View Full Version : Scarfing chine logs and sheer clamps.

Rational Root
01-12-2007, 06:30 AM
I've started building a Glen-l 14. I'm still cutting the frames, but soon I'll be at the stage of needing chine logs and sheer clamps.

These are up to 16' long, but the Oak boards that I can easily get are 9' long.

Enter the scarf joint.

I'm using balcotan, so I have no concern about the ability to hold, however I do have a few questions.

How much do I need to stagger the joints by ?

Presumably I want the joints towards the stern where there is less bend....

On the joints that will not be exposed to the water, the direction of the joint should be based on the tension in the wood. Ie the outside should be the peice with least bend, to hold the other peice in place ?? Any thoughts ?

On the joints for the outside rails, Presumeably the joint should face backwards, so that water does not meet the joint as I sail.

Should I aim to have the scarfts between frames, so as to avoid unfair curves and extra stress ? Or is it OK to have them sitting on a frame ?

Or should I just suck it up and find the 16' planks that I need ?:confused:

Thanks for your thoughts.



01-12-2007, 06:51 AM
A properly made, properly glued scarf joint will be just as strong as the wood and will present no opportunity for water intrusion.

To a point longer is better. 6:1 is short; 12:1 is long. With oak I'd use 12:1, but then I wouldn't use oak.

Orientation doesn't matter. It also doesn't matter if they fall on a frame.

It's good practice to stagger them anyway and looks better if they are visible. They can affect the woods ability to bend in a fair curve (not much though) so it's better to locate them aft in areas of less bend.

I'm not familiar with your glue. I've had mixed results gluing oak with epoxy.

Rational Root
01-12-2007, 07:05 AM
Balcotan is a low foaming Polyurethane adhesive that is aimed at the marine industry. The big plus for me is that it works in the cold and it does not give off nasty fumes.

I'm going to try a few test peices and then test to destruction, and try leaving a few out in the rain for a while.

I'll post the results.

Since I'll have a few of these to do, I see a jig and a lot of work for my router in the near future.


01-12-2007, 09:08 AM
If the planking is to be scarfed,just put the scarfs in the chine logs where they won't line up with the scarfs in the planking. A solid run of the planking should strap the scarf of the chines. Only reason I mention this is because in some situations, where one is limited to certain planking stock lengths,pre thought scarf placement could save from having to add any extra scarfs in the planking that it might take to stagger the joints. Just a thought.

Ron Carter
01-12-2007, 09:15 AM
There isn't a full length board in my 13'6" sharpie. I built a 8:1 jig for cutting scarf's with my router. I agree with McDenny. The other thing you need is a good gluing fixture. The only thing that will mess you up is a dog leg at the scarf because something moved during clamping. I have used polyurethane glue exclusively for joining and laminating oars, paddles and long members for the last 5 years with no sign of faillure.

Rational Root
01-12-2007, 09:35 AM
The plywood will be 8' sheets, and the oak comes in 9' sheets.

I will be careful to keep the frame scarfs away from the ply scarfs.

I believe that I am about to become very practived as scarfing.



01-12-2007, 01:55 PM
i just saw your website. very nice job! i just finished restoring a 1969 simmons, my 8th one. what happened to the frames in your boat?

01-12-2007, 10:53 PM
i just saw your website. very nice job! i just finished restoring a 1969 simmons, my 8th one. what happened to the frames in your boat?

Sorry in advance for the thread drift but I think the poster has his questions answered.

I omitted them via the frameless option included in the plans. Only thing I did differently was beef up the sheerdeck schedule to change the look,get rid of the joint at the sheer and foredeck which created a strong channel which subdued twist and flex from all stress angles. I actually worked this out on a computer program that was designated for a similar style 23ft fibreglass boat. It ends up surpassing not only the strength of the frames but also the thwarts as well.I gained 4" of deck space overall in this narrow hull.

Thanks for the compliments cluvrs and welcome to the WBF. Atleast now everyone knows where all the old Simmons went to. :)