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View Full Version : Need new prop for Thunder Tiger E-hawk...


jakjr
03-05-2006, 05:58 AM
My uncle has a Thunder Tiger glider (E-hawk 1400 I believe) which apparently lost half of the folding prop in flight the first time he flew it. He doesn't pay close attention to instructions so chances are he didn't even have it on right :rolleyes:

Anyways, we've looked high and low for a replacement prop for it and can't find one. As far as I know it's a 6x3.

Anybody know of one that will work? I see APC makes a 6x3 folding prop but it doesn't look like it would work with his spinner and I don't know what spinner he would need to get to use it. Any thoughts?

Thanks in advance :)

bhchan
03-05-2006, 07:16 AM
Go with a Graupner or Aeronaut folder. Check Hobby-lobby.com

http://www.hobby-lobby.com/camfold.htm
http://www.hobby-lobby.com/scimitar.htm

B.

Sky Sharkster
03-06-2006, 02:25 AM
Brian's right. The black "CAM" 6 x 3 folder is better than the prop supplied with the plane anyway! Hobby-Lobby.com
Ron

jakjr
03-06-2006, 04:46 AM
Thanks for the help, I think I will go ahead and get him one of the Cam setups next time I order from hobby-lobby.

Which mounting size will I need to get though, the 2.3mm or 3.2mm?

Sky Sharkster
03-06-2006, 05:06 AM
To Jakjr, If the motor is the standard "Speed 400" brushed size it has a 2.3mm shaft. The prop comes with a 30mm white spinner that is a perfect fit to the front of the fuselage.
I built one of these (magenta color)for a club trainer. It was donated to our club (Rocky Mountain Electric Flyers) by a local hobby shop. A couple of modifications that helped it fly better (in addition to the CAM folder) were to add 2:1 differential to the ailerons, in other words twice as much "up" as "down". Either a bend in the torque rod arms (forward) or a "V" shaped servo arm with the open part of the "V" facing towards the nose. This mod will prevent a tip-stall at low speeds and tight turns. The other modification was to warp about 3/32" washout into the tips with a heating iron. Same reason.
It's a pretty good flying glider and can be a decent aileron trainer if you "tweak" it a little!
Good Luck!
Ron

jakjr
03-08-2006, 05:06 AM
Thanks for the help!

glaros
10-24-2006, 01:19 PM
I am in the middle of putting my E-Hawk 1400 together.

Regarding Sky Sharkster's recommendations I have some questions:


What do you mean by "bend in the torque rod arms"? A photo would be great...
How do you "warp about 3/32" washout into the tips"? Can you do something similar without an heating iron?Thanks.

Sky Sharkster
10-25-2006, 01:34 AM
Hello Glaros, Welcome to Wattflyer! I don't have a way to post photos but the differential is pretty easy to understand; You're trying to get the ailerons to move more "up" than "Down".
With the wing upside down, you're looking at the aileron torque rods sticking straight up, right? They're threaded on top, for the small white pushrod connectors, but don't put those on yet.
Two pairs of pliers, one needle nose, the other regular jaws. With the needle-nose, hold one of the torgue rods tightly at the bottom (right where it comes out of the wing) , the pliers will be resting on the wing.
With the other set of pliers, bend the top of the torque rod forward, towards the front of the wing. About 30 degrees will be enough, a little more is OK but not less. You'll see the whole rod will try to move (pulling the aileron down), that's why you're holding it in place with the needle nose. You're putting a bend in the rod itself, about 1/2 way "up".
Now bend the other rod exactly the same amount, also forward.
When you hook up the torque rods to the pushrods and connect the servo, you'll see the ailerons will move a noticable amount more "up" than "down". If you move the transmitter stick to the right, the right aileron will come up about 1/4" (6.5mm) and the left one will move down 1/8" to 3/16" (3 to 4mm). That's "differential".
As far as the wash out, this is very helpful to prevent tip-stall, which this sailplane is prone to do.
What you're trying to do is this; Looking at the wing from the back, the bottom of the wing is (or should be) flat from the center out to the tip.
"Wash out" is a slight warp or twist that raises the trailing edge "up" at the tip. The center stays flat and the twist is a slight upward warp to the tip. If you place the wing on a flat surface (say, the left wing panel) the left center section, front and rear will sit flat, the left leading edge will sit flat, but the trailing edge will be about 3/32" above the surface. Both wing panels must have the same amount up "up" or washout to be effective.
You can do this by heating the covering, either with an iron, a heat gun or a hair dryer. It takes some help and be sure to provide your helper with an "oven glove" or other hand protection!
With your helper holding the center section, twist more washout into a wing panel than you'll need; After you apply the heat and it cools, some of the warp will "creep" out.
Holding the tip with about twice as much wash out as needed, run the heat source all over the wing, top and bottom...keep it moving, don't stay in one spot too long, just heat and loosen the entire wing covering slightly. Remove the heat and hold in the wash out until the wing has completely cooled, a few minutes. When you let go of the tip, it will "spring" back, but hopefully, not all the way back. It may take a few tries to get it right (and re-tighten the covering) but you'll get it. The really hard part is getting the other wing panel to match!
It's not easy but you'll be rewarded with a much more stable, forgiving and easier-to-fly model. Well worth it!
Good Luck!
Ron

