Wing Mast

[RobinJones]

Well after another day sailing banshee with her wing mast, it seemed like a good time to post a bit more information and pictures about it.

It's sailed for 4 days as of now - with some (very) limited success: sadly never coinciding with another cherub being on the water, so its all pretty unknown at the moment. First 2 were purely to see that the system worked, and prior to recutting the sail, so that i had some idea how much cloth to remove. As expected, this was horrifically slow, the battens didn't pop easily, which made the mast difficult to pop, and the added system needed tuning, but it worked to some extent. In that nothing broke.

Over that week, i made some major adjustments to the sail I'm using for it - riot van's old hyde main, reducing the luff curve from 180mm or thereabouts to nearer 50mm. Also made some minor changes to spanner angle, and the foot of the sail so the two brush past each other rather than snagging.

Following week, we turned up and rigged what looked to be a sail that was far too flat - so we cranked the batten tensions right up, which turned out to be a huge mistake, pushing the tension high enough that the top two would not pop at all. Limited success that day though, when a BIG squall hit, changing from 8 or so knots to somewhere in the low 20's I'd have thought - it seemed surprisingly responsive, after pulling the rotation limit string on, and an ace kite run proved the strength of it.

This weekend, after some more minor system tuning, elasticating, and batten tension adjusting, the boat seemed to go pretty well upwind and down - the angle of rotation seems to need to be very precise, and around 40 degrees upwind. Though once the groove is found, it seemed to point very very well, and perhaps go pretty quick - we weren't sure with no one to pace but a 14.

Overall still positive about it. Some tidying up needed with controls, i need a better boom slider for the rotation adjuster bar whatsit, since that jams sometimes (anyone got about 2 foot of old jib track and a jib car i could buy off them per chance?), and in hindsight 3mm vectran is scary thin for shrouds, so I need to get some steel ones made up or up to 4mm shrouds with heat shrink to protect from the UV.

More than anything though, it's just great fun to play with the boat, and i think I'm learning shed loads about rigs as I go!

Load of pics to be attached, feel free to ask questions/make suggestions/point out various stupid things I've done.

[dave_ching]

Looks amazing does it rotate well with the rig tension on high?
how does the jib work with the rotation ie the take of point on the mast does it have a track?

[Neil C.]

Looks like the dogs danglies. Maybe also a little bit scary! 
Good on you.

[RobinJones]

Hi Dave - the mast rotates relatively well, but I'm trying to think of a bearing kinda system to improve this - at the moment its just a dome headed pin (like on an rs600) in a slightly conical hole, so there is a fair bit of friction. It tacks relatively well when theres some wind, but in the light stuff its difficult.

The Jib, Forestay, and both Shrouds all come off the same fitting on the front of the mast, a little T piece that comes through the mast skin. This means the axis of rotation is between the mast pin and this fitting.

Neil - thanks! Certainly looked daunting the first time it went on the boat.

[JimC]

The sail can be pretty flat I think. My guess is that the leading edge camber that you would get from luff round is pretty much supplied by the mast over rotation, so only very moderate luff round shaping would be needed compared to a conventional mast/sail combination. My pivot was the same as a moth, about 1" diameter dome and socket. A carbon/graphite filled dome and socket might be worth considering, it would polish well in use and the wear shouldn't be too nightmarish I wouldn't have thought.

I used to put saltwater proof grease on my mast bearing, your club outboard maintainer should have some. Generous sailkote would be cleaner and might work OK.

[Clive Everest]

One tip from the A class.
If you leave it up in the dinghy park rotate it 90 degrees so that wind forces are not trying to blow it over sideways.
If it pitch-poles in the dinghy park. Join a club with a more sheltered dinghy park.

[RobinJones]

Jim, that's what I suspected (and what just about everyone I asked told me). So to me, the sail looks incredibly flat, in reality the effective camber including the mast is probably similar to that of a normal rig. She at least didn't seem short of power last week in very light conditions. I keep meaning to Vaseline my pin up, but forget every weekend. Its feasible this will sort it, though the cup and socket idea sounds like its not a bad shout - the cats use a large nylon ball and metal socket i believe, though their fittings seem unnecessarily meaty for Banshee.

Cheers for the tip Clive! Though, the thought of her sat there with the mast un-rotated will now scare me all week...

