My new boat is under construction, but i’m having trouble deciding which is the best way to join the beams. i bought some 25mm carbon tube that i intend to put across the whole boat, so i need to join two pieces in the middle of the boat, at a small angle. does anyone have any suggestions as to a good way of joining them? i have at my disposal carbon unidirection and mat and fibreglass mat.
Some composite companies sell ferrules that slide inside of the tube being used for beams. These ferrules could be mounted on main hull at whatever upwards angle is desired, and the carbon tube slipped over the ferrule and held in place by small SS screws. (or glued if you do not intend to break the platform down for travel.)
You could also use part of the carbon tube as a mandrel and make your own bigger tube up to let the beam slide “into” (instead of “over”). Fasten the tube to the main hull deck, and fair it in. Cross beam slides into the tube.
My own selection would be to use the “inside” ferrules, since they will probably be longer and offer more support.
Attached photo is of my homemade tubes being added to the floats on the MultiONE.
Download Attachment: [ smFloatTube.jpg](http://www.rcsailing.net/forum1/data/dick lemke/200471510136_smFloatTube.jpg)
Note that in the photo I had just started to fair the tube into the top of the float hull.
I suggest lashing.
You will want to cut the tubes on a taper so that the two tubes mate together at the right angle. Glue the two tubes together in the orientation you want. Then you wrap the two tubes with either carbon rovings, kevlar rovings, kevlar rigging line (fishing line) or any other woven line or roving material. When you are done lashing the tubes, wet out the lashing with 5 minute epoxy and you will have a strong joint.
I usually do not rough up the surface of the tubes when I do my lashings. That way, If you decide later to re-do the joint, it is fairly easy to cut the lashings at the split line and then “pop” the epoxy off of the tube.
I also use this method to attach eyelets to booms, etc.
Here are some lashings on my jib boom. I use green kevlar fishing line so it is difficult to see the lashings themselves, but the jib clew point is a stainless steel cotter pin bent to form the clew bracket and then lashed to the boom. The jib pivot is loose fit to the boom with a split ring so that I can remove the jib from the boat. The split ring is helkd in position on the boom by a wood bracket (on the other side of the boom) that is lashed to the boom:
Download Attachment: PA080005s.JPG
Another way you could do it, find some silicone tube with approx the same inside dia as the tube you are using, and make a jig to shape it to the angle of the joint. wet out enough carbon tow to fit inside the tube, pull it through and put the sillicone tube in the jig. when thats gone off cut away the tube and use the angled carbon rod as a joining peice inside the tubes…
Luff 'em & leave 'em.