Matti

Hi all!

Here's my new own-design speedster (not finished yet). What do you think, will it be able to fly? I've never built or flown this kind of planes and I just wonder...

What's your opinion about GWS's receivers? Are they ok for this kind of (dangerous?) planes?

Where to set the balance point?

Which prop do you recommend?

Any idea what would be its speed when using 6X4 or something?

Specs:
Wingspan 700 mm
Max thickness of wing 5 mm
Engine Cox TD 049
Weight 210-230 grams

BMatthews

How about a pic looking down right at the top of the model? From this pic the tails look a little small for the wing but it might just be the camera angle and wide angle lens. But intitial impressions are that it looks sweeeeeet.

I would advise against the GWS if you fly with other fliers at the same time. It's a single conversion and reviews in the electric parkflyer forums suggest that it can be glitched quite regularly in flight. At low altitude and high speeds that spells CRATER. They are also quite short ranged being meant for slow flying electric models kept in relatively close. A high speed racer like this can quite easily extend out to the max range in just a few seconds leaving you with sporadic or no control. Here again instant CRATER. We've had great luck with the Hitec 555 and Electron 6 and the FMA series of very small recievers. Also the "brand" name micros do well.

combatpigg

My Feedback: (3)

Hi MATTI, I like it! If you make the tail too small it won't be stable enough like BRUCE says. The electric pylon racers have very tiny, no, RIDICULOUSLY tiny looking tails, so who knows until you try it? Remember, it's always easier to get the knife out to cut a wing or stabilizer down than it is to make a bigger one. The TD engine will scream if you cut the prop down to 4.5", it will scream even more running a 4"-4 prop, but the piston/rod will break if you exceed 25,000 for too much time. If you lighten the piston by shaving material off the inside, the rod might be OK at 25000, DICKEYBIRD has more experience than I do about what a modified TD can do, maybe he can show you how to do the piston work?.

Matti

Thx for replies, guys! That already helped a lot

Yes, the tail IS small, but I think it might be ok because I used Ariane P5 as a base for my plane's dimensions:

http://www.aerodesign.de/modelle/F5D/ariane_p5.htm

My plane is something 73% of that. I can take better pictures when finished it (maybe tomorrow).

I know I shouldn't use GWS in it but... I must try it![>:] I'll do proper range checks before flying (engine running/not running), use mild 6X3 prop, adjust the mixture a bit rich and fill only 1/4 tank. Hopefully it's safe enough by that way. Throttle sleeve system would be must but I can't make it myself...[&o]

How about the BP?

combatpigg

My Feedback: (3)

MATTI, set the BP at 25%. Some guys do a test glide with no power to see if it is controllable. A speed plane needs to fly fast so I would not test glide it. The further back you put the balance , and still have control, the faster it will go. 30% might be the limit with the tiny tail

rpmtech

My Feedback: (6)

Those Single conversion receivers suck. Thay are good for micro helis and the like where you never get more that 20' from yourself.
Go with the Hitec Electron 6 or anything dual conversion.

Matti

Ok, I won't fly over 20' then!

I'll try with 25% BP.

Thx combatpigg & others

Matti

Ok, here are better pictures... Not finished yet but painting started. I'll use external pushrods: that's why you can see servo arms pointing out from the fuselage.

combatpigg

My Feedback: (3)

Very nice, MATTI! That's going to be fun to fly, do you have other RC flyers that you can race with?

Tim Wiltse-RCU

Matti,


Humm that thing looks fast just holding on to it!!!! Let us know how it does.


LAter,
Tim

BMatthews

The top view looks much better. It should fly fine. Start with the 6x3 and then move up to 5x4's and even 4.5x4.5. And sneak up on moving the balance point back a smidge at a time using the "dive test" in the glide after the engine cuts. Basically when trimmed for a hands off glide you then dive it at about 30 degrees and release the elevator. It should either continue in a straight line with no tucking or it should SLOOWLY bring the nose back up. If it noses up fairly quickly then move the CG back and retrim for hands off gliding. For a small model like this you can safely move the CG about 1/8 inch at a time.

Good luck with the flight testing.

jessiej

[How about a pic looking down right at the top of the model? From this pic the tails look a little small for the wing but it might just be the camera angle and wide angle lens. But intitial impressions are that it looks sweeeeeet.]

I expect the long tail moment allows smaller tail surfaces. I recall some of the unlimited rubber ships with fuselages long enough to carry a bushel or so of 1/8 ' strip having really tiny tail surfaces.

Keep us posted MATTI. looks like a great project!

jess

Matti

Thanks! Unfortunately here's no other speed flyers but hopefully this plane (if not crashed on maiden flight) is an example for my clubmates. There are some electric pylon flyers in the southern part of Finland, and also some Q500 racers, but I think this plane is quite unique...

Matti

Thanks Tim! Yes I will...

Matti

Thanks for excellent advice, Bruce. I'll follow your hints!

Matti

Yes, this sounds logical

Thanks! At the latest I'm going to try it next weekend. Then you'll hear a great success story or not so great one...[&:]

Matti

Now it's ready. I did only a modest painting and finishing because this is a prototype and I use GWS... Let's see, it's very windy today but maybe I'll test it. The weight w/out fuel is 232 grams.

combatpigg

My Feedback: (3)

That looks excellent! It turned out so light, not only will it be fast, but a great sport flyer too!

Matti

Well, it flew!And pretty well! The wind was awful but it helped when throwing the plane. I did only two short flights, but they revealed the possibilities of this plane[8D] Tomorrow I'll try with 6X4 and leaner mixture...

No major problems with GWS - if remembered to take off starter's leads off from the power panel

combatpigg

My Feedback: (3)

OUTSTANDING! Please draw a simple sketch of it if you can with the basic measurements. If you have an extra 6-4 prop, cut it down to 4.25", your engine will thank you. A 6-4 is too much for a TD 049, and it will make the model slower than the 5-3 prop

Matti

Yes, I will, but I have to rebuild and redesign it first because of some weaknesses in the fuselage; the vibration of engine caused cracks in the nose and the lubrication oil went in...But I already know what to do better and luckily this plane is nearly ARF - because of its simplicity!

The flying charasteristics are really good and with 4,75x4 prop (I modified it from 6x4) it flies F A S T!!

combatpigg

My Feedback: (3)

I can see where you would have a problem, I would probably use 1/8" thick spruce, bass, or poplar to anchor the engine mount wood to, and run those pieces back past the tank . I have used this same basic idea for C/L combat and something else will break before this does! If you do have a mishap it will break where the spruce strips meet the balsa, and that would be an easy place to do a repair. Some guys would also use 1/64" or 1/32" ply and sheet one side of the nose, back to the spars. I think for absolute rigidity to make the engine run better. All these ideas would sound real good if they didn't add any weight! If you cut the prop down and balanced it good, you shouldn't have too much vibration. Sometimes vibration can come from a sloppy fit on the crankshaft. I don't mean end play, but wobble [axial?] type slop. I'll bet that everyone who sees your plane fly wants to get one !

Matti

In fact if I think more precisely, I see that those cracks come from too robust use of the starter... Anyway, we have the same idea: I thought add some plywood to the nose in te strategic areas. I also discovered the tail a bit weak. 25g/m2 glassfibre for covering the fuse - that´s it! I'm pretty sure it's not too heavy. Hopefully!

combatpigg

My Feedback: (3)

MATTI, your plane was already so light that you could cover it with sheet metal and it would still be a good flyer!