[JP233]

Maybe I should find a new boat park space.

[Clive Everest]

In the past I have fitted big (50mm OD) ball bearings under mast steps.
It is amazing how well they cope with salt and sand.
Even when they look totally knackered.
They sure make the mast rotate freely.

On our Moth the mast sits on a 16mm stainless ball bearing.
This is screwed into the kink post and there is a 3D printed nylon mast step.
It seems to work ok.

[JimC]

I've got one of the alloy and plastic large diameter ball bearings from a Laser EPS mast in the garage somewhere. Bit bulky and troublesome to post, but it could be picked up from Epsom or Molesey. Or could probably bring it to QM when the open is on.

In the past I have fitted big (50mm OD) ball bearings under mast steps.

How do you manage alignment Clive? I was wondering about using a ball race on a spar footed self tacking jib setup on the Canoe, but alignment felt like a big problem in my head.

[Clive Everest]

I sat an RS600 style ball and socket on top of the bearing.
The bearing provided the rotation. The "ball and socket" the alignment
Clive.

[kerrgreg]

How did the mast hold up over the weekend robin? - interested to hear your findings for the 3 days

I was gutted to see you couldnt make it out on monday, but didnt catch why?

[RobinJones]

Greg,

It was a lot more successful than i expected to be honest!

Saturday, 8-10kts maybe, if that. Usually felt a bit slow if I'm honest, but had occasional moments of feeling high and fast, when i got the limit string set up right. This seemed crucial to getting it going well, and needed to be very exact. Never really lined up against anyone though.

Sunday, a few knots more. More of the time it seemed to sit in the fast groove, and a couple of times felt very very fast - led to the windward mark in race 2 before having some pretty major issues sitting in the lee of a 400, and my kite system being buggered - serves me right for not checking it over before the event! We lined up against Ronin once or twice in the second race, once we'd got used to it a little and at times, it did seem higher with the same speed at times upwind, though slow in lulls.

Overall, I think the conventional rig would definitely have been faster, but there were (occasional) moments where the wing seemed faster. The more wind there was, the quicker the boat seemed to be relative to others. The jib seems a lot more critical now, and there is a definite major feeling of it choking the slot if its set wrong - totally kills the power. I'm tempted to create some sort of a prodder for the top of the jib to open the slot a bit (similar to that on Nicks new boat/Fuzzy when last seen). Also need calibrations on the wing setting, there were a few times we seemed to find the sweet spot, but not very regularly.

Monday, when pulling the boat breaker on, there was the unmistakable sound of carbon splintering, as the T piece that holds the shrouds and forestay in the mast sheared 2 screws, and all the carbon holding it in, and travelled about an inch down the front of the mast. Should be an easy repair, and I've learnt from it, just a shame that it meant we missed out on the race!

[kerrgreg]

Gutting to hear about the breakage! as it certainly would have been interesting watching you switch gears in mondays breeze.

Glad to hear its working well at times, I really think its an interesting avenue to explore. And considering you stated before you didnt expect to bring it to events it seems to maybe not be a disadvantage even in this early iteration?

[RobinJones]

Can't be helped, even though it was unexpected - sailed it for about 9 days now in various breeze with various crews/helms, and it breaks halfway through pulling rig tension on!!

Thanks, glad you're interested in it, happy for you to take her out with the wing after sailing at an event or something! Yes, everything has run a lot smoother with it than I expected. I thought I'd have bigger issues trying to remove friction in the mast base, and getting a sail to set at all - but these have both proved easier than I thought. It certainly showed promise and I'll be pursuing it, though I think the obstacle now, is that it did not change gears well at all - so between Maybe 10 and 14kts of wind, the boat had a totally different feeling, being boggy and slow in 10 kts, and seemingly rapid at times in 14. Suspect this is due to the rig being very much static rather than dynamic, so where most boats rigs will to some extent self depower, my rig seemed to be set to 'slightly depowered' all weekend (just me speculating). I need more time playing with the controls and making little iterative improvements but it will be interesting to see where it goes - plus I now have an f16 main to play with, so we'll see what happens

As to it being a disadvantage or not at this stage, I do think round the course, my normal rig would have been faster, and I was very lucky to get a 4th. But definitely not as big a disadvantage as I expected going into the weekend.