I'm planning to scratchbuild a R/C skydiver and was wondering if anyone had experience using a 42" ThunderFoil parafoil kite for this purpose? Here is a drawing of the kite, it is available from PerformanceKites.com for $35 + S&H:



http://dryboxes.safeshopper.com/17/90.htm?734

On Spadworld.net, someone has built a couple versions of an R/C skydiver using this kite, and he seems to have had some good luck with it, but I was just hoping that perhaps some of the more experienced R/C skydiving enthusiats might be able to share some knowledge.

I'm going with this kite instead of a commercially available chute because I want to make a slightly smaller (and lighter) skydiver to use with an e-powered aerotow tug that I'm building (a Pilatus Turbo Porter ). I am trying to keep the weight of the diver down somewhat so that my 50" wingspan plane can have a reasonable chance of towing it aloft without a ridiculously high windloading. The commercial kits, at around 2.5lbs., are far too heavy; I need one lighter, and I'm hoping my scratchbuild version will be "the ticket".

Any help much appreciated!

Steve

Surfimp,
hard to fold, and will not open consistently. Tryed all last summer to make one work. Putting my man back together got old. When I did get it to open, What a nice flying foil. pic is of my Thunderfoil number Two, Thunderfoil number one did'nt open in a real high wind day and the rest is history.

THx, Wil

Thanks Wil. Were you using a drogue chute with yours? I am at this point mainly planning to use this as a paraglider (and not a skydiver) since my plane is not yet finished, so a well-performing foil is a good thing!

Do you have any tips on folding, rigging and trying to get one of these to deploy? It seems like one of those spring-launched drogue chutes would help. Looks like you added risers to the trailing edge of yours, is that right? Was the diver you used with this foil a scratch or kit built model?

Sorry for all the questions, and thanks,

Steve

Steve,

Yes I did have a drogue chute, from big to real,real big. The problem you run into is getting the frt. of the foil to grab the air, so the foil can fill up, and thats because of the Zero-porosity fabric. I had three lines coming off my drogue chute. Two of the lines went to the frt. of the foil to help open, and one went to the centre. Still no consistently. Zero-porosity means that the fabric has a coating so that air cannot move through it. Zero-P gives the canopy better performance, but it also means that it can be very hard to get all the air out of the parachute during folding, and makes it harder to open. This link is how I pack the Thunderfoil, it worked better then any other chute packing. I have one more thing I want to try before I give up on the Thunderfoil. If it works I will let you know, For a paraglider it will be great!


http://precision.aerodynamics.com/ps...treme_pack.htm

Thx, Wil

Steve,

One other thing you want to do to the Thunderfoil is Iron it. Ck out the pic.

Wow, thank you Wil! That is excellent information. Sounds like, when I get ready to do some actual parachuting, I'm going to need to build or buy a real parachute hehehe.

I made some progress on my "dude" yesterday. Will be about 12" tall when complete...now I've just got to find a GI Joe who wants to give his life to the cause...









Thanks again for your help. You are the spot-landing master, right? Cool!

Steve

The "dude" is done, except for his jumpsuit! I am going to have to sew my own because nothing commercially available is going to work.



Steve

Steve,

It looks great. Im thinking about making a man myself.

Thx, Wil

Thanks Wil! It's very easy to make one of these guys, the one I'm doing is based off of one a guy built in this thread over on Spadworld.net:

http://spadworld.net/viewtopic.php?p=52768

The design is a bit different from the Paramax, R/C Skydive USA and Solomon R/C divers, which are all based on the same general idea (which is off that old RCM plan as far as I know). The design I am using, which is based loosely on the Kavan Junior Jumper, attaches the arms directly to the servos (standard size). I'm not sure if you get as much throw this way, but I guess I'll just have to experiment and see how it goes.

I used a piece of 1/8" ply as the basis for the body, and basically zip-tied everything to that. Legs are made from 1/8" music wire bent to shape (to which I taped the GI-Clone legs), the arms are from 3/32" mild steel. If you go to the Hobby-Lobby website and download the instructions for the Kavan Junior Jumper you can see the shape you need to bend the arms to in order to attach them to the servo arms.

I am not sure how durable this set-up is going to be, or how it will perform. It may be really, really bad, but who knows! Only one way to find out.

Have you ever tried BASE jumping yours?

Steve

Hi Steve,
Wil is right when he says you cant get the parafoil kite to open. I even had it come out and stretch the lines out but it would not let air in. The set up you have on your arms works great on the smaller lighter jumpers but when you jump up in size and weight you will find that even metal gear 1/4 scale servos cant withstand the landings. Paramax, Skydive USA and Solomon R/C jumpers all started with the basic design of the late Wally Gitchel RCM jumper but we have spent years refining things like how to set the arms up so they wont strip servo gears on each landing, or how to get better odds than 50/50 chance the chute will open each time. Just the materials we use alone make our jumpers alot different. Paraglider chutes are a lot different in design. They use a very critical airfoil and require more lines to help it maintain its shape. They use more cells and most have an eliptical shape. When i talked to my chute maker about making one she just laughed at me. 40 ribs and all are different sizes. We are working on a 9 cell with a different airfoil. We are very glad you are involved and will be very glad to help with any questions you might come up with. Talk to you soon!!!

