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Old Apr 27, 2007, 10:12 AM
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Only a couple of days to get your planes posted for April. Lets make this hard for Mitja to decide:-)
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Old Apr 27, 2007, 10:23 AM
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thanks denny, just made payment, i look forward to receiving the kit.

cheers
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Old Apr 29, 2007, 02:47 PM
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Balanced the guppy today for a trial flight it took 144g to balance the plane using the centre of garavity shown on the plan.The weight and battery pack was as far forward as could be towards the nose cone this was with a 4 x nimh pack weighing 111g the total weight of the plane was 625g it flew like a brick I have a tail to rebuild and a wing brace to replace
The plane just nose dived and did not seem to have any lift
Previously posted a picture on page 45
Can anyone see if I've done something wrong or am I missing something
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Old Apr 29, 2007, 04:25 PM
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Hi,

Mitja, i have a question for you on www.flyfreak-hr.org/phpBB2
Please answer... It's a question about guppy of course

best regards

Ivan
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Old Apr 30, 2007, 02:56 AM
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Ireland, Kildare, Leixlip
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Quote:
Originally Posted by maltman
Balanced the guppy today for a trial flight it took 144g to balance the plane using the centre of garavity shown on the plan.The weight and battery pack was as far forward as could be towards the nose cone this was with a 4 x nimh pack weighing 111g the total weight of the plane was 625g it flew like a brick I have a tail to rebuild and a wing brace to replace
The plane just nose dived and did not seem to have any lift
Previously posted a picture on page 45
Can anyone see if I've done something wrong or am I missing something
Sorry to hear your maiden didn't go well.
625g seems quite heavy compared to some of the weights people have achieved but a glider this size should still fly okay at that weight albeit at higher speed with a higher sink rate. If it just nosed in from the launch there's only 3 likely problems I can think of.
  1. Balance is very nose heavy and there was insufficient elevator power to keep the nose up. This seems unlikely as you said you'd set it as shown on the plan.
  2. Wing or tailplane was built with incorrect incidence. Are you sure it was built accurately?
  3. Non-functioning or reversed elevator. Did you check the controls were working and in the correct direction before launching? I don't suppose you could have had your elevator reversed by any chance so that when you pulled up it went down? Was elevator set with just a little up trim for the maiden launch?
It's unlikely we'd be able to see anything but a major problem in the photograph.
If you can describe exactly what happened we can probably give a more useful diagnosis. For example did you launch it into a headwind or calm air? Was it a good launch? Did you launch yourself or have a helper? If you launched yourself did you get to the controls in time to try and avoid the nose-in? If you did get to the controls did it respond to elevator input? Did the plane stall before nosing in or just dive straight away?

Aidan
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Old Apr 30, 2007, 11:27 AM
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Northwest Oregon
Joined Jan 2006
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Aileron Wing Availability

It is my understanding that an aileron wing is available (or about to be available) for the Guppy.

Does anybody know the status (price & availability) of this wing?

Curt
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Old May 01, 2007, 12:54 AM
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Ljubljana Brnik, Slovenia
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Quote:
Originally Posted by maltman
Balanced the guppy today for a trial flight it took 144g to balance the plane using the centre of garavity shown on the plan.The weight and battery pack was as far forward as could be towards the nose cone this was with a 4 x nimh pack weighing 111g the total weight of the plane was 625g it flew like a brick I have a tail to rebuild and a wing brace to replace
The plane just nose dived and did not seem to have any lift
Previously posted a picture on page 45
Can anyone see if I've done something wrong or am I missing something
If CG was set per plans, (model supported at that spot on the wings, should lay horizontal, or slightly nose down)
if you throw model level and of enough speed,
if engine downthrust is set as on plans,
if elevator throws wasn`t reversed
then I suspect that something is wrong with relations between wing and tail incidence. In this case of nose diving, the tail has positive angle of attack instead of negative.

When I build Guppy, I check the angles of attack twice.

First when I glue together front and rear part of fuselage. I simply lay both parts on the plans. I bring into line the "wing saddle" part of the fuselage and check if the rear part of fuselage (one with carbon tube inside) goes as it is drawn on the plans. If necessary, I repair the joint, to get proper alignment.
Second, I check the upper portion of vertical fin! The upper line of the fin should be aligned with drawing. So, if necessary, tailor that line to match the plans. This is very important for the glider performance!

After gluing the front and rear part of the fuselage, double check again this alignment! If there is a slight difference, you can still sand down the upper line of the vertical fin. If now this line is slightly bellow of the line on the plans it does not hurt much. Important is orientation of line, not its exact position. One millimeter higher or lower, dont affect the appearance and performance, but any difference in ANGLE will affect badly!!

In case of Hotliner wings, you should check also if the wing is matched to the fuselage properly. If you install wing to the fuselage with improper angle of attack, (nose down attitude) then also the result will be nose down diving during launch. Check the drawing (section at wing root) and its balsa blocks, that serve for proper alignment of wing to the fuselage.

I hope, you will manage to solve the problem!

