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Old 21-11-2019, 01:25   #1
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Mast band heading South

Hi,

I have a 5 inch hollow spruce mast with 2 heavy duty stainless mast bands. I have just dropped the mast for inspection and notice 1 of the mast bands is slipping.

The method of attachment is clearly not substantial enough to cope with the considerable downward forces upon it. In particular the staysail foil forward and the mainsail throat halyard aft. I understand the mainsail luff should be good and tight and give the halyard a good tug with the help of a 2:1 tackle but no winch.

The mast bands are in 2 halves connected with 4 x m8 bolts each side, a 12mm through bolt and silicone sealant. It is definitely silicone which I hate with a passion but whoever used it must have thought it was correct at the time.

Having removed the mast bands the 12mm hole through the mast for the through bolt has become a 30mm vertical slot as the bolt has dragged its way through the wood.

I am wanting to secure the mastband in its original position and am looking for advice/ideas.

I am thinking of chopping a small square 25mm x 25mm out of the mast just below the original position of the bolt and making a similar sized hard wood plug with a semi circular groove in its upper side which I will line with a stainless steel tube 12mm ID cut length ways. Glue into the hole so the bolt bears on the stainless tube.

Definitely will not be using silicone as a sealant but undecided about what to use. Epoxy, Sikoflex ???????????????????

I am going to boat now and will take a photo of the slotted hole to post here later.

Look forward to replies

Thanks

Mike
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Old 21-11-2019, 04:16   #2
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Re: Mast band heading South

Your idea is basically sound. I would glue the wooden repair bit in with epoxy, but instead of a SS tube, I'd use G10. To bed the band itself, Dolfinite is the goo of choice, with Lanocote coming in close second.

Sometimes mast bands have a shoulder to rest on, like most cranse irons do at the ends of bowsprits. You could provide a shoulder by gluing a hardwood cleat under the band after carving out a hollow for the cleat to sit in. Wouldn't have to be big--just enough to spread the load and transfer it to the mast beneath.
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Old 21-11-2019, 20:42   #3
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Re: Mast band heading South

Benz is right that adding shoulders for the mast bands to bear on would be good to spread the load out.

Putting the bolt through a ss tube doesn't really change anything unless it is very thick walled therefore spreading the load out. Spruce is quite soft and easily crushed.

Another option would be to glue a large "Dutchman" (insert) of a much harder wood in the area of the bolt and have the bolt go through that.
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Old 23-11-2019, 00:38   #4
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Re: Mast band heading South

Attached photos.........

I happened to have 3 choices to hand (in mi shed) regarding the bolt support.

Brass tube, hollow GRP/carbon fibre broken fishing rod or broken carbon fibre golf shafts. All the correct size. I chose brass. You will see I epoxied a small DUTCHMAN insert in yesterday but only below the bolt.

Shoulders..........

I also have a piece of 110mm (about the right size) underground drainage pipe (the brown stuff) which in a short length (4 inch) could be opened up and clamped around the mast and glued and srewed in place below the mast band to act as a shoulder. It is considerably harder than any wood and means I would not have to cut a groove in the mast.

Thanks

Mike

Just heading off to find the URL of my image
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Old 23-11-2019, 00:44   #5
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Re: Mast band heading South

Unfortunately cannot find the URL of my images. I was hoping I would be able to choose an image from my picture library.

Mike
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Old 23-11-2019, 04:53   #6
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Re: Mast band heading South

Regarding a tube: the purpose of it is to spread the load, so the thicker the wall, the better. I would again steer you away from any metal and toward G10 or fiberglass. You can get such things from McMaster-Carr. Metal will not glue in as nicely as an epoxy-potted composite tube.
The pipe thing sounds fine, as long as you epoxy-pot it and the screws thoroughly enough that water. will. never. get. in.
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