Mast bushings for Spindrift Tens . .

[Pete McCrary]

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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[Jknight611]

Hi Pete, I suppose it is dependent on the weight of the glass,  this carpet I am glueing to the Flinders it won’t take many wraps at all!

[Hirilonde]

I used wrap and test fit.  I don't trust calculations for this.  It is easier to add material than sand it away.

[Steve W]

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.

[Pete McCrary]

Thank you, one and all.  I’ll get started with confidence.

[PadrePoint]

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. 
 

 

 

[PadrePoint]

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

https://messing-about.com/forums/topic/10540-capt-bones-core-sound-17-mk-3-14-kit-build/?do=findComment&comment=103113
 

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. 

[Pete McCrary]

Correct me if I’m wrong — but isn’t the just-described (Alan’s 10/3/2018) for permanently attaching tubes for a not-to-be-disassembled mast?  Inappropriate for a Spindrift 10 three-part mast?

[PadrePoint]

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. 

[Don Silsbe]

I’m pretty sure they are not intended to be separating sections.  Waiting for the shop to weigh in on this one.

[Alan Stewart]

Builders choice I think. The masts sections can be left loose or glued together. If made to be take apart then the bushings have to be wrapped and sanded to fit.  

[Hirilonde]

Take apart masts go well with nesting boats.

[Pete McCrary]

Also with trailered boats — all spars, oars, etc. within the hull.

[MattandTru]

Coincidentally, I just assembled masts for our CS 17 today.  I used 28" lengths of fabric cut from scrap, to use it up, but also to avoid the hemmed edge building up to ridges on the sides of the wraps.  I found I had to sand quite alot to get them to go together.  With the fabric I used, probably 24" or so would have been about right.  I pulled it pretty tight and squeegeed it tight in the wrap.  All went together great in the end.  Another check off the list. 

Matt

[Pete McCrary]

Matt.  What were the ID of the large tube and the OD of the small tube?  And did you note how many layers amounted to the needed thickness?

[Don Silsbe]

@Pete McCrary— Don’t overthink this.  It’s not rocket science.  I just eyeballed it.  Too little? Add another wrap.  Too much? Get out the 80 grit.

[Pete McCrary]

Got it done!  Not as difficult as I thought.  Alan’s 29” length of FG —  just about right to add 1/8” diameter to a 2” OD.  And I needed about 90” to add 3/8” diameter to a 1.5” OD.  Didn’t have to spend too much time scrubbing with 80 grit.  Here are the two small diameter poles nested within the big one.  Pretty neat.

 

Pete McCrary 

[Captain Tim]

Pete McCrary what am I missing? Doesn't it take more inches of tape to go around the 2" tube than 1 1/2" tube? It would seem if you used 29" to go around the 2" tube to make up an 1/8" bushing,  90" around the 1 1/2" tube would be way too much for the 11/2" tubes bushing. I figure half of 3/8" = 3/16 and that's only a 1/6" more than 1/8" Also, what did you do/use to clean up the ends after the epoxy set?

[PadrePoint]

I helped my neighbor girl with making bushings for her take-apart Spindrift 10 mast. 
 

We tried a dry wrapping using prescribed length to judge how close we got to making a good fit. I had an inexpensive caliper that could measure outside and inside measurements. As I recall, the dry wrappings were close enough to use for the bushings. As I recall I thought we might need a little additional material and cut material to have it on hand when applying the epoxy. 
 

We kept checking the measurements of the bushings as epoxied wrappings were applied and especially as we approached the correct size for the inside of the bigger tube. We needed to add some additional cloth for the desired thickness and it easily went on. The caliper was cleaned up with acetone and the cured bushings needed some sanding.  I have a tabletop belt sander that was carefully used to “shave” the bushings to the desired fit.  I suppose that had we taken off too much with the belt sander we could have built it up by applying another wrapping. 

[Hirilonde]

I did my bushings in stages, measuring after the epoxy set, but not fully cured, until they were the correct size.  I hate sanding any more than I have to and more than having to add wraps.