Center board pin made of G10 on Pearson 35

[Cyrus Safdari]

The Pearson P-35 center board pin is a bronze rod about 10 inches long and 5/8" thick with slightly tapered ends. It spans the center board trunk, and is held loosely in place by two bronze sockets on 3" square plates that are glassed-in on each side of the centerboard trunk. The sockets, where the pin ends fit and freely rotate are sealed with bronze pipe end-caps about 1" ID that fit on the outside threaded ends of the sockets. So to remove the pin you just unscrew the pipe end caps and slide the pin out of the ceterboard hole The pin hole in the centerboard itself is also about an 1", so there's quite a bit of slop with the 5/8" pin. The slop is intentional, so the when deployed and under pressure, the centerboard presses against the interior side of the centerboard trunk, so the pin itself just has to take the weight of the centerboard. The center board pin freely rolls in the sockets, I presume to reduce wear by friction (and it was in fact pristine when I slid it out. )

So here's the question: should I replace everything as-is, or can I substitute a rod of G10 material as the centerboard pin, and permanently glass it in place? The advantage is elimination of yet more underwater hull holes and potential stray current corrosion . G10 is quite strong stuff and with a 10" span should hold the centerboard, is sold in rod form as well as sheets, There would be no more free-rolling , but really is friction and wear really an issue considering the centerboard may be lifted and lowered only a few times at most rather than constantly twirling around it (and an oil impreg bronze bushing could also help with friction issues if necessary) BTW inspecting the centerboa4d pin just requires a cheap boroscope that is shoved up the ceterboard trunk from outside

[Sailmonkey]

How would you drop the centerboard for maintenance with the G10 arrangement?

IMHO your solution seems like it’s in search of a problem.

[dfelsent]

I would say you have a structurally proven solution.
I would not mess with it.
I’d have concerns about the abrasion resistance of the g10, and the lack of access for real inspection of a glassed in system.
Centerboard pins do wear.
I removed my 1-1/4” bronze pin for inspection and it had worn about 1/8” after 47 years.
Replaced just because, short money from a prop shop.

[Cyrus Safdari]

I already inspect the cb trunk using a cheap boroscope which comes in quite handy for all the dark tight corners of a boat.
If necessary it wouldn't be a problem to grind the glass to get to the pin and in fact If I do go back to the old arrangement I'd seal up the sockets with a gob of filler instead of relying on pipe end caps, it is simple enough to grind it out. I've become quite used to fb dust lol. On some boats this area is a perennial problem as owners report water accumulation in the pan on the two sides of the pin.

My main concern is whether the g10 has enough strength to hold the weight of the cb. They didn't have G10 back when the boat was made of course. Im no engineer but the numbers I see for tensile strength seem sufficient and then some. Bronze was originally used for corrosion resistance not because it is particularly strong. Abrasion resistance is indeed the other concern but I guess we'll see. I'll add the bronze bushing just to be extra safe since the bushing doesn't cost much anyway.

[BillKny]

G10 is great stuff, and has lots of great applications on boats, many under-appreciated... I do not think this is a good one.

Bronze in this application is perfect. It is highly corrosion resistant, and is also smooth and self-lubricating. G10 is very abrasive, and generally not suited to applications involving moving parts.

Like other posters I think you are over thinking this one. Especially the part about glassing it in and making it “permanent”. That’s a BAD idea.

The bronzer pins here last for decades. Just replace in kind.

[Benz]

Another vote against G10 here.
Also, being able to drop out and service the centerboard is desirable, I think. How will you get antifouling on the hidden part, or inside the trunk, if you can't remove it?
I had a centerboard break once while at sea. It was good to be able to dive under with two wrenches and get out the stub without having to haul.

[skipmac]

Originally Posted by Cyrus Safdari

Im no engineer but the numbers I see for tensile strength seem sufficient and then some. Bronze was originally used for corrosion resistance not because it is particularly strong. Abrasion resistance is indeed the other concern but I guess we'll see. I'll add the bronze bushing just to be extra safe since the bushing doesn't cost much anyway.

If I understand correctly this is the pin that goes through the top corner of the centerboard that allows it to rotate up/down or in/out of the trunk? So the weight of the centerboard is supported by the pin?

In this case you are not using tensile strength which is resistance to stretch, but shear strength and my guess is G10 will not compare with bronze in this regard.

Stick with the bronze.

[roverhi]

I've got a 53 years old P35. The C/B pin set up is simple, seems to last forever, easy to service if needed. In short, a cheap and elegant set up that works. Why reinvent a wheel that seems to have a lot of negatives. The center board pin is just a bronze pipe threaded on both ends and glassed into the hull. Change the pin if it is worn being careful not to twist the housing when you remove the end caps. Hold both ends with a pipe wrench when you unscrew the cap.

[Cyrus Safdari]

Originally Posted by skipmac

IG10 will not compare with bronze in this regard.

I checked - 20,000 psi shear strength for G10, about 1/3rd the shear strength of bronze but my whole boat weighs substantially less than 20k lbs so thats not an issue I suspect

I know that's how they did it 9rirginally, but times change and technology progresses.

[Cheechako]

Why "fix" something that already works well? There are always unknowns.

[Sailshabby]

I’m going to take a different tack; try it and let us know how it worked. Or didn’t.

[BillKny]

Originally Posted by Sailshabby

I’m going to take a different tack; try it and let us know how it worked. Or didn’t.

That's the internet for you...

Screw up YOUR boat a lot while we watch and laugh....

[Cyrus Safdari]

Not really hearing a rational constructuve grown-up discussion here... yes we`very covered weight & abrasion, anything else? There is nothing special and mysterious or magical about the pin arrangement, general unease with something new needn't trump rationality (or manners.)

[Benz]

Originally Posted by Cyrus Safdari

Not really hearing a rational constructuve grown-up discussion here... yes we`very covered weight & abrasion, anything else? There is nothing special and mysterious or magical about the pin arrangement, general unease with something new needn't trump rationality (or manners.)

On the internet you get opinions. Some of us have given them. How are they irrational? How are they childish? Why accuse the responders of rudeness when we've taken the time to answer according to our knowledge?
If you despise the opinions of people who have experience with centerboards, and pins, and boatbuilding, why not pay an engineer to answer your question? He can do all the maths and possibly give you the answer you apparently want.
If he doesn't, you can also tell him he's being childish and irrational and un-constructive and unmannerly.

[skipmac]

Originally Posted by Cyrus Safdari

Not really hearing a rational constructuve grown-up discussion here... yes we`very covered weight & abrasion, anything else? There is nothing special and mysterious or magical about the pin arrangement, general unease with something new needn't trump rationality (or manners.)

Pray tell what was irrational or nonconstructive in my response or, with the exception of two of slightly sarcastic remarks, all of the others?

Perhaps there is some frustration because you asked a question, got answers and recommendations from some very knowledgeable and experienced members all recommending you stick with the original design but rejected it all. So why ask if you've already decided?

At the end of the day, your boat, your decision.