Flew Drenalyn in 12 mph winds/prop test - RC Groups
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Apr 22, 2002, 03:39 PM
Motors beat engines!

Flew Drenalyn in 12 mph winds/prop test

Had the morning off today. Winds were 7 mph, expected to get 10-15 later. 38 degrees. ( brrr!)

Took 400 mm Drenalyn to my field that has a 15 mph windsock on it. ( 15 mph or greater winds, sock stands straight out.)

Proceeded to try these props: 8x6, 9x7, 10x4.7, 10x8 and 11x4.7, all on the same s1/qualcom powertrain.

8x6: FAST, but no real vertical. Long run time, prob 20 minutes.
9x7: Been using this one, works very well, decent vertical, 15 minute runs.
10x4.7: Slower, excellent thrust. Good climb angle. Amps should in theory be same as 9x7.
10x8: faster, better climb, seemed to be straining a bit.
11x4.7: slow, but almost true unlimited vertical. Will climb right out at perhaps 80 degrees. Hung and did a torque roll with this one. Seemed to struggle in the wind. Prob not enough pitch speed.

On none of these did I hit the qualcoms cutout or the pixie 7p's cutout. The motor seemed warm, but not hot on the biger prop sizes. I am using a heatsink with heatsink compound, and it was cold today.

During the morning, the winds just kept increasing till the windsock was almost straight out. I kept right on flying and doing rolls and loops without too much problem. Upwind runs were slower of course, but it was able to go upwind.

As far as what prop is best, I think I will stick with the 9x7 for most situations, but its nice to know that I can change the overall performance envelope with just a prop change.

I will probally try out the 10x4.7 at our next dome fly, but if we try out drenalyn pylon, the 8x6 will get its turn.
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Apr 22, 2002, 05:17 PM
Motors beat engines!
Update: Wind practically died, hit the park again to try out the 10x4.7 some more.

The plane flies quite well, but needs to be kept at 3/4 stick or more. ( the 9x7 flies fine at 1/2 stick).

It was obvious that I had a lot more thrust than the 9x7 so I proceeded to try to transition to hover. ( slow, gradually pull up as you throttle up).

Was rewarded with some brief genuine hover that would then
( s l o w l y ) sink straight down. Got away with it the first two times, flipping at the last second, failed the third and popped off the motor stick.

Two things:

1) Need to somehow rubber band mount the motor stick

2) need to lose about another 1 oz. Saw another thread here where the drenalyn was built from foamcore instead of fanfold and was just over 5 oz compared to my 6 1/4.

I think I've just scratched the surface here with this plane!

More to come.......................

Dean in Milwaukee
Apr 22, 2002, 07:30 PM
Registered User
dgoslee's Avatar


5.14 oz with (6) 110 NiCd.
Apr 22, 2002, 07:42 PM
Motors beat engines!
"5.14 oz with (6) 110 NiCd."

dgoslee, do you know what your battery pak weighs?

The qualcoms I'm using weigh exactly 2 oz. If your batts weigh only 1 oz, then I will have to find another way to lose weight, like cutting holes and covering with zagi tape.

Apr 22, 2002, 07:59 PM
Registered User
dgoslee's Avatar

Weight breakdown


Airframe = 3.60 oz.
(6) x 110 battery = 1.54 oz.

Apr 22, 2002, 10:06 PM
Motors beat engines!
Thanks Dan. Looks like an easy 1/2 oz then by going to foamcore.

Might still try to hole it out and cover. I'm soooo close to hover right now, I'd sure like to make it work.

The brief hover that I did get seemed pretty easy to hold, like the plane was meant to do it.

Apr 23, 2002, 06:06 PM
RPV builder & operator
Pierre Audette's Avatar
For comparison purposes, the mini-IFO hovers easily with a DX-A, 10x4.7 and 8x300 NiMH. However, I think it would be difficult to get an airframe as light, or lighter than the m-IFO.
Apr 23, 2002, 09:55 PM
Motors beat engines!
Pierre: With 8 300 nimh cells there should be a fair power advantage over the qualcoms, which I've read here are the equivelent of about 6.5 cells.

regardless, when I tried the 10x4.7, I was right on the verge of hover anyway. It actually hung for just a second, then slowly started dropping backwards.

I truely belive that if I can lose perhaps 1 oz, hover will happen.
I bought some foamcore last night, and the pieces are right now cut out and soaking. Hopefully I'll have them peeled and weighed tonight yet so I'll soon know if theres really any weight to be lost this way. If not, I can just do the same thing I did to the and_now I built, swiss cheesed the wings and cover with zagi tape. I was able to reduce wing weights by about 50% that way.

More to come.....................

Apr 23, 2002, 11:15 PM
Motors beat engines!