glaros
10-25-2006, 10:27 AM
Thanks Sky Sharkster, I will start with the differential that seems easier to do. Below are some pictures of the build progress so far. Build is very slow, the reason can be identified in one of the pictures...:)

- Additional wing spar attached for reinforcment
- Front wing socket had to be trimmed-sanded for wing to fit
- Stock motor water broke in and effect at the water color
- V-tail fitted

Sky Sharkster
10-25-2006, 11:15 AM
Hello Glaros, Good job on the build! Looks like you already have the black CAM propeller installed, that will help the climb. Your wing reinforcement is good, too. We never folded the wing but a student did manage to crack the center section during a high-speed pull-out...I put some epoxy in the crack and it's been solid since then.
I like your idea of having the 110 degree angle marked on the paper behind the tail! Much better than the small angle-finder provided in the kit. Very clever!
Hope the rest of the build goes well, this is a good small aileron glider and thermals well.
Our model has held up well, never been crashed and is still flying.
Good luck, let us know how it flys!
Ron

glaros
10-25-2006, 12:47 PM
Yes, I followed the advice and replaced the prollerer with the Graupner CAM, which fits perfectly with the colour of my plane:p

Have one more question about amp draw. With the stock motor, the Graupner CAM 6x3 and a 3 cell lipo what is the expected amp draw?

Sky Sharkster
10-26-2006, 01:17 AM
Hello Glaros, the amp draw of a 6 volt speed 400 shouldn't exceed 10 amps but with a 3 cell LiPo it probably will! The 3 cell has 11.1 volts and a motor will pull as many amps as it can (depending on the throttle position) even if it can't convert this much power to prop RPM. Result? A burned-out motor! Although it's tempting to run it at full throttle, with this much power available to the motor you're better off doing one of three things to avoid "burn-out". (1) Run the motor at 3/4 throttle. (2) Use a 2 cell LiPo (less input voltage) or 7-8 cell NiMH battery. (3) Use a 7.2 volt motor with the 3 cell and run it full power.
Telsawinger addressed this problem on a similar thread here; Go to post # 4 http://www.wattflyer.com/forums/showthread.php?t=10915&highlight=amp+draw+speed+400
He explains it much better than I can.
Sorry to bring the bad news, but 6 volt motors with 11.1 volt batteries have a very short relationship! It may last a few flights at full throttle (even for a short motor run) but sooner or later, more likely sooner, it will "cook" the motor.
Ron

glaros
10-26-2006, 09:44 AM
I run (the trial version) motocalc for the combination I plan to use and I attach the results. Max amp draw is 12A for 3 cells. Maybe the motor will last for a while with some throttle management. That's why a did the water break-in, to prepare it for a lot of volts (and because I have not done it before and wanted to try it).

Anyway, since a already have a spare 30A BL ESC can you suggest a cheap BL motor that will easily fit at this plane and an matching propeller?

Sky Sharkster
10-26-2006, 11:14 AM
Hi Glaros, There's a lot of replacement motors available, you might even be able to fit a small "outrunner" in the nose but it would be a tight squeeze. Here's some "inrunners" that will use a similar-sized propeller and 3 cell LiPolys. Your 30 amp ESC will work with these.
http://www.nesail.com/detail.php?productID=2926
http://www.multiplexusa.com/motors/Brushless%20Motor/400/6Direct.htm
http://www.nesail.com/detail.php?productID=3530
http://www.nesail.com/detail.php?productID=3405
Good Luck!
Ron

glaros
10-28-2006, 12:07 PM
Before trying to bend the aileron rods to create differential I tried the other method you suggested the "V" shaped servo arm. Since I do not have such an arm I tried to make one by heating and bending a straight one (picture). Do you think that it will work or should I make the "V" more steep?

