How do you make a mast tube?

[Tom Williams]

I just made my mast tube this weekend. I used the 4 wraps of 6 mil plastic but did it in two pieces. I taped the pieces using plastic packing tape. I wrapped the mast section/ plastic using 10 oz tape with about 1/2" of overlap. When this hardened I wraped it second time with some of the 6 oz. continuous cloth I had left over from the hull glassing.

When I dissassembled the mess, the two plastics slid away from each other (one stayed on the mast, the other tube). I had to wrestle the plastic out of the tube. I did this by grabbing the ends and twisting. The plastic rolled up on itself and broke free from the epoxy. It was no big deal but I should have used some virgin plastic. The piece I used had been around the shop for a while and wasn't as smooth and slippery as it should have been.

The tube looks great. I'll post pictures when I get a chance.

Tom

[JeffM]

Maybe I sinned in a former life, but this is getting ridiculous. Having made my tube and spent a week trying to get it off, I finally sawed it lengthwise. Then I patched the cut with three staggered layers of 6 oz tape. Before I did so (concerned that the tube might be too close-fitting on the mast), I put the tube back on the mast -- but this time over 6 mil plastic. (It was definitely necessary, since the difference in plastic thickness made at least 1/8" difference in the tube circumference. Now I have a beautiful, strong tube. Only trouble is, it's stuck on the mast again! It isnt as bad as before since I can twist it a little at a time using significant leverage, but it definitely doesn't want to slide off the pipe. I've got a strap wrench for applying twisting force, but haven't thought of a good way to pull it lengthwise.

[Designer]

I guess that you must have been really bad in a former life to have this much trouble.

I think that Tom is right, wrapping tape around the mast like a bandage would allow you to get a lot of leverage and become ever tighter as you continue to wrap. The way that I usually make a tube is to use cloth and drape it over the the plastic wrapped mast and wet out the glass and roll the mast as I continue to wet out glass. This way does not allow me to to put any tension on the cloth.

This is all academic to you as it does not solve your current problem but it may help some one else.

[JeffM]

I used 6 oz cloth rather than tape. I tried to pull it flat and smooth, but didn't think I was putting excessive tension on it.

[Dale Niemann]

I must have sinned plenty. Well, I hate to add more flames to the fire but the day before yesterday I made the mast tube. I bought new 6 mil plastic, wrapped it 4 times around the mast. Then I wrapped 50 inches of 8 oz fiberglass cloth around the mast. I came to 50 inches by mathematically expanding the 40 inches Graham recommended for 8 to 10 oz cloth. Since I was using 8 oz, I wanted to be sure to get the proper thickness. I basically wrapped it as Graham describes above. However, I did use the brush to smooth it down following the roll of the mast. It looked just great and had the right thickness. Of course I did both masts.

Then yesterday I tried to get if off the tube. BIG PROBLEM! I tried a huge pipe wrench, strap wrench, pounding on the ground, and drilling a hole in a 2x4 sliding it down and trying to use it with ropes and a pipe in the tube end (like a wheel puller) and then pounding on the 2x4 until it broke. After trying everything I could think of for a few hours, I gave up and decided to sleep on it.

Today I cut fiberglass tube lengthwise to get it off. Then wrapped one wrap of plastic on the mast, slid the fg tube on and spread the cut with a couple pieces of wire. Then I used some quick set epoxy just to hold it apart. Once that cured, I removed the wire, epoxied and taped the cut with two layers of 6oz cloth on the bias. Tonight, I slid it off with no problem and it appears everything worked out fine. I believe it will have the strength needed. As Graham suggested, I will overkill when glassing it in the boat.

Analysis of what when wrong: When I was initially beginning to wrap the plastic on the mast, it kept falling off. So I placed three very small pieces of clear plastic tape one on each end and one in the middle. I then completed the 4 wraps and again placed three small clear tapes to hold it. I believe possibly these tapes did not allow the plastic to twist on itself so that the fg tube could come off.

I really spent time a lot of time in the moaning chair over this, especially because I have done this once before on my Marples 3 meter tri and did not have a problem. Oh well, on to installing the tubes next.

[Dale Niemann]

I just had another thought (dangerous). Sorry, I can't let the mast tube go.

Graham, have you considered recommending a PVC tube as a mast tube. I used one on my Marples 3 meter tri and it has served very well in the 10 years I have had it. After the trouble I had and I see others having, maybe it would be a good choice. It would certainly be much less expensive than all that fiberglass and epoxy.

Incidentally, on the 3 meter tri the fg tube I made was for the rudder.

[Designer]

Boy, I really feel bad about all of the trouble that you two are having with the mast tube. I am wondering if that middle tape caused your problem. We typically make the plastic about 6" longer than the fiberglass tube and tape down the plastic only at the ends so that the tape can be removed after the tube is glassed.

I don't use PVC because I thought the bond would not be good enough for this highly stressed area. Also I don't think that it comes in the ideal size for our mast. Until this string I did not know that the fiberglass tube was such a problem.

[MikeY]

I've got a strap wrench for applying twisting force' date=' but haven't thought of a good way to pull it lengthwise.[/quote']

Might try one of these. Use them when climbing, not sure how well they'll grip a smooth cylinder.

http://www.chockstone.org/TechTips/prusik.htm

[JeffM]

Maybe that's my (other) problem: I taped the plastic to the mast full-length. (Couldn't imagine a little package tape could thwart me so completely!) I'm going to try Mike's knots next. Thanks!

[Peter Batchelor]

Might be a silly idea, but have you tried cooling the aluminium? Cover it with ice for a few minutes perhaps? This might shrink it just enough for you to remove the new tube.

Cheers, Peter

[JeffM]

Thanks, Peter. That was one of my first thoughts -- especially since there was snow on the ground at the time. No noticeable effect.

[JeffM]

Henceforward, today shall ever be known as The Day the Mast Tube Came Off!

My thanks to MikeY for his knot-tying lesson. Yesterday I hung the mast from a tree and then hung my own 200lb from the mast tube for many minutes. Nothing. Then I tied the mast to one tree, the tube to another, and tightened the rig (with the help of a couple of bowline "blocks") to several hundred pounds tension. Again, nothing. Finally I sat on the middle of the whole thing. After several minutes of this treatment, I finally got 1/16" of movement. I was nearly ecstatic. (But do the math.) Several HOURS later the last few inches came off in a rush and dumped my behind in the mud in the pouring rain. I couldn't have been happier than at that moment.

I don't know what the tensile strength of that type of 3" tubing is, but I'll bet I gave it a good workout today.

And if I ever build another similar boat, I plan to allocate 1/4 of the total build time to getting the mast tube off. (Or maybe I'll learn to follow directions...)

[i'll post a picture once I figure out how to.]

[Kidd]

Congrats on getting your mast tube off. I made one of mine last week. Used 6 mil contractors plastic and fg tape. So far I have used 2 teenagers and a wife to help twist and pull. After a long afternoon we still have about 8 to 12 inches left to get it the rest of the way off. hopefully tomorrow.