Arne Kverneland wrote:

Scott Dufour wrote:

Arne Kverneland wrote:

Jami.

It looks to me that that the vertical wall of that flange is quite thick. What about drilling a ring of eight or twelve 12mm holes around it and fit them with threads? With short 12mm bolts screwed into them, these should clamp the mast tightly. In case the mast tube is not too thin-walles, at least 4mm, it may work without distorting it. I would wrap the mast with a bit duct tape before stepping it, and I would also add a (say) 1mm rubber gasket plug  at the end of each bolt before inserting them. That would spread the load a bit and prevent electric corrosion problems.

If I understand your suggestion, Arne, this puts a whole lot of stress risers on the mast wall. At any given moment the full load forces will land on about 3, maybe 4, of these bolt ends.  

I know, I know, that is why I asked for a rather thick-walled mast...

Arne

Edit: One could beef up the high-load area from the inside. One could for instance turn a piece of timber, say oak, for a tight fit. Even a concrete plug would do. Concrete is very resistant against compression.

I'm getting ahead of myself here (because I haven't researched this point yet) but -

You are suggesting 'clamping' the mast to the step with bolts rather than boring a couple of holes through the step AND the mast allowing the bolts to pin the mast to the step.

I'm curious, why one method over the other?

Scott Dufour wrote:

Arne Kverneland wrote:

Jami.

It looks to me that that the vertical wall of that flange is quite thick. What about drilling a ring of eight or twelve 12mm holes around it and fit them with threads? With short 12mm bolts screwed into them, these should clamp the mast tightly. In case the mast tube is not too thin-walles, at least 4mm, it may work without distorting it. I would wrap the mast with a bit duct tape before stepping it, and I would also add a (say) 1mm rubber gasket plug  at the end of each bolt before inserting them. That would spread the load a bit and prevent electric corrosion problems.

If I understand your suggestion, Arne, this puts a whole lot of stress risers on the mast wall. At any given moment the full load forces will land on about 3, maybe 4, of these bolt ends.  

Arne

Edit: One could beef up the high-load area from the inside. One could for instance turn a piece of timber, say oak, for a tight fit. Even a concrete plug would do. Concrete is very resistant against compression.

Jami Jokinen wrote:

Holy cow! This was my initial thought while exploring at the local junkyard. Then it hit me - it was probably too good to be true.

I found a sturdy stainless steel collar that costs next to nothing. Absolutely fabulous (see photo).

The inner diameter is 131mm, and the lower part of my mast will be 130mm. I suppose this is unusable, because:

- no way of installing wedges

- too close a match to slip in and out the mast with a crane and a swinging boat

Am I on the right track here? The collar is dirt cheap, and there are several of them, so I could buy two and use the other on the mast step. If only the dia was 150-160mm...

Edit: what If I made a nice rubber gasket for the collar and the bolts, and install the collar every time the mast is being installed (every spring and vice versa in the autumn)? Would the tight-fit collar still be  a no-go?

https://www.mcmaster.com/#44705k553/=1cesuxo

You can go to my photo album and see pics of the installation.

The collar-to-mast fit was a greater than 1mm so I shimmed the collar to get a metal to metal fit...no wedges. My mast, at the base, is a 6 inch OD parallel-sided pipe. The collar is tight but will slide. To remove mast I'd un-bolt the collar.

Instead of drilling new bolt holes in the base I  found (7/8"OD x 3/8"ID) aluminum inserts and used the existing flange holes...used oversize washers to cover the insert when bolting the collar to the deck.

You do have to be more precise when lining up the deck hole to the mast step. I waited to drill the deck holes for the collar until mast was sticking out of the boat, sitting in the mast step, and bolts for the mast step started. Only then was I fairly sure everything was lined up close enough and the rigging crew could disconnect the straps to the crane.

Not sure what added complications I would have had with a tapered pole.

robert self

Jami.

It looks to me that that the vertical wall of that flange is quite thick. What about drilling a ring of eight or twelve 12mm holes around it and fit them with threads? With short 12mm bolts screwed into them, these should clamp the mast tightly. In case the mast tube is not too thin-walles, at least 4mm, it may work without distorting it. I would wrap the mast with a bit duct tape before stepping it, and I would also add a (say) 1mm rubber gasket plug  at the end of each bolt before inserting them. That would spread the load a bit and prevent electric corrosion problems.

From the safe position at my keyboard  -  good luck!

Arne

PS: The hard material in the flange will need a good drill press and thread-making equipment.

Or maybe set the position of the collar, not the mast step, as the mast is set up?