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| VVS [сообщение #1713] |
Tue, 26 October 2004 12:55   |
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Anonymous
Сообщений: 2315
Зарегистрирован: January 1970
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Гуру кайтостроения |
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вот копирую
Here you see the pictures of my latest kites, the higher the testnumber the better they are.... until now 
Here are the .kte of the testkites:
Test 1 (designed in FM 1.4x (i don't remember it for sure, but it was before the fixing of the plane in wich the profiles are rotated when adjusting the primairy bridle) (i didn't found the file anumore  )
This sledfoil is designed after we have flown the WARP, we have designed this kite with a couple of dutch kiteenthousiasts and it wasn't the first, but the first kite didn't fly at all so I don't count it anymore. This sled didn't fly out of the box, the AoA was to low so it luffed before it takes of To correct this I've foulded the TE back and tape it with ducktape, so the ratio of kite above the pivot line and below changed, and the AoA increased, but the tips where instable. To correct that I bended the rods in it to create a super reflexed profile. this worked and the kite flew nice, but there was no depower whatsoever. Also the construction wasn't correct, the fabric stretched, the seams began to leak and the endresult was that the kite doesn't fly at all anymore. Time for test 2.
Test 2 (designed in FM 1.5.5)
In the meantime, I've learned that Foilmaker does adjust the kite itself when you change the bridle and that the "neutral setting" is when the primairy setting is at 25%, this explained why the AoA of test 1 was to low. that kite was setted at 0% in the tips and at 25% in the mid. Also, Sieger came with the suggestion that we needed a cone shape in order to gat the wingtips stable, it sounded very plausible, thus I setted the primairo bridle at 33% in the tips and at 25% in the mid. This kite flew right out of the box, the wingtips where rockstable. But now the AoA was to high, the kite was prouned to stall. there was to much kite above the pivotline, wich I corrected in test 3.
Test 3 (designed in FM 1.6)
This kite is a scaled up version of test 2, and the distance between the Leading Edge and pivotline is decreased, to decrease the AoA and prevent stalling. This kite is build by Roger Stevens, a team-mate of our kiteteam the Swallows. It does fly nice, when flying in a straight line it goes perfect, but when turning to fast it still wants to stall. I think it's coused by the LE curvature wich is setted at 100%, in combination with the reflexed tipprofile the tip leading edge is to far from the pivotline causing a to big AoA in the tips.
Test 4 (isn't finished yet, designed in FM 1.6)
I've stepped away from the cone and designed the kite with the primairy bridle settings and CoL settings at 25% thus the FM planview is the real planview. I now believe that a hi performance sled doesn't need twist or coning, and that the AoA of a high performance sled is related only to the shape of the planview. To take in account the 33% setting in test 3 I reconstructed the real planview of that kite in Acad and matched the new FM planview with it. Further I decreased the LE curvature to 0% in order to prevent stalling with steering and making the kite more agressive. Another thing I changed is de AR, it's now 7. When the kite is finished I will post the results here and in the foildesigngroup.
Now test 4 is finished, I've tested it in medium and low winds and it flies nice. There is no collapsing yet en there is no stalling, but it isn't become wet yet. I've made the inlets like in de Firecrest, and have discovered that that doesn't work properly at a foilsled... to much leakage... The steering is much better than test3.
The groundhandling of this AR7 sled is not good... best is when somebody can help. I have to test it in stronger winds and with the buggy yet, when that's done I'll set the results online.
Update
I've tested the kite in high winds, the kite is stable in seewinds, but it has a tendency to luff in winds coming from land. Also there are wrinkles in the lowerdeck, parallel with the TE at 2/3 of the cord of the profiles. These wrinkles are an indication that the profile is bending somewhat towards the the bottom after 2/3 of the cord.
Reading the "Arcusers" group I heared about making a "tuck" in the upperskin. A tuck is taking away some fabric at the upperskin, parallel with the profiles with a maximum width at the highes point of the profile. A tuck is done when an Arc luffs in the center (tuck in the center of the kite in the upperdeck) or when an Arc collapses in the tips (tuck in the 5 or 6th cell from the tip in the upperdeck)
After some thinking why a tuck does help in the 2 situations above I came at the following theory wich I posted at arcusers:
An upperskin tuck does alter the shape of the upperdeck. The profileshape of an arc is greatly dictated by the shape of the upperdeck, so the whole profile is forced to take a new shape when the upperdeck is tucked.
The camber of the profile will be somewhat less. (or greater negative when the tuck is done in the wingtips)
The profile can function now at a lower AoA than before.
When the kite collapsed or luffed before the tuck (AoA to low), it will now fly good with the same AoA that it was before the tucking.
