Leisure 17, Alternative mast foot / tabernacle?

ProDave

ProDave

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Putting the mast up today manage to break the (already damaged) mast foot. It pivots on a pin through an alloy casting in the bottom of the mast. The pin passes through two holes one each side, one had broken some time ago and the other broke today.

We got the mast up and it is secure for this season but with no pivot point that works it will be a lot harder to lower and raise.

So we need a new mast foot arrangement. I understand original mast foot castings are not available.

I am thinking along the lines of a proper tabernacle. In it's simplest form that will be a bit of stainless plate bent into a U shape with a hole drilled through. A matching sleeved hole made in the mast and that will be the new pivot point, having the advantage of putting the pivot point a bit higher up.

Thinking the L17 is such a common boat, we will not be the first to break the original mast foot and someone must already have a design of an alternative tabernacle indeed someone may even sell one that we can just buy and fit.

Ideas please.
 
ProDave said:
Putting the mast up today manage to break the (already damaged) mast foot. It pivots on a pin through an alloy casting in the bottom of the mast. The pin passes through two holes one each side, one had broken some time ago and the other broke today.

We got the mast up and it is secure for this season but with no pivot point that works it will be a lot harder to lower and raise.

So we need a new mast foot arrangement. I understand original mast foot castings are not available.

I am thinking along the lines of a proper tabernacle. In it's simplest form that will be a bit of stainless plate bent into a U shape with a hole drilled through. A matching sleeved hole made in the mast and that will be the new pivot point, having the advantage of putting the pivot point a bit higher up.

Thinking the L17 is such a common boat, we will not be the first to break the original mast foot and someone must already have a design of an alternative tabernacle indeed someone may even sell one that we can just buy and fit.

Ideas please.
Click to expand...

A post on the owners association Facebook page or Forum will probably end up with lots of ideas:

https://www.facebook.com/groups/leisureowners/

https://www.forum.leisureowners.org.uk/index.php
 
The LOA sell some spares for the L17 so maybe contact them. I've found them very helpful and had a new rudder made a few years ago. Failing that, a stainless steel replacement would be easy to make by most competent fabricators. It's a pity the original was cast alloy as it's quite brittle - SS would be much better.
 
I think these things are made out of cheese-metal for a reason.
A mast is a big lever with which to put forces on the mast step which it is not designed to cope with. If you make the pivots very strong, it's easy to damage either the mast or the boat.
 
lw395 said:
I think these things are made out of cheese-metal for a reason.
A mast is a big lever with which to put forces on the mast step which it is not designed to cope with. If you make the pivots very strong, it's easy to damage either the mast or the boat.
Click to expand...

It has lasted since 1979 so it has not done bad. Apparently one half broke last time the mast was dropped when a gust of wind took it sideways when half way down so it was already weakened for this time around.

I have no issue with the concept of a "fuse" as long as when it blows, you can buy a new one, but you can't it would seem. So we are looking at making a modification instead.

One of the group is a member of the LOA so we will be having a look on the forum when he remembers where he kept the log in details......

I have also been given the nod of where there is a wrecked L17 and I am trying to make enquiries to see if it has the same mast as ours.
 
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This kind of mast foot and the subsequent failure of the lugs is very common around here. Oz. Yes your idea of a SS plate with sides is probably good. If you make the hole in the mast and the tabernacle further aft than middle it will make the action easier. Look at the geometry as he goes down. If in the middle the front of the base of the mast must rise while the back goes down. (ie lifts the mast) If it is at the back the front lifts easily and the back can be carved away to allow easy lowering. The hole in the mast only takes weight when lowering. It should have lots of free play so all mast pressure is on the base of the mast. Leave the original ali insert in place.
mastbase.jpg (24.1 KB)
This is a photo of my mast base designed for pivoting. It sits on a ss plate with a spine up the middle raised at the back for the pivot bolt. Note the 2 lugs are close together with one lug on the deck. So any mast swing results in slight opening up of the lugs on the mast so Ok with quite large mast swings. The front of the mast rises as she swings back not a problem with fractional rig and aft mounted shrouds. So I can leave all tensions normal except the forestay which has a high field lever.
The design of your old base is the worst of all as there is a huge leverage from the mast but still a large movement of the pin in the lugs with a small swing.
Note the area of my mast bottom filled in to cope with large pressures on a hard driven 21fter. ol'will
 

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I resurect this old thread, because a year and a bit on, we again raised the mast with it's broken pivot as we had done nothing to fabricate an alternative.