Thanks

Sky Sharkster
10-28-2006, 12:27 PM
Hello Glaros, the angle you've made in the arms doesn't look like it's going to provide enough differential. Another problem is that by heating and bending the arms you've weakened the material. When they cool they will be brittle (hard, no flex) and likely will snap under stress. I don't mean to sound too critical but we all want you to fly successfully and the aileron servo arm is an important link in the chain!
Try this; Do you have (or can you buy) a 4-arm servo control arm that has all four arms the same length? If so, cut off two arms that are next to each other. You're left with the other two arms, they will be 90 degrees to each other, right? They form a wide letter "V". Put these on the servo so the open part of the "V" is facing forward, the arms are "pointing" towards the front, left and right. of the wing. Each arm is 45 degrees to the centerline of the wing. This will provide a 2:1 differential, twice as much "up" as "down". You will have to make up longer pushrods, the ones in the ARF won't reach. You can purchase straight pushrod material from a hobby shop, Hobby Lobby.com, or many other sources.
Good Luck!
Ron

glaros
11-02-2006, 07:26 AM
You are right, I did not consider the weakening of the servo arm by heating. I will try to find a cross servo arm or bend the aileron rods to add differential movement. Thanks.

I am about to install the serco tray for the tail now on which I opened a second bay since I will use two servos for the Y-tail in order to have rudder as well. The manual suggests to CA the tray to the fuselage. Is is the way to go or maybe epoxy will provide more strenght?

For motor I will stick whith the stock brushed + lipo ESC + 3cell lipo as long as it lasts and then upgrade to brushless.

Sky Sharkster
11-02-2006, 11:37 AM
Hi Glaros, I think you will be better off with epoxy for the servo tray, just run a small bead around the entire edge.
You have a good idea for the rudder/elevator, making the airplane 4 channel. I didn't have an extra servo at the time. I built it as a club trainer, but if I was building it for myself, would have done the same thing!
Be careful with the throttle using a 3 cell LiPo! We've burned out 2 motors doing this, it's a lot more input votage than the motor will stand. If the plane makes a smoke "trail", land as fast as possible. Burning up a motor is bad enough, but if it melts a wire, you won't have radio control and will surely crash. I've had this happen on other brushed motors.
Good Luck!
Ron

glaros
11-10-2006, 07:33 AM
My E-hawk is almost ready for its maiden flight. The aileron servo is installed and I found a cross servo arm and formed the V servo arm for differential movement. Some more question though:

- The wing mount method with the two screws at the back of the wing does not look very secure to me and I think it will become less secure after installing/removing the wing a couple of the times. I was thinking of puting two carbon rods across the fuse and use rubber bands to secure the wing. Comments?

- Since a have a rudder is aileron/rudder mixing recommended?

- Is the reccomended CofG correct?

:)

Sky Sharkster
11-10-2006, 10:58 AM
Hello Glaros, The wing mount has held up for about 2 years but the holes for the screws have loosened a little. I put some CA glue into the holes and after it dried, ran the screws in-and-out a few times to make new threads. Do you have the little plywod pieces under the wing mount? Without these the wing will be unstable. The rubber bands won't hurt as far as safety goes, they allow the wing to move a little if it hits anything on landing.
For the first flights I'd recommend using the elevator/ailerons on the right stick and rudder/throttle on the left, no mixing. After it's trimmed and you're comfortable flying it, try mixing a little rudder with the ailerons until you start to see the turns become "smoother", that it it won't bank as much but will still turn normally. Again, this model won't fly well if it gets banked over too hard, it may tip-stall. Wide, smooth turns are much better.
The Center of Gravity as shown is good for training and trim flights but I ended up moving it back about 1/4" (5 mm) for better thermalling ability. This does make the elevator more sensitive so be careful!
Most powered gliders, including this one, will "Pitch" up under power, that is, the nose will come up too high and nearly stall while the motor is running, even though the model is trimmed to glide correctly. This is normal. At first, just hold in a little "down" elevator during the climb to keep the climb angle about 40-50 degrees. After you've flown it a little, you can try mixing a few degrees of down elevator trim to the throttle. This takes a few tries to get it right.
Good Luck with the flights, just make all your control movements gentle and smooth, Enjoy the glider!
Ron