Jump to content
  • 0

'Funsized' Rev kites ?


Choccy

Question

I would be interested in the science behind the possibility that one day I could own a small-Rev for the smaller framed person.

Most of you guys are average to above in frame and have good ballast (for want of a better word)

when flying your Revs in stronger wind situations/gusts, and therefore don't fall over so much, at all.

I'm concentrating more on not falling over (from the strong gusts) to actually learning how to fly :blue-confused:

I know children have been seen to fly Revs who are obviously smaller and lighter than myself.

I have a similar fear about being dragged over, when flying other types of kites.

I am much more confident flying smaller kites, and at best on a soft beach (which isn't always possible).

If this is a totally ridiculous idea, I'll delete this thread.

Please no flames.

Link to comment
Share on other sites

  • Answers 65
  • Created
  • Last Reply

Top Posters For This Question

Top Posters For This Question

Posted Images

Recommended Posts

  • 0
One thing that occurred to me afterwards. I find on a blowy day, if you double up the rods on the leading edge not only is the kite more robust but it also seems to reduce the pull a little. I think it has something to do with reducing the flex, as the sail of course "sags" in the middle when the leading edge flexes. I think it is this change in shape that seems to generate more power than had the edge not flexed.

Not explained very well, but hopefully understandable. I would be interested if others find doubling the leading edge reduces the power too, or if it is just my imagination!

Funny you should say that Gary and I were discussing the same thing Sunday we were both flying vented's I had a Rev Equipped SLE he was flying skiney Rev Equipped.

Link to comment
Share on other sites

  • 0
What did you guys conclude?

Pretty much the same as you, too much dishing in the sail creates too much drive.

Though strangely, at the other end of the scale the opposite seems to be true.

Pre Race Rods, if my sul would not fly with a Pro Use frame, I would try a P90 which being considerably lighter would allow me to fly in even lower winds. The down side was that it made the kite extremely floppy, which is strange but interesting experience. Race Rods are clearly much stiffer than P90 and probably, (I haven’t checked) quite a bit heavier. Yet I know a race frame will take wind range down even lower than P90.

Now we get to the pseudo science bit, and to be honest I’m not really sure I entirely understand this so it may be total bollocks but here goes. I wonder if in the same way my old physics teacher would tell us off for confusing “weight” and “mass” we are confusing “lift” and “drive”.

Lift comes from the amount of sail area offered to the wind and a flatter kite can offer a greater area (shortest distance between two points and all that).

Drive on the other hand, comes from the amount of air deflected by the sail, now this really is rocket science, Isaac Newton and all that. The bowed sail allows more air to be collected and channelled over the trailing edge.

Link to comment
Share on other sites

  • 0

I THINK we are probably not confusing the two. A sail doesn't really derive drive from air 'blowing' off the back, although that is what your intuition would tell you. It is the flow of air over it that causes lift. The lift works at right angles to the sail, in the opposite direction to the lines. If you start off in hover the force is exactly in alignment with the lines, which is why the kite moves neither forwards or backwards. Tilt the sail towards you (thumbs back) and the force line also tilts. Now the force is not in alignment with the lines, it is pointing forward of the lines, so the kite moves forward. In effect some of the lift force is being converted into forward movement. I think what happens when the kite over-flexes is that the center portion of the sail flops backwards, which is the same as it being tilted forwards, and the kite shoots off.

I am no hydrodynamic physicist, so may be way off the mark. But that is how it happens with boat sails anyway! It would be loads easier to explain what I mean with a diagramme, but that doesn't work too well in a forum!

Link to comment
Share on other sites

  • 0

Hey Jeremy ...

I have to say that as a fellow sailor and having worked for several sailmakers and mast makers over the years I have been looking at my new rev experience from a similar angle.. my thinking so far and flame away by all means...

1. Angle of attack ... most of what makes rev flying so unique is the way you can control the angle of attack of the two 'sails' independently for rotation as well as the whole kite to generate lift whatever the orientation of the kite.

