Mast Bend

[Alan Wheeler]

Deck stepped Del.
But if the back stays are lower, wouldn't the forward stay pull the top of the mast over and forward? Or are you meaning both fore and aft stays are lower?
Everything I have looked at so far that has a stay lower to it'soppsoing side, is reverse to what you just described. The back stays go all the way to the top and the forstay is down 3 or 4ft. But this is on semingly performance rigs and they have a significant bend including a taper to the mast. Any rigg more traditional all seem to have the aft and fore both at the top. But in adding to that, they also have a longer extension at the back of the head for the termination point.
With mine, having the forestay terminating higher, surely has to act in placing a bending moment on the mast. It would act the same way as dropping the opposing stay down the mast and having the higher stay pulling the mast over. But also in my situation, it is possible the hight difference is so small, that this is not causing a problem.
If the weather is anygood (which it isn'tlooking that way) I will have another crack at it in the weekend and let you all know what happens.

[delmarrey]

Alan Wheeler once whispered in the wind:
Everything I have looked at so far that has a stay lower to it'soppsoing side, is reverse to what you just described. The back stays go all the way to the top and the forstay is down 3 or 4ft. But this is on semingly performance rigs and they have a significant bend including a taper to the mast.

What you discribed here IS a fractional rig. What I guess I'm trying to get across is, it looks as though you need lower back mainstays to straighten the mast out. The only masts that I've seen to have the arch like what you discribe are the fractional rigs and the swept back speader (hi tech) unites.

But if the bottom of the mast has a forward rake then I'd say move the foot forward a bit to straighten it up. BUT, on the other hand is your mainsail boom racked up at the aft end with the main all the way up???

There are a lot of variables to deal with. Also the main mast seems on the skinny side in relation to it's height. Of course, I have heavy duty rigging (Z601-- 223mm x 138mm - (8 3/4" x 5 7/16" X 51 ft. tall)) for the size of my boats (racing rig) so I may be off there.

So, we'll see what your pictures show. A shot staight up laying on your back would really show the bend.

And does that bend change when your underway (sailing)?..............................._/)

[Alan Wheeler]

But if the main backstays came down lower, teh forestay is going to pull the top of the mast further foreward and increase the bend even further.
The mast is about 45ft, ovall profile and I would hazzard a guess as to about the same profile diamensions as yours.
I will see about getting a better photo looking straight up.

[delmarrey]

Alan Wheeler once whispered in the wind:
Del... the mast has a bend foreward (towards the bow not mainsail) for the first 2/3rds which is good. I mean by good in that it is not overly bent, has a nice curve and seems to fit the sail nicely. The next 1/4 is straight and then the last quarter takes a bend to the aft (into the mainsail).



The result is that the top of the mast is pulling the top of the sail forward, and screwing up the shape of the sail up there and I can't get it to fly how I expect it should do.

The first paragraph I thought you were talking from the bottom up. But now I see, from the second paragraph, you were talking from the top down. You guys on the other side of the world..............

Anyway, this sure changes things. I have to think about it for a minute..............................

Forget all this miscommunication from the past posts. Everything is backwards from what I thought.

Looking at the picture again I would say that the back stays would need to be tightened along with the back brace and then move the mast foot forward. Basically just the opposite of the last post. I'm not an expert on masts but in my profession straighten shafts, rollers, plate & etc., I've been very good at. And industrial rigging is on my resume'.

Sorry about the confusion

Hope THIS helps................_/)

[Alan Wheeler]

Hey that's cool Del, I just thought being on the top of the world and all, you would be looking down.

[CaptainK]

Alan.

Sounds to me that you have your work cut out for you here?

I wish you luck in getting that problem sloved and repaired!!

[delmarrey]

I'm a bit on the short side, so I'm always looking up to other people. But that's good when it comes to boats. The average boat has enough head room..............................._/)

[Alan Wheeler]

OK folks, here's an update. I have tried all sorts of things, and nup, nothing worked. So I called in a expert. Experts are like instructions to me. So it is always a last resort, but should have done it earlier sort of thing to me.
Well here is the problem. ummmm, problems

The mast section is too small for our boat and the length of the mast. It's 180mm x 135mm x 4mm (sorry I don't know the inches)and is 15m tall.(ruffly50ft)

The mast section has been joined in two places. He thinks that one of those joins is perhaps preloading the mast. Once the compression comes on, it then kicks out in the direction of the pretention.

