Mast Heel Questions

[Corribee Boy]

The mast heel or foot on my boat's suffered a bit over the years. It's structurally sound when in compression so it's fine to use, but it has tangs extended aft to form a pivot point that will raise the base of the mast to clear the coachroof when it's being lowered. These tangs are distorted and cracking.

It's an unknown alloy cast to a fairly simple form, and I was hoping to find someone to weld the cracks and build up the alloy, but seem to have drawn a blank unless I'm prepared to spend half the value of the boat. Things like JB Weld might be possible but the consequence of failure when raising the mast makes me nervous.

Does anyone know anyone who carried out this sort of welding work for reasonable money? Is it even possible? Alternatively, with time on my hands and a reasonable workshop, I could either work a billet of suitable alloy to shape, or even carry out a casting. Does anyone know the type of alloy that would be suitable for this purpose?

 

[anoccasionalyachtsman]

I've asked a couple of respected welders to tackle unknown aluminium alloys, and both refused on safety grounds. On that basis I wouldn't trust it.

How about a composite fabrication - a bit of stainless channel for the pivot arm and something else for compression/location. Even HDPE could work in some circumstances.

 

[Catalina36]

Consider binning the whole thing and re-creating a similar shape with all the same key dimensions in stainless steel sheet, if necessary laser cut and welded. Anything's doable but sometimes we think too hard.

 

[Corribee Boy]

Interesting that welders have dismissed this sort of thing on safety grounds: I was thinking that the unknown alloy composition would be the stumbling block in knowing what filler metal to use. HDPE would certainly be easier to work, so that's something to consider.

The stainless sheet idea would be fine for all the straight, square bits, but might prove difficult for the various curves. However I'm sure the piece could be redesigned with that in mind, so that's another option. The idea of a composite piece is quite attractive. Thanks for both your input.

 

[VicS]

The mast heel or foot on my boat's suffered a bit over the years. It's structurally sound when in compression so it's fine to use, but it has tangs extended aft to form a pivot point that will raise the base of the mast to clear the coachroof when it's being lowered. These tangs are distorted and cracking.

Wot's it like ? Like this?

 

[William_H]

Assuming it is of the style shown in Vic's picture. These were/are very common around here in the 18 to 24ft range though the lugs at the back of the base tended to be less robust. The problem is that any swing side ways of the mast puts enormous strain on the lugs. Snaps em off like cheese. As said I would go for a fabrication in stainless steel if only for the base part. Corrosion of course will be a problem but not so much if you use a compound on the faying surfaces and drop the mast each winter.
Just for interest these are pictures of my mast base on 21fter. The base is stainless steel with the ali mast with lugs welded onto the mast sitting on it. I have never worried about corrosion protection more than abit of enamel paint and never seen any problems. Note the narrow base for the lugs . Just a single pivot on the base to two lugs on the mast separated by 1cm. This means that if the mast does swing sideways there is not so much movement however you will see the lugs have been spread a bit with mast swing. This might seem a wobbly arrangement as the mast traverses down but it seems ok over probably 60 drops and 40 years.
Just as a matter of interest that ring attached to the side of the mast near the base is for attachment of the spin pole. It then clips into plastic clamps further up the mast. Works really well as a stowage for the wind surfer tapered mast pole using fairly small beak fittings. ol'will

 

[Corribee Boy]

It’s like that in principle, Vic, but William’s example is closer to the problem. There are two tangs, each about 10mm wide, with the main halyard pulley between them. The overall width of 30mm or so is far too narrow to withstand any twisting or swinging of the mast as it’s raised, hence the deformation. Cheese is an apt description which I’ve used before.

A redesign with a wider base seems on the cards.

 

[lw395]

It’s like that in principle, Vic, but William’s example is closer to the problem. There are two tangs, each about 10mm wide, with the main halyard pulley between them. The overall width of 30mm or so is far too narrow to withstand any twisting or swinging of the mast as it’s raised, hence the deformation. Cheese is an apt description which I’ve used before.

A redesign with a wider base seems on the cards.

I think the problem is, something has to give if you apply any bending force when raising or lowering the mast.
If you make the heel fitting really strong, you'll just rip the tenon off the deck.
Maybe make the bit which gets bent an easily replaced cheap item?

 

[Corribee Boy]

I'm actually pretty careful when rigging the mast, and it's stabilised with temporary shrouds when going up or down, but the pivot design can't accommodate much lateral or twisting movement, and doesn't have the strength to tolerate it. I've checked the channel fittings to the deck and they're fine but the partially weakened tangs are an obvious failure waiting to happen.

I should be able to post some pictures later... I know, I should have done it first...

 

[Corribee Boy]

I hope these pictures are visible: If so, the extent of the problem is fairly obvious, crack, missing section, and all. The roll pin marks the position of the halyard sheave. The whole base section of the fitting is only one inch across.

It seems possible that keeping the mast plug section, but bolting it to a new, wider heel will increase stability and durability in a fairly simple way.

Edit; sorry, images duplicated. I apologise for the waste of electrons.

 

[lw395]

What I don't like about that, is that the fragile pivot at the back appears to be the only thing locating the mast fore/aft when it's up and you're sailing?

 

[Corribee Boy]

Yes, that would be true. I'd planned to deal with that with a new hole and bolt positioned further forward, if I didn't manage to renew the whole thing before launching.

 

[William_H]

That base fitting is horrible to my eye. I reckon it is a fitting used for mast top or boom end. The area taking the real pressure is quite small as you say. I am amazed it has lasted this long. I would think the bottom of the mast should be full sized to spread the load. To use the pivot axle as an axle for main halyard turning sheave also seems bad. (if it does)
However regarding the narrow width of the hinge. This is good in one way that actual movement at the axle for say 10 degrees of mast swing sideways is far less on a base of 30 mm than on Vic's pictured base of more like 10mm. So while forces are greater to damage the lugs lots of free play can allow movement without too much damage. Just on the subject of mast swing if your boat is afloat when you lower the mast any swing will take the mast weight to one side heeling the boat encouraging more swing so be careful.
Re Iw395 comment re location of the base of the mast. Provided lugs are intact there should be no problem with locating fore and aft the base of the mast as when sailing there should be no real force trying to move base fore or aft. That is all mine has. NB however mine has that spine to stop any tendency to move sideways or twist. If in doubt however a pin in the middle going in to the mast base fro m the deck base will locate it positively when mast is vertical.
Now for a few ideas for OP. I have a lot of success with a slot in the side of my mast for halyard exit coming at at a small angle down to a turning block on the deck. I use a wire halyard so need a small piece of SS rivetted to the ali mast to stop chafing at the exit. (or you cna buy a special slot cover)
I think I would look at getting a base like Vic's picture in SS. Cut that fitting down to a flat base to attach to the SS top plate. It does have a useful plug effect to take the pressure of the mast walls down to the base. ol'will

 

[Corribee Boy]

William, I've just managed to read your post through again and what you say all makes sense - actually redesigning the fitting to allow some free play while the mast's being raised, but controlling it with the temporary shrouds, is indeed the way to go.

You're also right about it being both heel and cap fitting. There's an identical fitting at the mast head with a crane for the forestay riveted to it. Given the composition of the cheese metal, that's another thing to worry about.

The halyard sheave is further back into the fitting than the pivot, but it's still weakening the fitting. I've been looking at bringing all lines back to the cockpit anyway, so altering the mast exit shouldn't be too difficult to achieve.

It's been a bank holiday here but I'll be making some calls tomorrow to get some prices and we'll see what comes up.