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Mast bushings for Spindrift Tens . .

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I just reviewed Alan’s video on mast bushings where he used 29” of FG 3” tape (cut to 1.5” for the lower bushing) — to increase the 2” od tube up to the id of the 2.25” (bigger tube) — an increase of just 0.125”.  That’s in fairly close agreement with my calculation of 5.333... wraps, assuming FG thickness measurement of 4 layers at 3/64”, or 2 layers = 0.0234375” (one wrapping) and ignoring epoxy effects.  Five.333... wraps on a 2” od would be about 33.5”.  But I’m going to go with Alan’s 29” — which is just 87% of my calculation and thickness assumptions.

My calculation for the 1.5” od tube up to the id of the 2” tube (an increase of 0.375”) would be about 16 wraps around the 1.5” tube.  At that diameter the length (by my calculation) would be about 75”!  But by using Alan’s real-life experience to get an extra 0.125” on the 2” tube — wouldn’t 87% of my 75” (i.e., 65”) be a better choice?
From experience, do any of you builders have a length recommendation for adding a 3/8” thick FG bushing to a 1.5” od tube?

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I wrapped mine and at the green stage measured with calipers.  I added an extra wrap or two until I was just a bit over. The I took my orbital sander and brought it into a nice snug fit by laying the tube on a flat bench and rolling while I sanded. Very easy and it came out really nice.

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I spotted a method Alan described for joining two mast pieces; I don’t recall where it was. 
Basically, bushings were created, a couple glass strips were placed from the top bushing around the end and back up the other side (these strips held things together.) The wrapped end was inserted into the larger mast piece while everything was still wet. With even wrappings and a good tight fit, the joint self-aligned the two pieces. 



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  • 2 weeks later...

Ah... I found the link I saved to Alan’s mast joining post:



I did this approach for my first of four joints. It used a lot of fiberglass tape, more than I thought I’d have available for the other three joints. I decided then to make 2 inch bushings to fit and added the cross-cross layers over them to hold things together when inserting the still-wet bushings into the other tube end. It worked very well for me. 

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I didn’t realize what your goal was. I am unfamiliar with the details and options of other boats. 
My build called for permanent mast joints. I thought Alan’s approach was effective and efficient for that purpose. 

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