Keel stepped mast leaning on mast collar

[venntim]

I've just added a bit length to the forestay as my mast has been a bit too upright for good pointing. It's a single inline spreader 7/8 rig with runners. The mast step is positioned as far aft in the mast foot as it goes, but the mast is still lightly leaning on the mast collar.

My question is that is there a danger of fatigue in the front section of the mast at the deck collar level? Or should I opt for a bit shorter toggle (changing it would mean taking the mast down again)? I haven't yet had a chance to measure the rake, but with an tried and true eye-balling method it looks ok, not too excessive.

Looking forward to your ideas!

 

[DanTribe]

Do you have an adjustable mast foot plate?
On my Ufo 31 I can fine tune the rake by moving the foot a notch forward or aft. This can be done without removing the mast and there is enough adjustment in the rigging screws, so no need for toggles.
If it's a Selden mast, speak to a local agent, in the UK they are very knowledgeable and helpful.
Nice looking boat.

 

[john_morris_uk]

I'm slightly confused by your question.

Do you really have an adjustable mast step where the mast sits on the cabin/keel floor?

Keel step masts always have 'chocks' where they go through the deck so they can be 'tuned' a little fore and aft and centralised there and I suppose the foot could have a variety of positions to allow for different choices of rake. It's not a set up I've seen on a yacht (but I've seen it on a dinghy so it might exist?)

In any event the mast collar shouldn't be hard over to one side or squashed to fore or aft.

 

[venntim]

Ok, sorry about confusion. The mast foot is notched, see a pic at: http://balticsailing.blogspot.fi/2013/05/stainless-steel-mast-foot.html

So far, there hasn't been any chocks on my mast, which I've noticed is not very satisfactory and lead to a broken turnbuckle at the mast collar, see: http://balticsailing.blogspot.com/2012/10/the-top-5-breakages-of-sailing-season.html

I've tried raking the mast by moving the mast foot forwards, but that didn't do much difference – that's why I added a 7 cm toggle to the forestay. Maybe I'll just have to take the rig down again and try a bit shorter one.

 

[William_H]

Who told you raking the mast would improve pointing. That is something I could not accept so easily. However if you like the mast raked well that is OK. I don't believe a bit more rake will significantly affect weather helm. So if the boom is not too low fine.
I am not really experienced with keel stepped masts except that I understand the mast is intended to bend from from the keel base to the forestay back stay etc in a smooth bend. Any fouling of solid objects like the deck would introduce a hard spot in the bend. This probably doesn't matter as they do it with chocks as said in dinghies. And of course you may not go in for serious mast bend anyway. More likely all you will see is some chafing at the contact point at the deck. And of course possibly damage to the soft collar. So I would say g sailiong and have a look at the mast when it is working hard and later check the collar for chafe. It may be quite OK. Certainly not a likely source of fatigue. go0od luck olewill

 

[charles_reed]

I've just added a bit length to the forestay as my mast has been a bit too upright for good pointing. It's a single inline spreader 7/8 rig with runners. The mast step is positioned as far aft in the mast foot as it goes, but the mast is still lightly leaning on the mast collar.

My question is that is there a danger of fatigue in the front section of the mast at the deck collar level? Or should I opt for a bit shorter toggle (changing it would mean taking the mast down again)? I haven't yet had a chance to measure the rake, but with an tried and true eye-balling method it looks ok, not too excessive.

Looking forward to your ideas!

View attachment 32306

Yes - and the insurers turned down the claim averring that one should use neoprene wedges. That has raised eyebrows with all the riggers to whom I've spoken.
It's probable that any keel-stepped fractional rig is at risk of panting and fatiguing at the deckhead collar. Mine was replaced with a 45% larger cross-sectional area, after working out the dimensions from base principles. Loic Gilbert of Z-Diffusion did that for me.
The insurers were Navigators & General - I'm now with GJW.

PS there should be an equal clearance, all the way round, between the collar and the mast, before you drive home the hardwood wedges. If there isn't you have to change the position of the keel mast step.

