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Jan 04, 2004, 11:22 AM
FASST flyer
KatManDEW's Avatar
I switched my Yak from pull-pull on the elevator to push-pull with a carbon rod, and it cured my pitch sensitivity problem. I must confess that I asked a real good pilot fly my Yak with the pull-pull setup on the elevator and he didn't notice any problem with it, but I didn't like it at all. I have several of these foamies, and a boatload of other planes, so it's not just a figment of my imagination - my Yak was very twitchy on the the pitch axis with the pull-pull setup on the elevator.

>LeeU: I wonder about the durability of the floppy disk hinges at cold temperatures... I use a double beveled rudder on all my foamies, with pull-pull, and I use the small Robart "1/2 A" hinge points. It's working well for me so far. The only downside I can think of is that you can see the hinge points through white depron if they are inserted in an area that is not painted or covered.
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Jan 04, 2004, 12:24 PM
AKA Cardboard Keith
Club 20 king's Avatar
Here's my Mini 3dx flown built and flown today. Fly great!
Jan 04, 2004, 12:27 PM
AKA Cardboard Keith
Club 20 king's Avatar
1 more
Jan 04, 2004, 12:29 PM
AKA Cardboard Keith
Club 20 king's Avatar
Will paint it later today just had to get out a fly!!
Jan 04, 2004, 01:24 PM
Registered User

YAK won't hover.........Why???

I just finished a YAK with a GWS 350 w/ 6.6:1 gearing and an 8 cell 720 mah nimh pack. AUW is just under 12oz. At full power, the plane is very light, but it will not hover, it just slowly drops.

I read about this setup hovering at half throttle and just can't believe it! Anyone have a possible answer???

Oh, I haven't re-timed the motor. Is this a necessity?


Jan 04, 2004, 01:42 PM
FASST flyer
KatManDEW's Avatar
>galloping ghost: We've discussed this with other folks having the same problem. I would be willing to bet money that your problem is those 720 mah NiMh batteries.... Many of them have extremely poor voltage depression characteristics. When you put a high current load on them (amps) the voltage drops severely, and thus also your RPM. Try attaching a voltmeter and running the throttle up, and watch the voltage.....
Jan 04, 2004, 02:20 PM
Registered User
Thanks for the reply KatmanDEW. I'm using a relatively new pack. I've got around 10 cycles on it. It has never performed as I expected it should. Had it in an overweight 3DX at first and the plane would barely fly. Re-propped to an 11/8 and it was better, but nowhere near 3D level performance.

Can you recommend a source for a quality pack?


Jan 04, 2004, 02:34 PM
FASST flyer
KatManDEW's Avatar
I'm using lipolys on all but one of my electrics now, so I haven't looked seriously at NiMh or NiCd battery suppliers for awhile. The one NiMh pack I am still flying (in my E3D) is from New Ceations and I think they are a reputable vendor, but I don't have a high opinion of the 720's in general. Hopefully someone on here can give some feedback on a good source of good 720's.

Lipolys are the best solution, IMHO, and the batteries themselves are not really much more expensive, especially for these small planes, when you consider the additional capacity and cycle life. But if you don't have a lipoly capable charger that adds to the cost.

I've got a BOATLOAD of rotten useless 720's, from back before I figured out that the batteries were my problem.
Jan 04, 2004, 02:35 PM
Hubb's Avatar

mini 3DX

club 20 king,

what size is the mini 3DX?? ive never seen one before. what is your power set-up? give the details man!

Jan 04, 2004, 02:47 PM
Registered User
KatmanDEW, if I went with a Li-Poly pack, would I want a 2S1P or a 3S1P for a stock GWS 350? Wouldn't a 3S1P burn up the motor?

My buddy just bought a lipo charger so I could charge them at his house

Where are you in Ohio? I fly out of Thistledowns Field in Napoleon, OH.
Jan 04, 2004, 03:56 PM
fix-it-up chappie
tolladay's Avatar
As long as the pull-pull lines are the same length, the placement of the servo is not significant. You can even cross the lines, run them through holes in the fuselage, etc. The rest of the geometry has be exact (control horns centered on the hinge line, servo arms perpendicular to the control horns, etc), but the servo placement in not that important.

galloping ghost,
My modified 3DX (a 3D-51) will hover, and even climb slowly on a full pack at WOT. I use the 5/4 AA 800 mah nimh batteries from Wattage, and my planes weights 13.3 oz. At 12 oz your plane should easily hover. KatManDEW is correct in that the problem could be your batteries. He is also correct in that the best solution is switching to li-polys.

Did you try warming up the pack prior to flight? Nimh batteries are sluggish when cold, and almost always perfom much better fresh off the charger, while still a little toasty.

RCL, dsbeliever
Thanks for the help. I just had to download it using Internet Exploder rather than Netscape. Since there was actual WORK involved, as well as THINKING, I was naturally at a disadvantage.
Last edited by tolladay; Jan 04, 2004 at 04:02 PM.
Jan 04, 2004, 04:50 PM
Registered User
Tolladay, thanks for the tip. My batteries are cold; I'm charging them in the garage and then bringing them in and testing thrust in my hobby room. It acts like the voltage is dropping, but I don't have a way to check it.

I'm certainly disappointed in the thrust I'm seeing with this setup. I can see Li-Polys on the horizon.

I'll ask again: What is the premiere Li-Poly pack for the GWS 350 w/6.6:1 gearing?
Jan 04, 2004, 04:56 PM
Registered User
Dennis Everett's Avatar
Something else you could do it your not ready for lipos,get some kan 650 battery packs,they are nimh,and mine will hover on a 7 cell pack of them, sell them...Dennis
Jan 04, 2004, 05:42 PM
FASST flyer
KatManDEW's Avatar
>galloping ghost: Again, it sounds to me like you have some of the all too prolific, garbage 720's. IMHO, those 720's are the worst thing to happen to electric flight. I know of way too many people, online and in person, who were turned off to electric flight because of those junk 720's. They almost caused me to give up on electric flight, as well as some others that I know of.

I can't speak from experience because I'm running brushless instead of the GWS 350's, but I know some folks who are getting good use out of the 350's with 3 lipolys. But most of their flying so far has been indoors, where your not fighting the wind, and you can't ride the throttle hard without running into the walls or ceiling

I don't see the GWS motors in any of the motor calculators (which has always baffeled me), so I can't run any numbers. I'm guessing that hovering capability with the GWS 350 and 2 lipolys on a 12 ounce airplane would be marginal. Possible but marginal. Tim shows it with 17 ounces of thrust on on 2 lipolys in his motor guide. I can't remember any of the reports from folks using 2 lipolys. Maybe someone who is doing so will speak up.

When you "prop up" the GWS 350 on two lipolys, to get good thrust out of it, it pulls quite a bit of current, and current is a large part of what kills brushed motors, or anything for that matter. So I'm guessing that they won't live a real long life even on two cells, when pushed hard.

I know that you can get at least 20-30 flights, or more, from the GWS 350 and 3 lipolys if you go real easy on the throttle, which is not very easy to do outdoors.

Best bet of course is to go brushless, but that adds even more to the tally as you then also need an expensive brushless ESC.
Jan 04, 2004, 05:42 PM
Registered User
would a himaxx 2015-4100 fly the 40" yak? i have the 36" but i want something with a little more wing.

Cary C

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