Mainsail roach & backstay

[charles_reed]

Having fitted a new, stronger, taller and generally more adequate mast - I, in a rash fit of enthusiasm, got Jeremy to make me a new fully battened main with an aggressive a roach as you see on Open 60s and Farr 52s.

With the old main on the boat goes like the clappers - but the poor thing looks a bit shrunk.

Unfortunatley the new main overlaps the single standing backstay by 40 mm on the top batten 150mm on the 2nd batten and 65mm on the 3rd batten.

I've had a number of recommendations, some half-baked and some quite good.

These range from:-

1. Cutting 200mm off the foot (Cariad Voiles)
2. Taking off the roach (lots of neurotic yotties)
3. Fitting twin running backstays, I've a two panel rig with 22 deg on spreaders, (Bernard Bossé & other dedicated go-faster freaks)
4. Fitting a single-line, 2:1 purchase reef just above the cunningham, which should give just enough clearance to allow the roach to clear the backstay.

I've already got 4 reefing points on the main and only 3 sets of in-boom leech lines.
The elliptical tip of extra roach, apart from increasing the efficiency of the main by about 28%, gives me an additional 18% of area for those nauseating light air conditions one suffers in the Med

Now what suggestions would the august,learned and experienced readers of this BB like to make and what solution would they recommend.

 

[vyv_cox]

Can you extend the cap fitting aft about 15 cm? It should be possible to project the backstay outside the roach without adding too much weight aloft and still retaining sufficient strength. If necessary some triangulation downwards each side of the track should be possible without interfering too much with the headplate of the main.

 

[charles_reed]

The problem in extending the backstay cap-fitting is that you dramatically increase the mechanical advantage of backstay to the mast.
I should perhaps explain that, with 22ó stagger on the spreaders the backstay is mainly used to bend the mast and change the mainsail camber rather than hold up the mast (except on the run in heavy winds).
Loic Gilbert (of the mast-maker) is particularly averse to extending the mast crane - in fact that's part of the problem - the original drawing specified a 250 mm crane, the modification carried out by Z-Spars was to fit a 150mm crane but at 40ó to the horizontal.

 

[bedouin]

I know that on conventionally battened sails, having a few inches of overlap between the roach and the backstay is not usually considered a problem. I imagine that it is more problematical in a fully-battened rig, but I seem to recall someone mentioning using hinged battens to help it pass the backstay.

If you are convinced that you must remove the overlap then the easiest solution must be to reduce the roach - any other way of reducing the sail size like those you mentioned must end up loosing more sail area than cutting the roach - albeit somewhat cheaper.

 

[qsiv]

If thats the case why not copy the Farr 40 /Mumm / Melges approach.

Fit a stiff fibregalss batten horizontally to the masthead, and attacha very strong line down to the backstay. Then, when you ease the backstay purchase, the stay itself is left out and away from the leech of the main. It's much quicker and easier than tucking in flatteners, but may be tedious if you were to short tack up a non existent Med river!

 

[Jacket]

without knowing how many battens you've got in total, its hard to say how well this would work, but how far would you need to move the base of the backstay aft by to reduce the overlap to a sensible amount. I saw the Beneteau First 27.7 at the LIBS ansd it had a small platform built extending out the back, to which the backstray was attached. Might this work for you?

 

[jimi]

Why do'nt you just buy a new boat to match your new main, it'll probably be cheaper in the long run and sail better too?

 

[Twister_Ken]

Runners if...

...you've got the staff, or the multi-tasking ability to handle them in a middle of heavy gybe - which with your existing rig is probably the only time you'd need to get the new runner on real quick.

 

[charles_reed]

Looked at that and it would need something like an additional 1.45m extension on the stern of the boat - which has a transom hung rudder and the backstay tangs on the very outside

 

[snowleopard]

just go for it?

i would expect the weight of wind in the sail would bend the battens and allow them to slide over the backstay. if they snag, a bit of webbing sewn over the end of the batten pocket to smooth out any snags and a plastic sleeve on the backstay should allow tacking and prevent undue wear. (gybing might be a bit more risky)

 

[charles_reed]

Good one that - of course the boats you mention all have a 25ó sweep back on their spreaders, which makes the rig utterly self-supporting.
With my 22ó I do definitely need that backstay support under running condition and especially when one does a gybe under spinnaker.

