Backing plate

[emnick]

I intend fitting a backing plate to the transom of our boat for a hydrovane I was considering aluminium plate to spread the load. What's the opinion of using Sikaflex to bond it to the hull? or should I use epoxy, if so is there a mix I should be using.

I was looking at the Sikaflex as it would IMHO follow the contour of the laminate .

Thanks for any help

 

[robmcg]

Our hydrovane has one backing pad in ply glassed over, the other in hpde plastic. Both are sikaflexed in place.

 

[William_H]

If you use epoxy add talc powder or microballoons to thicken the epoxy to a conssitency sufficient to fill all the uneveness of the inside transom.
As suggested there are better materials than aluminium for the pad. You could use the cutting board type plastic. Another alternative might be carbon fibre laid up with epoxy over the area starting larger area then reducing the area to remove stress raiser edges. As many layers as seems right but something like 6mm should help a lot. good luck olewill

 

[Rigger Mortice]

Aluminium would be fine, just make sure it's thick enough.

Fix it with either epoxy or sixaflex, whichever you fancy and have to hand. They would both do the job perfectly well.

 

[emnick]

I was going to use 10mm ally plate, leave the skiaflex to go off slightly and tighten fully when cured. would you think that OK
Thanks for replies

 

[rivonia]

Try CT1 it works when wet and once applied and cured cannot be removed- without a huge amount of brute force.

 

[vyv_cox]

I was going to use 10mm ally plate, leave the skiaflex to go off slightly and tighten fully when cured. would you think that OK
Thanks for replies

Perfectly OK. I fitted backing pads for my Yacht Legs 20 years ago. Although i used 20 mm Tufnol for the pads I followed the same method you propose. They have never moved since. I suspect the slight flexibility that Sikaflex gives is good for the small amount of flexing that may occur with a yacht hull, whereas epoxy could well crack.

 

[Rigger Mortice]

I was going to use 10mm ally plate, leave the skiaflex to go off slightly and tighten fully when cured. would you think that OK
Thanks for replies

Absolutely fine.

 

[emnick]

Thanks for all the replies

 

[oldsaltoz]

I intend fitting a backing plate to the transom of our boat for a hydrovane I was considering aluminium plate to spread the load. What's the opinion of using Sikaflex to bond it to the hull? or should I use epoxy, if so is there a mix I should be using.

I was looking at the Sikaflex as it would IMHO follow the contour of the laminate .

Thanks for any help

Is the transom solid fibreglass? because the methods above seen to be for solid glass transoms, not always the case, some have ply or foam between the skins and need a totally different approach.

Good luck and fair winds.

 

[emnick]

Thanks..............I am pretty sure its solid fibreglass

 

[oldsaltoz]

Thanks..............I am pretty sure its solid fibreglass

Then have you considered protecting the exposed fibreglass in the bolt holes?

The 'normal' practice is to drill the holes oversize so you have a 6 mm gap around the bolt/fixing.
This is then filled with a mix of epoxy resin hardener and Micro-fibres (after taping the inside to avoid fall out) and allowed to cure then re drilled to the desired size.

This ensures the exposed edge of the new hole is not only sealed against water ingress but also made stronger.

Good luck and fair winds.

 

[Rigger Mortice]

Thanks..............I am pretty sure its solid fibreglass

You'll find out when you drill it. My transom has a core....Gelcoat, Grp, 3mm core, GRP..... The whole lot is about 6mm thick. I've fitted backing plates for various things without problem. If you are using Sikaflex just make sure that it fills the hole for the reasons Old Salt says, but TBH I wouldn't worry about reinforcing it if the core is only a thin one. (Sorry OS!)