2. Sail shape/power ... from what I can see there is very little seam shaping or 'luff curve' in the kite construction so the flying shape is a result of what you and I would call sheet tension but in this case its the shock cord (bungee) that holds the verticals.. tighter = flatter, slacker = fuller sail so perversely the sail gets fuller and more powerfull in a gust and flatter (less powerfull) in a lull (do people ever replace the bungee with alternatives?) however this is more then compensated for by the bend in the leading edge which in effect dumps the power and introduces twist so the sail de-powers automatically (more bend = less power) ... much like a windsurfer mast which responds to gusts by flexing etc etc (oops straying off sport again)...

So the logic to me is the bendier the leading edge the more forgiving the kite will be to gusty conditions and the less it will pull ... Try a shockwave in 20+ knots, all together stiffer structure is very much on/off in terms of power and you can only really control the amount of power via angle of attack/break.

Obviously the key to the Rev experience is matching the right rods with the right kite and the right wind strength to automate this gust response and finding the sweet spot... case in point vented B-series ... No SLE so nice and forgiving, perfectly balanced and as a result wonderfully flattering for us newbies to fly!

Looking at the rev range it seems the more you progress (?) towards the power/speed series the more 'locked in' the flying shape becomes and the more 'challenging' the flying experience .... I will test this theory when my blast 2.4 arrives and my ambition:ability ratio plummets into the negative!

Good times :kid_devlish:

Link to comment
Share on other sites

  • 0
Looking at the rev range it seems the more you progress (?) towards the power/speed series the more 'locked in' the flying shape becomes and the more 'challenging' the flying experience .... I will test this theory when my blast 2.4 arrives and my ambition:ability ratio plummets into the negative!

Hello Jonesey

You make for interesting reading/points with your sail knowledge.

Although fluid dynamics was never my strong point (yuck!) ;)

Do you have a B-series in your collection ?... of course you have ;)

Looks like there is getting to be quite a little 'collection' of Bees in the county!

I'll leave you big chaps to play with your Blasts/shockwaves and the like :blue_wink:

Good winds.

Link to comment
Share on other sites

  • 0

Yep, I see your point about power dumping. A bit like mast prebend or putting bend in a light rig with the vang. But doesn't that assume you have some chord precut in the sail so the bend can take it out and flatten the sail? I need to think it through some more.

Link to comment
Share on other sites

  • 0

oops .. just checked again (thanks Sparky) and there is in fact a degree of curve in the sails leading edge.... I suspect that the lighter the kite (SUL) the more curve (havent got one yet to check ... another reason to buy more) so on any given kite when the leading edge bend matches the curve in the sails leading edge the sail is in effect flat (not withstanding tip/sheet tension) any less bend the sail 'powers up' any more bend the sail de-powers and its probably time to change up to a stiffer rod.... Make sense??

Think I need to stop thinking and start doing....

Link to comment
Share on other sites

  • 0

Jonesey,

No seaming, about 3 inches luff curve.

Spar bend exagerted by bridle being attached to the spar ends in addition to wind power & bungees.

If bungees replaced by fixed line at both ends, I would expect a more progressive power up/down as the sheet tension remains the same.

Have you started builing yet?!

Sparky

Link to comment
Share on other sites

  • 0

Jonesey,

Your next analysis is to establish the comparitive stiffness of the spars.

If you build the spar and then put one end on the bathroom scales - you will need 0.1kg accuracy, and then push down on the other end. After a reasonsable amount of bend you will notice that the weight will not increase, so that becomes spar bend weight. Once you have done the analysis you can post the results for the rest of us. Clearly you will need to do the mixed spar (lighter tip spars) as well as the standard, 2, 3, 4, Race, SLE rods.

Secondly sail load will increase if bungees are replaced by fixed line, so plastic cringles may be requried to prevent sail ripping.

Standing by...

Sparky

Link to comment
Share on other sites

  • 0

Sparky ...

Happy to start analysis as per your request ... I assume you are happy to apportion a percentage this years Olympic budget to the project or would you prefer to fund a longer term test with a view towards 2012 where I assume you will have used your influence to have Weymouth hosting the first Quad line demonstration event??

P.S.

Only other area we havent discussed is the effect of panel layout/thread orientation and cloth weights ...... any takers??

Link to comment
Share on other sites

  • 0

Jonesey,

You have just pointed out, without realising it as usual, that Chisel beach is an excellent flying venue. N or S winds allow clear breeze and the oportunity for you to develop your underwater techniques.

