Nisse/TMFK

Have just finished this model and installed a FujiBT50.
Any suggestions regarding choice of props?
My idea is to break in with a Menz 20x8 and then run with a 20x10

3dd

My Feedback: (6)

that was my choice for my 15 pound sukoi with fuji 50 and it worked out great

jack01

My Feedback: (3)

It sounds good! Is this your first biggun'?

Nisse/TMFK

Yes, this is the first !
I have also started a thread with a question about using the pressure from crankhouse to carburator for a smoke system. Do you know anything about this? My worry is that when I start the smoke, pressure to carburator will decrease and engine will cut.
You can see my Extra in "news" at our club's webpage.
http://www.oktv.se/hemsida/tmfk/

jack01

My Feedback: (3)

What smoke pump will you use? It won't work with a straight tap off the crankcase going to the smoke tank. You could do it coming off the muffler, but you won't get enough flow on a plane this big. With the crankcase operated smoke pumps, the changing pressure from the crankcase moves a diaphram much like that on a gas engine carb. That way, there is not a noticable loss of pressure in the case. On that plane, the TME smoke pump would work fine. It's an electric smoke pump so it needs a 4.8 volt reciever battery, but that's not really that big of a deal. I've got a TME pump on my 40% with a 50 ounce smoke tank, but you won't need nearly that much. Just put the biggest one space will allow, and make sure it is over the CG since the smoke oil weighs more than fuel does, and as you drain the tank your CG will change. Your fuel tank should already be over the CG, but if it isn't, you need to change that.

If you have any questions about flying the big birds just post it here. There are plenty of people willing to help out.

I thought I saw your picture on the Downonthedeck Freestyle. You still planning on competeing?

Nisse/TMFK

The local hobbyshop says that the pressure from the crankhouse would be sufficient for a smoke system. So my idea was to Y-split the tube between the crankhouse and the carburator (that way I don't need to drill a new hole in the crankhouse). But you say that my gas engine has not got enough pressure?
I have already built a bridge for the fueltank moving it over the CG. (The ARF had the whole tank forward of the CG. Maybe they built it like this to be able to sell more Extras.........)
Is it ok to use same battery for the smoke pump as to the ignition?
When I was reading about the videocompetition I (by mistake) entered myself. I have told Joe (I think this was his name) that I hope to enter but first I need to get some practice with this new plane.
Graupner is sponsoring a competition for giant scale machines in sweden (like the TOC) over 6 weekends in different locations all over sweden. This year they will also have a "rookie" group which I hope to be able to join.
Last year there were 27 guys that competed and you will find some nice machines and some good flying experience there. Interested to check out some pictures? -> http://w1.401.telia.com/~u40123755/
I'm planning to do maiden flight (without smoke...) in the next 2 weeks and I hope she flyes as good as she looks.

jack01

My Feedback: (3)

The pressure is enough to run the smoke system, but you need a pump to do so. The crankcase pressure runs the pump, which in turn pumps the fluid into the muffler. You did well on moving the fuel tank. Although you could have gotten away with it, you don't want to have to deal with changing flight characteristics as the CG changes.

You don't want to use the same battery for the ignition and smoke pump for 3 reasons:

1. The smoke pump could drain the ignition battery and cause a deadstick.
2. You don't want to have anything connected to the ignition system that could transmit radio "noise" back to the radio gear. Thats why you use a plastic servo arm on the throttle and a nyrod or a metal pushrod with plastic ends. The smoke pump itself could, but probably wont, cause some radio interferance. With it also being connected to the ignition system, you could be magnifying what little there is, or adding some where there isn't any. My smoke pump didn't generate any interferance, but you need to range check it anyway. If it moved, it could generate interferance.
3. Although under normal operation the smoke pump would drain the ignition battery, you could just use a very large battery. However, electric motors draw more more amps when they are under load, or start up. This small of a motor won't draw that much more when it starts up, but when it is under load it will. If you get something that clogs the line, but still allows some smoke oil to go through, then your smoke pump will draw more amps than you had originally planned for, and your battery will go dead sooner.