T-33 Spring-air minis HW609 - RC Groups
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Apr 25, 2001, 11:19 AM
Registered User

T-33 Spring-air minis HW609

I have a NIB T-33, a set of Spring-air minis and an HW 609. I am thinking about buying an 920-4 to power this plane. Does anyone think that this will all work together. I'm thinking 8or9 cells (2400). The plane must rise off of grass. Any comments, suggestion, or sanity checks are appreciated

Thanks in advance

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Apr 25, 2001, 11:46 AM
jrb's Avatar
Hope Herb sees this, as he (I think) has done an Ultra/609 T-33; though hand/bungee launched.

Think he used 10+ cells and pulled 50 amps; was his fastest combo, but not his prefered (I think again).

Nose gear mounting shoulf be OK, wing mounting ??? Off grass???? Power and strength the big questions.

I say bungee launch and land with retracts; a servo operated retract might be able to work with a smallish servo when only used for extending retracts(?).
Apr 25, 2001, 03:07 PM
Lithium Member
Herb's Avatar

Yes indeed I have a T-33 powered by and HW 609/Ultra 920-4 combination, and I fly it now on 12x2400 cells. I had to strengthen the wing significantly by fiberglassing so they would not bend and twist or fly off,

It's quite heavy at 62oz, but I think I over-did it. Power in is around 12Vx55A=660 Watts, so I needed an ESC rated at 70 Amps.
It hand-launches fine (although sometimes I use a bungee as well),
http://aeneas.ps.uci.edu/edf/t-33_mwe.mpg (1.3MB)

To get the power of the Ultra, you need to draw quite a few amps, which means larger batteries unless you are willing to put up with a 1 min flight .

On the Ultra 920-4 you can use fewer cells (say 8 or 10) but then you might have CG problems (since the Ultra is kind of heavy) and ultimately after all that expense not that great a performance - it's all a trade-off.

The retracts (3 gears) would add quite a few more oz of weight, plus steerable nose gear, plus carving out that space in the nose...

I have been thinking about retracts in the T-33 as well (3x Robart minis), but more along the lines of a lighter setup with still lots of static thrust. Maybe an 1114/4y or 1010/2y or fun-480 -even in the Kyosho fan- might be more suitable due to the above weight considerations.

But maybe if you build yours light, reinforce the wing slightly (carbon fiber tape on bottom), use 1250 or cp1700 cells and keep the tot weight under 55oz it will be ok - or even better than ok!

Do look at Robert Wagoner landing gear conversion (non-retract) for the T-33,
Apr 25, 2001, 04:42 PM
i did roberts conversion on mine and it works well.fixed gear with servo only added 1 3/4oz.
it's not a heavy duty set up but on a paved runway it works well.........gregg