Beam Trough Advice

[Adrian Hall]

I am building the beam troughs on my Tiki 38 and the plan book advises that you "glass all ply surfaces before assembly". Is that all I need to do? I would have thought that the inner surfaces would be subject to enormous chafe, and that the friction between beam and trough would mean that I would be down to bare wood in no time at all. Am I worrying too much? What have other builders done, and what would they have done differently if they had had to do it all again? I believe that you can add graphite powder to epoxy for high friction surfaces. Has any builder gone down this route? Your advice would be appreciated.

Adrian Hall in the UK

Web Site: buildingkira.com

[Axel]

The beam rests on hardwood blocks at both ends of the trough and does not rest or touch the trough itself. There is also space on the sides and you will install shims between the beam and the sides to keep the beam stable. These keep the beam off the sides. I think the glassing is to build up more epoxy for rot prevention since that area will not see the light of day very often. Also, the beam should have a rubber pad under it where it rests on the blocks. I have heard of builders adding some extra glass to the beam top where the lashing ropes will sit. Not sure that's necessary but you can do that at any stage.

The base dimensions for the wind vane are 230 X 200. Plans seem to say the base is 20 mm ply. Not sure about that. The Vane blade for a large boat is 1200 X 450 (top) & 230 (bottom)

[Ron Hall]

Adrian,

Axsel's description is spot on. The beams rest on the pads, and are centered in the trough by the shims on either side. If you have done the lashings correctly, the beams will not move in the regular course of sailng, and chafe is simply not an issue.

General advice on the beamtroughs/beams.

The pads allow you to level the beam attachment points so they all sit flat and level at the same height from beam to beam and side to side. If they are not level you will have additional difficulty in getting all of the center structures to fit correctly. Use a tube with water in it to level the pad tops. I made pads of hardwood (Ash, purpleheart or some other rot resistant wood better) with a hole in the middle. The pads were heavily glassed on top, and then sanded (on a stationary sander) until they were level with the others. then glued in. In some cases I had to make a new groove (because the other one was sanded off), and the inside re epoxied. Everything in the beamtrough, particularly the bottom and the bottom joints, should be heavily glassed. After you have glassed the beamtrough pieces and glued them in place, put a healthy filet along the bottom and glass over the filet, the bottom, and well up the sides in one piece. Repeat if you like. The danger is that the troughs flex some and could start to open at the joint, allowing water to enter. Water, dampness will sit in there, and you cannot inspect it easily, so you need to make sure it is absolutley waterproof going in. Make sure the hole in the pad is big enough to allow adequate drainage.

My beams are protected on the bottom by 3/32 inch delrin pads that are put on the beams with screws and 5200. They extend an inch or so beyond the pad on either side, and are there to keep the hardwood pad from crushing the softwood beam at the edge of the pad.

Make the beamtroughs at least ten mm wider on each side than shown on the plans. The beam troughs are simply too narrow, and you will not have room to fit the shims on their sides if you make them the per plans dimensions. The shims are there to allow you to get a tight fit and overcome the fact that not even the most meticulous builder will be able to align all six troughs perfectly enough to insert the beams. One or more of the troughs will be out of square, and the shims allow you to make up for minor imperfections. But the per plans width is too small to account for the adjustment most builders need to make to account for the differences in beam trough alignment. Hanneke has signed off on this, and you can make your life a lot easier at the install stage if you give the troughs an extra 20 mm.

The beams are softwood, and will crush at the pad edges and where the lashings go over the tops of the beams. I used white oak pads on top of the beams, glassed in with three strips of glass going up one side of the beam, over the lashing pad, and down the other side. I did this on the advice of a New Zealand builder whose beams had started to crush along the top edges after some five thousand or so sea miles. A more elegant solution is stainless pads (maybe 1/8 in) that form a short U-shape over top of the beam, with the sides on top of the beam bent up to retain the lashings and keep the pad in place. For the outside pieces, the outside of the U could be bent up to form a cleat, and the inside bent up with holes in it to retain halyard blocks, turning blocks, etc.

In any case, glass all of the beams all of the way around. Do that for the beams and all of the exposed wood anywhere on the top. Glass all of the center structures everywhere. I know it is slow and tedious, but you will make your life much easier down the road. Even well-painted wood that has been heavily epoxied will not last nearly as long as a glassed surface.

Good luck and eventually happy sailing.

[Frank Olsen]

Adrian,

I wholeheartedly agree with Ron about making the beam troughs a bit wider. My Pahi31 has similar troughs and dimensions, and ended up too tight. I had to fight beam alignment for days, trying to get all beams in the troughs, fudging the hull positions and swapping the beam positions. Finally got it, and I only had 4 beams to deal with!

Frank

[Jeff Kittle]

Only one caution. The Tiki 46 had the same trouble with the beam troughs being too narrow and as of 2007 the plans had been changed to reflect the needed increase of 10mm. I'm not sure if the Tiki 38's plans had the same changes made also.

Sue