B&R rig with inner forestay

[40 South]

Originally Posted by cwyckham

I'm not a Hunter expert, but why would you have a B&R rig and a backstay? Isn't the whole point of the B&R rig to sweep the spreaders back far enough that you don't need a backstay? Has somebody added one?

That's how the early one came from the factory!

[40 South]

Originally Posted by Pauls

Regarding staysail loads, if the staysail is attached half way up the mast and is heeling the boat, say for example 30 degrees, then the heeling load at the staysail attachment is twice that of the heeling load on the jibstay attached at the masthead to achieve the same 30 degrees heel.

Swept spreader rigs can be designed to take both heeling (transverse) loads and fore/aft loads. Or not. If designed to take both loads the shrouds will be quite a bit stronger.

You can do an analysis of the rig to determine if the intermediates are up to this load without the help of runners. But frankly, if the rig wasn't designed for a cutter stay, why would they be?

The alternative is to just fit runners, which fully addresses the issue, no doubts or maybes, and gives you a stronger rig. This is the best solution.

Thanks Pauls for addressing the question. Runners is the way I will go if I fit the inner forestay.

[sailorboy1]

Lots of modern B&R rigged Hunters without backstays have inner forestays. Mine came equipped to install one from the factory (I haven't).

Enough said.

[knockabout]

we run 3 headsails on furlers
the mast has been strengthened inside by cutting the track
from another mast an driving it inside then reattaching all the
anchor points. we use 2 poles to pole out the no.1 and no.2 headsails
we have double lower stays to the spreaders and lighter backstays
opposite the take off point for the no.2.
we rigged the stays for running backstays with high field levers
and found them a nuisance short-handed and fixed the stays to
the rear lower stay take off point which works fine.
we sailed her like that from dbcya in Darwin south around Australia
via Hobart back to mackay, qld.
only drama under hard up-wind. the inside stays loosen up
and rub the paint off the back of the spreaders (but who want's to sail up-wind anyway).
take care that your mast section is strong enough to have a hound pulling
on it.
there may be a factory engineered and tested staysail system for your boat design

good luck
err on the side of safety

[UNCIVILIZED]

Originally Posted by UNCIVILIZED

why wouldn't you attach the runners in the standard position, opposing the pull of the new stay? Would they pose the possible danger of inverting the spar there?

I made this comment for several reasons:

-- B&R rigs are setup with a built in dynamic tension system which I've never studied. So I don't know what, if any, Achilles's Heels that they have.

-- Hunter's rigs aren't true B&R rigs as I understand the setup on such boats, which complicates the above.

-- You can invert almost any mast, given enough tension pulling the tube aft in the wrong spot. Especially if it's unopposed, or poorly opposed by tension on it's forward side.
For example, when trimming the Main via tuning the (slender) spar on a racer, you frequently have someone checking spar bend when adjusting the Runners & Check's, for this reason.

So if someone cranks on the runners too much when there's naught to oppose it's pull. And or the rig, in this case a factory re-designed version of the B&R, isn't designed for a lot of load in this area... Then you could invert it, & Bad Juju would likely follow. Up to & including a Gravity Storm.

-- When you have a Trysail up, or a Main reefed down to it's 3rd or 4th reef, the head of the sail can put a Lot of aftward tension onto the spar. And on some of the more svelte sticks out there. The Trysails are sized so that their head is in about the same place on a spar as the Babystay's attachment point. Or in some cases, the Staysail Stay's.
In order to prevent overloading that part of the mast tube in the aft direction.

Particularly if/when, the Trysail/deeply reefed Main, is the only sail flying. And the winds are in the high double digit range. So that the loads on the spar can get a bit extreme. Which is especially relevant on high strung mast designs.

Something that Hunter's B&R, may or may not be. But given that it; has no backstay (on some), is purpose designed to be bendy in the fore & aft plane, & that it has 2x as many stays as conventional rigs; then the math ain't too complicated. For me anyway, concerning them being "high strung" or not.

However, I may be a bit misinformed about them too. Hence my curiosity about adding a 2nd headstay to them.


