Furnished content.
(from Lumberjocks.com)
I needed some long reach clamps for my current project, so I made 3 sets of long reach C clamps of different lengths. The first ones I made from 3/4” Baltic Birch. This turned out to be a mistake. The material is far too flexible at that length, and because of that, it does not exert as much pressure as I'd like, only about 20 lbs. It might be okay for a shorter clamp, but for these long ones it was somewhat of a disappointment.
UPDATE: The Fix is In! – Zip Tie to the RescueThis simple modification overcame the excessive flex and gave me 40 PSI at the clamp face.
The fabrication of the second set was also somewhat of a disappointment, but I got better clamping pressure, 40 lbs. I didn't make the shoulder wide enough, and I cut the groove too far up from the underside of the top piece. Because of this, the wood had a tendency to split at the shoulder of the clamp, so I had to reinforce that with zip ties. The material I used is Ash that I recycled from an old futon frame.
The last and most successful set were also made from recycled Ash, and also achieved 40 lbs. of pressure, but with a much shorter throw. I made all the right moves with these, shoulders wide enough, groove cut not too far up.
IMPORTANT: If you decide to make these clamps, the wood where the threaded insert goes needs to be supported front to back with a Bessey style clamp and on both sides with an F clamp. The hole that the insert gets threaded into needs to be lubricated with paste wax as well. If you don't take these precautions, the wood will split.