# Backing plate material for stanchions



## benajah (Mar 28, 2011)

Hi all, I did a search but didn't come up with anything. I need to fix a loose stanchion and not sure of the best material to use as a backing plate. The existing backing plate is really small, about four and a half square inches and i want to put something bigger. I have some 16ga sheet steel, some plywood also, but wanted to see if there are better materials to use.


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## BELLATRIX1965 (Jan 2, 2007)

I'm afraid sheet metal will not do much for you under stanchions! I buy 1/8" thick stainless steel from the "scrap" bin at a local machine shop (cheap!) and make my own custom backing plates. Just be sure to use bi-metal saw blades and cobalt drill bits, or you will get frustrated trying to cut it!


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## pdqaltair (Nov 14, 2008)

While SS is certainly good stuff, your going to find 1/8" aluminum MUCH easier to work with and sufficient for your needs. Corrosion is only an issue if you have way too much leakage. Sheet metal shops and sign stores should have scraps. FRP is also a good material; 1/4" is a good general purpose thickness.

If you aren't into scrounging scraps, McMaster Carr has everything.


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## olson34 (Oct 13, 2000)

Use a 3/8" in plate of G10/FR4 plate.
McMaster-Carr

Something about 6 X 9 inches, or whatever will fit well. Moosh it into place with thickened epoxy. Redrill the holes oversize in the deck, fill with thickened epoxy, redrill for the bolts.

Bed the base in your choice of marine goo, and you're good to go... for another 20 years... plus.


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## mitiempo (Sep 19, 2008)

I agree with olson34. And when you re-drill after potting the deck holes you can tap the holes for the bolts easily as well. If the holes are tapped between the deck and 3/8" G10 you almost don't need the nuts but I would certainly use them as well.


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## benajah (Mar 28, 2011)

Thanks for the suggestions. My friend, who has not a lot of experience on boats went sailing with me on Saturday. He is a big dude, 230 or do, and I didn't think to brief him on how to get on and off a boat and he just grabbed a stanchion to climb on and wrenched the he'll out of it, pulling the bolts loose, the outboard ones are pulled out a good 1/8 inch.
Which raises another concern. My boat is a Cal 2-27 and I haven't messed with the stanchions yet, will try to work on it tomorrow, but it seems to me that if they pulled out that far....were they installed with a backing plate? I can't see the fitting now because there is a cosmetic shell over it that is the size I mentioned before.
I'm worried about what I am going to find when I get everything exposed. Oh the joys of boat maintenance.
At least if this happens to be a weakness I can go through and rebid and redo all of them before I run into problems in the future. Good to know beforehand.


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## studentt (Aug 25, 2010)

I would advise NOT using plywood as a backing plate material for your stanchions. If a leak does develop, you may be depending on mush to hold your stanchions in place.


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## SlowButSteady (Feb 17, 2010)

studentt said:


> I would advise NOT using plywood as a backing plate material for your stanchions. If a leak does develop, you may be depending on mush to hold your stanchions in place.


Plywood backers should have 2 or 3 coats of thinned epoxy (applied to the bolt holes as well) to prevent this from happening.

My '75 Cal 2-27 originally (so far as I can tell) had no backers on any of the deck hardware. Unless you have tons of karma racked up, and the nuts on the bolts were just loose, for a stanchion bolt to pull out like that your boat almost certainly has some rotten core. The good news is that 2-27 decks were all plywood cored (again, so far as I can tell), so the rot may not have spread very far.


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## mitiempo (Sep 19, 2008)

Plywood core spreads wet and eventually rot farther than balsa will. The balsa is end grain where the plywood has a laminar structure and the moisture will spread through it quickly.


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## SlowButSteady (Feb 17, 2010)

mitiempo said:


> Plywood core spreads wet and eventually rot farther than balsa will. The balsa is end grain where the plywood has a laminar structure and the moisture will spread through it quickly.


