Switchback AUW? - RC Groups
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Sep 30, 2002, 01:29 PM
Registered User

Switchback AUW?

Hi, all,

Just finishing my Switchback Sport (great kit, Doug!) and put it on the scales to check the weight.

AUW (less batteries) is 12.5 oz, right at the spec'd 6oz/ft wing load rating. Batteries (depending) would put it up between 16-20 oz. (8-10 oz/ft)

Too heavy? I'd hate to have its maiden voyage be its last...

Is anyone else flying (successfully) a "beefy" SB?

Doug, if you catch this thread, what would you recommend as an absolute max AUW for the SB Sport?

Thanks, all
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Sep 30, 2002, 01:31 PM
Leave me alone!
Martin Hunter's Avatar
Hi Bob,

I hate to ask, but how did yours come out so heavy? Heavy covering?

I've flown my sport wing on floats at about 17oz, and that's just with the stock power setup. She still flies VERY nicely at that weight, but just has less vertical. Keep in mind that there's also the additional drag of floats in my setup, so I'm sure you'll be fine.

Sep 30, 2002, 01:39 PM
A Clinger
rclark's Avatar
My SB 3D (original) came in at 9.5oz dry weight. Add a battery at 6 oz and up to 15.5 AUW. Completely stock.

Added retracts, new canopy, and a BL motor; came in at 12oz dry weight. With battery up to 18oz AUW. Flys great -- just a little faster....

Where did the extra weight of your plane come from if stock???? You should be fine though for flying it this way.
Last edited by rclark; Sep 30, 2002 at 01:45 PM.
Sep 30, 2002, 02:12 PM
Registered User
I suppose I should have been more specific. We're not quite stock...

A large chunk of the weight is from the Speed 400 motor w/3:1 gb. (Guesstimate: about 4 oz. - should have weighed the airframe before installing the motor...) Weight also includes radio, servos, esc.

Probably a little of it is the covering (regular oracover on the fuz, lightweight oracover on the wings/feathers.)

I just want to get a little confidence factor that if I try a loop @ 18 oz, I won't instantly fold a wing, or some other failure...

Sep 30, 2002, 03:17 PM
Mountain Models Wannabe
CoClimber's Avatar
Bob, empty weight should be below 10 ounces but I think you will be fine. Let us know how that motor works out.

Sep 30, 2002, 03:55 PM
Suspended Account

What where your figures for AMPS and WATTs with the C drive and 10x8 at NEAT?

Mine is flying, AUW 15oz's.. but no big vertical like yours did. I want to see how my power compairs and re-prop if needed.

Sep 30, 2002, 04:00 PM
Mountain Models Wannabe
CoClimber's Avatar

I was drawing 12 amps static. Did you time the motor? My empty weight is 9.4 ounces.

Sep 30, 2002, 04:20 PM
Suspended Account
You can time the 300?? Ugh.. no, I didn't... Not sure how or what I'd be looking for...

Sep 30, 2002, 04:42 PM
Mountain Models Wannabe
CoClimber's Avatar

Timing the motor


Note the red dot on the back plate of the motor. You will see that it is to the left of a tab. You need to rotate the plate clockwise so that it is to the right of the tab the same distance. I use a pair of ground down 90 degree needle nose pliers that I insert into the two holes in the back plate.

Sep 30, 2002, 05:02 PM
Suspended Account


ok, thanks for the info Doug. I can't seem to find any tools I can get it to turn with. My makeshift stuff gives. It's gonna take quite a bit more effort than I thought.

Sep 30, 2002, 06:13 PM
Suspended Account
Well, cycling the battery seemed to help, I'll have to get some ring plyers to adjust the timing.

I have had loads of fun with this plane, and I haven't even had the chance to trim it out yet. Every time I have flown it has been windy like crazy, and it does get blown about some, but man does it handle it well.

I flew it around until the battery died today... wind strong enough that it was hard to make forward progress at times, but fun none the less. I'm ready to take it out again, too bad the battery isn't charged yet...

Sep 30, 2002, 06:41 PM
A Clinger
rclark's Avatar

You probably know this; but in my experience all my batteries perform better right off the charger. Seems to have that little extra 'kick'. Oh if your looking for better performance -- get a BL LOL ....

BTW, not all motors are created equal. I just swapped out a 370 in my Zero and the performance is down with the motor. I saw this with the SB as well when I was flying stock..... Some good, some bad.
Last edited by rclark; Sep 30, 2002 at 06:44 PM.
Sep 30, 2002, 07:16 PM
Suspended Account
rcclark, yeah, I understand. I'm using an 8 cell 500 (AE?) pack that I used on my projeti. I believe they are heavyer than what I could use... I just went out on another fresh charge and timed it. I was WOT for 5 1/2 minutes. And since the wind died down, I got it trimmed down, and though it's not limitless.. it will climb up quite nice... I gotta say I love this plane. I've been so long without a 4 channel plane that now it's time to start throwing in some rudder...

Sep 30, 2002, 07:36 PM
Truss-Loc Monkey
Stevens AeroModel's Avatar
I have found it easier to re-time the 300 motor leaving it in the GWS gearbox - gives you more to hold onto to keep the motor from spinning. I use a cheap pair of snap ring pliers from Checker auto (cost me all of $5) - You should be able to find them at pepboys as well.

Oct 01, 2002, 05:59 AM
(aka Cliff Lawson)
Wright Flyer's Avatar
Originally posted by BNA Bob
I suppose I should have been more specific. We're not quite stock... A large chunk of the weight is from the Speed 400 motor w/3:1 gb.
Bob, I've done that. For a while I was out of EPS300's so I dug out a Graupner Speedgear 400 4:1 with a 12x10 folder prop and found that this flew the Switchback very well but, like you, I found it was VERY heavy compared to the design weight (especillay because I use 600AE NiCd's rather than NiMh cells). Oh, and my plane is covered in realtively heavy SolarFilm as well.

The nett effects of all this added weight was two fold. First the plane had more momentum which meant that it would carry speed up through a loop better than the "stock" system. Also, probably because of the large prop, it would roll faster than normal. However that large prop did not have enough ground clearance which meant I had to hand launch (landings were OK as it was a folding prop). You may be OK because with 3:1 gearing (rather than my 4:1) as I guess you're probably using a 9" or 10" prop?

The second effect of all the extra weight was that the landing gear just wasn't up to it. It would bend out dramatically (which also made the prop clearance thing worse) and in anything put a perfectly greased landing it would bend back an inch or more. I repeatedly bent it forward again until it eventually snapped and I replaced it with a slight heavier guage wire.

So while the SP400 route is OK for a temporary solution I don't think I'd recommend it for all time. If you haven't glued the landing gear in place already then one REALLY great improvement you can make is to turn it through 180deg so the "Y" points forward and the gear is much nearer the prop. This will prevent a lot of nose-overs on landing when flying that very heavy system.

In fact I think the gear through 180 mod is the best change I made to my Switchback so that when I built number 2 I just installed it that way round from the start. Now that I have the Mega brushless which is quite a bit heavier than the EPS, probably back in geared 400 territory, having the wheels on this way makes landings an absolute breeze!

Last edited by Wright Flyer; Oct 02, 2002 at 06:35 AM.