Mitja
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Old May 01, 2007, 09:37 AM
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Bok Mitja,

imam pitanje za tebe na flyfreaku

pozdrav
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Old May 01, 2007, 10:27 AM
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Quote:
Originally Posted by Aio_1
If you wanted to stay with the cheap brushed motors it's still worth considering lipo cells. They're cheap enough now that providing you've got a lipo capable charger (and preferably a little experience with NiMH or NiCD) it's a very attractive choice.
A Speed 400 7.2V with folding 6x3 on 3s lipo should be a good option. The 6V motor is very efficient at 3s voltages but would need a gearbox. If I remember correctly the 7.2V can handle a 6x3 on 3s but do check the current. Under 10A is fine for short runs or ~8A for continuous running.
A more attractive brushed option in my opinion is a long can 400 motor (like the Permax 480) with a 6x3 folder on 3s. These are the same diameter as the standard speed 400 but are longer and weigh a little more. They'll handle about 16A to 18A at 3s voltages and if memory serves they draw ~16A on a 6x3 on 3s. Although the motor weighs a little more you can easily come in at or below the original weight by using lipos. Depending on the duration you want I'd aim somewhere between 1200mAh to 2100mAh capacity for the cells. 1200mAh would weigh around 100g or less and at most the 2100mAh would weight about 175g (this would be for high discharge cells, TP prolite 2100 weight ~140g).

If you want to use a brushless motor as well there are a huge number of options. Generally outrunners would be best for a glider like this unless you want to fit a gearbox which can be more efficient but bumps the price up. The ungeared inrunner options would include the higher wind Mega 16/15 motors and Warp 4 motors which would could spin an 8" or 9" prop. These are similar in diameter, length and weight to a speed 400 so they shouldn't cause any headaches.

If you decide on an outrunner there's lot's of choices!
Hyperion Z2209/?? or Z2213/?? or G2213/??, Hacker A20-20L or A20-??M, AXI 2212/?? are all obvious suggestions.
However if it's possible to balance the Guppy with a very light setup and you don't feel the need for vertical climbs I'd be inclined to consider something a little different. You'll have no problems fitting the Flyware MicroREX220/12/1300 which is 22mm diameter, weighs just 32g and can handle about 100W on an 8" or 9" prop (I think a 9x5 would be about perfect). A speed 400 6V on 8 cells and a 6x3 is only about 50% efficient and will run around 7.5V and 12A for 90W input but on a very small propellor.
The MicroREX should easily beat that efficency and will deliver significantly more power to the prop. The prop will also be a much more suitable size and overall performance would be considerably better. Then consider the weight savings:
you save about 40g on the motor and lose a little of that on the bigger prop. If you used say TP1320 cells you'll save about 120g over eight 2/3A NiMH cells. That's say 150g saved which is a very large percentag eof the total flying weight. Of course it might not be possible to balance the plane with such a light setup in which case you can either go to larger cells and increase your duration or a bigger motor and get vertical climbs (although that doesn't seem right for this plane!)

I'm not trying to say you should go to a brushless lipo setup there's still a place for nickel cells and brushed 'can' motors; but there are definitely some attractive lipo/ brushed or lipo/brushless options.

Incidentally the cost of the MicroREX setup would be about as follows:
MicroREX220/12/1300 motor: 49 ($64)
Hyperion 3s VX1200 cells: $43
CC Thunderbird 18 ESC: $39.95
The folding prop will also cost a bit more than the typical plastic 6x3.

Hope this helps,

Aidan
Do you think an AXI 2208 would be adequate?

Tom
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Last edited by Trisquire; May 01, 2007 at 10:33 AM.
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Old May 01, 2007, 12:08 PM
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Thanks for your help Mijka and Aiden.

I tried removing the tube today to salvage the fuselage but I have to rebuild it as its so well glued in. Probably a rebuild is the best idea anyway and I will pay close attention to your relavant points.

The tail tube was alluminium and fractured without bending at all a clean circular break near to the main fuselage was the result of the very light impact so if any others are thinking of using metal tube DON'T.

Mijka could my use of the metal tube have any bearing on the amount of lead required to balance the plane I would have thought there was not a lot of weight differance between the carbon fibre tube.

The test flight was on a frequently used slope into mild wind to test if it glided properly before fitting my outrunner lipo and esc you know the result. All checks were made before the test flight so I like yourselves think my build was at fault.

I still think its a beautiful plane.

Post again when rebuilt I'm getting the carbon fibre tube Fridays it should be ready for a new flight soon.

Kelvin
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Old May 01, 2007, 09:36 PM
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Toronto, Canada
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Quote:
Originally Posted by kr3cik
Hi
I want to present a Guppy from Poland (Gupik in my native languae ). It was build by my friend Lukas. He changed a bit the wings. He made the wingspan a bit longer and changed a bit consruktion of wing tips (which is shown on photos).
I send thanks for Mitja from Lukas
Wow, nice wings.
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Old May 01, 2007, 11:54 PM
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Ljubljana Brnik, Slovenia
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Quote:
Originally Posted by Trisquire
Do you think an AXI 2208 would be adequate?
Tom
Of course!
Just routing of the electric wires should be done with care!

Mitja
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Old May 01, 2007, 11:57 PM
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Talking about wires of brushless motors installed in Guppy, I will show you, what approach take Dejan, builder from Slovenia:
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Old May 02, 2007, 05:04 AM
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O.K. guys, the April contest is over!
I have hard time to decide about the winner...

Results coming soon.....

Mitja
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Old May 02, 2007, 05:33 AM
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maltman, made a Guppy with hotliner wings.
Unfortunately his Guppy did not perform well and he needs some changes.
Nicely covered model.


tlgibson97 made a nice model for the flight simulator RealFlight. I like it! He choose original design!


Lukas from Poland made a slightly larger Guppy, with interesting geodetic outer wing structure. Such structure is very stiff on torsion.


cooper 998 build a nice covered Guppy.


dr.MadMan build two Guppies. The second one, with attractive color scheme is a really fine flyer! I seen it couple times in action!


tlgibson97 build a Guppy with "snake-alike" fuselage color scheme!


And the winner is......
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