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I am looking at converting my boat to have the lines run to the cockpit. Most of the hardware doesn't come with backing plates but I know you should use them to distribute the load. I also don't see much in the pre-fabed variety either. What do you use?
Depends on the loads you're expecting, and what you are fitting it through. Sometimes I just use a big washer, sometimes a plate made from 3/16th stainless, sometimes a bit of half inch marine ply.
As mentioned before, it really depends on the loads on them. I am also not combining different metals, in order to reduce the risk of galvanic corrosion. You can get pieces of 316 steel here on fleebay cut to size. Much cheaper than what the stainless shop close to where I work would charge. I've also used large stainless washers, Nylon washers and as I cannot get StarBoard in the UK, HDPE chopping boards.
Yes they offer marginal resistance to compression, but nowhere near that of G10 or SS. The Achilles heel of HDPE is that it is highly FLEXIBLE...
HDPE is poor choice for a backing plate unless you go really, really, really thick, and even then it would be a last choice for me.... The purpose of a backing plate is to distribute load across a wider area of the structure by making teh backing plate stiff and resistant to flexing under load.....
It is not about compressibility, HDPE is marginal in that regard but doable, it is about material rigidity/stiffness and distributing the loads on the deck structure across a broader area...
I'd use 3/16" G10 Garolite from McMaster-Carr.. You can cut it with most saws (yes, it will ruin the blades) and drill with any drill. It is stronger in compression than Ssteel and will not cause any corrosion.
As you can see from Marksf's post, polished S/S with acorn nuts is the best looking. I prefer to use it or fender washers (on lower loaded hardware) in areas where the backer is visible. Save the Starboard/G10 etc. for the hidden stuff.
Polished S/S is definitely the most work but it looks the best by far and you're only doing it once.
Unless you have a drill press and a band saw with a metal blade I'd strongly recommend getting them roughed out by a machine shop - they can flame/laser/cnc cut the pieces and punch the bolt holes instead of drilling.
File & sand to 1200 then polish them on a $40 Harbour Freight polishing wheel.
The backing plate is only one component – you must also think where you are positioning the hardware – some places have balsa core which cannot take the compression when you tighten the bolts. If this is the case you’ll need stainless spacers to put the bolts inside – they will take the load without damaging the deck. And don't forget the butyl....
The backing plate is only one component - you must also think where you are positioning the hardware - some places have balsa core which cannot take the compression when you tighten the bolts. If this is the case you'll need stainless spacers to put the bolts inside - they will take the load without damaging the deck. And don't forget the butyl....
remove the core around the bolts and fill with thickened epoxy to prevent compression use a countersink to allow butyl to form O ring around the bolts
my $ 0.02
Starboard, and cutting boards are not sutable for backing plates. The plastic they use is junk, and will deform under light compression loads applied for any length of time. I don't know who first thought of them, but it is a terrible idea.
The prefered is either a stainless plate, which should be available at almost any metal shop for a couple of bucks, or G10. G10 is a fiberglass board made under high pressure, and is extremely strong. It does tend to ruin blades, but bi-metal or carbide blades work ok. Just go slow since the board won't disperse heat like cutting into metal will.
I have just cut and am installing aluminum backing plates. I have cut and drilled 35 so far and installed about 6. Epoxy the holes, butyl the bolts, stainless bolts, nuts and washers. I also have wrapped the bolt shafts and under the washers with neoprene tape, hoping to keep the ss and aluminum from touching. We will see. The reason for aluminum is that I had lots on hand.
G10. Takes paint well if exposed. Nasty stuff to cut or drill press, go slow to prevent heat build up. Bi-metal blades/whole saws. Vacuum and dust mask a must.
I used to buy it at McMaster, but seems small pieces are available on Ebay for very short $$$.
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