That makes sense, but I've seen a couple of cases where moisture/rot didn't spread very far in plywood (however, those may have just been anomalies).


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## mitiempo (Sep 19, 2008)

And balsa, while a good core material can have problems if the gaps (kerfs) cut into balsa to allow it to follow the curve of a deck are not properly sealed with resin. Improperly sealed they allow water to travel easily throughout the core.


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## ntspinner (Sep 11, 2009)

*Stanchion backing plate*

I too am researching the type of material for a backing plate for my CS27 Stanchions. While doing a thorough cleaning of the deck I noticed a crack in on of the stanchion base. I looked further and realized that there is no backing plate at all in any of the stantions.

It would seem everyone is in favour of aluminum plate. I was checking metal supermarket and there are different type of aluminum. Would anyone know if there is a difference. I sail in the great lakes so no salt corrosion to worry about.

Thanks,


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## mitiempo (Sep 19, 2008)

Any aluminum in your case could work. Fiberglass placed with thickened epoxy is a better choice though. Holland Marine has stanchion bases for the CS27.

Holland Marine Products


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## sailak (Apr 15, 2007)

olson34 said:


> Use a 3/8" in plate of G10/FR4 plate.


Is that a plastic? Checked your link but didn't see G10/FR4.

Thanks -- in need of some backing material as well.


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## mitiempo (Sep 19, 2008)

G10 is a prefinished laminate of fiberglass cloth and epoxy. Available from McMaster Carr or you can make your own easy enough.


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## carl762 (Jan 11, 2010)

You'll definitely want to use Butyl Tape (see sticky of Maine Sail's) when you rebed your plates. I'm sold on the stuff and will be using aluminum backing plates and the tape when I eventually redo all my stanchion plates and other hardware.


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## tommays (Sep 9, 2008)

At least on my Cal 29 the bases are way to SMALL on deck and no matter the backing plate size they would dammage the deck










With a bit of planing and a a few bucks at the waterjet place










We are good above and below deck


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## mitiempo (Sep 19, 2008)

ntspinner

I second the choice of butyl. Everything the CS factory installed on your deck, as well as the hull/deck joint was originally bedded with butyl.

Here's a great how-to link by another CS owner.
Re-Bedding Deck Hardware Photo Gallery by Compass Marine at pbase.com


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## johnnyandjebus (Sep 15, 2009)

ntspinner said:


> .
> .
> I was checking metal supermarket and there are different type of aluminum. .
> Would anyone know if there is a difference. I sail in the great lakes so no salt corrosion to worry about.
> ...


NT 
A couple of thoughts;
1) As already mentioned any type of aluminum will do.
2) You mentioned metal supermarket, a great source. With that said you might consider finding a metal recycling yard and buying used. In my home town KIMCO has a huge metal recycling yard and the employees will allow you to wander around and find what you want. If I recall correctly I paid 2-3 $ a pound for aluminum plate last time I was there. You may not find perfect pieces to fit your needs but it will be noticeably cheaper than buying new. Buy more than you need and a couple of good blades for the hack-saw.

John


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## Waltthesalt (Sep 22, 2009)

I put 1/8" SS backing plates on my Cal 29 stanchons. The original installation was only washers. It wasn't all that hard to cut with a fresh hacksaw blade. I wouldn't use plywood. With aluminum you've got the chance of accellerated corrosion dissimilar metals with the bolts which are likely SS.


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## mitiempo (Sep 19, 2008)

I agree dissimilar metals are not always a good idea but up under the deck and bedded properly it shouldn't be a problem. The only connection is the bolts & nuts, unlike a mast fitting where there is much greater contact and it does get wet regularly. 

Whatever you use for backing place it with thickened epoxy because of the uneveness of the area.


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## sailak (Apr 15, 2007)

mitiempo said:


> Whatever you use for backing place it with thickened epoxy because of the uneveness of the area.


