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Author Topic: Thornback Mk II with custom panel layout  (Read 3790 times)
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Bledula
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« Reply #15 on: April 03, 2011, 11:06 AM »

Thank you again for all the suggestions. I glued the C-clips in the appropriate places and the kite flies great. Just the top spreader seems to be a bit loose. I did cut it according to the specs so maybe it's supposed to be that way.

I flew it for the first time today in a slight breeze with dropouts to 0. Overall a great experience. I even managed my first trick when there was slightly stronger wind. Takeoff to a very unstable fade for a few seconds and an accidental but successful recovery. I tried to fly to the edge of the window and stall there with some little success. I was however never successful in getting the nose of the kite to fall toward me in attempt to set up for an axel. I'm gonna need a lot more practice. Years of practice.

All this abuse did leave a mark on the kite. I broke the lower spreader somehow. I will try to find a replacement hollow carbon spar somewhere in town but I have a feeling that I will be repacing them some more. Therefore...

I would like to frame the kite properly.

Ian since you are the designer behind thornback could you recommend a proper frame? Any one else please post your suggestions as well. If possible include all recommended pieces of frame such as central T, ferrules, standoff connectors, leading edge connectors or end nocks. This will be some investment so I would like to avoid keeping the wrong part of the kite unchanged. Also which spars are most likely to be the victims of my learning process so I should order extras? The spreaders, lower leading edges or maybe something else entirely?

A suggestions for a good bridle line with low stretch are also very welcome and much appreciated. Mine stretches and shrinks considerably. Since I won't be able to buy any of this in my country I will go shop hunting across europe or even US hoping to find a single shop that can deliver all these things for a reasonable price.

I hope this is not too much to ask for but I'm afraid that I will not move forward without your help at this point. Any and all suggestions are very much appreciated.

Sent from my Dell Streak using Tapatalk
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sugarbaker
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« Reply #16 on: April 03, 2011, 11:51 PM »

I am in the process of building my own version of this kite, and I have purchased spars and connectors to frame as the following.

skyshark p200 for leading edge.
skyshark p300 for spine.
skyshark nitro (black diamond clear coat) for lower spreaders
and pultruded carbon 6mm upper spreader.
3mm carbon standoffs.

I'll use APA leading edge connector (size CA I believe is what I have now)
R-sky center T
APA standoff to LS connceter and Jaco sail to standoff connectors (3mm).

For leading edge tension/wing tips I'm using HQ connectors (as used on HQ, Skyburner, Jest of Eve and others)... I've also used Ken's (Blue Moon Kites) style leading edge tension that would work well with how you've sewn your sail.

As far as what I've broken, I've only ever broken a lower spreader during flight... otherwise it's whatever part happen to hit the ground (spine and lower leading edge).  I've never had the misfortune of breaking the upper spreader or upper leading edge, although I have seen it happen to someone else).

Regarding bridle line... there is specific line to use and I know our host (Steve) carries it in 100lb and 170lb weights (I will be using 100lb bridle line from my current inventory).  All of the parts I've mentioned can be purchased from him (if he is willing to ship internationally).
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inewham
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« Reply #17 on: April 04, 2011, 04:55 AM »

Just the top spreader seems to be a bit loose. I did cut it according to the specs so maybe it's supposed to be that way.
...
Ian since you are the designer behind thornback could you recommend a proper frame?
...
A suggestions for a good bridle line with low stretch are also very welcome and much appreciated. Mine stretches and shrinks considerably.

The upper spreader is intentionally a little short since this helps with rollups and makes the kite a little more precise. You can try a longer spreader but watch the back of the sail - if the line of the sail from the nose to the end of the standoff starts to curve your upper spreader is getting too long and the kite will become less precise and more unstable.

There is no proper frame, the kite is pretty forgiving and people have built them in 6mm, GForce, Dynamic, Skyshark and ISTR one in old Easton rods. I originally designed it with a 6mm leading edge and Avia GForce UL spreaders. Since then I've replaced the leading edge with P200s which sharpens response but the spine is still 6mm pultrude. A Skyshark 5PT lowerspreader and P200 should be fine.

The connectors I used are no longer available but APAs are the best you can get.

I'm currently using a roll of the bridle line Level 1 use but most spectra cored bridle line should be fine. However, for my prototype bridles I always use climax dacron rokkaku line - on the short length you get in a bridle the stretch is insignificant, its tough and its much easier to adjust knots with. Really any good quality braided 100~150lb dacron should be fine if you cant get bridle line.

I would guess the things most likely to break would be lower leading edges and lower spreaders.
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Bledula
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« Reply #18 on: April 04, 2011, 09:19 AM »

Thank you for the quick reply. Today I found out that the only shop in town that sells hollow carbon kite spars is out of stock for a few months...I guess I'll try luck in some model shops for some shorter spars.

