Setting Cast Bronze Masthead

[Alan]

Rather than continue the original thread, I decided to start a new one since I have one specific question.

I think I have decided to use a cast bronze mastband. The mastband has four ears which I will use for the forestay, the peak halyard block attachment and two lazy jack connections.

My question concerns how you keep the mastband from slipping downward or rotating.

It seems like there are several possibilities:

1. a throughbolt through the mastband and mast
2. three or four screws through the mastband and into the mast.
3. wooden blocks glued and screwed to the mast just under the bottom edge of the mastband.
4. shaping the mast so that there is a shoulder i.e., a larger diameter section just under the mastband.

Any thoughts whether any or all of these make sense? Or perhaps a better way altogether?

[George Ray]

Shoulder!

Single Pin can split the spar
Few screws and a pin would probably work but make me nervous
blocks will work but are just little partial shoulders

[Woxbox]

2nd vote for the shoulder -- holes are where rot gets started.

[Todd Bradshaw]

Shoulder. Just out of curiosity, what is supplying the tension to keep the forestay tight?

[Thad Van Gilder]

I have a shoulder on my mast bands and a single screw.

Thad

[Alan]

This is a cat boat mast, so there are no shrouds. I guess the forestay is mainly there to offset the weight of the boom, gaff and sail.

[Alan]

Thad: I suppose I am stressing too much over this one detail. But, could you tell me roughly how big a shoulder you have under the mast bands? Is it just something small like 1/4 of an inch or something much more substantial? I would like to avoid oversizing the mast too much to avoid extra weight.

I think your option of the shoulder with one screw is the best idea I have seen yet.

Thanks

[johngsandusky]

I have a shoulder on mine, and on the bowsprit. I also shaped the new bowsprit so the collar would be a tight fit. Rather than drive it on and shave the wood, I heated the collar by boiling. This expanded the metal enough to slide on easily. It quickly cooled and tightened. In the past, metal bands were heated in fire for this method, but I thought boiling would be enough, as I didn't want to scorch the wood. It worked fine. I think 1/4" should be enough.

[Thorne]

Building in a narrow shoulder is the way to go. We still don't know the size of the boat or mast in question, but I'd say build the mast to the original planned diameter, and install a mast band just a tiny bit smaller.

I'll admit that I've used a non-shoulder method on my 14' dorys mast -- I cut a narrow band of leather at a slight angle (slightly thicker at the bottom) and glued it to the mast with PL Premium. Then I drove the mast band onto it with a wooden mallet and used a bit more PL to fasten it in place -- not very 'yare' but worked just fine on a small boat with low sail and forestay loading.

[Thad Van Gilder]

The shoulder on Ivy's mastbands is the thickness of the mastbands. the one screw is to hold the mastbands in place when stepping and lowering the mast... You don't need it when it's up.

My bowsprit has a similar fitting, but the shoulder is bigger... more like 1/2 inch all the way around, rather than the 5/16 or so on the mast.

-Thad

[Alan]

Thanks everyone for the replies. I will make the mast diameter slightly bigger (around 3/8 inch) and then cut it down where the mastband will be. Hopefully, I can achieve a tight fit, otherwise a screw just to keep in place should do

This forum is really great!