I have just compleated a detailed measurement of the whole rig and he will check the design is correct. I would hope so, as that should have come off of the blue prints.

The bad news is, the mast has to come down.
The good news is, he thinks the mast section will be OK, even though it is too light for the rig. He thinks he maybe able to solve the problem with a diamond stay kinda design. But that has to be checked with ther design guy once he gets the measurments. Lets hope it works, as I can't afford a new rig.

[CaptainK]

Alan Wheeler once whispered in the wind

It's 180mm x 135mm x 4mm (sorry I don't know the inches)and is 15m tall.(ruffly50ft)

That's 7.08in X 5.31in X 0.16in Mast height is 49ft .21in tall.

Wheels, considering the problem, definitely have an expert work on it. You may need to install oversized rivets in the connection, as the holes may have been oblonged. It also sounds like the mast may have been affected by over tensioning. When the rig is reinstalled, it would be a good time to calibrate your home made tension scale for future use.

[delmarrey]

I did suspect the mast was on the lean side but a joint in the length pretty much explains it now.

Sometimes you just have to be on location to really see what is going on.

Good luck..........................._/)

[Alan Wheeler]

To continue the saga. I have had the "experts" run the figures and it seems the mast section is indeed to light. A section of 7lbs/ft is called for and I suspect the present one is half and maybe even lighter than half that.
The scary part is, the extrusion is estimated at around NZ$5K. I haven't recieved a firm quote yet.
However!!. I have been thinking.
I have two sets of blueprints for the boat. One shows the rig layout for a ketch and the other for a Sloop. The Sloop design calls for a mast height of around 48-50ft. The Ketch design has no length printed on it. But it looks shorter. If the print is to scale. I maybe able to calculate the exact length. I just don't have the BP's here at the mo. The present mast is 50ft, which for the Ketch rig, maybe to tall and is certainly too tall for the mast section. So to the experts, here is my question.
Can I cut the mast down in length with no detrimental affects. I understand the main would need to be recut, but that's not a biggy. The Genoa does not go all the way to the top. In fact it is no where near the top, so that won't need to be changed.
I would have to relocate spreaders and terminal points for rigging. Is that a problem having holes in the mast not being used? like.. will they be weak spots??
Thoughts anyone???

[CaptainK]

I hope that you'll get that problem fixed as soon as possible, Alan!!

[Rick]

Man-O-man! Going to a ketch rig would necessitate moving the location of the main mast for a given hull design to sail to an optimum set of conditions.

Even "slutter" rigs, like mine, are a compromise towards gaining the benefits of a stays'l in that a true cutter has the mast further back than a sloop for a given hull.

Another factor to consider when thinking about going to a shorter mast and sail is the wind shear factor. A one meter difference on a 50 ft mast makes a difference in the Carribbean, for example, in being able to get more horsepower from the wind which has a very measurable shear in speed from the deck to the top of the mast.

In the Pacific on the west coast of US there is not much shear and so a shorter mast is not much of a problem. What do you know about NZ wind shear?

If you can bite the bullet and see about a larger mast section,used? Or will a diamiond rig really solve the problem? Try to keep the 50 ft so that the rolling and pitching action of our boat does not change, which it will with a ketch rig.

[Alan Wheeler]

Just to clarify Rick. She IS a Ketch rig. But the mast height is more toward the height the Sloop rig would call for. At least I am presuming the Ketch mast height is supposed to be shorter than the sloop. I could be wrong.
As for wind shear, yep it shear blows down here.

Ultimate is a mast section of appropriate size. I don't know how I will afford it, but I will find away. May have to put the fishnet stockings on and stand on a corner under a street light. It will need to be a dull light though.
I really don't want to go down the track of diamond stays and so on, it is just going to be hell on sails and so forth.