good source for ss backing plates?

[coopec43]

Originally Posted by cyrano138

Thank you, was going to ask about this. Did you need to treat it with mold release or anything like that?

I lay my polyester/CSM backing plates up on a sheet of bendable metal.

Once the lay-up has "gone off" it is a simple matter to remove the lay-up by bending the metal. If you didn't use bendable metal one of these will do the job.

[s/v Jedi]

Originally Posted by cyrano138

Thank you, was going to ask about this. Did you need to treat it with mold release or anything like that?

Like I wrote: I waxed it. I used Minwax paste wax but think any wax works.

[cyrano138]

Okay, thank you all for the help. I'm going to post results when I get to it. Like I had posted earlier (I think), I had purchased about 8yds of 1708 and a gallon of poly resin that I had intended to use for tabbing in new bulkheads, but I decided to use epoxy and 10oz instead after reading that 1708 might not be the best option. The 1708 seems like it would be fine but sometimes after reading so many conflicting opinions about something I'd rather just go with a less controversial option.



Anyway, thos way I can put it all to good use and make some backing plates with it so I don't feel like i wasted a hundred bucks.

[Spot]

Originally Posted by cyrano138

Okay, thank you all for the help. I'm going to post results when I get to it. Like I had posted earlier (I think), I had purchased about 8yds of 1708 and a gallon of poly resin that I had intended to use for tabbing in new bulkheads, but I decided to use epoxy and 10oz instead after reading that 1708 might not be the best option. The 1708 seems like it would be fine but sometimes after reading so many conflicting opinions about something I'd rather just go with a less controversial option.

Anyway, thos way I can put it all to good use and make some backing plates with it so I don't feel like i wasted a hundred bucks.

Glad you found a solution that is already bought and paid for.

I had an experience recently too where I was told to and did buy 1808 +45/-45 and after checking the 'numbers' via software and discussing with an engineering contact, I really should have just bought 0/90 or an epoxy compatible mat. In my case I think I have enough room on the yard goods to cut my pieces at 45 degrees to make the fibers 'go' 0/90 for the layers that will benefit from on-axis fibers.

[cyrano138]

Originally Posted by Spot

Glad you found a solution that is already bought and paid for.

I had an experience recently too where I was told to and did buy 1808 +45/-45 and after checking the 'numbers' via software and discussing with an engineering contact, I really should have just bought 0/90 or an epoxy compatible mat. In my case I think I have enough room on the yard goods to cut my pieces at 45 degrees to make the fibers 'go' 0/90 for the layers that will benefit from on-axis fibers.

I feel like this is one of those kinds of things that won't seem like a such a big deal in retrospect, but that was the basic point I had heard, too, about the angle of the weave.



For whatever it's worth, my cal20 had fairly thin bulkheads tabbed in with one layer of chop strand mat and one layer of 8 or 10 oz cloth and those seem rock solid. I couldn't budge one with my whole 200 lb of weight perched on top of it. So, probably it'll be just fine no matter which way you go.

[Spot]

If only I had bulkheads...
Going from 2 to 3 layers biax is a bigger change (14%) than rotating the layers (5%), but that 3 layers with 2 on axis allows me to match/ever so slightly exceed the properties of the CSM that was in there without additional or exotic materials.

[coopec43]

What is the best sort of backing plate? Is it one that is rock solid like a 3mm stainless steel plate or a resin/glass plate with a slight give? I'd worry about "hard" spots with something like aluminum or SS. What would be wrong with Polyester/glass with tapered edges or G10 (with tapered edges)





https://www.boatus.com/expert-advice...backing-plates

[s/v Jedi]

Originally Posted by coopec43

What is the best sort of backing plate? Is it one that is rock solid like a 3mm stainless steel plate or a resin/glass plate with a slight give? I'd worry about "hard" spots with something like aluminum or SS. What would be wrong with Polyester/glass with tapered edges or G10 (with tapered edges)





https://www.boatus.com/expert-advice...backing-plates

Exactly! Tapering is relevant for so many things with sailboats. From rope splicing to fiberglass core materials to scarf joints to chain plates!

[Wind River]

Why tapper the edge of G10?
Wouldn't a nice thickened epoxy filet do the same thing? You are bonding the backing plate with it anyway. Squeeze out the excess, smooth it around the edge. Done!

Add some milled fibers if you want some extra strength but that makes it a bit harder to get a nice filet (the one in the picture has milled fibers)

[coopec43]

Originally Posted by Wind River

Why tapper the edge of G10?
Wouldn't a nice thickened epoxy filet do the same thing? You are bonding the backing plate with it anyway. Squeeze out the excess, smooth it around the edge. Done!

Add some milled fibers if you want some extra strength but that makes it a bit harder to get a nice filet (the one in the picture has milled fibers)Attachment 262991

I suppose there are several ways of going about it.



This article is worth reading:


https://www.practical-sailor.com/boa...ate-need-to-be

[s/v Jedi]

Originally Posted by Wind River

Why tapper the edge of G10?
Wouldn't a nice thickened epoxy filet do the same thing? You are bonding the backing plate with it anyway. Squeeze out the excess, smooth it around the edge. Done!

Add some milled fibers if you want some extra strength but that makes it a bit harder to get a nice filet (the one in the picture has milled fibers)Attachment 262991

That’s looking great! Ready for mounting the seacocks or flange adapters

[skenn_ie]

Milled fibres (flocked cotton) is used a lot in homebuilt aircraft construction, particularly where 2 glass layups come together.

[campbdon]

I was thinking of using some 1/4" G10 pieces on the inside of my fibreglass transom to back an outboard bracket. Can I simply use the pieces as is (ie: drill holes for bolts and using nuts to compress) or are they meant to be epoxied or glassed to the surface they are backing

[cyrano138]

Originally Posted by campbdon

I was thinking of using some 1/4" G10 pieces on the inside of my fibreglass transom to back an outboard bracket. Can I simply use the pieces as is (ie: drill holes for bolts and using nuts to compress) or are they meant to be epoxied or glassed to the surface they are backing

I don't have as much experience as some of the guys and girls on the forum, but I can say after spending an entire day grinding rotten backing plates that had been glued in place off of the inside of my transom, don't glue your backing plates in place. They should never be permanently fixed. I'm sure someone else can weigh in if the transom-mounted-outboard-backing plate is a special case, but you should be able to remove without much difficulty and replace if needed. I'm sure g10 can crack or fail, and your don't want to be stuck removing it with a grinder.

[Nepidae]

I'm not sure what G10 is but when I need backing plates, I use this (https://www.mcmaster.com/fiberglass/...rs-and-strips/).

I was getting my windlass mounted on a bow pulpit and someone wanted to put a SS plate in place. Total cost was $5K and that seemed high.

Found out about FRP and this has served well. Did the job for under $1K.

I think I glued the plate and then used the windlass bolts as additional support.

Good luck.