Unless the area is very uneven does it need the epoxy? Would using epoxy to stick the backing to the deck/bulkhead/etc just transfer any stress to the area at the edge of the backing? If not glued down it will prevent pull through yet not localize any stress.


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## mitiempo (Sep 19, 2008)

If thickened epoxy isn't used the backing plate will be only against the parts that stand proud. Epoxy will spread the bearing surface to the entire area of the backing plate. I would do this on any boat.

The CS27 needs the epoxy. The deck overlaps the hull flange creating a 2 level surface under the stanchion bases. It is not smooth like in Tommay's picture. I know as my boat is also a CS 27.


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## ntspinner (Sep 11, 2009)

Thank you all for your help. I agree with Brian. You need epoxy with the backing plate as the surface is uneven. Brian what is the best method to ensure that the epoxy is spread evenly between the plate and deck. I see other threads mention the use of a syringe. Your thoughts and guidance is appreciated.

Nasim.


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## mitiempo (Sep 19, 2008)

Mix the epoxy well and then add the thickener, colloidal silica is a good choice. When it is the consistency of peanut butter cover the plate with it and don't be stingy. When it is put in place remove the excess.

Syringes are great for filling holes in the deck.


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## BluemanSailor (Apr 28, 2009)

Has anyone considered using Starboard as a backing plate? 
any thoughts? 

Just brought a boat and will need to replace the really bad wood backing plates that exist there- there not wet or rotted yet but I really don't like wood.


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## overbored (Oct 8, 2010)

Starboard is about the worst thing you could use for a backing plate it is to soft and flexable. the bolts will not stay tight. one of the best is G-10 plastic laminate around 3/16" thick bonded to the structure with thickened epoxy. these plates were installed to replace very badly warped starboard plates that were 3/4" thick and the bolts had been tightened so many times that they were half way thru the old 3/4" plates. the old plates weighted about 2 lbs. each compared to the G10 at 2 oz. each.


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## mitiempo (Sep 19, 2008)

I agree Starboard is a bad choice. In addition to its softness a good backing plate is epoxied to the underside of the deck to strengthen it and Starboard doesn't stick to anything reliably.


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## SloopJonB (Jun 6, 2011)

mitiempo said:


> And balsa, while a good core material can have problems if the gaps (kerfs) cut into balsa to allow it to follow the curve of a deck are not properly sealed with resin. Improperly sealed they allow water to travel easily throughout the core.


Which is the case in anything that wasn't heavily vacuum bagged. I have repaired both and the water went WAY farther in balsa than in plywood. In the balsa deck there were areas of multiple sq. feet that were turned into something resembling peat moss while in ply, even with top skin separation the ply only got damp in smaller areas and NONE was rotted or even softened.

Was I just lucky?


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## SloopJonB (Jun 6, 2011)

I like using aluminium for backing but I do it a little differently (with excellent, long lasting results) than what has been posted here.

First, s/s is very nice polished up but very hard to work with. I use 1/4" aluminium - 1/8" inch seems skimpy to me - it it easy to bend.

Pick up a small offcut at a metal recyclers - just work out the surface area you need beforehand. Cut the plates to size & shape with a jigsaw or bandsaw, then file & sand the edges to remove burrs and round them over nicely. Center a stanchion base (or other hardware as appropriate) on them and mark the holes. Drill the holes slightly over size to aid in sliding the bolts through from the top of the deck - alignment of these long holes can be problematic so a LITTLE clearance is a big help.

Next, drill the deck holes oversize for epoxy sealing (potting), heavily wax the top of the backing plate before applying thickened epoxy - this will keep the plates removable which I prefer. Cover the plates with thickened epoxy and moosh in place - clean off the squeezeout and secure them in place with whatever works - duct tape has served me well. Use the squeezeout to back fill the holes from the top. The purpose of setting the plates in epoxy is to ensure there is full contact with the usually rough underside of the deck, otherwise the plate will ride on the high spots.