 

[charles_reed]

Re: just go for it?

Tried gybing in about 12 knots (true) of wind and all except no 2 batten got past.

It was a little exciting for the few moments it took to get the main halyard freed!!

 

[Martin_Billings]

How about a vertical post/frame around the taffrail area to alter the angle of the backstay without changing the mechanical advantage?

 

[LadyInBed]

Lower the boom by 4 or 5 inches.
Far too easy an answer, so it either isn't possible or I haven't understood the question!

 

[Martin_Billings]

Sounds good, but possible secondary problem: Unfortunately the newly lowered boom overlaps the heads of the crew by 40mm....

 

[LadyInBed]

Get shorter crew /forums/images/icons/crazy.gif

 

[AlanPound]

IIRC the Dashews use this approach deliberately in their recent designs. They reckon that in heavy airs, the sail blows past the backstay ok (I think they have some kind of thin plastic (mylar?) protective strips on the sides of the batten pockets near the leech, to avoid chafe).

In light airs (just when you need all of the sail) they put in a reef prior to tacking.... which I guess is fine if you tack only once a week, but a tad boring if you are taking back and forth - however, in terms of sail area, you may as well leave that reef in, as you probably end up with no less sail than you had with your old main...

Alan

 

[charles_reed]

Alan,

I think you may be on the right tack - incidentally I've got some of the HDPE tape Dashew refers to. It's not available in Europe and I had to import from New Jersey. The backing adhesive isn't really strong enough, but I've found it great if you sew it in place.

I've tried gybing the sail past the backstay, admittedly in just 12 knots apparent wind, and I'm afraid No 2 batten jams comprehensively. Which just goes to show that you can't believe everything you see in print, even by such a practical designer as Steve.
He reckons that "Beowulf's" main used to overlap by 22", but if you look closely you'll see he's using twin running backstays on the main and the mizzen is unsupported.

Incidentally Steve Dashew also designed the 2-man powered sailplane which holds the round-the-world-non-stop record. The HDPE saved about 6" of the wingtips when they were trying to get the aircraft off the ground.

I suspect the running backstay route is the best to go down but I'm loathe to re-step the mast - getting a 44% greater cross-section down to the keel was a real shoehorn operation and I know that I may have a mutiny on my hands from Jean-Marc (the SAGA chef d'oeuvres) if I ask for the use of the travelift grue again in March. As it was 2 of his lads lost large areas of skin off their knuckles and had some near-misses with fingers. Being a devout coward I was wearing heavy protective gloves.

At present I'm looking at a single-line reef, just above the cunningham, with Harken in the US checking out the reaction forces involved.

As I've already got 4 reefs in the main (the single-liner will be No5) this has to be an external, and to overcome the main flaw in single line reefing (frictional loss) I'm designing it with a 2:1 purchase with the flappy end coming back to the cockpit.

Theoretically that will be faster and less work, for a single-hander, than hopping around with a pair of running backstays, but I've yet to put it to the test.
Other benefits of the route I've chosen is that you just have to sew on some tape for a pair of Carbo-57 blocks on the sail, and not put a pair of permanaently incriminating reef-eyes in the sail (all those holes must reduce the efficiency of the damn thing in any case); the area and efficiency of the sail means that I'll be reefing in any case just above 12 knots apparent, which is only a F2/3 to windward, tho' it could just be F6 offwind if there are a few breaking crests running.

 

[jimi]

Like most of my good ideas this might be stupid but could you not put a little roller thingie on the backstay to try and a)help the sail past b) minimise damage?

 

[charles_reed]

Good lateral thinking Nigel - the boom position is, in fact 30mm higher than on the original mast and there is more than adequate clearance for my 1842mm height.

However:

Lowering the boom would require changing/shortening the gas-strut and/or re-fixing its lower cleat farther down the mast. That would require drilling out and redrilling 10 large monel rivets and 3 bolts on the gooseneck and 8 rivets on the vang fixing. These are large rivets, requiring a pantograph or power riveter. Whilst I've got a breast-operation riveter doing those rivets is right at the limit of its capacity.
Additionally, the FMEA we did on the original fracture suggested that the juxtaposition of the vang fixing to the restraint of the coachroof cap was a significant factor in the work-hardening and subsequent fatigue-fracture of the original mast.

For this reason it was one of the first solutions to be evaluated and rejected.