I 'm seeking advice about mast wedges and partner clearance and want to share a little progress and an experience with sleeving a mast. A photo in Arne's Froken Sorenson part I appears to show notches cut for several wedges with a small clearance between mast and partners. I'm wondering if I'm seeing that correctly. On the Com-pac 16 I'm going for a keel stepped mast rather than my original tabernacle plan and don't know much about clearance and wedging. I went with a partially sleeved 3 ½ inch aluminum mast rather than 4 inch which was the obvious choice for strength and weight. The planned tabernacle would have had the mast held in 2 laminated wood blocks, at the pivot and base with the top one hinged with a hefty long bolt. The bolt would have been aft of the mast and through the tabernacle sides and laminated top block. The whole thing with a 4'' aluminum tube was getting pretty wide side to side and fore and aft in proportion to a 16 ft boat. I decided to go with an internally sleeved 3 ½ inch mast then later to drop the tabernacle plan. The 3 ½ inch tube without a sleeve has 27% less bending strength than the 4 inch but still has a safety factor of 1.47 with 400 lbs added to the boats empty displacement of 1100. Adding the six foot snug fitting internal sleeve, four feet of it above the partners, should give me more where I expect most of the stress to be.

The 14ft. aluminum 6061 t6 3 1/2''x .125 inch tube is sleeved for that first 6ft with a 3 ¼ x .125 in snug fitting tube. The upper 5 1/2 ft. will be wood. Sliding in the first inches as a test showed it to be a tight but potentially doable fit. Tube specs cite very slight allowable differences in diameters and wall thickness and a minor variation or gouging could make it go extra dry. I was preparing for a battle with no turning back but a suggestion by a local machine shop teacher and the cold weather here made all the difference. After going over the inner tube with an emery cloth strip, I set it outside for the night with the temperature at 0 F. The outer tube came in the house at 70 F degrees. In the morning to my suprise and delight I was able to push the tube in by hand and only used the heavy hammer and a wood block lightly to bring it up flush. I'm told that dry ice is sometimes used to contract metal for a fit. I had thought to reduce the hard spot at the upper end of the sleeve by cutting six 10 or 12 inch long very narrow V slots but didn't want complications inserting the tube. Instead I just put a small bevel in the top. With the longer mast planned I added panel 7 back in at the foot so I will have a slightly shortened batten six and a boom shortened by a foot. I guess that should work OK. Doesn't look bad on paper, even closer to that ear listening for the wind.

Jonathan Snodgrass wrote:

And yes I will ask Roger Taylor for his source of lighting pole, unless any eagle eyed member who knows the answer from his published articles tells me first. 

Roger provided the details in another fora. They are now in Junk Info > Useful Links > Sails, Masts and Gear.

David

Indeed.  Thank you very much for all that. 

As regards the taper for the step, I think that Charlie would turn one piece to form the plug (to fit into the top of the bottom section with a hole with a clearance fit for the top section to secure and centry it) and the tapered section. 

Your comment about water ingress through the top of the taper rings true.  I think that water is getting to Lexia's foremast step and it could well be getting in through the top of the taper.  Charlie Hutton did have some very sticky very strong tape from the Formula One world, and one run of that round the top and bottom of the tape might reduce any water ingress. 

As regards RI, NY.  No comment.

And yes I will ask Roger Taylor for his source of lighting pole, unless any eagle eyed member who knows the answer from his published articles tells me first. 

Jonathan

JDS,
Weight is not an issue. The heavier tube is low down, and above that, you can reduce the diameter substantially if you want to, but take into account that a mast that whips like a fishing rod at the top shakes the wind out of the sails and increases wear and tear. Weight aloft does indeed increase the rotary moment of inertia, but the effect of this is to slow down the roll, not to decrease its amplitude. For example, Badger has a 6 second roll with her two solid wood masts, Tystie has a 3 1/2 second roll with her tapered alloy mast.

Two more examples: Mingming II has an 8 inch mast on a 24 ft boat, to be proof against all eventualities, and she seems to be carrying it well enough. Fantail has a 6 inch x 3/16 mast on a 26 ft boat, and a sail of the same area as your main, and I saw when I sailed her that it was of the correct stiffness and didn't overburden the boat.
If you go for "third time lucky", I for one would like to be sure that you have a mast that will get you as far as Newport RI.

For the step in a two piece mast, I would cut a 6 inch length of 5.562 x 5 inch tube, mount it in a lathe, and turn a taper of 2 degrees. This will leave a tiny step at the top, as I wouldn't want to bring it to a feather edge. I would bond this over the top of the lower tube, and bond the upper tube into the lower, with polyurethane sealant (with a few backup rivets). I've recently had a close look at a pair of mechanically assembled two piece masts, and my hunch was that water was getting into the boat by trickling down the outside of the upper tube, through the join, and down the inside of the lower tube. On Fantail, there is only this bonded joint, no rivets. The contact area is so huge, with a 10% bury, that there's no likelihood of a failure.

My mast is a one piece tapered tube, like Roger's. Atlantic Spars bought the remaining stock from Proctor Masts, but it's long gone, now. I think Malliemac got the last mast made from this stock.

I think you'll have to ask Roger directly where he bought his tapered light pole.

David

Thank you for your comments.  Helpful and food for thought as always.

Jonathan