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Author Topic: Thornback Mk II with custom panel layout  (Read 3795 times)
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Bledula
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« on: March 30, 2011, 06:26 AM »

Building thornback Mk II designed by Ian Newham with custom panel layout.

I just discovered this forum and noticed that Ian Newham is a moderator here so I thought I would post my build here as well. Credits go mostly to Ian since this was based on his plans.



This is my first build except for the plastic bag version of 66% Thornback made just before this build.

   

Thornback Mk II designed by Ian Newham with custom panel layout

Name: Thornback Mk II
Weight: 307g (without tail weight and bridle)
Wingspan: unknown
Sail:    
    White Icarex P31
        Midnight Blue Icarex P31 (black wasn’t in stock anywhere within 600km from here)
        Dacron tape (25mm folded in half for trailing edge, 50mm folded for leading edge, 70mm             for nose pocket, mixed for wing/tail tensioning and various reinforcements)
        Sports bag material black (nose reinforcement, heavy duty stuff, much stronger than your         usual Sports bag)
        Sewing tape 6mm (double sided tape applied to every seam without exception)
Frame:   
    6mm hollow carbon spars (the whole frame)
        3mm carbon spar (stand-offs
        3x end-cap
        3x split nock
        4x stand-off connector
        4x JACO stand-off sail grabber
        4x EOLO leading edge connector
        1x EOLO middle T
Lines:     78kg dyneema (leech line, wingtip tensioning line, flying line leaders, yo-yo line)
    75kg 2x30m Climax Profiline set (flying lines)
    70kg dyneema bridle line (this things stretches :-( )
    Thick polyester line (this is for handles)

Kitebuilding

Sail

   

I made a point to align everything 100%. I used same colored thread for sewing the sail. White for while parts, blue for blue parts and surprise surprise black fro black parts to ensure that the sails looks as clean as possible and my mistakes are less noticeable. My sewing machine often dropped a stitch and this way you will not notice as much. It is also much harder to notice that my thread torn more than 10 times when I was sewing the trailing edge. When I was assembling the sail I first applied sewing tape to one piece of sail. Then I secured it on the board and aligned with the next piece. When everything aligned 100% I took off the cover film and taped those pieces together. That is also the reason why I’ve chosen to sew everything with shorter 3 step zig zag stitch instead of the long one that most people use. Since taped seams hold very well by themselves I considered sewing is mostly cosmetic and I like these shorter seams better.
All pieces of the sail are have their pattern aligned with the spine except the long piece that goes along leading edge. That one is aligned with the leading edge because it’s mostly tensioned from nose to wingtip due to the curve on the leading edge.

 

The trailing edge is reinforce by mylar along the full length on the back side of the sail. Mylar reinforcement is also applied to the spine along where the 2 halves join. It’s 20mm wide so that it aligns perfectly with the overlapping Icarex and it’s all sewn through together.

Wingtips



I don’t want to put any holes in the sail until I absolutely have to. Holes can always be added but removing them really requires very good knowledge of black magic and I’m afraid I skipped a few lessons here and there. So I decided to sew in a small loop from 25mm Dacron folded in thirds. Small enough so that it is barely noticeable and just big enough to get the dyneema line through it. I also didn’t want to sew anything on the back side of the kite so the order in which it is done is from inside out is: sail + Mylar, leech line, trailing edge, Dacron loop and finally leading edge. The sewing that you see had to be done by hand because I had to sew through all that material and if I count correctly it’s 12 layers of Dacron + Icarex + Mylar + Dyneema line and as a sewing bonus it’s also 10 layers of sewing tape. That’s 22 layers of stuff to sew through. I did the holes using sewing machine and sewing was done by 2 needles crossing themselves from opposite sides. If this breaks down then I can always make holes in it. The red line in this picture represent the leech line sewn into the trailing edge.

Nose

I did a few changes to the nose. The nose bag was sewn after the leading edges. The order in which I put in the various pieces together can be seen on the last picture. This allowed me to try a few things before I decided on how exactly am I going to sew this thing together. I didn’t have any Kevlar at hand so I did the whole thing from cut pieces of 70mm Dacron strip. On top of it I used thick vinyl (or something) coated fabric that is similar to those used for sports bags. I originally purchased various webbing but this thing is same as strong yet much more pleasant to work with a cleans well too.

     

The front side of the nose is intact. I wasn’t comfortable cutting along the leading edge so I decided to do the cuts on the back side of the nose as you can see in 3rd picture. I did sew the front side of the leading edge but mainly to keep things in place. I will let you know after a few crashes if this nose holds to it’s promises.

Upper spreader reinforcement

   

Not much to say about these. Just your ordinary reinforcement secured by sewing tape and sewn.

Central T reinforcement

 

The central T reinforcement and spine tensioning is from one piece of Dacron. Sewing tape is applied between all layers of materials where the cutout is.

