For corrections to the numerous errors in Rowland's plans look at my errata page.
FLOW FORM (Enlargement)
>>I've had a close look at the big flowforms Art Ross from Vancouver
>>builds. He has built a few in the 500-1500 square foot range, along
>>with smaller sizes.
>1500 feet^2? That's a BIG kite.
Yes .... I suppose it is. On Sunday (8th) I was flying in Gourock.
I put my FlowForm up at 12.00 and ATTEMPTED to bring it down at
17.00 It took two of us to walk it down on 400' of line. My FlowForm is from
Rawlings book and is 2m by 1.5m (approx). So its not big,
but in a strong wind it pulls like a horse. In a medium wind I fly
it on 600lb line.
However, 500 to 1500 sq feet is not unusual. Look at the festival
kites, and in particular Martin Lester's MegaLegs. They are about 50' long.
>>The main change is to make the airfoil thinner and move the high point
>>forward. There's not a lot of science necessary; flowforms are
>>relatively forgiving about cross-section. Guessing from only having
>>seen his kites, the body proportion is roughly 3-4 units span to 5 units
>>chord. He also uses longer "legs" than the book plans show, partly for
>>stability and partly for effect.
>By legs I suppose you mean the keels?
No, he means legs. The FlowForm has a "sort of" U shaped trailing edge.
The centre of the "U" is open, and the two ends are (generally) closed.
In Lester's legs (and Natelie's legs) these sections are extended, and
the "heel" on each foot is open.
>5:4 sounds like most of the flowforms I've seen; mostly but not quite square.
>(sort of like a TV screen)
Mines approx 4:3, so it is relatively high aspect ratio. It is also
"flat" rigged (as apposed to "crown" rigged).
>>Cell width (the spacing between ribs) doesn't scale linearly for either
>>flowforms or parafoils. For 30 square feet it shouldn't be a problem,
>>but for larger foils you need to put the ribs proportionally closer
>>together to get the cross-section to keep its shape.
I don't agree on this. The FlowForm (lets call it an FF) scales up without
any problems. Again, refering back to the MegaLegs there are only 3 keels
and 5 risers. There appears to be no attempt to increase the number of risers
to improve the section. In my FF I have 5 keels and 9 risers. I feel confident
that I could scale this up to probably 2 or 4 times the dimensions (4m x 3m or
8m x 6m) without having to alter the the shape, or increase the number of keels
or risers. However, I rekon that the 4mx3m would require at least 4 people to
land it in a strong wind. I have thought about building a 4mx3m, but it might
be too much of a problem to manage on the site ... but I'll probably do it
anyway ... in black!
I strongly recommend the FF in Jim Rowlands book on soft kites. I think that
his FF is the best flying soft kite that I have. Of all the soft kites that I
have (1 FlowForm, 3 parafoils that I have built, 1 TakoTako, 1 MantaRay, 1 small
foil) the FF flies in the least wind, is the most stable, and flies in the
highest wind (I have not yet found an upper limit). Next year I expect that the
FF will become my regular "travelling" kite with 500lb dyneema (at present it is
the small 1.5m x 1m foil with 300lb spectra).
>Got any suggestions (Pat, are you out there? This means you!) for dealing
>with, laying out, cutting, etc., the large pieces of fabric for the
>top and bottom of the kite? I mean this in terms of laying it out, marking,
>cutting, etc. I'm not really used to huge pieces of fabric, but I have
>no interest in a little flow form...;-)
My 1st suggestion would be to buy Jim Rowland's book. His FF looks something
like the plan below.
Leading Edge
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In his plan he has three pieces for the back, and 3 pieces on the front.
I use 4 pieces. That is, where JR uses 1 piece for the centre section I divide this
in 2. This makes it more manageable, easier to scale up, and improves the build
quality (because it is neater to join the risers to the top and bottom surfaces when
you are also joining together two pieces of cloth anyway).
I also work from left to right. That is, I do not do the top (sewing the top sections
together, with their risers) and then do the bottom (join top to bottom with keels),
neither do I do the left half then the right half then join them (I used to do this but
there is a neater way). What I now do is start from the left, all the way to the right,
and when I get to the last seam (lets say top left to last risers) I turn the kite in
on itself, so that I make that last seam inside out. When I do this the whole FF is
contained within a single cell. I then turn that inside-out, and close off the trailing
edge. So, when it is finished there are no outward facing seams, and the kite looks
excellent (and everyone wonders how the hell you built it, as it appears to defy solid
geometry). I have now used this technique twice, one on the 100sqft foil, and on the FF.
