Epoxy or Sikaflex??

[scottnewcombe]

Ok So I've successfully removed the rotting transom from my 27' motorboat. The remaining framework is now cleaned back ready to receive the new ply. Cheque book in hand I am about to go off and buy ply, fixings and epoxy pack when someone at the club says "Oh I suppose you're putting that back with sikaflex then?". Hadn't thought of that?


I was planning on coating the ply with epoxy all round before fixing it. Then bonding it to the framework with epoxy (and silicon bronze screws)and then sheathing the outside with fabric afterwards. I have written to Wests who are sending an info pack etc.

Any thoughts on the where's and whyfores of each?? If sikaflex should it be a special type, does it need a primer, will it stick OK to the epoxied ply??


I need to get the transom on quick because the gybes from other club members are unbearable. "Aren't those deck drains a little big" "Turning her into a jet ski then?" "I take it you're not putting her into the water tomorrow then?" very funny I'm sure.


Cheers

Scott


<hr width=100% size=1>

 

[AndrewB]

I think you are better going with epoxy.

Sikaflex (291) is essentially a sealant. It is a soft-setting, rubbery, one-part polyurethane. It cannot be 'painted' on like epoxy and the wood would have to be fully prepared before-hand with paint or varnish. Even though it has also serves as an adhesive, it won't add much mechanical strength and you would have to rely on the screws to provide that.

However, the suggestion to use it is by no means impractical. It is strongly waterproof and suitable for underwater applications; it would be cheaper; its good specially if there is a lot of gap filling; and it can be painted over.

There are a range of other similar Sikaflex products that offer UV or flame resistance, and one outright adhesive. But they would not obviously offer you anything extra.

 

[kgi]

what's the boat used for?, if its a displacement hull, you could use 3M 5200, similar to sikaflex, very strong, has good gap filling properties (with in reason), can be painted, is resistant to just about everything, and generally is good for sticking anything to anything (just look at how much ends up on your hands). if its a planing boat then i don't know if i would use sikaflex/5200..........hope this is of some value......keith

<hr width=100% size=1>

 

[Boathook]

I would use epoxy. With the correct fillers and thickeners it will fill gaps and be strong. If done correctly any screws will only be needed to hold the transom in place whilst it dries.

<hr width=100% size=1>

 

[scottnewcombe]

Thanks chaps

Kind of confirms what I was thinking. It is a planing hull but the engine that is currently installed only pushes her along at 8-9knots. The V8 Chevvy engine was replaced by an old 2.5 BMC well before I bought her.

Many thanks

Scott

<hr width=100% size=1>

 

[oldsaltoz]

G'day Scott,

The pack you have coming should contain a pack of fibre material, when mixed with epoxy to the consistency of tooth paste, it makes a very strong water resistant Glue with excellent filling and bonding properties. Just don't leave any proud for sanding off later, you will find it's difficult to sand off.

The pack should also contain some closed cell balloons, again, mixed to the consistency of toothpaste, it makes a great filler for fairing, easy to sand and leaves a smooth finish.

Using epoxy will no doubt cost more, however, you will only have to do it once.........

Just take your time, make sure any fresh cut edges are re coated with epoxy. When you have it all in place and sanded off, give it three coats of resin, wet on tacky, then a final light sanding ready for paint.

Tip. Epoxy resin will leave a wax like deposit in it's surface, formed during the curing, try not to sand this wax back into the surface, wash it off with tap water and a plastic scourer till the water no longer beads.

You can also save on harsh expensive chemicals to clean up: use white vinegar, then wash in soapy water and rinse. If a resin roller (Small threaded steel type) is covered in resin that has gone off, you can retrieve it by burning the resin off with a gas flame, but please not in the kitchen......

I hope this helps

Andavagoodweekend. Old Salt Oz /forums/images/icons/cool.gif

<hr width=100% size=1>

 

[scottnewcombe]

Thanks mate

I'm quite looking forward to having a go now.

Scott

<hr width=100% size=1>