From an older thread, , ,

Originally Posted by Float Flyer

Mike, my electric world is not nearly as problematic and batteries allow me to move the CG around pretty easily with no nose weights etc, but I have absolutely no way of keeping the exhaust scale, so I did not even try. you certainly get much closer with a turbine, but still I don't see any way of not cheating a bit. you really only notice the exhaust when you are up close at that 3/4 rear angle.

How far did you have to cheat the width on the nacelles to fit gear with the turbines in the forward position?

FF

No cheating at all.
3 3/4" pipe clears the main gear with plenty of clearance room to spare.
Exactly 100% scale.

Mike I'm waiting to see who will build a scale Comet. I love the small wing mounted turbines. I think a small scale lightly built jet with 30mm fans may turn out to be the most practical size. I see you have a lightly designed CAD frame that could be laser cut in various scales. I was custom building GWS EDF30 fans, cutting the 10mm hub out, then installing new hubs with 12mm Feigao motors. The power was reasonable, but nothing like what folks have today with off-the-shelf manufactured micro fans and higher C lipos. It seems very possible, considering that a 7+oz, 22" 30mm fan ME262 flys well with an older 3s-480 Pro-Lite, and the Feigao remotored fans. That was with lower thrust custom fans. With folks getting 40gms or more per fan now, even a bit of loss due to reduced scale outlet sizes would still produce enough thrust for a lightly built Avro C-102, Comet, Nimrod, etc. There's also the possibility of inlet cheating, done inside the wing frame.
Bill

Those nacells are really far apart.
One engine out could spell disaster.

I'd say electrics would be an excellent candidate for that.

Notice the very small exhausts.
It's a similar problem with the C-102 Jetliner, but the exhausts diameter on the DH Comet is worse, , , smaller, , ,

This would most likely be impossible in turbine, the overall weight would be over the regulation limit for sure.

But in electric might be much better.

It's a plus having the main gear situated outboard.

Originally Posted by Mike Emilio

Those nacelles are really far apart.
One engine out could spell disaster.

I'd say electrics would be an excellent candidate for that.

The little plane is an electric EDF30 jet and flys well. The idea I was thinking about was using the EDF30 fans to build a Comet. It would have to be built without scale looking sheeting however, which goes against my grain, but could fly with 4 fans. The newer off the shelf fans with high-C lipos would be more practical than the ones I build and used a few years ago.

Probably need to have a covered spar fuse, but maybe possible with 4 30mm bl EDF units:


Bill

What span is your C-102 intended to be Mike?
I guess about 70"?

I've not used EDF myself because of the halving of flight times through the inefficiency of the fans, but either that C-102 or a Comet with it's long tube fuselage would probably benefit from my now standard method of laying 1/16" soft sheet down on the board and adding part-formers to make the fuselage sides which can then be joined together to make the whole fuselage. It benefits from my not having to waste material to make a frame strong enough to then apply the skinning. The skinning material is an integral part of the structure.
Just a suggestion, but any weight saved is doubly worthwhile for EDF.

Originally Posted by eye4wings

What span is your C-102 intended to be Mike?
I guess about 70"?

I've not used EDF myself because of the halving of flight times through the inefficiency of the fans, but either that C-102 or a Comet with it's long tube fuselage would probably benefit from my now standard method of laying 1/16" soft sheet down on the board and adding part-formers to make the fuselage sides which can then be joined together to make the whole fuselage. It benefits from my not having to waste material to make a frame strong enough to then apply the skinning. The skinning material is an integral part of the structure.
Just a suggestion, but any weight saved is doubly worthwhile for EDF.

Yes, you can't build EDF light enough. There's a nice Comet plan at the Traplet site, but it is pusher. There's something about doing one of these without props that appeals to me. Those beautiful thin nacelles just don't look right without props.

One thing about flight times with many EDFs, is that after a few minutes you've had enough anyways.

The building style I of was thinking of, would be something like the Gates Leajet that Flying Models featured roughly 5 or 6 years ago. The builder go the EDF50 plane to fly on a small 7 or 8 cell Sanyo NiMh pack. He motivated me to build a light, brushed airliner using the 12V brushed fans. They really are not worthy of 3s operation, but they are still holding up after several flights. It's the only airliner I have, and is a cartoon looking thing, but it was a successful effort to build a light airliner with low power fans to boot.

The nearest I got was a couple of Meteor F3s which used pusher props, the smaller one Gunthers and the larger, DIY 4-blade black jobs that looked far too small to get it off the ground. These models both used brushed motors and NiCads, and flew for the usual sort of times. Ten minutes for the smaller, seven the larger.
The larger one is here...
http://www.youtube.com/user/R0binF0w.../2/bCil6oy4hTo

Although it was quite hard to see the props in flight I fully sympathise with the desire to go the more purist route. They look right static as well as flying - which is my reasoning for using scale props on a scale model.

I imagine being the pilot of an EDF, the screaming sound is not conducive to calming the nerves? Is that what you mean by a shorter flight time being 'enough'?

Originally Posted by eye4wings

The nearest I got was a couple of Meteor F3s which used pusher props, the smaller one Gunthers and the larger, DIY 4-blade black jobs that looked far too small to get it off the ground. These models both used brushed motors and NiCads, and flew for the usual sort of times. Ten minutes for the smaller, seven the larger.
The larger one is here...
http://www.youtube.com/user/R0binF0w.../2/bCil6oy4hTo

Although it was quite hard to see the props in flight I fully sympathise with the desire to go the more purist route. They look right static as well as flying - which is my reasoning for using scale props on a scale model.

I imagine being the pilot of an EDF, the screaming sound is not conducive to calming the nerves? Is that what you mean by a shorter flight time being 'enough'?

It's pretty much just the entire experience. I guess it depends on the subject also. With the performance jets, between the speed, crisp neutral handling characteristics, and the anticipation of a long, fast landing glide with very little drag, you're just ready to get it over with after a few minutes.
Bill

So a flying session for you is a few episodes of 3 or 4 frantic minutes interspersed by long recovery periods?

I'd have to say that I have to a degree accepted the restrictions imposed by age and these days design only sedate models that I can fly in a reasonably relaxed manner and enjoy the sight of the model in the air while doing so - so I fly for longer. My limit is in reaching the boredom barrier!

Originally Posted by eye4wings

So a flying session for you is a few episodes of 3 or 4 frantic minutes interspersed by long recovery periods?

I'd have to say that I have to a degree accepted the restrictions imposed by age and these days design only sedate models that I can fly in a reasonably relaxed manner and enjoy the sight of the model in the air while doing so - so I fly for longer. My limit is in reaching the boredom barrier!

Short answer, No. Society has found other means to accomplish that.
The jets fly well, but are not GWS Slow Sticks. I enjoy the fast pace, but it's not something that you want to just keep doing for long periods of time. In a way, that is actually boring. That is, unless you're one of these modern crazy video game obsessed youths.
B

Originally Posted by eye4wings

What span is your C-102 intended to be Mike?
I guess about 70"?
, , , ,

Span is 196" (16 feet)

The plans are available from Christine Smith.

Look here: www.cmsmithplans.com

WOW! That is serious airplane!
That should be stunning - can't wait for the eventual video!... but will have to!