Got all the cardboard off the foamcore board, weighed all the foam pieces foamcore vs fanfold.

Fanfold: 54 grams

foamcore 30 grams

24 grams savings I belive is about 7/8ths oz, so with no other changes my Drenalyn should drop all the way down to 5 3/8ths oz.

The downside I see is that the foamcore seems much more fragile and flexable. Hopefully a flight test coming in the next 24 hrs or so. Maybe a true hover with 10x4.7?

More to come..............................
Apr 25, 2002, 07:22 PM
Motors beat engines!

Completed foamboard Drenalyn. Weight is just under 5 3/8ths!

Thats a full 1 oz under fanfold Drenalyn. I put on the 10x4.7, pointed it straight up and hit the throttle and it seems like its trying to climb. I say seemed as I have to keep a bit of a grip on it as its trying to flip over too.

Flight report is going to have to wait till winds drop some. We have gusts to 30 today.

Will post a flight report asap.

Dean in Milwaukee
Apr 26, 2002, 04:39 PM
Motors beat engines!

Got a break on the weather this morning. Winds 5-10mph, well within the limits of Drenalyn on 9x7 prop, but not the 10x4.7.

On the 9x7with the fanfold 6 3/8oz plane, you could dive and pull up into vertical and maybe get 1 full roll before the plane would fall off and head down fast.

On the 9x7 and foamcore 5 3/8ths oz plane, the same manuver is likely to go two or more turns, and then try to hang on in a hover position. It can now be done without the dive first too. Really works much better minus that 1 oz.

I wound up replacing the front 1/3rd of the fuse with pink fanfold as the foamcore just was'nt strong enough and was getting damaged. The pink is more than strong enough, no more damage.

There were several people at the field today and I wound up answering alot of questions on the plane after each flight. They were all a bit suprised at the performance this el cheapo plane had and how long the flights were.

Best move of the day had to be climb steeply into the wind with low ground speed, pull up, roll, and come out higher than you went in by 4 ft or so, then repeat and repeat. It appeared positivly anti-gravity!

Very fun day!

Dean in Milwaukee
Apr 27, 2002, 06:39 AM
RIP Azarr - "Old age is not for sissies"
Azarr's Avatar
My Depron version came in at 173g or 6.05oz, using 2HS55s, 1HS50 and 3 Tadirans for power. I've been playing with the "D" gearing on the GWS IPS with 11x8 & 12x8 in" props, and like this combination best so far. Hover is no concern with the 12" prop.

I'd love to have one under 5oz.

Last edited by Azarr; Apr 27, 2002 at 08:23 AM.
Apr 27, 2002, 10:52 AM
Motors beat engines!
With 3 cells and 3 servo's, I don't think you can really get down to 5 oz. Your airframe weight is probally only 1 oz right now. At that weight, there really is'nt much fat to remove.

Perhaps a change to qualcoms? My paks weigh exactly 2 oz with connnectors, and can handle much more current than the tadirans with out damage. You would need to experiement with different geaing and props though due to the lower voltage.

I am also using 2 hs 55's, but obviously there are lighter servos around. They are overkill for Drenalyn.

I really made no special effort at weight savings and I'm at 5 3/8ths using the qualcoms.

Apr 27, 2002, 12:39 PM
RIP Azarr - "Old age is not for sissies"
Azarr's Avatar
Hi Dean,

I may try the qualcoms, they're sitting here, just never got around to trying them. My 3 cell 850 tadiran pack weighs 57.9g or 2.06oz with the JST conector. 2 Qualcoms with the protection circuit is almost the same weight. I would expect to have to go to a lower gear ratio, not sure that I'd gain anything, I kind of like swinging that big prop.

Are you running 2 cells and 2 servos? Eliminating the one servo would get me down to about 5.5oz are since I would also be eliminating the linkage. I'm actually thinking about trying an "E" or "F" drive and the 14" prop just to see what happens. I am pretty happy with the combo I'm flying although I'm not sure the rudder is a necessity. I'm waiting until I can get it outside to make that decision.

Apr 27, 2002, 12:52 PM
Motors beat engines!
I am running two cells and two servos.

I did'nt realize the taderins were so light.

I did go to the 4.14 geared s1 drive in an effort to load the motor more than the 5.86 dxa would have. I have played around with some different props and find that unless the wind is very low, the plane will fly better with a higher pitch speed, despite the loss of some static thrust.

In wind, my combo actually flies better with the 8x6 than the 10x4.7, but my favorite outdoor prop is still the 9x7. Winds up to 10 mph really are'nt too big a deal.

I have'nt tried the rudder, and at this point I'm not really inclined to try. Very fun on just two channels.

Perhaps you should try stripping out your rudder gear just to see how performance increases with the loss of weight. I was quite impressed with the increase I got. Well worth the effort.


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