The result is fantastic.
Building a parafoil is a huge pain in the ass, and building a FF is a pain in the ass.
The reason the FF is less of a pain is because there are less parts (only 5 keels above,
only 9 risers, in the parafoils I have 13 risers and 21 keels). It is largely a repetitive
task, so make templates for: the risers, the keels. When you make the keels make sure
that you get the weft and weave in the correct orientation. That is
\ /
\ /
\ /
\ /
\ /
\ /
\ /
Assume that the / is the trailing edge of a keel. Cut the cloth such that the natural
length of the cloth lines up with /. You should then cut a strip of ripstop (again lengthwise)
and hem the leading edge \ of the keel with that strip. That way you will have a keel that
will not distort under load, and will be durable (and you will have a nice kite for a long
time :-). So, this is obviously expensive. You dont do a "best fit" to maximise usage when
cutting cloth. You do a "best fit" that maximises the orientation/strength of the finished
product. In my FF which is 2m by 1.5m (approx 3m square) I need 12m of ripstop. If I double
the size I expect I would need about 20m (and that still corresponds to great value as far
as I am concerned).
You need to cut holes into the back and front surfaces. I hot cut with a soldering iron. To
get circles of the correct diameter I measured all the cups, glasses, saucers, soup plates,
dinner plates, my pizza plate, pots, pans and medicine bottles in the house, until I identified
the closest matches. I then used these objects as templates.
If you work left to right, and think things out well in advance, YOU SHOULD NEVER HAVE MORE
THAN 2 CELLS TO THE RIGHT OF THE NEEDLE AT ANY TIME. Therefore, it is not really the width
of the FF (or parafoil) that is a problem, but the length. And length really isnt a problem
(is it Boys :-). To accomodate the width I sometimes put a chair to my left to rest the
material on, or I roll it up and weigh it down with some large object (and that is my Phd
thesis, I knew it would come in handy).
The bridle is a dawdle, but expensive. I think I used in excessive of 120' of line for the FF,
and more than 250' on a parafoil.
In summary ..... do a bit of reading, do a bit of thinking, make you templates, cut your cloth,
hem all the parts, and then assemble. Give yourself lots of time (templates one day,
cloth cutting some other day, hemming on a Sunday (good therapy), assembly on Saturday, rig and fly
on Sunday). You might feel like giving up after cutting the cloth (I certainly felt that way on
each of the parafoils I built). When you start hemming everything you definately swear that you
will NEVER do this again. Assembly is great fun. You see a parafoil/FF appearing before your very
eyes. It is as if it grows out of the sewing machine, getting bigger, and bigger, and .....
and the room is full of material. I love it! And then you finish it, fly it, and say
NEVER again. And then someone asks how did you do it, and you tell them, and then you think "I bet
I could make it AT LEAST twice as big, and in black".
I just finished building my first parafoil/flowform/single-line (well, the first single line since I was a kid--and the first since I really started to sew) and it was really quite fun to do. It's an 8 square-foot kite, based on the plans in Margaret Gregor's _Kites for Everyone_. The plans are very easy to follow, and the kite was actually quite simple. My biggest mistake was in deciding to make an applique'd kite the first time through. My second biggest mistake was in not measuring the tops of the outside cell-walls before cutting the top of the kite. Gregor calls for a piece of fabric 42" long, but due to the way I drew my airfoil section, this length was actually 44". This I have a 2" wide strip sewn to the front! This is a definite hint for anyone planning to make a parafoil: measure that top! The bottom isn't a problem, as it's simply the chord. This was also my first experience with binding edges, and that went reasonably well. The binding I used was a bit stretchy, and got tautened a bit while I sewed it on, so the fabric is very lightly bunched up in places, but it doesn't seem to have effected the kite. It was quite a thrill to finish the kite and fly it--more of a thrill than most of the dual line kites I make these days. Perhaps it was just because it's so different from most of my kites, maybe because it's my first single line. The kite flew beautifully the first time I launched it! I'm rather excited at the prospect of making a bigger FlowForm when I can afford the fabric. I highly recommend the experience to anyone who hasn't built such a beasty yet. FlowForms are much easier than most other parafoils (fewer ribs, etc.) and I was surprised at how easy it all went together. It's quite neat to watch it take shape under the needle!