After curing, redrill the holes in the deck, put a small countersink in the top surface - this will create a small "O-ring" of caulking - VERY effective.

Prefit everything to ensure you have drilled straight - make any clearance adjustments required then tape off around the deck surface, apply caulking to the top of the deck and the underside of the fitting. Despite your best instincts DO NOT caulk the underside of the deck or the backing plate. If you do this, the top surface can come unsealed and you won't know since the under surface can remain sealed - I prefer to have the leak show up so I can fix it.

Replace the fitting and plate, then bolt it down tight with S/S fender washers and acorn nuts. This gives a very sanitary look with no head ripper threads showing. Don't do the "gasket" method Don Casey recommends where you snug down and leave until cured, then fully tighten. It sounds good but in actuality, you can't prevent some movement of the fastener when retightening and this will compromise the seal. The O-ring on the countersink will, at a minimum, hold enough sealant securely when the fasteners are fully torqued into wet sealant and there is no chance of breaking the cured seal.

After curing, run a razor knife around the bases to cut the cured sealant from the edges of the bases and peel the tape away - Voila - perfect, neat, fully removable, sealed hardware.

Enjoy for many years.

Another trick, when making backing plates for genny track or other long rows of bolts is to use appropriately sized Aluminium channel - taper the ends of the "sides" of the channel up to the underside of the deck and you will have nicely recessed nuts the whole length.


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## casey1999 (Oct 18, 2010)

olson34 said:


> Use a 3/8" in plate of G10/FR4 plate.
> McMaster-Carr
> 
> Something about 6 X 9 inches, or whatever will fit well. Moosh it into place with thickened epoxy. Redrill the holes oversize in the deck, fill with thickened epoxy, redrill for the bolts.
> ...


What is the best way to cut the G10 epoxy plate?


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## mitiempo (Sep 19, 2008)

A good metal blade in a jigsaw works well. 

SloopJonB

Fender washers with acorn nuts will not stay locked in place without a lock washer. Or better yet, use nylocks after the fender washer.

I would have no problem if the aluminum backing plate was not waxed. It's adhesion to the underside of the deck will strengthen the area. If possible stanchion backing plates should be a fair bit bigger than the stanchion base.


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## cghubbell (May 8, 2009)

mitiempo said:


> A good metal blade in a jigsaw works well.


Emphasis on GOOD blade. There is a big difference in quality between the cheap store brand bi-metal blades and the Dewalt or Milwaukee blades. If you get the wrong ones you can burn through one in less than 30 seconds of cutting. The G10 is not easy to cut, but I think it's the best stuff to use. It's very hard to get as good a layup making them yourself as the manufactured ones.

I used structural FRP (the grade one below G10) for my backing plates, and it is very good. If I had it to do over, I would go with G10 though.


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## mitiempo (Sep 19, 2008)

I use Bosch blades on a Bosch heavy duty jigsaw. Stainless isn't a huge problem either unless it is too thick.


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## overbored (Oct 8, 2010)

casey1999 said:


> What is the best way to cut the G10 epoxy plate?


Carbide coated blades work best on G-10 and Bi metal blades for stainless and slow down the blade speed
DeWalt DW4843 8 Carbide-Coated Reciprocating Saw Blade (5 Pack) | AceTool.com


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## olson34 (Oct 13, 2000)

casey1999 said:


> What is the best way to cut the G10 epoxy plate?


I have dulled up several kinds of saw blades over the years, but the best solution I know of is to measure and plan for your new backing plates as you strip off the stanchions. Then have the plastics supplier trim them for you. They have a diamond blade saw. Around here there is no charge for cutting, and even if there was a modest charge I would pay it. 

