G10 for chainplates

[GinoDelG]

Has anyone tried using G-10 for the backing material on their chainplates. I need to replace my badly corroded plates on my CD28 and I'm trying to decide between stainless steel, aluminum, starboard or G10.

[rtbates]

If it's the same G10 that circuit boards are made of I'd think it would crush too easily..And you'd be hard pressed to find it in thick enough pieces, I'd THINK...

[Maine Sail]

G-10 is pretty bomb proof, extremely strong and used very often in highly loaded areas. Ocean Planet the open 60 Vendee Globe boat used a lot of it as does Morris Yachts. It makes excellent backing blocks and will not crush. You can get it up to 1" thick, if you want to pay for it.

I have done some pretty extensive load testing with it for drilling and tapping into for seacock backing blocks, and it might as well be a nut.... I have loaded up a single 5/16 X 18 bolt into 1/2" GPO-3 (GPO-3 is similar to G-10 but made with polyester resin as opposed to epoxy) and exceeded 1000 pounds of pull in a direct line...

Here's a video of 1/2" GPO-3 with three drilled & tapped 5/16 X 18 bolts, and no thru-hull fitting, exceeding the ABYC seacock standard by 300 pounds. Despite being loaded to over 800 pounds the flange left no impression in the face of the GPO-3..

http://www.youtube.com/watch?v=KKTKQUcvU9w

[GinoDelG]

Impressive video. What's the advantage of fiberglass plates vs stainless steel? Also, since mine are for chainplates aren't the stresses much higher? And finally, how difficult is it to cut and drill this material?

[Maine Sail]

Impressive video. What's the advantage of fiberglass plates vs stainless steel?

No possibility of pitting or crevice corrosion if it gets wet..

Also, since mine are for chainplates aren't the stresses much higher?

The vast majority of boats on the water, including many "blue water" built boats such as a Cape Dory, bolt chain plates directly to plywood bulkheads and many use only fender washers.. For chain plate backing plates G-10 or GPO-3 is far stronger than a marine ply, won't rot and won't corrode. Even if used for sandwiching plywood bulkheads it will more evenly distribute the load over a larger area of the plywood as opposed to just fender washers.

And finally, how difficult is it to cut and drill this material?

Not too difficult and far easier than SS. It does however eat blades and drills for lunch.....

[darmoose]

Very impressive, but aren"t you pulling on two bolts? What happens if the force pulls only against one bolt (which according to Murphey"s law it always will)? Try positioning the pulling force opposite one bolt and position two bolts on the leeward side. This would represent the most vulnerable condition,no?

Darrrell

[Maine Sail]

Very impressive, but aren"t you pulling on two bolts? What happens if the force pulls only against one bolt (which according to Murphey"s law it always will)? Try positioning the pulling force opposite one bolt and position two bolts on the leeward side. This would represent the most vulnerable condition,no?

Darrrell

Already tested that. One bolt in a direct line pull, which with a flanged seacock is not a direct pull, exceeds the ABYC standard by at least 300 pounds...

I am uploading a video now of a piece of home made polyester/fiberglass sheet, which is slightly less than 1/2" thick. I brought it up to over 800 pounds. I have had GPO-3 & G-10 over 1000 pounds per bolt. This is double the ABYC standard for seacocks. That flange just happened to line up that way and was not done purposely. I already knew how strong just one bolt was.

[rtbates]

That's certainly NOT the G10 I see on our circuits boards...

That's some tough stuff!!

[Maine Sail]

Very impressive, but aren"t you pulling on two bolts? What happens if the force pulls only against one bolt (which according to Murphey"s law it always will)? Try positioning the pulling force opposite one bolt and position two bolts on the leeward side. This would represent the most vulnerable condition,no?

Darrrell

Here's the video of regular old home made fiberglass sheet. It was slightly thinner than 1/2" and that is a 5/16 X 18 threaded bolt drilled and tapped directly into the fiberglass sheet....

http://www.youtube.com/watch?v=ZclHNSxr1xs

[Stan W.]

On my CD28 (1979) there are pieces of rebar welded to the steel backing plate and glassed to the inside of the hull. I presume they are intended to transfer some of the load away from the hull-deck joint and onto the hull itself. Personally, I would be reluctant to deviate from that design concept, and I'm not sure how you would duplicate it using G10.

[darmoose]

Main Sail

Is pulling directly inline parallel with the bolt (like you are doing in the second video) the same as pulling perpindicular to the bolt like in the first video? I might think that pulling perpindicular is more dangerous because any flexing of the material might work the threads somewhat and cause an earlier failure. Do you think so?

Darrell

[2tocruise]

I used 3/8" G10 plate to anchor and support our inner forestay. By my calculations it would support more than 7000 pounds before failing via tear out (the clevis pin tears out like sticking a pencil through a piece of paper and pulling). Even assuming a less than perfect bond to the hull it exceeds a reasonable factor of safety. Also used it as backing plates for the staysail sheet blocks.

Turns out it's a very similar system to that used by some of the America Cup (monohulls) rigging anchor points.

For backing plates on your typical CD "chainplate", the most likely failure faced is crushing. The padeye pulling up will cause the washer and nut on the bottom of the plate to crush through the G10. Trick is to use the largest fender washers you can get to help spread out the footprint. Crushing is weakness of all composite materials, so fender washers should always be used if possible.

I would consider G10 to be an excellent choice, but would be hesitant to try to make my own. Key is to get a high fiber to resin content, something difficult to achieve using home build methods. Of course, the commercial stuff is also harder to machine. I found that an oscillating blade (fein multimaster, bosch, etc) does much better than a reciprocating (jigsaw) type. Cobalt drill bits too. Working G10 is much closer to machining metal than cutting fiberglass.