In article <18146@umd5.umd.edu> jeffy@syrinx.umd.edu (Jeffrey C. Burka) writes: >This was also my first experience with binding edges, and that went reasonably >well. The binding I used was a bit stretchy, and got tautened a bit >while I sewed it on, so the fabric is very lightly bunched up in places, >but it doesn't seem to have effected the kite. I had a similar problem when sewing the fabric onto the vent of my 15m foil. I measured the vent to size, because the vent fabric is very stiff and easy to measure, then just sewed the skin fabric onto it. On one seam, I was sewing with the ripstop on top and the vent underneath. On the other seam, I was sewing with the vent on top and the ripstop underneath. The difference in fabric tension resulted in the "vent-on-top" seam consuming 60cm more ripstop along the 15m seam. Just to make things worse, I did a re-inforcing zig-zag, before deciding that it was no good and un-picking it all. :-(
Jim Rowlands describes construction of the frog as very difficult, and likely to be a real test of your skills. I've built a few stick kites, a few ram-air sleds, and the Rowlands Multitube and Flowform, and so consider myself an intermediate builder. Nevertheless, I couldn't see anything in the plans that seemed greatly beyond what I've done before, and indeed, it didn't present any difficulties of the order Jim seemed to be indicating. Unless, that is, you're aiming for professional accuracy, which would certainly be well beyond my abilities, and harder to achieve with the frog than, say, the flowform. As with most of the designs in Jim Rowlands' book, there are a number of errors. In the case of the frog, they all become obvious at the stage of making the templates, and are easily corrected. For the record, these are the errors I found, and other comments: 1. Materials - I can't see how Jim used 7m of fabric unless his was somewhat narrower than mine. Using 1.5m wide, you should only need about 5m, but if you can't cut 5 ribs or 4 legs from a width you'll need more. I used 2 shades of green - a leaf green for the front and undersides of the ribs and a dark slimy green for the sides and back. I did the fronts of the eyes red with a black pupil shaped like a rectangle with concave sides. 2. Several figures in Table 1 (Rib Shape) are wrong as follows (erroneous figures in brackets): 20.0 23.5(24.0) 1.0 25.0 24.0 0.5(0.0) 30.0 24.5 0.0(blank) 65.0 28.5(29.0) 112.0(102.0) 0.0 3. The length of the back is about right - mine came out 0.5cm too long. As with most parafoils and flowforms it seems to be a good idea to cut the back long and trim after sewing the ribs. 4. The shape of the body pieces is not specified. You have to adjust them to get the right lengths of the outer curved edges. 5. I couldn't see why the outer body pieces were made in two then sewn together before sewing to the outer ribs. Why not just cut the outer body pieces as single pieces? However, if you sew them each to the outer ribs first, you can sew them on with the hem on the inside. You can then join them together, inside out, again getting the hem on the inside. Incidentally, Fig 7.13 shows an upper body piece for one side and a lower for the other. To get a set for one side, one of them should have been shown as its mirror image. 6. Sewing on the eyes I found about the hardest part. After a lot of thought, I just went ahead and did it. My hems around the backs of the eyes where they join onto the back are a bit wonky, but you wouldn't notice it in flight! 7. The tops of the legs are shown curved in an S shape but no dimensions are given for the curve. I did mine straight, and used a straight hem where the legs join the back and front, only using curved hems where they join the outer body parts. That seemed to work ok. 8. The 75 degree angles shown on Fig 7.14 refer to the leg centre line, not one of the edges. (Obvious? It took me a few minutes to realise.) 9. Jim's method of sewing on the legs leaves the last bit of hem on the inside thighs as an outside hem. It's easy to eliminate this, giving a tidier result, as follows: Sew the upper and lower leg pieces to the body, with them folded back over the body, to get the hem on the inside. With the leg pieces still folded back over the body, sew the upper and lower leg pieces together (inside out) down to the knees. Now turn the legs the right way out, plunge your arm down the poor creature's throat, grab a leg, and pull it (inside out) through the front opening. You can now sew it down to the foot. The only disadvantage is that you may find you haven't got the upper and lower leg pieces properly lined up so the knee and foot bends don't quite line up between the upper and lower pieces. If I were building another, I'd put marks at the same place an inch or two down each side of each leg piece, and make sure they were lined up before starting to sew the thighs. 9. Whilst sewing on the legs and down the thighs, it's very easy to get an extra layer of fabric from somewhere under the needle - take care! - Philip (P.S. I'll archive this posting on my Rowlands errata page at http://geocities.datacellar.net/CapeCanaveral/Hangar/6767)
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