Following this theory, the wrinkles in the lowerdeck should become lesser or go away because I'm going to bent the profile in the opposite direction than it's bent now.
Next, I tested this theory because I-U test 4 has a tendency to luff in the center and has wrinkles in the lowerdeck. I made a testtuck with aid of ducktape, and the results are following my theory, the kite has lost it's tendicy to luff, and the wrinkles are gone. The tuck I made is somewhat to big, the kite has now got a tendency to stall. Some experimenting is required now to get the right tuck, and I've to find a way to implement the tuck in the .KTE file for test5.
Buggy P arc surfplan file See the link page for Surfplan.
This is a kite inspired by Peter Lynn's F-Arc, but intended for buggying, I haven't build it myself yet, but Phil has. Here is his test raport on this kite posted at Foildesign:
Hi All
Just a quick note to all you sled builders out there. This weekend I took my
newly built
Buggy P-Arc out for its official test flight with varying degrees of success.
I built the kite using Surfplan v 3.0 on the default settings from Henry Kulk's
design. I
made the kite itself out of 2nds ripstop (I had nothing else to hand!), dacron
for the
sleeves and 4 mm fibreglass for the battens. All seams were taped, with
overlapping seams
between panels.
The kite inflated well, although it doesn't seem to retain pressure too well
(this I
believe is from using inferior materials in the 1st place. If I made it from
Chikara or
Icarex things could well have been different!) I tested the inflation of the
kite
initially using a household electric fan and found within a few minutes
pressure had
dropped dramatically after switching it off.
On the flying field, the kite inflated quickly just by using the valves, but
would
probably been quicker using the deflation seam on the trailing edge (a velcro
closed
extension to the main panel forming a tube through which air can enter or exit).
Once the kite had enough pressure to fly it flew really well maintaining good
steady speed
through the window and not the rapid increase/decrease across the power zone as
with other
kites I've flown. I tried to luff the kite while it was at the top of the
window, and
although it did luff it soon recovered itself enough to fly away before
crashing to the
ground.
I next tried to reverse fly the kite (using the brakes to land) and although it
worked on
several occasions I wouldn't recommend it - flying the kite from forward to
backwards
placed too much pressure on the thumbs.
During a ground pass the kite had a major trauma! The whole of the right hand
side of the
tip batten assembly came away from the kite leaving the batten inside the
dacron sleeve at
the end of the flying lines but not attached to the kite. The moral of this I
think is
that next time reinforce the attachment points. I didn't bother on this
occasion which I
now regret, but it won't prove too have to retro fit them.
I managed to get some pictures of the kite in flight which I've uploaded into
the pictures
area of the group in the folder Buggy P-Arc. The picture, Buggy_6 shows some
deformation
on the leading edge, which I cannot explain, this problem was noticed only when
tension
was released from the brake lines - can anyone give an explanation?
The upshot of it all is that I was impressed with the kite enough to start
building
another one already - this time a baby version 1.5 m sq., rib thickness
increased to
18.5%, and AR 4.5. I decided to go this small as I'm lacking a storm kite in
the kit bag -
hence the working title of Storm P-Arc. The kite should be ready for test
flights this
weekend (weather willing) and I will report soon.
Phil
I think this is a nice sled to begin experimenting with this kind of kites, it's certainly not a perfect sledfoil yet. I still want to build it, with proper reinforcement and 3 airintakes, placed closer to the nose if possible to solve the inflation problem.
Update:
I've build meself a buggy P arc, it flies nice but it doesn't inflate wel at the profile nose. I'm pretty convinced it has to do with my profile choice, the Jojo RM profile doesn't seem to be optimal in a sledfoil. The reason is that the tipprofiles are inflated well. For the next one, I go for the MH108 profile. as centerprofile. I think that the goal of the Buggy P arc, an easy to build sledfoil is in reach. The 11 center panels and 12 profiles are identical and needs 1 template for 11 or 12 pieces of fabric.
The steering is good, the kite doesn't stall. The stability in gusty winds isn't optimal, it hasn't the super stability of an Arc, but it more like a normal foil.
Going for the next one
(отдельно ссылки на файлы которые у тя наверное тоже не откроються)
втрой тест <a href="http://members.home.nl/hkulk/files/inverted%20test%202%203.3m.kte" target=_blank>http://members.home.nl/hkulk/files/inverted%20test%202%203.3m.kte</a>
третий тест <a href="http://members.home.nl/hkulk/files/inverted%20test%203%206.0m.kte" target=_blank>http://members.home.nl/hkulk/files/inverted%20test%203%206.0m.kte</a>
четвертый тест <a href="http://members.home.nl/hkulk/files/inverted%20test%204%206.0m.kte" target=_blank>http://members.home.nl/hkulk/files/inverted%20test%204%206.0m.kte</a>
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