 

[john_morris_uk]

Yes - and the insurers turned down the claim averring that one should use neoprene wedges. That has raised eyebrows with all the riggers to whom I've spoken.
It's probable that any keel-stepped fractional rig is at risk of panting and fatiguing at the deckhead collar. Mine was replaced with a 45% larger cross-sectional area, after working out the dimensions from base principles. Loic Gilbert of Z-Diffusion did that for me.
The insurers were Navigators & General - I'm now with GJW.

PS there should be an equal clearance, all the way round, between the collar and the mast, before you drive home the hardwood wedges. If there isn't you have to change the position of the keel mast step.

In my experience the wedges at the mast collar are usually hardwood or a VERY dense and hard black rubber. Any decent rigger should be able to source some for you, although the last time we had a keel stepped mast I machined our mast wedges out of some scraps of mahogany. They are usually numbered or marked so you can put them back in the right place. The ones I have seen (and made) are inserted from above the deck (obviously slide the mast collar up first) and are machined as an 'L' shape or with a slight lip so they can't fall through if the mast flexes. Having said that, they are usually so tight that they have to be hammered in.

I would be very anxious about sailing a boat with a keel stepped mast without wedges in place. The only time I have done it the mast moved quite alarmingly in the mast collar as the boat was sailing.

I have a book showing that there should be five wedges. Fore and aft, either side on the beam and in the two front quarters of the mast. That said, the keel stepped mast on a boat I sailed recently had wedges all the way round.

PS The term mast 'wedge' is a bit misleading as it implies a 'wedge' shape and all the ones I have seen and used have been machined with parallel sides to 'just' fit and provide a good flat surface for the mast to bear against.

 

[venntim]

William H: You're right, pointing is not affected by rake, my bad... What I meant to say was that I've had substantially less rake than my sisterships and I haven't seen the stellar pointing that's usually assosiated with these boats. As my sails are pretty fresh, I suspect that the culprit is mast trim. I'm not talking about any super rake here, more like a subtle change... Boom position is not a problem, but I may have to shorten the runners a bit. The picture I attached is from the last summer and it really doesn't show the rake (in fact there wasn't any).

After a three trips to the mast crane, I'm now pretty happy with the trim. The mast is not in the middle of the collar, but with the rig tension on, it doesn't rest on the back of the collar either. I've got some rubber wedges on the back and on the sides as well and will add one in front, too. I spoke to the local Selden guy and he gave his ok for this setup.

Many thanks to you all and fair winds.

 

[pmagowan]

My mast was missing the wedges when I bought the boat and it did not seem to effect much when sailing but the mast had significant wear where it passed through the collar. We put on some stiff rubber to protect it.

 

[doug748]

... Having said that, they are usually so tight that they have to be hammered in.

I would be very anxious about sailing a boat with a keel stepped mast without wedges in place. The only time I have done it the mast moved quite alarmingly in the mast collar as the boat was sailing.....

Yes, I would as well. As I understand it, the point of keel stepping is that that the mast is held firm at deck level.



This is my mode of operation:

With all rigging loose. Fore and aft wedges

Fit the aft (rather softer) rubber wedge. Very tight, jiggle into position with washing up liquid

Draw the mast back at deck level using a doubled strop to the cabin top winches. (Winch untill I see little spots of light playing before my eyes and then a bit tighter)

It is now just possible to insert the forward hard rubber block, with some hard work.


I don't have side wedges, if you feel you need them, go lightly or you could crush the mast.

 

[Phoenix of Hamble]

PS The term mast 'wedge' is a bit misleading as it implies a 'wedge' shape and all the ones I have seen and used have been machined with parallel sides to 'just' fit and provide a good flat surface for the mast to bear against.

To add to John's point about parallel sides (that I complete agree with!), a better system is to have two wedges, both triangular, and laid opposed to form a wedge with parallel sides... this way, it can be 'tightened' into the gap, rather than having to be made exactly the right size.

Also, FWIW, my wedges are hardwood, fitted from below.... I agree that from above is better, but that means disturbing the mast boot in my case, and currently it's nice and watertight..... however, as stated above, mine are in so tight, and also further retained by a well attached trim ring inside the coachroof, that if they fall out, then its a consequence of much bigger problems!