mast tube clearance

[sscoville]

How much play should I have in my mast tube?  I think I have about 3/8".  Too much?  I suppose this is easily remedied by building up the mast with some glass at the bottom and where it bears on the top of the tube.

[Tom Lathrop]

Way too much for my tastes.  I have no number but just want the mast to be able to rotate easily.  1/8" total is a gracious plenty if the tube and mast are circular.  I lube mine at base and deck with past wax. 

[sscoville]

Way too much for my tastes.  I have no number but just want the mast to be able to rotate easily.  1/8" total is a gracious plenty if the tube and mast are circular.  I lube mine at base and deck with past wax. 

Solution other than starting from scratch?  Will my idea of fiberglass bearings on the mast at the base and top of the tube work?  Or am I missing the function of the tube?

I think I used too much plastic around the mast.  It did not get stuck though! :-D

[PeterP]

I am assuming the following: your boat is a CS and your fore deck  is all in place. To cut out the old tube and put in a brand newie would be a serious case of back -breaker. I would try the bearing approach -I don't see any harm in that. The looks of it may hurt your ego more than anything else. PeterP

[Tom Lathrop]

Solution other than starting from scratch?  Will my idea of fiberglass bearings on the mast at the base and top of the tube work?  Or am I missing the function of the tube?

I think I used too much plastic around the mast.  It did not get stuck though! :-D

No problem.  FG bearings will work fine at base and deck.  This is just like the mizzen set up.

[sscoville]

I am assuming the following: your boat is a CS and your fore deck  is all in place. To cut out the old tube and put in a brand newie would be a serious case of back -breaker. I would try the bearing approach -I don't see any harm in that. The looks of it may hurt your ego more than anything else. PeterP

The boat is a BRS 17.  I have not installed the fore deck or the tube - I have only fabricated the tube.  If I had the fiberglass on hand to do it over, I probably would.  The fg bearings seem like a very easy fix.

So the function of the tube is just to keep the forward compartment watertight?

[PeterP]

Look, to make the bearings you will need some fiberglass. Probably tape - so why not just go ahead and use the tape to make a new tube? PeterP

[sscoville]

I do have the tape.  Maybe I will redo it.  I would think that using tape would leave a spiraling ridge all the way down the inside and outside of the tube.  On the inside this seems undesirable as this would scrape the mast every time it was stepped and unstepped (these are wooden masts), no?  I'm going to need to order some more glass to sheath the bottom anyway, but I wanted to be finished with this step in the build.

[PeterP]

I make my tubes out of tape - same stuff I use for joint taping. Make sure you have lots of epoxy in the first layer. Don't worry -the plastic covering your mast will give your cured epoxy beautiful smooth finish. At any rate your wooden mast will get scuffed up no matter what unless you protect it. I am thinking along the lines of rub collars or good fat coating of epoxy. That is something to be considered before you make the sleeve.  Now that I think about it if you lay a fat coat of epoxy on your mast - say 3/16" fat that will take care of your  3/8" gap. (Here I am presuming that you stuck the mast in the sleeve and had a gap 3/8" on one side- correct?) PeterP

[Peter HK]

I had an old, bent, 50mm diameter aluminium mast (wrong alloy) from a previous build that I cut and used to make the struts for supporting the masts while trailering. As the masts on a CS17 are 2.5 inches (63.5mm) diameter the gap was significant- over half an inch.

I wrapped 75mm (3inch) tape around the plastic covered tube until the thickness was about right and when cured slipped it off and cut it into a couple of neat rings - one for each strut. I drilled and screwed them to the tube. The foot was done with a plywood heel.

They were quite neat in the end.

[sscoville]

(Here I am presuming that you stuck the mast in the sleeve and had a gap 3/8" on one side- correct?) PeterP

 

Correct.

[PAR]

Make two HDPE collars or rings to fit the mast tube. They'll be thin but fairly easy to machine up with a drill press and a hole saw (especially if it's an adjustable saw). Make it a press fit around the tube for the upper on and as a plug for the bottom. The HPDE will act as a bearing surface, it's self lubricating and will prevent the mast from getting dinged up.

[Tom Lathrop]

Paul,

He has 3/8" clearance total.  That means there is a 3/16" gap.  To leave some space for stepping the mast, the collar would have to be no more than 1/8" thick.  Such a HDPE collar would be extremely weak even if he could make it.  I would not attempt it.  How would it be secured?  HDPE shatters under load in winter. 

Gotta vote against the PE collar.

[PAR]

Yep, I don't worry about cold HDPE, because it just doesn't get that way here and I did think about the thickness of the upper ring, which will be thin.

Possibly the upper ring could be mounted on the tube, so you can have the meat, though now securing is an issue (I'd use an "interference fit" if fitted on the mast). Maybe wide enough to accept some through bolts or screws into the deck or thwart.

The bottom still can be a plug with an over sized lip. Maybe ultra high modulus stuff will make a better bearing in the cold.

In any case it's a fairly easy problem to solve, I just like these self lubricating plastics in this application.

[sscoville]

I was going to cap the bottom with a more rot resistant species of wood anyway.  I think I'll just make the cap oversized and make an epoxy bearing on the mast where it bears on the top of the tube.