case before it is fitted to the boat certainly makes life easier and avoids the need to find a helper to squint from the transom advising on whether the hole is square.I would differ in one respect;rather than using a floating pin,I would use a bolt.Furthermore I would drill an oversize hole through the board-3/8 inch or so greater than bolt diameter.Through this hole I would fit a bush drilled with a clearance hole for the bolt and of a length that just allows it to fit within the case.At both ends of the pivot bolt I would fit a rubber washer and then a stainless washer so that when the bolt is tightened the lack of movement at the case sides,due to the presence of the bush,allows a good deal of clamping force to be applied to the rubber washers.It will also resist the leverage of the board wringing the sides of the case apart.

[StevenBauer]

Jim used a bronze pin on his Elver - "Cofresi" - but he used a bronze drain plug to hold it in. So it's easy to remove quickly:

http://www.imagestation.com/picture/sraid176/p10e1b09e3a8f0dce8e4041cd07dc3dde/f359323d.jpg

[J. Dillon]

I have a similar arrangement as Bob has shown.

An added tip when re installing the board when you have occasion to remove it for mainenance is to use a mirror to align the board pivot hole with the case. Then you can tap the pin in easily.

On my boat it is impossible to get your eyeball down there but the mirror makes it easy. BTW use a big mirror. ;)

JD

[Mrleft8]

Originally posted by StevenBauer:
</font><blockquote>quote:</font><hr />Perhaps the most valuable information that Bob just gave you is: Drill the pivot holes in the C/B case before you install it in the boat! Man, I wish I had done that! :eek:

Steven</font>[/QUOTE]Me too! :rolleyes:

[SparkG]

I don't see how that keeps water out of the wood on the inside where the pivot goes through the case.

[Bob Smalser]

If they are exposed to view, bolts don't look very professional.

http://pic3.picturetrail.com/VOL12/1104763/6490387/83400489.jpg

Instead, simply use a length of SS allthread with two acorn nuts. If you want it to behave like a bolt, simply silver braze one nut in place. Or like above you can simply cut your own threads with a die.

[Bob Smalser]

Originally posted by SparkG:
I don't see how that keeps water out of the wood on the inside where the pivot goes through the case.All wood surfaces inside and out have one coat of red lead and two coats of alkyd enamel, with the pin bedded in bedding compound on top of all that. Add to that the construction detail that doesn't crush any wood with unneeded fastener torque, and no raw water will reach the wood for a long, long time.

The builder won't crush any wood with that bolt, he'll just torque it sufficiently to bring the neoprene gaskets into play. But one day somebody will overtorque that bolt, probably with more goo ILO the proper repair of replacing the gaskets.

But from my observations, what kills CB trucks is mostly the mast, not the board, in small boats. Unstayed masts put sideways pressure on the thwart, which has a lot of leverage mortised as high as it is into the trunk, and eventually unseals the bedlog joints, letting in water. The board contributes, however, with sideways pressure on the pin bores in the opposite direction....but with much less leverage.

The pin design I'm using is ancient because it works. Besides simplicity, its principle advantage (besides no crushed wood from overtorquing a bolt) over tighter and stronger methods is that the board is free to move from side to side within the trunk, unconstrained by bushings, which can overcome considerable damage to the board after impact and still function. The pin pressure from the board is more on the hardwood pin caps than the softwood bedlogs.

With simple, marline-lashed wire side stays, the trunk has the best chance of lasting as long as the rest of the boat.

[ 07-09-2005, 11:12 AM: Message edited by: Bob Smalser ]

[DougWilde]

I used 1/2" PVC plugs.

A description can be found on the lower quarter of this page:

Center Board and Case for Williwaw (http://dbwilde.home.comcast.net/Williwaw/ctrboard.htm)

With this method the only holes are for the pivot pin and they absolutely sealed with a lot of epoxy.

Doug Wilde

[mwybo]

Thanks for the comments. I will go with Bob's technique. The bronze bar has been ordered. Since I have no red lead I will overdrill the pivot pin holes, fill with epoxy, then redrill to size.

Next question - should I put a layer of fiberglass cloth on my centerboard? Other Pooduck builders, did you do this?

Thanks again. This board is a great help for a first time builder.

Mike

[Venchka]

Searching Building/Repair is very much alive and well.

Follow these instructions:

Search Instructions (http://www.woodenboat-ubb.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=011955)

Wayne
In the Swamp. :D

[Ian McColgin]

Bob's version is most elegant. For those interested in a simpler system:

The board is supposed to be just a bit loose in the case. If the hole in the board has a tight fitting bushing - bronze or iron or even PVC pipe - that is just a tiny nudge proud of the board but still fits albeit quite tightly in the trunk, then board and bushing can be slipped in place and the whole held down with a bolt and fender warshers. The bushing will absolutely prevent any drip and will keep you from warping the bedlogs or CB case when you tighten.

Reshaping the bolt and nut heads to having long parallel flats beveled to a pleasing arc - rather like a rectangular carriage bolt head - will make it pretty, snag proof, and still easy to remove.