Scaled Down Dowel Delta Experiment

by Peter
(Wollongong, Australia)

Tethered and behaving

Tethered and behaving

Tethered and behaving
Another angle
Pop-fin close-up

Since the local hardware barn had 6mm and 4mm hardwood dowels, but not 5mm, I decided to adopt a two-pronged approach. The plan is to build two delta kites - one using 4mm, then one with 6mm. So far, I have made the 4mm version.

I consulted delta expert Dan Leigh's site at

http://www.deltas.freeserve.co.uk/plan.html

and concluded that the cautious approach for a first delta would be a 90 degree nose, with spar lengths and wingspan appropriate for 4mm dowel. The spreader would be a bit larger, at 6mm diameter.

So, my scaled down kite has leading edge spars of 75cm, a vertical spar of 71cm, and wingspan 1.42 metres. I pretty much followed Dan Leigh's plans, choosing spar length by interpolating between his non-metric size recommendations.

I only got fancy with the keel, and made it a "pop fin" by leaving the front of a double-sided construction open. The idea apparently is that under line tension it stays closed, but pops open when tension is off, stopping dives...

It certainly pops open, but whether THAT stopped any dives remains unclear, since so far it hasn't dived ;-)

The first test flight was in winds varying from around 6 to 23 km/hr! The wind was building from an average of around 7-10 km/hr up to around 14-17, but when I saw a gust of 23 km/hr on my wind meter, I decided that it was time to bring the kite down. After all, it's a light wind kite!

The small delta handled these conditions well - it was stable. It only occasionally went up to a really high angle, once I think with some thermal assistance that pulled it almost vertical. It was confused then, for a few seconds, smoothing around in elegant circles of indecision. As expected, this was followed by some downdraft that sent the delta back to only perhaps 40 degrees for a minute or so.

I did notice some rippling and flapping near the trailing edge at times, which has both good and bad points. The drag probably contributes to stability, but also reduces lift somewhat.

The first flight was on an overcast day, with rain threatening. A second flight on a sunny day with fluffy clouds confirmed that the little delta flies well. This flight was in winds of around 10 km/hr average, with a few gusts to 15. It was a South-Easterly, which made for interesting photo challenges, since in the middle of the day the kite was flying *directly* into the sun! I tethered the kite, and walked around to get a different angle, avoiding the flare.

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About Accuracy etc
by: Peter

Thanks Tim -

I took your advice about putting the heavy ends at the *bottom* :-) I also bent the wing spars together in my hands to check that they flexed more or less evenly.

The photo is deceptive, since my towing point is actually at 50% of the spar length.

I probably have an accuracy habit, since before I started doing the MBK thing I was building very small fighter kites (wingspans of around 50cm or less).


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Nice Delta
by: Tim Parish

Thanks Peter - good post. You must have done a great job with accuracy and dowel selection for the kite to remain in the air at those wind speeds! I guess the towing helped too, since it looks a little more forward than on the MBK Dowel Delta.

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Wind Speeds


Light air
1-5 km/h
1-3 mph
1-3 knots
Beaufort 1

Light breeze
6–11 km/h
4–7 mph
4–6 knots
Beaufort 2    

Gentle breeze
12–19 km/h
8–12 mph
7–10 knots
Beaufort 3    

Moderate breeze
20–28 km/h
13–18 mph
11–16 knots
Beaufort 4    

Fresh breeze
29–38 km/h
19–24 mph
17–21 knots
Beaufort 5    

Strong breeze
39–49 km/h
25–31 mph
22–27 knots
Beaufort 6

High Wind
50-61 km/h
32-38 mph
28-33 knots
Beaufort 7