tabernacle bolts - Vivacity

[Guy]

I have a Vivacity 20, with an alloy mast just over 20' in length. I am having trouble with the stays (they are too long - and I'm waiting for some Noresmen terminals in the post) but that's not the question for now.
The tabernacle has two bolt holes. The top one is the fulcrum for raising mast. Then there is a bottom one. Last season I sailed with both bolts in and a 10mm pad of wood to fill the gap at the base of the mast (between base of mast and base of tabernacle)
In a sailing magazine I saw a similar tabernacle with the fulcrum bolt removed. This got me thinking.
At the moment, I know the stays are too slack and this is what is happening:
Downwind, mast has a bend forwards (if you look up the mast track), so I go back and strap the two rear stays together to get the mast straight).
Then, when I'm on the wind, the mast has a bend aft.
So that means the base of the mast is held firmly, yes?, but the top of the mast isn't - there is no equilibrium between the forestay and the two rear stays, is there?
Is that right so far?
Now the stem head bottle screw is real tight (i think - roller furling gear makes it hard to tell - bottle screw is really tight by hand, put it that way) and almost to its limit of turns(I should say the forstay is 6mm diameter and the two rear stays are 4mm each), but the rear stays are not really tight. If I tension the rear stays even a little bit, they bend the mast backwards (but the tension in each rear stay only has to be half the tension in the forestay, yes?) So this bending backwards doesn't make sense to me first of all.
I thought I'd take the bottom bolt out of the tabernacle so the mast could pivot (that'd get rid of this bending, yes?) CAN I REMOVE THIS BOLT? IS IT SAFE TO SAIL LIKE THAT?
Then, I'd rake the mast back a bit (that'd extend the stemhead bottlescrew a bit so I had some turns to play with) and I'd cut the two rear stays shorter, and try to get the proper tension on them (seriously, they flop about at times).
HOW DOES THAT ALL SOUND?
I don't think the hull (grp) is distorting.
Any advice welcomed.
Thank you.

 

[Strathglass]

Where are you located Guy? It sounds as if your rig is too slack and needs set up properly. I would suggest that you certainly keep the spacer under the mast, even fit a thicker one if possible. Without seeing the craft I would hesitate in making any further suggestions.

 

[Guest]

It is certainly NOT unusual to sail with BOTH bolts IN. With correctly set stays, really the two bolts are only securing the foot of the mast and should have no real role in the rake etc. other than keeping the foot in place.
In all twin bolt pivoting boats I have sailed / owned, I have kept BOTH bolts IN.

I have never seen significant rake change in a mast when sailing up or down wind, in fact I've never really looked, but it sounds to me as though you really have slack stays all round.

Finally to say that you can gain extra screw adjustment on the forestay etc...... No, it all depends on the balance of the rig, raking the mast aft will increase tendency to weather-helm, or the need to reef main early before genny etc.

My advise is to get a person knowledgable in these matters to your boat quick, before you make expensive mistake .... if you cut / alter your stays and find you're wrong ..... ouch !

There must be a rigger near you somewhere, if you belong a yacht-club then even better ..... there must be others in the club to help / advise / assist in the determination ?????

Where are you anyway ?

 

[Guy]

Dear Nigel, Thanks for the reply.
On the East coast.
Yes, I'm sure the stays are too slack, BUT, do you think I have created a problem for my self by increasing the forestay diameter from 4mm to 6mm?
People say you can't over tension rigging by hand. But... if I have 6mm forestay and two 4mm rear stays, WITH THE SAME SIZE bottlescrews all round, then I am thinking that what these "people" say is wrong. (Assuming two bottlescrews the same size, then 5 turns will tension a 6mm wire differently from 5 turns on a 4mm wire won't it? - or is that wrong?)
I have tightened the 6mm forestay by hand as much as I can, and then a bit more with a SHORT lever. I don't know the tension coz I can't feel the stay (roller furling)
But if I then go to the back of the boat and find that putting even a slight bit of tension on them bends the mast backwards (ouch to the bottom of the mast by the way, the strain on those old,
bolt holes in the mast must be getting big, yes? due to the fact that it can't pivot) then the fact the mast is bending backwards indicates that the forestay is in fact STILL too slack...doesn't it?
That's the question then, do you think the forestay is still too slack even though I've put a bit of leverage on it?
ALSO, most people probably would have just put the correct tension on the rear stays and not looked up the mast and therefore not have noticed the bend- I have because I am too fussy for my own good, and having taught myself all this sailing lark recently, I am still double checking every little thing I do-but can you tell me, how much bend is allowed in an alloy mast just over 20 foot in length and quite old?
Thank you.

 

[PuffTheMagicDragon]

Just a horrible suspicion: When you say 'bend' do you mean 'bow'? I ask because you do not mention the lower shrouds and if these are not fitted then you could get 'bowing' in a fore-and-aft direction. Regarding the thicker forestay, this is not a problem; I had done the same thing on my Vivacity when I had fitted the furling genny. The difficulty in tensioning is not caused by the thickness. As you know, the mast on the Viv is so far forward that the forestay makes a very narrow angle with the mast. It therefore becomes quite difficult to tighten sufficiently. I would set up the forestay first and THEN tighten the backstay. (I had a single one which divided into two at a height of about six feet). When tightened properly you should have very little sideways sag on the luff of the genny on a good beat. Don't worry about distorting the Vivacity; they were sturdy little boats and it is probably easier to pull up the stemhead fitting!

Wally

 

[Guy]

Dear Wally,
Thanks for that. Yes, I do have lower stays and I've tried playing with those to see if that would fix it. I think it is a bend because it seems to start from half way up the mast.
I see your point about the forestay angle and therefore getting enough tension. How much pressure did you put on your bottlescrew (at the front) when tightening up?
I set up the rig as you said, forestay first, then the back ones. I am beginning to think that I simply haven't tightened the forestay enough - and the trouble is, because of the roller furling gear, it's hard to feel how tight the forestay is. All I have to go on is feeling the bottlescrew - not exactly satisfactory. I will look for any sag on the luff of the genny now that you have mentioned that.
Thanks
Guy

 

[Guest]

Sorry for late reply ......

Tabernacle bolts are normally sloppy fit,as I said they have no part to play other than keeping the foot from moving.

If I lean on my backstays, I have a 25ft Motor sailer, I will rake my mast, probably a few cms. - I would think it more because the backstay will 'give' under my weight.
If I hold the furling genny and shake it, I can see the whole stay and gear move significantly, probably a good 10 - 20 cms side to side at 1/2way point.

Now when sailing ...... the side stays, babys and cap, should slack slightly on the lee side so that they can be seen to be just tiny bit slack by the eye. Tack and then the others should be same, with former now tight and taking load.

If you have a backstay to twin bridle, that is a single stay comes down to a twin short stay out to aft corners. Then a simple trick here can solve the question and find out if you are set-up right ........

Take a length of line and actually bind to bring the two stays together at the mid point to really tension them up while sailing .... watch what happens to the tiller feel, does she want to turn up into wind - weather helm, does she want to turn away from the wind - lee helm, does she balance up ..... this indicates the set / rake of the mast and also the relative positions of each sais centre of effort etc. which is changed as you rake / bend the mast etc.

My advise is still to grab someone in the club / marina, or a rigger and get him to look at it ..... once you have eliminated that side, you can then play with backstay tensioners as above !

(Most people haven't noticed on their own boats what you have seen on yours ...... so enjoy your boat and sailing !)