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-   -   My SPAD Gnat... (http://www.rcuniverse.com/forum/s-p-d-aircraft-coroplast-design-178/2457040-my-spad-gnat.html)

-pkh- 12-22-2004 01:00 AM

My SPAD Gnat...
 
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Here are some pics of my SPAD Gnat. This is my third SPAD, and it is by far the most fun for the $$$ and the time required to build it! I've got a .15 Enya on it that I got for free... just had to buy a muffler for it. It's got a Hitec Electron-6 RX in it... that's the smallest dual-conversion RX I could find (didn't want to fly a nitro plane at a club with a single-conversion RX). The batt pack is a 4-AAA 650mAh NiMH cell pack, to help keep the weight down. Got a Hobbico Voltwatch batt meter, and an Hobbico Air Alert beeper to make recovery easier if it goes down in the brush or the corn! I just have standard Futaba S3004 servos in it and a 4oz low profile fuel tank.

How does it fly??? Pretty well. It could use a more powerful engine, but the price was right on this little .15 Enya! This engine's pretty old (was seized up when I got it), but it's never been run as far as I can tell. I ran a couple of break-in tanks, and it's starting to perform a little better now. The fuel tank is mounted behind the engine, and is higher than the carb, so fuel flows into the carb and fills it up if it's not running! It seems to run fine when it's horizontal, but tends to die when it goes nose up. If this problem continues, I plan to buy two 3oz tanks and mount them on either side of the engine, and hook them up in series, like the main tank & header tank setup on most helis.

Our club secretary wants me to build him one of these Gnats, now! He plans to put his OS .25 FX on it! I think after I see how his flies with that engine, I'll probably have to get my Gnat one too!

-pkh- 12-22-2004 01:04 AM

RE: My SPAD Gnat...
 
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BTW, here are a couple of photos of the Hitec Electron-6 RX next to my standard sized 7 channel RX (a Hobbico 7ch RX that is just a rebadged Futaba RX). I was amazed at how small this thing is...

DLSmith2 12-22-2004 10:28 PM

RE: My SPAD Gnat...
 
-pkh-,

Gnice gnew Gnat! :D

What did you have for an all-up weight, and what prop?

Blue skies,

DL

-pkh- 12-22-2004 11:34 PM

RE: My SPAD Gnat...
 
Thanks!

I haven't weighed it, yet, but I can... I'll post it later. To really shave weight off, you could go with micro servos, a single conversion RX, and forget accessories like the Voltwatch and Air Alert.

So far it seems a 9X4 prop does best. I tried an 8X3, figuring to get some more RPMs out of the .15 Enya, and a little more power, but I could barely keep it in the air with that prop! The 9X4 APC worked well, and I believe I had a 9X4 Master Airscrew on it and it worked well too. I think this is all pretty engine dependent, though. A newer .15, like a Magnum XL-15A BB would probably have more power, and may worked better with yet a different prop.

It's pretty rugged... I've had several rough landings with no damage (except for a busted prop now and then), and today I nosed it in and just broke the "Walmart kitchen cutting board" engine mount. Just have to cut another out and she's flying again! I've found Master Airscrew props hold up a little better than APCs on those "less than perfect" landings!

-pkh- 12-23-2004 12:33 AM

RE: My SPAD Gnat...
 
...she weighs in at 2lbs 6.7oz (no fuel)...

-pkh- 12-24-2004 08:35 PM

RE: My SPAD Gnat...
 
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I decided to add a header tank to my Gnat...

Since the main tank isn't wrapped in foam, it gets shaken up pretty badly, and I get a lot of air bubbles in the fuel line, making it hard to tune the engine just right. This is just a 1oz tank, so it will add minimal weight, and should let me run the main 4oz tank bone dry before I get any air in the carb's fuel line. I'll let you know if it *actually* does help after I fly it next week!

For some of you plane guys who may not be familiar with header tanks (they are common on helis, but not planes)...

This is just a small tank that stays completely full of fuel (i.e. virtually no air at all) until the main tank runs dry, so any vibration due to the engine doesn't generate air bubbles in the fuel line to the carb. It does give you a little extra capacity (1oz extra, in my case) but once you run the main tank dry, the header tank begins to fill with air and generate air bubbles in the carb line, and you get poor performance once again...


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