Bonding Wooden Pads to GRP

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WoodyP

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I wish to fit a calorifier and will need to to bond some wooden pads to the hull to level up the base and to screw it to.

I would be grateful for suggestions as to the best way to achieve a bond that is simple and strong. I assume that some sort of epoxy is the way to go, but idly wondered if some of the builders fix stuff (eg Sticks Like ****) would be good enough for the purpose.
Thanks,
G.
 
I find West System with the micropore filler to be very, very strong.

Simple to use if you use the metered pumps. Doing it by ratios proved difficult last time; when I thought I would save the expense of the pumps. /forums/images/graemlins/smile.gif
 
If this timber is going low down in the hull I would look at treating it with an epoxy first then using epoxy resin and micro fibres to glue it into position.

Method:
Cut and shape timber including any holes to be drilled. Wipe to remove any dust and apply epoxy mixed with 30% Methylated Spirits, this will thin the resun and assist penetration, apply extra on the end grain; when tacky apply 4 coats wet on tacky to avoid sanding between coats.

The area they will mounted will have to ground back to glass to get the best bond, wipe clean, mix epoxy and add micro fibres to about tooth paste consistency, apply and smooth out with the tip of a broom handle, small fish paste jar or the back of a plastic spoon to form a gusset. Clean up any excess when still wet because this stuff is very hard to sand off after setting.

Use shallow containers to mix epoxy to avoid heat build up, put 2 latex gloves on each hand, when they get sticky just pull the top one off.

After curing sand off any sharp bits and apply a paint, flow coat or mix some white pigment into your epoxy resin and paint that on. Epoxy must be protected from UV light to avoid deterioration.

Micro fibres make a very strong and hard glue, if you try pulling the timber off, the timber will break, but not the micro fibre joint.

Hope this helps.

Avagoodweekend......
 
That's a very good description.

The hardest part I find is devising some means of holding the pad in place on a bulkead or under the deck, until the epoxy sets. I usuall end up with bendy sticks wedged against the opposite bulkhead or the deck; which is ok until you forget they are there and knock them down /forums/images/graemlins/frown.gif
 
PU adhesive is very simple & very secure & fully waterproof.
Sand mating surfaces with coarse paper for extra strength.
As Twisterowner says, wedge against something opposite.
Can get as quick as 5 minute setting, but I'd wait longer than that before I started screwing.
 
No more nails or the screwfix generic is very effective on GRP. I used it to stick rubbings strakes to my tender, it survived lots of hard use and being out in the weather. I still feel it's a bit of a bodge for use on a yacht though! It does not cope with really wide gaps, I would choose epoxy if the inner surface of the hull is very 3D. Calorifier mountings should be quite strong as they are heavy items when full, and you would not want it breaking loose in a knockdown.
 
That's a very full description of a proper job. The mounting is low down in the hull behind the engine. I would try PU adhesive, but I know in my heart of hearts that this would leave the wood exposed and possibly open to rot at a later date. Also, I don't want to have to put it all together again if it breaks loose, because it is next to the prop.
Thanks to you all for your suggestions, and thanks to Oldsalt for the "how to do it" which was just what I needed. /forums/images/graemlins/smile.gif
G.
 
It is interesting that none of the posters suggested the alternative of glassing the wood blocks in. In that case the composition of the glue is not terribly relevant.

That's what I did and that's what I'd expect of a professional installer. The stresses from a full calorifier in a seaway are considerable.

But then of course you may all have engine bearers of wood stuck to the inside of the hull.
 
I've just done exactly that with a watermaker mount....

Initially, I shaped the 'legs' of the plinth to fit the hull contour, and then sikaflexed them down (291).... and then decided that this wasn't enough, so trimmed the excess Sika off, and put several layers of epoxy and glass down and around each leg and a further 8" onto the hull.... its a solid as a solid thing now!
 
Twisterowner,

Avoid props if possible, they can apply too much presure and squeeze out the reain leaving a weak joint.

If you must use props (sometimes we have to) make sure you have small spacers under the item to ensure the depth of glue is maintained.

Andavagoodweekend......
 
Whilst I agree this gives a strong mount, unless one epoxies the wood to the hull and make a generous fillet so the glassing aheres all over the wood block the strength is mainly in the glassing with the wood as a backing for the mounting screws.
 
additional question

very interesting descriptions!

May I ask, if the inside hull is painted, before epoxying anything to it, is it necessary to scrape the paint off and bring out the rough laminate ? Or will the paint give sufficient adhesion when loads may be high?

I glued and epoxied a few things to painted laminate and they are still at their place, but they were non-load bearing items, anyway nowhere near the resistance one expects from calorifier fixing points..

tia
 
Re: additional question

[ QUOTE ]
Or will the paint give sufficient adhesion when loads may be high?

[/ QUOTE ]

No. Even if the epoxy made a good bond with the paint, the paint has not made a strong enough bond with the grp.
 
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