You're going to have a short list of piece sizes, and quite a few will be the same size. Use some 3/8" G10. Bed it in thickened epoxy. After doing way too many of these with misc. props holding up the backing plate from below while it cured, I realized that all that was needed was to locate the plate accurately and then drill down thru one or two of the old fastener holes -- undersize the hole enough to allow you cut some 1/4-20 threads in it. Then butter it up and have your helper drive a 1/4-20 bolt down from the top and sock it up as tight as needed while the epoxy cures.

Post cure, drill out the holes again and bed the bases down with good sealant, and "Bob's your uncle". 

Best,
LB


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## mitiempo (Sep 19, 2008)

And on the stainless a bit of cutting fluid or oil helps as well, especially if the material is thick or it's a long cut.


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## tommays (Sep 9, 2008)

SloopJonB said:


> Which is the case in anything that wasn't heavily vacuum bagged. I have repaired both and the water went WAY farther in balsa than in plywood. In the balsa deck there were areas of multiple sq. feet that were turned into something resembling peat moss while in ply, even with top skin separation the ply only got damp in smaller areas and NONE was rotted or even softened.
> 
> Was I just lucky?





















Lucky 








The water will travel the length of the plywood core piece AND the bond is only to the outer most skin and will peel really easy after it gets wet


























I cant tell the difference between my G10 areas and balsa core areas and the highest stress part of my boat










The mooring post is in drilled and sealed balsa and ZERO compression when runing in the hardware

























The stanchion bases are ALWAYS to small


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## SloopJonB (Jun 6, 2011)

mitiempo said:


> A good metal blade in a jigsaw works well.
> 
> SloopJonB
> 
> ...


Brian, I have never had a problem with the acorns loosening but lock washers can't hurt. I find s/s nylocks hard to get and very expensive and to my eye, they don't look as good as acorns. Re: making the plates removable, I agree that is just a little neurosis of mine - I just prefer to have ALL hardware removable. The Gougeons went so far as epoxying winches down instead of bolting - NOT!

I agree backing plates should all be larger than the hardware above, especially for stanchions - they are about the hardest pieces to brace and seal but their size is determined by each piece of hardware.

I find a lot of backing plates are way overkill - huge plates under winches are not necessary for example. The pressure on them is almost entirely shear so the backing plate provides little support. On my Columbia 43 the original winch mounting had only little regular size washers, not even fender washers and there was no problem after 35 years of use from New York through the Caribe to L.A. and thence to San Francisco - nothing loose or leaking or pulled up into the deck. Plates are needed where the load is tension, not compression or shear but I frequently see major hunks of metal backing up hardware where they do nothing but cost money and time. Fender washers are plenty for LOTS of stuff, you just have to analyze the load vectors.


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## mitiempo (Sep 19, 2008)

SloopJonB

I believe backing plates should become part of the boat - ideally fiberglass or G10 epoxied in so as to strengthen the entire area. And I never put looks ahead of function. And nylocks aren't that expensive. 

I did however buy some metric lock washers for the fasteners for a Lewmar hatch yesterday at an exorbitant price.


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## pdqaltair (Nov 14, 2008)

*A circular saw with a carbide blade is WAY faster and lasts...*

... way longer. That said, it's not great for the blade, so I reserve a blade for this and other rough use. But it won't dull the blade quickly, not compared to sabersaw blades. I imagine you will get hundreds of feet per blade.

A table saw is much easier and safer in terms of cutting smaller plates. That is my method.

Then pretty it up with a hand grinder with a 100 grit disk.

__________________

The other problem with Starboard (and polyethylene in general) is that it creeps under load, slowly warping. The result is that over time NO LOAD will be carried by the edges of the plate. It might be OK under a fitting that could be served by washers, but not under anything highly loaded.

___________________

While I agree in principle that it is better to bond the plate to the hull, if the hardware is ever to be replaced (a windlass for eg) and a different shaped plate is needed, this should be considered, along with the curve of the surface and the layup (solid or cored). Bonding isn't always the best answer... just most of the time. For stanchions, I think I would.


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