Thanks Ken, much appreciated. Now that I've fiddled around with this project for a few days I've really begun to appreciate how much work went into getting these things really sorted out The kit price, especially when I consider the complexity of making a chute, starts sounding more and more reasonable all the time!

Now that I've gotten to this point in the project, I'm realizing that little 50" Turbo Porter (to be powered by an AXI 2820/10 brushless with a 10 cell NiMH pack) may not have enough "oomph" to carry even my relatively lighter "dude" airborne. For that matter I don't even know how successful the Turbo Porter will be, seeing as it's another scratchbuilt design!

So, since I have no other power plane to use as a parachute plane (and no interest/intention in purchasing a gasser), hopefully the ThunderFoil kite will work OK for paragliding with my homemade skydiver. If it works with the Turbo Porter as well, that will just be gravy!

Steve

Hi Steve,
How much does your jumper weigh. You should be able to make your electric work. You will just have to make an easy climbout. Several guys use 40 size trainers to carry there 2 1/2 to 4 lb jumpers. Put some kind of shield in front of the man to smooth the air around the man and be easy on the controls and climb out and a 50" span should get you in the air. Talk to you soon!!

The drop rig setup we use on our telemaster is removeable see the pics below. You need to cut drag as much as possible so you should cut the bottom of your fuse so the chute will stick up in the fuse.

Hi Ken,

With all respect for my late friend Wally Gitchel, his design for a R/C skydiver was not the basis for the Paramax design. A guy named Jurgen Vollmann designed the Parafoil canopies and jumper bodies in Germany in the middle 80's. The rights to this design were sold to the Krauss' who still make Paramax products. Also prior to Wally's interest in R/C skydivers, the Robbe Charly was available and was used here locally. The Charly operates the control arms directly from the servo output shaft. As pointed out, this can lead to stripped servo gears and it's probably best to use metal gear servos.

Paul

Ken, thank you for the tips. I wasn't sure if a simple elastic band release was sufficient, but it looks like it works just fine. Do the guys ever get tumbled coming off of those types of releases? Seems like it might make them want to barrel roll

My diver is currenty around 12-13oz. without his chute, backpack or suit. However I may be taking most of the action figure leg material off to save on weight, I'm just trying to decide whether I will need more or less weight to get good glide performance from the ThunderFoil.

Paul, thanks for the clarification. I based my statement about the similarity of the Paramax "Mike" to the Solomon R/C and R/C Skydive USA products on the basis of how the divers appear to function in the photos on the respective websites. I understand the latest version of the Paramax diver has the more sophisticated dual-action arm to increase control throws, but it still looked--in general--to be similar to the basic design from the Konrad Riggenmann plans in the February 1976 edition of RCM. Apologies if I've made a mistake; if so it must be one of those cases of independent development of very similar designs. After all, there's only so many ways to build an R/C skydiver

EDIT: This is frustrating. I tried adding a link directly to the Riggenmann plans page on RCM, but the RCU board code choked on it. In any event, if you go to http://www.rcmmagazine.com and do a search for plan # 631 you can see it.

Thanks all for the great information. I look forward to my experimentations!

Steve

Steve, We did find that a elastic band had a griping effect and would roll the man out of the box so trying different materials we found the black or white 1/4" wide elastic found in the sewing dept. of Wally World or K-Mart worked great. Sew loops on the ends and your ready to go. This also allows you to adjust the thightness around the man which needs to be were the man cannot move at all once loaded. As for the weight of your jumper, I would think your plane will work. Talk to you soon!!!!

Thanks again Ken! I'll post more progress as I am able to get to the project. Hopefully the kite will arrive this week and I'll get to do some testing over the weekend.

Steve

I got the kite today Took it down to the beach at lunch to give it a try, flew pretty nice. Seems the shape of the inlet on the cells would not be very beneficial to ease of inflation; they are curved to face downwards (which is into the wind when flying as a kite, but not in what would seem to be the ideal location for a parachute). In any event, hopefully I will get a chance to rig this up over the weekend and try it out as a paraglider. Should be exciting!

Steve

Hi Steve, Did you get a chance to give it a try over the weekend?? How did it go??

Not sure if you can tell from the pic below but the front of the chute is angled down to keep air pressure in the chute as the chute is coming down. Paraglider chutes even have the top portion of the cell opening closed across the front now.

No Ken, not yet as I am going to have to re-rig the lines on the kite to make them work for the paraglider. But I'm working on it!

Thanks for clarifying about the cell openings, that was helpful.

Steve

Who Can Make It To Joe Noll????
Who Is Going To Wil's July Rally???

Entry Form List send your entry form and entry fee in as soon as you can!

!. Wil Jones
2. Jim Boone
3.Jack treadman
4. H. C. Perry
5. Paul Reiner
6.Gary Van Fossen

Thx, Wil

Entry Form List send your entry form and entry fee in as soon as you can!

!. Wil Jones
2. Jim Boone
3.Jack treadman
4. H. C. Perry
5. Paul Reiner
6.Gary Van Fossen
7. Rich LaGrange
8. CR Fowler
9. Jamie Albright

Thx, Wil