Also, I'm with Snowpetrel, on the Solent Stay thing. And the location of the head of such a stay. As you can even set such stays up so that the stay's lower end, connects to a tang, either; in the Solent position, or in the regular Staysail Position.

A staysail itself won't really know the difference of where the stay's head's attached to the spar. And having such flexibility as to where you can hang sails of of it is a big perk in my book. Since you can reconfigure your rig for the conditions in only a moment or three.



With regards to resolving the stresses involved with where to attach staysail stay's tang, & runner tang's. There seems to be some missing information on how stays are commonly attached. Ditto on spreaders.

As when designing a spar, on a lot of boats, it's the norm to add a doubler plate to the mast, overtop of the compression tube, which houses the bolt which holds on the shroud tangs.
And said doubler plate, often encompases the area under the base(s) of the spreaders as well. So as to strengthen the mast walls in those high load areas.
An example of such can be seen on Cal 40' masts, here http://www.cal40.com/files/TEMP001.pdf
Plus, barring this, generally the strength of a lot of mast tubes are beefed up via other means, when designing & constructing spreader bases, & tang attachments.


So, such can also be done when adding tangs for runners. And it's commonplace for "extra" mast support to be built into the attachments of the various types of inner forestays. Even if it's just the addition of a "nose" to serve as the stay's tang.

Similarly, with Carbon Fiber spars, extra material is built into the tube in the vicinity of high load areas. However, with them, you definitely need expert input, prior to adding Any fittings to the spar.
And on wooden masts, there's often blocking inside of them in these areas. In addition to the fact that the spreader bases on them generally have a significant sized metal "footprints" for attaching such fittings & rigging assemblies.


BTW, while I'm not familiar with Hunter's modified B&R rigs. It's common to add "permanent" backstays to boats which don't (or marginally) need them. So as to be able to bend the mast, for better trimming of the Main. As well as being able to tune headstay sag.

[Snowpetrel]

One of the big advantages of the B&R rig is that the reverse diagonals pretty much eliminate the chance of the mast inverting.

I don't see any special reason why a cutter stay can't be done, but you are probably going to need a rig designer to OK it, unless you can find a good precedent for your model. The fact that other models of Hunters have inner stays is no guarantee your particular model can safely be retrofitted with one. It depends on two many individual factors to be certain. I suspect you would probably get away with doing it either way, with or without runners. But without proper analysis its just a wild assed guess.

I have done the numbers for my mast on my 40 footer, not a B&R rig. And I would need to upsize the intermediates to safely cope with the worst case heeling loads. Thats with the addition of runners. Which dont take much of the side load. Others seem to get away with it, so I suspect the real life loads are not as bad as the simplistic statical analsis I've done shows.

[GILow]

Regarding the forces on the staysail.

I recently needed to pound into 35 knot gusting winds and atrocious seas to get home. We have a very robust and relatively short mast with running backstays to handle the staysail load. Our sail area is very modest by modern boat standards.

Because of the wind strength I was under staysail alone and I got to feel the shock loads on the running backstays which terminate close to the cockpit. I can tell you they were soaking up huge amounts of energy. I cannot imagine any rig configuration I would trust in that situation other than stays directly opposing the staysail itself. I ended up rigging both running backstays just for peace of mind.

Matt


Sent from my iPhone so apologies for weird autocorrect typos.

[leftbrainstuff]

Originally Posted by a64pilot

You have to wonder why it's not done, or at least I do.
Does add cost of course
Compared to my Genoa, I think the loads imparted to the mast by my staysail to be minor?

Silly question, is there room for one?

That assumption is unlikely to be supported by an engineering analysis.

You also need to consider the dynamic, or harmonic, loadings. If the mast deflects out of column then its buckling resistance degrades significantly.

The first test is to identify how the staysail loading will be reacted. This can be done visually by any engineer with at least an undergraduate knowledge of mechanics of materials.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Bill whitmore]

If it is a true B&R rig (both diagonals and reverse diagonals with 30 degrees spreader angle), then Keep minimal tension on your backstay and do not add running backstays ( the reverse diagonals serve that function). Also, backstay tension will cause the leeward stays to be loose and floppy under normal sailing loads and greatly shorten the life of the wire.