I like the frame that sugarbaker describedbut with 5PT as lower spreaders:

upper spreader   6mm pultured carbon (0.24in, 82.5cm)
lower spreader   5PT (82.6cm, 15 grams, OD 0.312, ID 0.244, W 0.034, OD 0.234, ID 0.18, W 0.027)
spine         P300 (82.6cm, 17grams, OD 0.292, ID 0.244, W 0.024)
leading edges   P200 (82.6cm, 15grams, OD 0.289, ID 0.244, W 0.022)

Anyone thoughts on this? Upgrades/Downgrades? I went with 5PT for spreaders because it's quite frankly cheaper if I'm going to be breaking them on a regular basis.

Putting a ferrule in the leading edge P200 seems pretty straight forward even though I'm not so sure about using my 6mm endnock on the spine anymore. Will it still fit even though a it's going to be a little more tight?

But I have so many questions about everything else. Wish there was a shop nearby so I could just go and see for myself...

P300 is only 82.6cm long while Thornback calls for a longer spine. This should be done same as leading edge I suppose. But how about the ferrule at the central T? I only found Premier Center T at this site. Will it do the trick for P300 and 6mm ferrule for 5PTs?

I looked at the different sizes of APA leading edge connectors and I cannot seems to match them up with the spars. They all seems to be simply too small. I will continue crunching these numbers tomorrow because it's giving me headaches when thinking I might not find a viable suppliers after all...
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inewham
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« Reply #19 on: April 04, 2011, 01:34 PM »

Putting a ferrule in the leading edge P200 seems pretty straight forward even though I'm not so sure about using my 6mm endnock on the spine anymore. Will it still fit even though a it's going to be a little more tight?
...
P300 is only 82.6cm long while Thornback calls for a longer spine. This should be done same as leading edge I suppose. But how about the ferrule at the central T? I only found Premier Center T at this site. Will it do the trick for P300 and 6mm ferrule for 5PTs?

You could put your spine nock on a piece of 6mm and slide it inside the P300 - might need a bit of tape to take up any slack

Its OK to join the spine with a ferrule near the T, in fact on older kites the length of the spine was often 82.5 + whatever you cut off the top spreader so that was usually  ~ 1m.
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sugarbaker
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« Reply #20 on: April 04, 2011, 05:10 PM »

I like your choice to use 5pt for lower spreader.  It is easier to ferrule together (The nitro requires some shimming to ferrule with a 6mm solid ferrule).  For the end of my spines, I do use a 6mm extension to get the proper length, and for the tail end of the spine, I actually prefer a softer rubber end (I use an APA standoff connector) as it seems to do less damage to the velcro/strap used to secure the spine in place.

John T. at Sky Burner recommended APA connectors size CA.  Thats what I use for this particular frame.  They are snug, but can be placed easily if you use a little soap.  (another method I use is to heat them up for 10-15seconds in the microwave,,, which makes them very hot and probably lets off some toxic fumes, but they slide like butter... I'm not recommending this as it could be a health hazard). 
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Bledula
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« Reply #21 on: April 21, 2011, 10:24 AM »

Hi. There was amazing weather for flying today with roughly 12km/h wind and clear sky so I took advantage of that. Unfortunately I managed to put another dent in the thornback.

Somehow my spectra loop for wingtip tensioning ripped right through the dacron loop that I sew into the wingtip. Apparently 2.5 cm dacron folded in thirds is no match for spectra line.

What are your suggestions on a repair? Simply put holes in the wingtips? Use bridle line for wingtip tensioning?

Sent from my Dell Streak using Tapatalk
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inewham
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« Reply #22 on: April 22, 2011, 12:39 PM »

I always sew some dacron rok line into the leading edge from the bottom cutout to the wing tip and tension the wing tips with that. Neve had any problems with tearing or holes getting bigger that way.
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Bledula
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« Reply #23 on: April 24, 2011, 02:57 AM »

That's what I wanted to do when I read about it on your page. Especially liked the part where you say you've never seen one wear out and that it can be replaced.

However I could never figure out from your pictures how exactly is it made. Maybe that leach line line hanging in those pictures confuses me or something...

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inewham
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« Reply #24 on: April 25, 2011, 04:38 AM »

I sandwich it between the sail and the dacron as I sew the leading edge on; as I sew the leading edge the stitching goes trough the sail and the rok line. I sew it from the cutout to the tip, maybe 20cm? and sew with a serpentine stitch (like a curvy 3 stitch zig-zag found on Bernina machines) so its constantly crossing the line.

If I was making a kite for someone else I used put a stopper knot a few mm past the end of the LE and then tie on a sacrificial piece so that it can be changed if it wears. On my own kites I rarely bothered to do that and just used the end of the sewn in piece to tension the LE. I recently had the first one snap - on an 8 year old kite. So then i just tied on a sacrificial piece.

Its completely seperate from the leech line
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