Inwmale and Outwhale Joinery and Installation

jpowers123 · Post by **jpowers123** » Sun Dec 20, 2009 3:37 pm

I began attepting to fit my inwhales and outwhales today and ran into a big problem. I had cut a scarf joint to join both the inwhales and outwhales. While trying to bend the inwhales in place, both joints gave way. Not sure if the epoxied joints are supposed to be able to survive that type of stress. I glued with west systems and some of the fibers. Should I have been even trying to use a scarf joint here? Or, did I have a glueing problem?

Glen Smith · Post by **Glen Smith** » Sun Dec 20, 2009 4:23 pm

The scarf joint must have at least a 7 to 1 taper. You must apply straight epoxy to both joining surfaces until it will no longer absorb any. Then wipe off excess epoxy and apply thickened epoxy to the joints. Clamp lightly and allow to set for 24 hours before attempting to install inwales/outwales.

jpowers123 · Post by **jpowers123** » Sun Dec 20, 2009 8:21 pm

I think I must have not let it set long enough or something and I most likely did not saturate the joint enough. I also did not apply straight epoxy the first time. I went right to the thickened. I have reglued and will see what happens after a 48 hour wait time. I was at a little less than 24 hours this time when I started clamping them on. Thanks for the help.

What disadvantage would there be to a butt joint at the center if using screws?

Glen Smith · Post by **Glen Smith** » Sun Dec 20, 2009 8:50 pm

jpowers123 wrote:I think I must have not let it set long enough or something and I most likely did not saturate the joint enough. I also did not apply straight epoxy the first time. I went right to the thickened. I have reglued and will see what happens after a 48 hour wait time. I was at a little less than 24 hours this time when I started clamping them on. Thanks for the help.

What disadvantage would there be to a butt joint at the center if using screws?

If you didn't apply straight epoxy first you ended up with what is called a dry joint because the wood absorbed some of the epoxy, making the thickened epoxy a drier mix and losing its adhesive properties.

A butt joint wouldn't have any strength at all. Applying a downward pressure on the gunwales at a joint could very likely result in damage.

jpowers123 · Post by **jpowers123** » Mon Dec 21, 2009 2:33 am

Thanks again for all of the assistance.

Rod Tait · Post by **Rod Tait** » Mon Dec 21, 2009 7:33 pm

It may also depend on where your joint is. If you have them near the ends to save on some lumber costs, the stress near the ends is quite harsh. I have had some blow on me even with 12:1 scarfs and lots of correct gluing. The scarf should be in the middle of the boat where there is the least stress and the scarf top to bottom with the bending occurring oposite and horizontal which puts less stress on the joint.

jpowers123 · Post by **jpowers123** » Wed Dec 23, 2009 9:46 pm

I actually have the joint in the very center. I believe I may have had a glueing problem. I have recut the scarfs, they are a little over 6 inches long, have re-epoxied and wil give it until the day after Christmas to dry, 5 days, then I will have another go at it.

Rick · Post by **Rick** » Thu Dec 24, 2009 9:58 am

You should be fine with the joints amidships. I had an inwale snap while bending to the sheer formed by the high ends on my Huron... with the repaired inwale, the scarf angle was only 5:1 and it was strong enough to take the bend.

Something that might help with the strength of any scarf joint is using plain epoxy... I don't think epoxy thickened with fine sawdust will form as strong a joint and epoxy that's allowed to thicken on it's own with time and then applied after a first coat to soak the end grain will be stronger... my $0.02 only.

Tom in MN · Post by **Tom in MN** » Mon Jan 25, 2010 4:54 pm

You could also try pinning your scarf joint with a dowel. After you have pre treated the surfaces with epoxy and have rewetted and clamping it up for the final, take your drill and drill a couple of small holes across the scarf and insert a couple of dowels that are also wetted with epoxy (and we pre-wetted whe you did your scarf faces). This will give you added strenth and help prevent it from separating.