combatpigg

My Feedback: (3)

No, it's got to be either one or the other just for the sake of making everything fit. The danger of running a line pinch that doesn't positively clamp off the line is frying the engine if a trickle of fuel still flows. The fuel in these systems is under more pressure than some realize. It might be a good idea to rig up a TT.40 type guinea pig to test the working range and sensitivity of the valves I picked up.

It would be nice to see a detailed view and description of how the Germans set their planes up.

MJD

My Feedback: (1)

Gotcha. So even the same servo on RNV and pinch isn't an option eh? What about pulling a line off at the limit of travel as an option, with 3/4 stick travel dedicated to useable mixture? Just thinking stupidly out loud..

MJD

combatpigg

My Feedback: (3)

I think it depends on how hard you want to make an idea work VS how badly you need the idea to work. Inside the SD cowl with just the RNV and line pinch to hook up, the plumbing gets pretty busy. You could run a seperate control rod off the servo arm for the MCV, the trick is cramming everything in there neatly.

RocketRob

My Feedback: (1)

The Bob Violet RNV are still available. They sold off all the rest of the Ducted Fan stuff but they still have a "couple" of RNV's as of about a month ago. I had to call them to find out.
On the ME163 I am using one and it would allow for a full lean cut out, if you set it up with that in mind. I have mine set up in a middle capacity and just screw down the needle a bit more as I have a nice big OS carb to shut down with transmitter trims.

Mike Connor

My Feedback: (5)

Why not use a gradual fuel line pinch as a RNV with full stick movement a total shut off. During static runs we control the fuel flow with our pinch test and a servo should be more precise. Our ears have to tell us what is right in either case. Just a thought.

combatpigg

My Feedback: (3)

I called BVM within the last couple months and asked for a RNV. The person who answered the phone acted confused and put me on hold. When she came back, the word was they didn't have any. At that time I silently cursed Rocket Rob for buying up all the last units...
What I ended up doing was getting a Perry MCV and a Prather MCV.
The Perry unit is a rotating barrel valve and the Prather is a lever driven cam lobe that just squeezes the fuel line progressively. I don't think a "squeeze valve" will give consistent control or enough resolution since the linkage would need to be very stiff and refined.....but I don't know yet.

mk1spitfire

Great work c/p. Hope you can get video for us to all enjoy. Exclusive 200mph club is surly around the corner for you.

combatpigg

My Feedback: (3)

I took the SD out for another spin today. Same set up exactly as before to see if it would repeat the 195 run.
I launched it this time at 23,000 though. The thrust really went up for launch, it shot out of my hand pretty good. There was no big delay waiting for it to get going, it was screaming at the highest level I've heard yet. The 7.6% extra power needed to hit 200 mph sounded like it was there. After the run I confidently walked up to the plane, tripped the readout and the damn thing "said"....1.....9......9...... [:@]
The engine still wasn't hot, the glow plug was frazzled but still able to light up. At no point during the run was there any hint of a sag, it had to be running in the ball park of 30,000. It is still being launched below the usual rpm that the racers go with.
The bad news is the prop broke a tip, the wire that holds the pipe to the engine broke again and the screws that hold the cowl to the plane have burned their way through the FG laminations, even with extra wide washers under the screw heads.
So there was just 1 run today.

iron eagel

Cool!
Sounds like better than 200 is indeed possible...

Mike Connor

My Feedback: (5)

A slight mod to the engine cowl or maybe cowl the elevon linkage. Too close to quit now.

combatpigg

My Feedback: (3)

Yeah...as long as nothing goes snap, crackle or pop, it's just a matter of repetitions now. There wasn't a breath of air out there today to help the speed, either.
The cowl must be vibrating enough to generate heat and chafing action to the hold down screws?
Here is a comparison look at the modified chopped fiber Q40 prop that went 199 with a true CF strand Eliminator prop that has yet to be tried [here].
A photo to compare some of the different props and their subtle differences. The wood prop on bottom is a Q15 prop from way back when.
See how wormed out the cowl screw holes got? Fiberwashers might do the trick?

lfinney

My Feedback: (44)

and use nylon screws as well, but hey your knocking on the door, congrats!, got a prop thats a smidgen smaller, and give it another run, i have very few problems when i use nylon screws and bolts on high rpm airframes, i am using 8-32 nylon screws on my current fun plane, with rpms north of 16k on the ground and zero hole fretting

mk1spitfire

great.!! 199!

What about a lighter battery?

combatpigg

My Feedback: (3)

I'll raid the hardware bins at the store today. Nylon screws scare me a little if the heads snap off. I've been using #2 sheetmetal screws with thin flat washers thinking that I knew what I was doing...they work OK on lower revving stuff if you check them from time to time.

The smaller battery idea is doable, I think...depends on the CG outcome. It has a AA pack now, I think they weigh 5-6 ozs or more? That's like half an engine there.

For now, I'm going to tighten things up concentrating on fixing what broke yesterday...make it better than before and try a run with the Eliminator prop. I think once the magic number gets posted, then I'll be more willing to experiment...even though a 200 reading from a HF? doesn't mean that much, it's still a barrier to cross.

mk1spitfire

lighter prop? more rpm? polish airframe?

iron eagel

Wow, there must have been a lot of vibration or flexing of the airframe to do that.
My guess is there is some twisting of the airframe where the left front hole was blown out. Your cowl probably is under a lot less stress than the airframe so when the stress is transfered to it the holes are what suffer all the wear. This is the type of thing you get running high performance engines, like twisting the frame of a 57 T'bird putting a 390 in it, btdt...

Still it sounds like your going to have the first Demon to pass the 200 mark, great work CP!
Hope everything stays together for you.

Flyboy76

My Feedback: (14)

well Mike... it's ready for covering........ i cannot claim to have built it though. Made a deal with a buddy who is a real good builder and traded him some stuff for building services. It's going to get a TT .46 to start until i'm used to it... then something faster. I've got some yellow ultracote that has chrome spots all over it for the bottom and it'll have white on the top with a couple maple leafs and a very colourful wingtip... should be alright for contrast.

Geoff

MJD

My Feedback: (1)

Well look at that, a naked Demon! The TT .46 will haul it around "just fine". I like my neon wingtips so far.

So.. you don;t want darker on the bottom? I'm not partial to yellow is all, not as a colour but visibilty-wise.

MJD

combatpigg

My Feedback: (3)

The most important thing for me is to tell the top from the bottom. I only want the bright "gingerbread" on top and the bottom to be simply dark. If I get a flash of color, then I know in an instant that the plane is right side up.

Flyboy76

My Feedback: (14)

I could go daker i guess.... i just thought that it would be a good contrast witht he chrome and yellow vs. white and red... thats all. I already been snooping around for a faster engine for it as well... probably just do the shake down flights with the TT .46 then move to some thing faster...

geoff[>:]

MJD

My Feedback: (1)

Hey, those colours might work fine for you. I just avoid yellow as I had a rough time with a yellow model once. If you like it use it!

I painted a huge black "this way up" arrow on the bottom of mine on a white center background, I can see it at about any distance. I posted a pic somewhere here, but I can't find a copy on my hard drive.

MJD

mk1spitfire

Agree, funny my magnum is dark on top and bright pink underneath! The reverse. Fly the dark graphics on top,roll and catch a glimpse of pink.
All about instant recongnition, which ever way you choose.!!