Fixing cleat to deck without backing plate

[Ric]

I want to attach a Spinlock PXR camcleat to a part of the deck of my boat where it is not possible to access the underside of the deck to fit a backing plate. Is my only option self-tapping screws or (worse) open-heart deck surgery to gain access to the underside?

Any tips to make self-tappers more permanent?

 

[pappaecho]

You might epoxy a pad above the deck with self tappers as well to spread the load

 

[Boathook]

I would not trust a cleat fitted with self tappers. Best to open up underneath and reinforce as required and use bolts with suitable large diameter washers. If time is spent on the 'patch' covering the hole it can look quite neat.

 

[Searush]

Self-tappers won't survive the first snatch on it. You must use bolts & a backing pad.

I had to cut a hole in a cosmetic double skin liner in the heads, I made a wooden cover from 2 bits of thin ply, one fitted inside the hole, the other was an inch bigger all round. Glue the two together & varnish to have a cheap & attractive hatch cover. 3 countersunk domed self tappers hold it neatly in place. It looks as tho it was meant to be there now.

 

[Spyro]

Bad idea, you really need a backing plate. Whats the reason you can't get access? Is there an inner moulding?

 

[Lakesailor]

Can't see the reason for a backing pad. The loads will be parallel to the grp moulding. It's a cleat.
However self tappers are going to be very suspect. So on that basis some small holes to allow the fitting of bolts with washers and nuts will be needed. But as you say there is no access how about some of the blind fitting solutions used for plasterboard. Fit with Sikaflex to avoid movement and leaks.

 

[gus]

If the space below where you wish to fit the cleat is confined and can be filled with resin or epoxy through the fixing holes, it may be possible to tap a threaded hole into the filler. That way the fixing bolts can have much more to grip onto and should hold the cleat secure.

 

[VicS]

It depends on the loads

I put self tapers in with a dab of Araldite
Not had one pull out yet but there no real load on any off them

 

[William_H]

Fixing a cleat

I would suggest you purchase a tap for the appropriate sized screw.(4mm?) A decent tapped thread will be a lot stronger than the randomly gouged grip of self tapper. Now if your cam cleat has only 2 fixing holes and you are doubtful about the fixing strength. (The load is sideways to the screws.) Then make a plate to expand the mounting base. This could be from fibreglass about 6mm thick or stainless steel. If you go stainless steel you may choose to cut a larger hole in the deck so that a nut on the under side of the plate for the actual cleat bolts can fit in. The bolts then around the outside of the plate are tapped into the deck. For fibreglass base just epoxy the f/g into the deck then tap the 2 screws for the cleat into the plate and deck and add screws around the outside for more strength. (if you wish)
So much depends on the loads you expect the cleat to take and how over engineered you want the solution.

Mine are 3/16 WW tapped into the cabin top but then with a washer and nut. When you screw it in you don't need a helper to hold the screw while you tighten the nut. I use a battery drill on low speed with the tap in the drill. So quick and easy.
good luck olewill

 

[Deleted member 36384]

It depends on the loads

I put self tapers in with a dab of Araldite
Not had one pull out yet but there no real load on any off them

This is a very good suggestion. The Gudgeon Brothers book on boat building demonstrate tests carried out on screws epoxy glued in place using various methods. The pull force exceed the yield strength of the screw metal in some of the tests without any shear failure of the base material.

The web site below has various articles and one is about mounting deck hardware, I think its in the very top link (not in the table of links). Note that the screw in epoxy test results are in their book, which you have to buy.

http://www.westsystem.com/ss/fiberglass-boat-repair-and-restoration/

Lakesailor's comments on the load direction is very relevant and this could be an easy job to do.

 

[Ric]

I did fix them with araldite - but would a splodge of gel coat filler be even better?

I did also look at those blind fastener thingies, but they're not stainless so would not last long. If I could find some stainless versions they would do the job.

 

[Chris_Robb]

Can't see the reason for a backing pad. The loads will be parallel to the grp moulding. It's a cleat.
However self tappers are going to be very suspect. So on that basis some small holes to allow the fitting of bolts with washers and nuts will be needed. But as you say there is no access how about some of the blind fitting solutions used for plasterboard. Fit with Sikaflex to avoid movement and leaks.

Lake sailor lives on fresh water - rust is not a problem to him!!!!!

Do you want a bodge or a proper job?

 

[flipper]

This is a very good suggestion. The Gudgeon Brothers book on boat building demonstrate tests carried out on screws epoxy glued in place using various methods. The pull force exceed the yield strength of the screw metal in some of the tests without any shear failure of the base material.

The web site below has various articles and one is about mounting deck hardware, I think its in the very top link (not in the table of links). Note that the screw in epoxy test results are in their book, which you have to buy.

http://www.westsystem.com/ss/fiberglass-boat-repair-and-restoration/

Lakesailor's comments on the load direction is very relevant and this could be an easy job to do.

You can download the whole manual for free (first link on that page) It's really useful. See page 52 for fastenings without a backing plate.

 

[Deleted member 36384]

You can download the whole manual for free (first link on that page) It's really useful. See page 52 for fastenings without a backing plate.

The book with the test results is this: -

http://www.amazon.com/Gougeon-Brothers-Boat-Construction-Materials/dp/0878121668

Its not the same as "Fiberglass Boat Repair and Maintenance" in the link that I gave in my post and where you have kindly listed the page number. However, some of the methods are in both publications.

 

[Lakesailor]

Lake sailor lives on fresh water - rust is not a problem to him!!!!!

Do you want a bodge or a proper job?

I was forgetting some of you have to be so careful

Like the two links suggested.
I would certainly go for an epoxy paste into some oversize holes with the screws or bolts set into the paste. Avoid voids beneath the base plate.

 

[flipper]

You could also try epoxying a SS nut into the oversize hole and use a release agent on the bolt so you can get it out after it goes off. In principle you will have a nut firmly fixed in place to screw into as well as the threaded epoxy.

Apparently hairspray works as a release agent but it didn't on the job I was doing so had to cut the whole lot out and start again.

like I said...'in principle'

 

[lw395]

If the deck is balsa or foam sandwich, a method that works pretty well is to create a void in the balsa or foam, then fill that with an epoxy/glass mix.
The void can be created by drilling from the top and using a sharpened allen key in a power drill to mullah the balsa. Hoover out, stuff with chopped glass, then pour in warm epoxy.
Or squirt it in with a syringe.
It should bond to both sides of the deck sandwich.
You could put a stud or coach bolt in the epoxy and have a nut above the fitting perhaps.

It depends what the fitting is for.
Cleating some minor control line or towing the yacht?