My tech budget cannot deal with current product, however we will of course step in when we find there is a hole in the spar range that need new rods. What about one piece rods? This would prevent the hard spots where the current Rev spars join, and give us a better constant luff curve bend. I didn't look this morning, however I doubt this hard point is taken into account in the current luff curve.

I think Airx 500N - VMG (31 grams /sqm) would be ideal, athough it is very difficult to print onto. Hard finish, little stretch - work for a long time then break, so you know it is done!

Probably want to orientate warp parrallel with leading edge. Difficult one this, I think I can argue for fill parrallel with leading edge too.

Agree?

Sparky

Link to comment
Share on other sites

  • 0

Probably.... But obviously anything not Rev stock is cheating! (not to mention copyright/patent etc!)

might email Lolly and see what custom materials options are or if a 'bring your own' material option exists!!

On the other hand we could just practice more and learn to fly what we have properly first ...

Link to comment
Share on other sites

  • 0

There is an option to use your own materials option I think where rev sell you the branded centre panel. Means they get some money for their copy right I believe. Don't think they would be happy if you ordered 40 a month though!

I was thinking. The angle of attack is massive normally. I suspect the kite behaves like an aerofoil when you do say an inverted float.in which case the belly would be relevant. But the rest of the time is is a big air ram. Reduce the angle of attack of the centre of the sail as you do when the leading edge bends to far and it is very likely to drive like a horse. Think of what happens dead downwind when you loose your pole downhaul. The spin nearly pulls the boat out the water and is a sod to get down.

Sparky - can you not have a word with the committee and get revs as a 2012 Olympic class?

Must try and fly with you guys in the better weather. You sound suitably nuts!

Link to comment
Share on other sites

  • 0
Must try and fly with you guys in the better weather. You sound suitably nuts!

I was thinking the same thing - you guys would get together and melt our brains too.

Sailor> The inverted stuff you were showing me the other day - is that what they call the float ?

The "bowtie" I mentioned which happens to me sometimes is probably caused by my enthusiam to get the darn thing to lift backwards.... is that what you meant by oversteering/overpowering it ?

Strange that as my tiny wrists aren't used to pulling that hard!

I'll keep practising.

ThanX.

Link to comment
Share on other sites

  • 0

The float is slightly different. In fact the float is two different things. One, the inverted float, is similar to an inverted hover, and I am sure being able to hover upside down is really a precursor to it. Stoneintheshoe Bob pointed my in the right direction to learn it, and very happy to show you when there is no wind.

Yes - by over controlling/over steering I do mean getting over enthusiastic with your your wrists and yes it does result in a bow tie. If you put on too much break (and it doesn't take much to do this, certainly even your tiny wrists can do it), then one of the tips will blow round and hey presto! Bow tie. Think about holding the handles really gently and near horizontal, controlling the amount of reverse with just you pinky and ring finger, a smooth pull to your hips to launch with modest reverse, gently does it, let the kite fly itself. At first aim to get just a foot or two off the ground with no wobbles, then gently return back down (Avoid full speed dives into the ground - control that speed as well as you can). Then increase the height you can gently reverse up to in increments, and back down. When that is off to pat have a go at hovering. At least that's the way I got there! Also remember to take a break to rest your wrists and clear you mind - don't let it become a frustration or you will learn nothing. The final stage is to learn to hover at all the angles - upright and vertical (Which you can do of course) but also at 45 degrees both upside down and the right way up.

Remember being able to hover in any orientation is the basis of almost everything else. With out a stable hover you cannot do slides, clockwork, precision, de-powering and controlling the kite (Which you will really love).... Getting the hovers right gives you a hugely increased repertoire I found - a very freeing experience! A few minutes practice two or three times every flying session is one of the best investments you will make in your flying.

BTW - I have no idea why holding the handles horizontal helps, but it does! Mystery of the day.

Link to comment
Share on other sites

  • 0
The final stage is to learn to hover at all the angles - upright and vertical (Which you can do of course) but also at 45 degrees both upside down and the right way up.