Spine tunnel and spine tensioning

The spine tunnel is from your usual 25mm Velcro positioned a bit further up to allow some space for placing weight between it and the split nock. The leech line is sew into the trailing edge as mentioned earlier and is from one long piece of Dyneema line. It is tensioned around the split nock as shown in the last picture. Then it goes inside the spine tunnel and is secured above the central T in a similar fashion the wingtips are. I’m not sure about how effective is the leech line going to be considered that the trailing edge is from a very stiff Dacron.

       

Further down to the end of the spine a second layer of Dacron is added to make the reinforcement stronger. The soft side of Velcro is sewn further down the reinforcement so that it aligns with the other half when the spine is tensioned. I made the soft side of Velcro 10mm shorter.

Stand-offs



As I mentioned before I don’t like making holes in the sail unless I am really forced. I sewn together 2 layers of Dacron. I punched 3+3 holes in this and added a third free layer underneath. This was applied to the sail before the trailing edges. If this proves ineffective I can still cut it off and punch some holes in the sail but so far seems to be fairly solid.

Bridle

I used the bridle described by FlyingWolf in his build of Thornback. Since I don’t know how to do any tricks yet with this kite I didn’t want to make an overly complicated bridle. His bridle seems perfect to me in the sense that it’s completely adjustable. The biggest letdown when making the bridle was the realization that my bridle line stretches quite a bit. On a 60cm line it stretched as far as 63-64 cm. I tried to pre-stretch it as much as I could prior to making any cuts and making both sides as symmetrical as possible but I have a feeling that this is going to be a problem sooner or later. Luckily the bridle line can always be easily changed.

Frame

I made the frame exclusively out of 6mm hollow carbon spars because that’s the only thing I could get my hands on. If I feel that I need something more stiff for the lower spreaders I can always but it later. I wasn’t really sure how to exactly frame the kite by the instructions that I’ve read so I just used the measurement stated in Ian Newham’s plans. Except for the stand-offs which have been cut slightly shorter due to the way I implemented them. The spine is also a bit longer because I made the nose a little pointier and thus longer.
Once I get a good feeling of what a proper kite should feel like I will maybe make a different frame but for now I will learn with what I have.

Handles

As the Tom’s Kitebuilding site says, if you can build your own kite, you can build your own handles. I chose this design because it feels comfortable. Both handles are made to fit my hand but the white ones are slightly smaller. Let’s say the white ones are meant for my lady and black ones for me but I intend to borrow the white ones quite often.

 

Kite bag

If you can build your own kite and your own handles why not a kite bag as well? It has pocket for spars, 8 pockets for kites and 7 pockets for handles/lines. From the outside it has normal handles in the middle and 3 pieces of white webbing with adjustable clips. Same thing but with thinner webbing strips is on the inside for every kite pocket.

 

My Tips

I had quite a few difficulties when using my sewing machine that kept breaking my thread, dropping stitches, loosing tension on one side of the seam etc. most of this was resolved by adjusting various doodads but I did do a few adjustments that made the sewing job a bit more consistent.

 

1. Middle line - my machine doesn’t have one and I often needed it so I took a bit of transparent tape and permanent marker and made a very thin line (I just made a thick line on 2 pieces of tape that had very thin rift between them). To avoid smearing it I covered it with another piece of transparent tape.
2. Sewing guide - I couldn’t live without this improvised sewing guide when sewing the trailing edge and leading edge. It several pieces of vinyl covering tape put together to the precise height of my trailing edge. It’s also cute with a knife to have a clean edge to hold onto.
« Last Edit: March 31, 2011, 04:11 AM by Bledula » Logged
mikenchico
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« Reply #1 on: March 30, 2011, 07:48 AM »

Nice write-up, you really got into it, not just a kite but handles and a bag too, nice job. As far as I understand the changes you made everything sounds real good to me, I especially like the way you did the nose without a hot cut on the edges, looks very smooth, I couldn't see in the pictures where your cut ended up, I'll have to study them some more.

Tape holds but on Sport Kite's where there are some pretty high stresses sewing is really recomended. You might try the Glue Stick method rather then tape in some area's to cut down on dropped stitches, some machines really don't do well through multiple layers of tape, ours included. A light dusting of Spay Glue on things like the center T to tail area works also, just lightly dust the Dacron panel & let dry to a tacky feel.

Looks great, thanks for posting the details.

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fidelio
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« Reply #2 on: March 30, 2011, 01:03 PM »



what a first post! welcome to forum!
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inewham
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« Reply #3 on: March 30, 2011, 01:18 PM »

Thanks for posting that Vojtech thats a fantastic first build, wonderful build quality and a great first post  Cool

You forgot a picture of the whole kite so I hope you dont mind if I include the photo you sent me:
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art
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« Reply #4 on: March 30, 2011, 04:48 PM »

Congrats on the build. The end result is stunning.
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Bledula
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« Reply #5 on: March 31, 2011, 05:29 AM »

Thank you Ian for the picture. I added a thumbnail of the kite to the post.

Thanks for the other tip tips as well. I think that things like spray glue are going to be hard to come by around here but I will give it a shot when I get my hands on it. A lot of things on this build is greatly improvised and I spent a considerable amount of money on postage alone trying to get some decent supplies for building it.

