How to join metal mast sections?

[Johannah]

I have been noodling about this Summer with a couple of boats and a couple of possible masts. We can make a recycled wooden mast work on one 14 footer, but I keep coming back to the advantages of multi-section tubing which would require less modification (the other mast can then go elsewhere). This boat has a mast step built for tubing and I am loathe to cut it up more than necessary, not at all if possible. Here's the problem: How do you join sections of tubing of different diameters so that the joint is strong but will come apart easily? The Core Sound builders are the ones who know this stuff, but I am asking here on the main forum because I'm not building one of Graham's boats.

If the mast is left as one piece, what is the best way to attach the sections? Rivets?

[Craig]

Jo, does one fit just right into the other? If so you can join them with rivets. If one is much smaller than the other ( assuming ~1-1.5" tubing) you can join them with a wooden plug turned to just slightly less than the inside diameter (Id) of the lower piece and smaller yet than the Id of the upper section but still a nice fit. You want the wood to stay tightly with the lower unit and slip off of the upper. Let the weight of the rig hold the upper unit to the lower. The length of the plug needs to be comensorate with the strength of the tubing you are using. A good 6-8 " inside a 1.5" tube. Hope this helps...

[Johannah]

Craig, I am trying to picture the wooden plug. The mast would be in 2 or 3 sections and I would like it to come apart for ease of trailering but it is not crucial. Sections should fit into one another fairly easily, judging by a read through of comments from Core Sound builders, but the match is unlikely to be perfectly snug so the wooden insert sounds good. Wooden reinforcement would also be necessary, I think, where the minimal hardware will attach. I was concerned about the strength of rivets (they don't look like much) but machine screws or bolts won't work where you need a smooth surface. Braver souls than I might take a crack at building a carbon fibre mast, now that kits are available for a reasonable price. It's really funny to see the small box which holds the components for such a project.

[Craig]

What diameter and how long is this mast Jo? What can be done is to use galvanized fence top rail sections. They are made to fit together and have a narrowed end to fit into then next section. A pice of wood ripped down to fit inside will stiffen them up. Please give me a bit more information about what you are trying to do and I can give a more specific answer for you. After re-reading your last post you may have a good canadate for a birds mouth mast. They are light and strong as all get out. ( Don't over build them like I did). Tell me what the sizes are you need/want and we will work it.

[Johannah]

Thank you Craig and Ray! Craig, after reading every comment on masts for the past year from the B&B builders, I think I will pop for the better alloy tubing. I can get it from a supplier up near Reading for not too many bucks. Ray's explanation of the epoxy/glass bearings makes sense , but I assume I would also need wood plugs, if not for a snug fit, then for reinforcing the tubing where hardware is attached. My sail is set up for lace-on use, though I prefer to use ties, maybe with beads. The tie and bead system has worked OK on a small rig on our kayak. As Ray mentions, I would just as soon be able to pull the sail down in a jiffy so will need a halyard, downhaul and place to tie the sprit boom. Our other rig that I scrounged has stays and track for a roped luff. It seems a shame to have to do lots of mods when this fancier rig would go better on another boat anyway. Also, it's in sections which are a bit tricky with the present sail. Money looks to go out the door for sail mods, or hardware so why not just pop for the pipes that would fit? Mast length will be in the range of 17 to 18 feet.

Ray, what prevents the bearings from shifting up and down onthe tube? Similar fittings on our laser are riveted in place.

[Craig]

Where ever possible do it right the first time! That is always the best route if you can use it. The heavier gage, as Rays says, shouldn't need reinforcement.

[Johannah]

Your comments are saved and printed, added to my mast notebook. I will bring the edited version along to the tubing supplier (not for a while because Wild Child returns to school Tuesday so I turn back into a long-haul cab driver). I do better in "guy" shops if I have my homework with me. Clerks seem to be nicer. Works also when car shopping.

We're off to go Lasering today and Monday. I'd rather be in a sharpie but on the water is better than not. Happy Labour Day to all.