Modern backing plates on Gunboats, HH, or TP 52's etc...

[NOCALSAILOR]

How are backing plates done on new high performance boats? As I was placing a epoxy buttered  aluminum plate up to the underside of the deck I had a thought. New race/performance boats can't be doing this. Is the new practice to add more laminate to the stack before the infusion?  Any pics or info would be great.

Thanks

 

[drew584]

Don’t know about bigger boats but I know that at the factory I worked in years ago they had a double nut assembly with a bolt glassed into a bulk head for the chain plate eye bolt to thread into. Surely these larger high performance boats aren’t simply placing a backing plate under the skin?

 

[Sailabout]

G10 or something like that

 

[mpenman]

Remember that carbon conducts electricity. Most high end multis are carbon these days.

G10 is the product of choice but it depends the application.

 

[Zonker]

Yes extra laminate in the stack, often oriented in the primary load direction like for a big winch. 

And E glass backing plates. If you really want to save weight with big winches you make them in a ring shape. The middle is mostly wasted. 

 

[Sailabout]

Different design I guess if its solid carbon versus cored deck and you are worried about bolt crush?
I will ask a buddy that has built a few Cats Tris and TP's

 

[teamvmg]

All deck gear positions are planned at design stage. High density foam inserts go in place of the standard grade core. Extra laminates inside and out

 

[basketcase]

Yes extra laminate in the stack, often oriented in the primary load direction like for a big winch. 

And E glass backing plates. If you really want to save weight with big winches you make them in a ring shape. The middle is mostly wasted. 

I have always used c-plate for backing structure. If you are building in carbon why would you step down in strength for a reinforcement?

 

[Zonker]

Cause it's just a big washer. E-glass plates like G10 are more economical and probably good enough for out of plane compression versus a custom carbon washer.

 

[basketcase]

Cause it's just a big washer. E-glass plates like G10 are more economical and probably good enough for out of plane compression versus a custom carbon washer.

ya, theres the thing. my last bunch of builds have not been anything near economical. But, mostly nothing near a 'custom carbon washer', its c-plate. you use it the same as g-10, its just.... better.

 

[Zonker]

In the Z-axis? I'd love to see some data anyway. Z axis compressive strength is not easy to find.

 

[basketcase]

In the Z-axis? I'd love to see some data anyway. Z axis compressive strength is not easy to find.

anything I would have would just be anecdotal. all i know for sure is that on the last 10 or so big builds i have done.... all c-plate. g-10 is easy to get and cheep. easy to spec it for repairs and production boats.

 

[peterbike]

2 questions ;   what is,    g10 ?

                         what is,  c plate ?

 

[Raz'r]

2 questions ;   what is,    g10 ?

                         what is,  c plate ?

G10, compressed fiberglass/epoxy laminate. usually. G10 is kinda a generic term, there are many different types of glass/resin used

Carbon plate. similar, but carbon...

 

[Zonker]

https://www.mcmaster.com/grade-g-10-garolite/

 

[Geese]

I’ve been using G10 taped to the deck with key inserts in it. No through bolting, no deck penetrations. Ok for stuff in shear like clutches and footblocks. 

I like the sound of no holes, can you expand on this. What tape, what resin? Do you think this would be adequate for attachment points for the tramps or bow nets on a tri? I’ve seen the rod thing but that seems to take a lot of man hours from blogs I’ve followed.

 

[Geese]

I like the sound of no holes, can you expand on this. What tape, what resin? Do you think this would be adequate for attachment points for the tramps or bow nets on a tri? I’ve seen the rod thing but that seems to take a lot of man hours from blogs I’ve followed.

I know you said in shear and not tension, just trying to get my head around this, I’ve read about recessed G10 rods epoxied in and then tapped (female threads) or turned into what could be described as soft pad eyes for a bobstay. Is what your are describing a pad epoxied on the deck or are you breaching the top skin? 

 

[El Borracho]

I buy 3mm carbon plate (like G-10) from the online suppliers. Pre-cut. Seems far stiffer than G-10. I’m not so sure if it is really compressive strength that one is looking for in a backing plate. I think the selection criteria is bending stiffness to spread the load. Sometimes shear is a factor if bolts are apt to tear horizontally thru the hull. Unusual though. Hulls tend to be plenty strong for the equipment mounting. It is the point load of the bolt that needs to be addressed. Does not take much to greatly spread the load (square law) of a bolt and washer.  The carbon plates allow me to skip the heavy s/s fender washers. Standard washers under the nuts are fine. I adhere them permanently with lightweight-filled epoxy paste. Sometimes with a release layer against the hull if the fitting might be removed someday. 
 

Often another plate is directly under the fitting, outside, to eliminate crushing the deck laminate. Especially pulpit bases. Looks good too. 
 

A rod glassed in does not address spreading the load over a large area of core. Its connection to the skin is problematic. But might be a good idea for other reasons. Seems like a winch fastened that way might launch at the wrong moment. 

 

[Zonker]

Stiffness is important in a washer plate. Here's the classical stress distribution of a bolted joint with a washer.  

If the washer is stiff (it needs to be relatively thick to be stiff) then the pressure cone is larger and the resulting stress in the core/laminate between the washers is reduced. A fender washer is not stiff and just deforms under load, crushing the laminate locally. It does resist tearout for lower loaded items.

Imagine a washer made of silly putty. The nut or bolt head just squeezes it out of the way and it performs no useful purpose in spreading the load. 

So now that I have thought about it, a carbon washer plate makes good sense and does probably allow you to use 3mm instead of 4mm G10.