laminating and glueing teak / oroko

[djs]

Your advice is needed.
I need to fashion a tapered block to site a heater flue on the coachroof. The current one has split and has been gummed up over the years with what looks like sikaflex. The small leak is damaging internal woodwork and so it's time to do the job properly.

It's tapered in order to provide a horizontal surface for the flue chimney on a slopeing section of coachroof. The majority of the block will sit on an inlaid teak surface but will overlap the gelcoat of the coachroof on one side.

the wedge will need to be ~50mm thick at its thickest, reducing to ~20mm at the thinnest. It will be 210mm diameter. Current one is circular but i think i'd prefer to make its replacement square with rounded corners to increase the thickness of wood and hopefully reduce the tendency to split.

I can get hold of unplaned teak or oroko planking in a sufficient width but not at 50mm thick. So I think the way forward is to laminate planking to first create a block of sufficient thickness.

Views sought on:
whether laminating is the way forward rather than continue to search out a block of sifficient thickness.
what is the best option for glueing the teak / oroko to create the block?
would I be better using unplaned wood to create better surfaces for glueing?
what is the best option for glueing the block to the deck (teak decking and gelcoat)?
any other thoughts and advice.

thanks in advance
Dave

 

[srp]

Laminating is fine. I would use epoxy thickened with microfibres. A planed surface, not sawn, is best, and clean with acetone or meths just before glueing up. It will need clamping to close the glue lines. Clamping might be difficult if the parts are tapered before assembly - maybe do the tapering afterwards if you have the tools, or possibly use small screws between the laminates to prevent sideways movement.
For fixing to the coachroof I would probably use screws from the inside (you might want some sort of backing plate) and bed it down with Sikaflex, or a non-setting mastic such as Arbomast.
When you discover the price of teak, you'll decide to buy iroko, which is just as good for a job like this (but the dust is an irritant when sanding or machining).

 

[Poignard]

Here's one I made earlier! Not the shape you wanted but, as you can see, it is laminated. The wood is mahogany and the laminations were glued together with thickened WEST epoxy.

I arranged the lamination so that the grain of each piece was at 90 degrees to its neighbour. I bedded it down on the coachroof with window frame sealant.

The s/s flue flange was bedded down on a rubber gasket, which leaks a bit. I will rebed it using a heat resistant sealant.

When glueing teak/iroko it is important to degrease the mating surfaces with acetone. Mahogany is nowhere near as oily but requires varnishing or painting for protection.

 

[wrr]

Teak and Glue

If you are planning to varnish the timber, what passes for mahogany would be easier to work and glue. If you are planning to leave it bare, then teak would get my vote. You might be able to source some offcuts if there is a wooden boatyard near you.
However, I have seen some failures of epoxy with teak, This could be particularly an issue if the flue gets warm, as the wood may move and the epoxy may soften. I have reverted to using resorcinol (/phenol/formaldehyde) glue for teak (was Cascophen, now called Polyproof) or, alternatively, a polyuretane such as Semparoc (Balcotan replacment).
In either case, careful preparation, solvent degreasing and appropriate clamping are essential.

 

[Blueboatman]

Made mine ( square) from meranti which is usually available in 50mm at your local independent timber yard as it is common for external window cills and you can probably get a decent offcut.
I was always going to paint mine black cos, well stoves n all

Now here's a trick if you are not familiar with woodworking.
Fit a 24grit flexi sanding disc to a 4 inch angle grinder and you will very quickly shape the block to the convex under-profile for the coach roof.
I throughbolted on sikaflex bedding and inside I made up a ( teak) roundel for neatness where the flue is cut through the cabin liner..
Hope some of that helps..stay warm