> I know others must have had a similar situation. I need to scarf 1/4"
> x 3/16" red wood strips together and I can not get a good stable
> scarf.

Which direction are you cutting them? If you use an 8 to 1 ratio on the 1/4 inch side you get a joint that is 2 inches long. If you do it on the 3/16 side you get a joint that is 1-1/2 inches long. Depending on the direction this strip is going to be twisted when it goes on, you may get better results by flipping the strip 90 degrees from how you are doing things now.

If the twisting and bending is extreme you may want to go with strips that are even thinner. If you make them full-length these will be delicate until they are mounted -- but 1/8 or 1/16 inch thick wood is extremely flexible.

>  A fresh cut then with MAS slow cure epoxy

>  A fresh cut with 5-min epoxy

> I have not tried use wood glue yet (tonight?).

Any of these glues should have worked. Epoxy may set in a few hours, but it builds up its strength as it cures, and may take a week or more (at room temperature) to come close to its maximum strength. Even if the MAS soaks into the wood grain the cut you make should have the same capillary action, and hold enough resin in place to form a bond, assuming it was mixed right and it was allowed to cure. Thin layers of resin do not build up heat as they cure, as much as thicker applications, so maybe you would want to put a light bulb near them for half a day to provide a bit more heat and facilitate the curing process.

> With MAS epoxy the next day the joint was completely unattached (I think
> MAS is just to thin and penetrated into the wood and there was not enough
> epoxy left for the joint.

> With 5 min epoxy, the epoxy was nice and thick and stayed with the joint.
> But when I removed the clamps this morning one of the joints broke. I
> think 5-min epoxy is just to stiff and will not give. I did not have the
> time this morning to check the strength of the other scarf joints.

if the scarf is long enough (say 12 to 1) then there should be enough surface area that even a stiff glue should hold.

> I need a good strong joint because the scarf will be on a tight curve (I
> am planning on construction with no staples). Does anyone have any
> suggestions about to create such a strong scarf joint for such an
> application.

Actually, you don't need a strong joint at all. As you apply strips you are just backing up each joint with another strip. As long as you stagger the joints, like rows of brick have staggered joints, you get a sandwich of two strips surrounding a strip with a joint.

> I am thinking that I need to create more surface area for the glue to
> adhere to. However I fear making the scarf joints any longer, for when I
> bend the strips in my bending/glue up mold the section by the scarf will
> not bend like the rest of the wood.

The opposite is closer to the truth. The longer the scarf joint the more it will appear to be like a continuous piece. Imagine the two extremes: the first would be a butt joint. A drop of glue on the endgrain of two strips would not flex right, and would be very week. Then consider a VERY long taper. The thin part is very flexible, but it is bonded to a thicker area on the matching piece. Throughout the length of the scarf joint the outside measurements of the wood are even, but along the length you geet a progression of slightly thinner wood being supported by an exactly opposite, slightly thicker piece.

Consider a few joint options: you could do a lap joint. Cut each end of the wood to 1/2 the thickness for a distance of an inch, then glue these together. The 1/2 thick parts interlock to give a part that is full thickness, but the joint is only 1 inch long. For a longer joint, you can make the lap two inches long, or more.

Hope this helps

Paul G. Jacobson