There is one thing I was meaning to ask while I was reviewing various kite plans.

Why is the leading edge cutout for the lower spreader connector much longer than the cutout for upper spreader? Is it to relieve some tension on the leading edge when the kite is being stored?

Also do you glue the C-clips on the leading edge spars to prevent them from moving? How do you remove them when you need to adjust something or replace the frame?

For mikenchico. Here's a quick sketch of how I did the nose. Not sure if it explains it or just makes it more confusing but the middle sketch should speak for itself.

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inewham
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« Reply #6 on: March 31, 2011, 06:49 AM »

Why is the leading edge cutout for the lower spreader connector much longer than the cutout for upper spreader? Is it to relieve some tension on the leading edge when the kite is being stored?

Also do you glue the C-clips on the leading edge spars to prevent them from moving? How do you remove them when you need to adjust something or replace the frame?


If you make the leading edge from two 82.5cm lengths of carbon with a ferrule to join them and you want to store the kite folded in half, the long cutout allows you to pull the LE apart and slide the lower section part way out without moving the lower fitting up and down the spar.

Yes, you should glue the c-clips with a spot of superglue then when you want to remove them you can tap them to break the glue. Alternatively if the glue really won't break grip the open ends of the clip with a pair of pliers and twist a little.
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mikenchico
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« Reply #7 on: March 31, 2011, 06:58 AM »

Thanks I figured it was something like that, I hadn't pictured that top foldover though. Very nice.

Yes there are usually stoppers at the spreader connectors, c-clip's, cut rings from end caps, or even some vinyl or rubber tubing from your auto parts or hardware store. They go below the spreader connectors usually so you can disassemble the kite still. The longer cut-out on the lower spreader aids in assembling the kite and allows you to break apart the leading edge for travel.

Oh Ian beat me  Wink

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« Reply #8 on: March 31, 2011, 09:39 AM »

Amazing building very well done!
I usually use adhesive shrinking tube from electrical hardware store to make elbow fittings stoppers, as Prism does. I like it a lot more than C clips just because they look cleaner.

Paolo
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mikenchico
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« Reply #9 on: March 31, 2011, 01:51 PM »

Amazing building very well done!
I usually use adhesive shrinking tube from electrical hardware store to make elbow fittings stoppers, as Prism does. I like it a lot more than C clips just because they look cleaner.

Paolo

Yes, another good alternative, anybody who does submerged water pumps would be a ready source.

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Bledula
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« Reply #10 on: April 01, 2011, 02:52 AM »

Thanks for the tips. Since I tried to make the sail as exact as possible I feel bad that I haven't taken the same approach to the bridle and frame. In order to fix that I have a few questions to which I haven't found an answer yet and since I don't own a bought kite I have no way of comparing it.

1. How to measure for the correct placement of leading edge connectors?

I marked the specified positions on the sail but I am using APA connectors which are not as wide as the space in the plans. The C-clip seems to be the same so maybe it's enough to glue the C-clip in the right place? Also when I positioned the upper spreader on the leading edges according to the plans it didn't go through the center of reinforcement. I know that upper spreader placement makes a difference so I'm wondering if I did the right thing by moving it up a bit to the center of the reinforcement.

As I wrote before I cut the spreaders to the specified length so any movements up or down will end up changing the sail shape.

2. At what points is it best to connect the bridle to the frame? Currently mine is connected always between the C-Clip and Connector. This probably raises the whole frame a about 2mm to the front.

I will try to re-measure my bridle as soon as I get the time since my bridle line was quite stretchy. I suppose besides getting a different bridle line my best bet is to try to pre-stretch it as much as possible and then do any measurements? If I do this should I expect the bridle to shrink considerably after some time?
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inewham
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« Reply #11 on: April 01, 2011, 12:54 PM »



There is about 5mm diference between a Tradwind and an APA connector so depending on your datum you might want to move your c-clip up 5mm

However kites aren't that sensitive really so it won't make a huge amount of difference if your connecotrs or bridle are a few mm out.

I always loop the bridle around the frame between the bottom of the connector and the c-clip like so:
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« Reply #12 on: April 01, 2011, 02:19 PM »

hmm..
i always have the lower bridle legs attach to the spine and the Lower Leading Edges below the fittings...and then the top leg of the bridle attaches above the Upper spreader fitting...hmmmmmmm.....
just done it that way... Roll Eyes
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Bledula
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« Reply #13 on: April 02, 2011, 12:59 AM »

Thank you for the advice. I am going to measure everything again and glue the C-clips.

Then I will re-stretch the bridle and adjust that as well.
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« Reply #14 on: April 02, 2011, 05:31 PM »

I know people have mentioned C-Clips and shrink-wrap as useful stoppers to keep leading edge connectors (and center Ts) in place.  I have also taken vinyl end-caps, cut off the closed end of the cap and slid the remaining vinyl sleeve into place.  I like this as it is clean, sticks out less than c-clips and I find it to be easier to deal with than shrink-wrap.  Just thought I'd throw that out as an option! 

Your kite looks great.  Thanks for posting all of the detailed photos. 
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