But I paid more attention to what is there and I think I see an easy solution.

The existing mast base, the bit that is attached to the boat, already has a flange either side with 4 holes. So it would be easy to fabricate two stainless steel L shaped side pieces to simply bolt onto what is there.

The pivot point needs to be raised about 6" that would enable the mast to be lowered flat and still clear the hatch.

So the one bit of this new design we need help on is making the pivot hole in the mast. I am sure there is a lot more to it than drill a hole through the mast and put a bolt through. I feel it needs a tube (aluminium) passed through the mast. and somehow secured to give a more robust pivot. And yes I like the idea of drill the pivot hole as far aft as possible.

So any ideas how to fix a pivot tube through the mast?
 
A slight thread drift, but I really am pleased to see so many L17's still in use, I had one of the early ones (my first boat) back in the late 60's.
Great little boats, bought ours direct from Cobramold when they were still manufacturing in an old Nissen shed n Stanstead Airport.
 
ProDave said:
Where we keep ours there is also another L17 and we are moored together on the same pontoon. Interesting the subtle design changes that occured over the years they both have quite a few differences in the detail of the top moulding.

And they still make good day sailors.
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Not just a day sailer, used occasionally to cross over to Cherbourg from Christchurch,
I do still remember the half hour 'lecture' by Arthur Howard (designer) at the Earls Court Boat Show the year we bought her, on how he was arguing with Cobramold that they were stepping the mast to far forward.
Still trying to find some photo's of her back in the early days, I lost a whole photo archive at one point years back, so am missing a lot of my early work and personal pics, but hopefully one day I'll turn up some images.
 
My first boat wasa Leisure 17, and she arrived with one side of the mast step missing and the other side broken. I was able to get two pieces of s/s angle cut to the correct size and with holes drilled to match the original ones.
I found, for solo mast raising/lowering, that a gin pole, and a 2:1 purchase tied to the forestay worked well, and sheets run from opposing spreaders down to blocks tied to stanchions were useful in keeping the mast centred. I really needed two pairs of hands, though?.
 
Did you keep the mast pivot right at the bottom of the mast?

My thinking is make a tabernacle to raise the pivot point about 6 inches. The trouble witht he pivot right at the bottom of the mast is you have to catch the mast in quite a tall cradle befoer it hits the hatch. Raising the pivot would allow the mast to just about come down all the way and still not hit the hatch.
 
ProDave said:
I resurect this old thread, because a year and a bit on, we again raised the mast with it's broken pivot as we had done nothing to fabricate an alternative.

But I paid more attention to what is there and I think I see an easy solution.

The existing mast base, the bit that is attached to the boat, already has a flange either side with 4 holes. So it would be easy to fabricate two stainless steel L shaped side pieces to simply bolt onto what is there.

The pivot point needs to be raised about 6" that would enable the mast to be lowered flat and still clear the hatch.

So the one bit of this new design we need help on is making the pivot hole in the mast. I am sure there is a lot more to it than drill a hole through the mast and put a bolt through. I feel it needs a tube (aluminium) passed through the mast. and somehow secured to give a more robust pivot. And yes I like the idea of drill the pivot hole as far aft as possible.

So any ideas how to fix a pivot tube through the mast?
Click to expand...

The hole in the mast, if you do that, does not necessarily have to have a reinforcing tube inside. The bolt should be quite loose in the hole such that all loads on the mast when sailing are through the bottom of the mast. ie no loads on the bolt. Bolt may be helping locate the mast bottom fore and aft and sideways. So the only loads on the bolt and sides of the hole are when the mast is half up half down. However an alternative might be to raise the base of the mast above the deck by wood or GRP then put a SS clamp around the mast bottom with legs aft for the bolt pivot. This will also raise the base of the mast as she goes down but will tend to increase tension on cap shrouds initially. (watch out for that) ol'will
 
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