Rainer Hoffman – Bow Kite Part IV

It’s the Easter long weekend and it’s raining… Perfect kite making weather! Finally got back to the Bow Kite today, and managed to finish it.

I still have a number of tweaks I want to do but essentially here is what I did.

I “borrowed” some 3mm fiberglass from a 6 foot circoflex that I made in Dieppe last fall for all of the discs except the number 1 and number 6 ( the two smallest). I planned on using some vinyl tubing type fittings to hold the curved spar against the horizontal spar at the back of the disc but didn’t bother. (this is one of the tweaks I may try).

Once I got all the curved spars in and cut to length I added the horizontal spars. I used Sky Shark P90s as it was all I had that was substantial enough. I let the spar protrude 1 inch on each side of the kite, this is to allow room for the end-caps and c-clips (do-hickies).

So for the challenging part, the tension lines. Since the largest HQ Nock I have is 6mm it would not fit over the SkyShark spars. So I thought I would drill them out… BAD Idea… I Don’t have precise enough equipment and I think it would have been far too thin anyway. So back to the drawing board. I fought with vinyl end caps for a while trying to figure out how to tie the knots so that I could guarantee everything would be even and symmetrical etc… again no luck.

The problem I had was knowing how long to make each line segment and how much line would be soaked up by the knot/loop that I was going to use. So I got a pencil and paper and went to work figuring out the length of each segment’s tension line. So the first one was pretty easy. Since the discs and the main sail are 90 degrees and the tension line would form a right angle triangle, all I had to do was dust off my trigonometry and the Pythagorean Theorem. πŸ™‚ So the first segment is 66.8 cm. I was off to a good start, but then I started looking at the other segments and realized I couldn’t calculate the rest using the same formula. With a bit of figuring and the help of excel I was able to calculate all the segment lengths. Although most of the segment lengths a roughly within a cm of each other (except the top and bottom) I still found my excel calculator helpful as I could enter the spar diameter and determine how much extra line I would need for the loop and knot.

Then I just marked off each section on the tension line, used the knot allowance to tie a loop and that was almost the same diameter of the spar. I simply slipped it over the spar, added a c-clip to keep it in place. Finished it off with a vinyl end cap on the spar. It worked very well, and was simple and precise (and I hop accurate πŸ˜‰ ).

I have published the calculator here.. if you would like to have a look (and verify my math) πŸ˜€

So after all that here is the result! Of course it was raining when I finished it and no wind.. so the in flight pics are me running like a mad man down my drive way.

don’t ask who the goofy guy is πŸ™‚

  1 comment for “Rainer Hoffman – Bow Kite Part IV

  1. Clara
    3 May, 2006 at 10:25 pm

    It’s nice to see kids with constructive hobbies – keeps them out of trouble. πŸ˜‰

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