This is why I needed the extra bit of coaching:

Groz & I can hover in all the angles from about 7 o'clock through to the 5 o'clock position but not the upside down one (yet).

When it is a decent wind day, what percentage of time do you dedicate to precision practise compared to freestyle fun ?

Antman> that's a pretty funsized kite, quite a rainbow!

Link to comment
Share on other sites

  • 0

Choccy ..

That's a good question... I would be interested to know how people spend their flying time... as a newbie I am finding its all about practice and learning, trying to do the stuff you see in video's and read in these forums.... not so much freestyle fun... don't feel qualified to slack off yet!

With the different kites, lines, rods and handles I use, I find the first few minutes are all about balance and figuring out how twitchy the set up is in the prevailing conditions and tweaking accordingly (ok I used to trim sails for a living I cant help it!!) ... I then seem to spend the next 10 minutes hovering inverted (or trying to) ... for some reason that's the one thing that tells me whether I am set up right/comfortable to try and develop other areas ... currently that means trying to learn clock turns ... always clockwise for me .. just cant get any feel for going anti-clockwise yet which I guess will be the next thing ... work on the weak areas...

Most of my sessions are limited to an hour at the end of the day before its time for bath and story time (young kids can really limit your flying time!) so I normally rig up the Shockwave for the last few minutes to see if Ive learnt anything... going back to the 1.5's then seems like slow motion and I can convince myself driving home that I'm getting it ... dream on! :blue-sleepy:

Link to comment
Share on other sites

  • 0
So the logic to me is the bendier the leading edge the more forgiving the kite will be to gusty conditions and the less it will pull ... Try a shockwave in 20+ knots, all together stiffer structure is very much on/off in terms of power and you can only really control the amount of power via angle of attack/break.

Good times :kid_devlish:

Sorry I disagree when the wind picks up I tend to go with a SLE leading edge in my teabag it pulls less because the sail is not bagging in the middle, and is less twichy ?

Link to comment
Share on other sites

  • 0

Hmm .. SLE hadn't factored that in ... so what we need is a unified theory of everything ... interesting

Ok my simplistic sailing brain (sorry haven't developed a kite brain yet) says that the amount of leading edge bend is the key in relation to the curve/shape (what we would call luff curve) of the leading edge ... like any sail/spar combination the relationship between these too elements is key to control and power delivery/generation ... so depending on what kite/design/sail at some point the SLE comes into play as any loss of gust responsiveness will be offset by a better flying shape in the sail ... (if I'm starting to contradict my earlier posts then that's because I'm thinking out loud ... always dangerous in my case) ...... and again this is complicated by bungee tension and general ability of the sail and frame to hold the designed sail shape in higher winds .... sails on boats getting progressively flatter (less drag) and less 'powerful' as wind speed increases and I cant see why the same wouldn't be desirable in a kite?

Actually thinking about it I will put my hand up and admit that for the first 3 weeks I had my rev I flew it with the vertical spars in front of the sail (duh ... read the instructions stupid!) ... in any breeze control was 'interesting' as the sail was too full and able to 'pull' the kite around the sky .... as soon as I reversed them all was well and I was suddenly back in control (relatively) ... no change in anything but sail shape .... or was it just that the break lines were as a result connected to the sail via the bungees in this set up so all controls had a built in delay/vagueness .. tweak break line, stretch bungee then pull sail as apposed to tweak line pull rod together with sail.....

Discuss!

Link to comment
Share on other sites

  • 0
Actually thinking about it I will put my hand up and admit that for the first 3 weeks I had my rev I flew it with the vertical spars in front of the sail

Not an uncommon problem... many folks have fallen to this mistake.

We saw someone up "Watership Down" last year struggling because of the very same error.

Even the best.... have to start somewhere ;)

Link to comment
Share on other sites

  • 0

Choccy- have you tried tails on your kite in higher winds?

The kite's air speed generates pull; adding drag slows it down and reduces pull, not to mention looks great in the sky!

I sometimes attach a pair of 100' ribbon tails or 36' tube tails to the ends of the vertical spars when the wind picks up.

The only trouble is they can easily tangle on bushes or other things on the ground and can be a handful to put away when the wind is blowing hard.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

Announcements


×
×
  • Create New...