how can we get this much bend,
http://sailinganarchy.com/fringe/2007/images/tucked%20in%20for%20the%20upwind.jpg
[and would it be good] on a footy? it seems the rig bend discussions have mostly been on fore and aft bend. wouldn’t it be easier to bend the mast sideways, and it shouldn’t accomplish the same thing…? [gonna have to try it on the new design!]
I’m investigating a manufacturer of carbon fishing rod tips here in UK. For a price he can even give you differential fore-and-aft and transverse bend.
The good question though - unless you have a cat rig - is how you control forestay sag.
I can see very bendy rigs having huge benefits in Footys.
hmmmm, i have a blank fly-fishing rod i was supposed to use a a mast for a 50" boat i designed, that is tabled indefinetly now, huh, [evil laugh] the dremel may have a job this weekend!
I think it would be fair to say at this point that Footy masts so far have been telegraph poles. I reckon we can reduce diameter by about half.
As for sagging forestays…well in my Original BobAbout design I used a solid forestay for the jib(1.5mm s/s wire) no reason why this can’t be 1mm carbon rod.
I think that automatically depowering rigs could help Footys solve downwind handling problems…any may be helpful upwind as well.
My Una rig design automatically bends off sideways with increased pressure.Though in this case that comes from the “boom” twisting rather than mast bend,overall though though the effect is similar.
Cheers
Brett
But a solid forestay that is really solid will restrict mast bend. Thios may not be disastrous, but most people full size would fit runners
thats why you bend it sideways. you can have the mast held rigid up top, and it’ll bend in the middle… and forward down wind… right?
At the risk of being beaten with axe handles since it is a known method of mast/sail control on beach errr, ummmm - kittys … 
a uni-rig with rotating mast would allow the mast to bend to it’s thin foil thickness sides, automatically flattening the sail for high wind, while still allowing sail twist at the top for overpowering gusts. Mast bend once rotated would be fore/aft and controlled by diamond wire tension. For light conditions, do not rotate and use the fullness cut into the sail luff, perhaps adding desired additional camber by a positive inhaul.
Fishing rod blanks have a spine which should be found and then the mast should be installed accordingly.
Played with something not disimilar on a model Oil Tanker attempting to save fuel by incrasing use of wind for propulsion when running more with a following breeze. To windward without helm control these were almost useless and couldn’t be relied upon hence scrapped as an automatic device.
Used a rotor joint similar to a shoulder socket ball joint for base of mast with stays on all axes (4) with springs coupled at the central pivot each with varying tensions. Hard to explain but basically the stays were routed through a point on the deck back to the mast and attached to a spring.
Depending on wind pressure and direction these woulk allow for bending of the mast in almost any direction with opposite force being applied to avoid collapse. Problem was the model was 20 feet long and I doubt there would be small enough springs that could compensate for a model yacht. Model was designed to carry upwards of 5 sails per side.
As R/C yachts inherently must be automatic at all times and behave without interference from the helm except intermittent rudder sail control I doubt these would be effective.
Yachts aren’t the only things with sails. Some interesting developments since in the use of Kites on big tankers. Even some yachts have tried this form of design with interesting consequences.
Now that we’ve got our forum back, can we resume this very interesting thread.
Some weeks ago, Bill Hagerup asked me why I favoured bendy masks (can’t remember whether it was privatelty or on the forum - but the intention was clearly that I should start a thread). Because the forum was suffering at the time from a little too much ‘wall to wall Angus’ I didn’t do anything about it. Possibly the time has come (even if only as air freshener!).
Most Footys have stiff rigs that are almost certainly vastly over strength. Mast bend is small and badly controlled.
A standard bendy mast bends forward in the middle as the wind speed increases. This is because the ‘shape’ of the sail is made by setting a sail with a curved luff on straight spars. Bend the spar and the shape goes away.
This is good. As the airspeed over the sail increases, the ideal shape is flatter: the parallel of the wings of a Hawker Hurricane and a Eurofighter is not exact but it will do for the purpose. In terms of a yacht, one effect of flattening the sail is to reduce heeling force - in other words the boat will stand up to more wind.
A bendy mast that bends sideways at the top has even more dramatic effects. Sideways bend at the top rreduces leech tension and dumps lift (=heeling force) at the top of the sail, In the mean time the bottom of the sail is unaffected and continues to drive as usual. This is why it is better than easing the kicker (vang in American). Because we are getting rid of heeling force at the head of the sail, the affect on stability is huge: we can carry the same rig in perhaps 2-3 metres/sec wind speed higher (=4-6 knots). Generally the rig is arranged so that the bending and unbending is automatic - like a tree bowing to the wind. This means that a lot of the struggling you would have to do to keep the boat in a straight line through the puffs is done by the boat itself, cleanly and without fuss.
This is standard practice in big boats. I haven’t managed to prove it not Footys yet, not because my 25 m towing tank has gone wrong, or because my CFD software doesn’t work but becxause tryiing to help grow this class in UK and internationally takes a great deal of time. All it needs is a piece of sandpaper to rub down a shop-Bought carbon tail boom for a ‘chucky’ glider.
Happily I now have an associate who is much better at making things than I am and has time free. Hopefully I’ll have a progress report and some pics in a week or so!
Now gentlemen and ladies, over to you.
AAAHHHHH! (Large sigh of relief)
I have often thought that the masts and booms that were being used in general practice seemed a bit heavy in relationship to our little boats. I have just been following general practice around here. But what is to prevent one from using a part of a fishing rod, which are generally tapered? I can pick those up at yard sales and swap meets for next to nothing.
Now in respects to using a bendy mast, would one have to stay it to get the proper bend in the right place? And, the next question, do you folks put luff curve into flat panel sails?
Bob
PS.
‘wall to wall Angus’
If it wasn’t for your interesting topics we would all suffer from lack of knowledge:zbeer:
Bod - I’ve used unstayed massts made of two pieces of Aluminium tube on a 21’ cat ketch (basically see the rig of Red Fox on my Photobucket account http://s111.photobucket.com/albums/n138/angusrichardson/red%20fox/ ). That worked very well except for when the builders failed to use high duty aluminium on the show boat at the Southampton Boat Show: very embarrassing. Two different diameters of tube were simply joined by a fishing rod joint. Laser, Finn and OK dinghies use much the same method with an unstayed mast.
That was unstayed. Other layouts use swept-back spreaders to push the middle of the mast forward (most dinghies)
I haven’t, tried fishing rod tips yet but they’re in the pipe-line and potentially cheaper and bendier.
Yes, you definitely should put leff round in. Look on Amazon for books by Jeremy Howard-Williams. Plenty around in the USA, including second hand.
As Brett points out, his unstayed unarig design will bend off alot, thereby spilling air. This is a similar effect to the “stretchy stay” potential discussed recently. I think it offers tremendous benefit in the Footy class.
Of course, rotating wingmasts on iceboats (as seen in the opening photo of the DN) have used this for many years. It is a totally different sort of bend than the unstayed unarig, with most of the bend found in the middle 1/3 or so. Lateral mast bend can have gust absorbing benefits thru sail flattening & increased twist. I have incorporated it to a more limited extent on my composite wingmasts. Jeff Brown had further discussion on the topic last spring after he set a new speed record:
http://www.rcsailing.net/forum1/showthread.php?t=3335