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  1. #1
    MJD's Avatar
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    Another promising glow conversion lekkie candidate. And Merry Christmas too!

    This just makes more sense every time I look at it. The Blink can wait, the scratch built .049 speedster can wait, and the Profi .049 is going straight into this thing.Why piss around?

    128 sq in
    MH43 airfoil
    All-moulded construction with live skinned hinges
    Airframe + Profi .049 + prop and spinner nut = 205g
    2 channel flight pack: 300mAh 2S LiPo, 3A regulator and switch harness, 6ch lite receiver, 2 x 8/9g servos = 53g.
    Add 15g for the bladder tank and that's a total of 273g = 9.63 oz.

    Round it up for incidentals and you get 10oz for a wong loading of 11.25 oz/sq ft. That all works for me.

    Next move is to fit the engine. I reckon I'll be sawing the top half of the fuse off back to firewall location, fitting a mounting plate and firewall, blending this into the fuse, then sealing the engine off with tape to form a plasticine cowl plug.

    I ran the engine once, indoors so no tach, but it spun the snot out of a 4.2x4 APC. I am impatiently waiting for the piped version to emerge, but still no word. Maybe R&D isn't going as well as hoped, the target release date I last heard was Jan 2013.

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    So that's my hybrid 1/2A / "extreme speed" forum project.

    I just finished my wife's Christmas present about ten minutes ago. A shadow box display of her mother's baptismal certificate, her mother's infant ivory comb and brush set, and a four-generation photo portrait of mothers, starting with her mother as an infant. I am quite pleased with my handiwork, though I was getting anxious earlier, I have trouble with things that aren't airplane parts. I'll reserve final judgement until I see it with clear eyes in the morning.

    So to all of you here that celebrate Christmas, have a wonderful Christmas, I have some wrapping to do then off to bed finally. If I was still drinking I'd be on the second quart jug of egg nog and the rum bottle would be seriously depleted by now. To the rest of you, happy holidays and safe travels. I snagged two weeks off, my wife is a teacher and is off until the 6th, so now I get to do chores for another week and a half.. ;-)

    Oh yeah and Santa came early - I opened the post office box to find a pair of NIB OPS FIRE ducted fan .45's, snagged off the classifieds for a reasonable figure. Another delta project is in the cards I see.
    Last edited by MJD; 12-25-2013 at 01:46 AM.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  2. #2
    aspeed's Avatar
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    I like your Profi better than my Fora. I was hoping to put a pipe and carb on mine, but it doesn't allow for that. Yours would be fine. All you really have to do is shim up the liner somehow to get 180 degrees exh, and find a pipe. Likely about .020"? Unfortunately you would need to remove that amount from the top of the liner to keep the same compression, maybe a bit less because you do want less compression with a pipe. You could still go back to stock this way. CS has a pipe, or you could try Hobby Planet. We need video of your plane flying when you get it going. There are people that have to see this. I have a scale just like that one, I don't use it any more, I got the digital Crappy Tire one when it was on sale for $10. It goes lbs, oz or grams.
    Last edited by aspeed; 12-25-2013 at 09:30 AM.

  3. #3
    MJD's Avatar
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    For now I'm content to run open exhaust, and see where that goes. Again, the delayed release means I can't help thinking there are developmental problems.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  4. #4
    aspeed's Avatar
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    You will have your hands full even without a pipe. It may even fold up the wing the way it is.

  5. #5
    MJD's Avatar
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    No way. This airframe has been flown as a lekkie over 180 mph. The wing loading of this setup will be significantly less than electric. I was worried about it when I was thinking of dropping an F2D .15 in the nose, but not with the Profi .049. For the .15 will go up to a bit more wing.. maybe 160-200 squares on a very rigid wing.. Sun Racer IV or a bit bigger, that kind of thing. Looking at the Profi Junior .15 as an alternative to a combat engine.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  6. #6
    aspeed's Avatar
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    I was told the Profi and Fora .049 put out about the same power as a sport .15. Is the Profi Junior .15 the F2A (speed) piped one? Because they are going 200 mph with thick lines slowing them down.

  7. #7
    hllywdb's Avatar
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    Who makes the plane? Looks like a lot of fun with the Profi! Any target as far as speed? Inquiring minds want to know

  8. #8
    MJD's Avatar
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    If was to state a general target of mine, it is to achieve 150mph on an .049. I think that will not prove too difficult. I believe some figure like 165-170 could ultimately be achieved. However will be happy to get whatever I get with this combination. With this aircraft I simply want to get a feel for how much airframe this engine can pull around. By all accounts, this is a small airframe for a 1/2A engine at 128 squares and 7.2 oz less radio. I'd put five bucks on 140.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  9. #9
    MJD's Avatar
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    Quote Originally Posted by aspeed View Post
    I was told the Profi and Fora .049 put out about the same power as a sport .15. Is the Profi Junior .15 the F2A (speed) piped one? Because they are going 200 mph with thick lines slowing them down.
    It's not their top end F2A .15 as understand it. Still have to find these things out. I have no doubt that 200mph+ is realistic for a .15 RC model. It might take an F2A engine to do it though.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  10. #10
    hllywdb's Avatar
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    My calculator says a 5" pitch at 32K will get you to 150. The airframe is slick enough and at 10oz it's not going to need a ton of thrust. Just going to be a matter of prop choice to keep the motor happy.

  11. #11
    aspeed's Avatar
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    I believe the Junior can do as good as the others in the right hands. They are just sorted through at the factory, and the faster ones sold for more money. I could be wrong. If you get in a dive you can get some pretty good speed if you were almost on the pipe before the dive. There would be a lot of testing with pipes I am sure.

  12. #12
    combatpigg's Avatar
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    I think the size of the plane at that weight is right in the sweet spot for some thrilling flights.. Just keep it on a short leash until you start to get your "1000 yard stare" dialed in.
    WHO GUNNA FEED MAW KEEEIDS..???

  13. #13

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    I have a plane close to that one with a Norvel that turns that prop at 29,000 and it is right around 120-125 at 11 ounces. you will need a good throw on the launch with it. you loose a bunch of speed over the elctric version with the head out in the airstream like it is. you can add a small balsa block behind the engine to fair it some and helps.
    AMA # 126183
    Fly light, fly fast and fly low.

  14. #14

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    one thing I would like to try one day is two of those wings to make a small biplane for a 15.
    AMA # 126183
    Fly light, fly fast and fly low.

  15. #15
    MJD's Avatar
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    Quote Originally Posted by airraptor View Post
    I have a plane close to that one with a Norvel that turns that prop at 29,000 and it is right around 120-125 at 11 ounces. you will need a good throw on the launch with it. you loose a bunch of speed over the elctric version with the head out in the airstream like it is. you can add a small balsa block behind the engine to fair it some and helps.
    I plan to go the full Monty by forming a full speed top cowl by making a plug out of some profile plates and plasticine - no sense going halfway. With the output of the Profi and some streamlining I would be very surprised if I could not reach 140, and will be very pleased with more. I may find out otherwise but I have a feeling 150 is realistic with some effort. Apart from the 4.2x4 I have some 4.125 x 4.5 and 4.125 x 5 CF speed props. If I streamline the front end enough I should be able to get rpm back up by trimming those a bit and still have enough disc area. My .061 turned the 4.125 x 4.5 at about 32k static as I recall.

    If the Junior is 90% of a current top end F2A engine I'll be content with that. Even though the Euro crowd has reported mixed results with converted electrics, I think that if you choose wisely it is a great way to cobble up a speed project without starting from scratch.

    Here's a question showing my ignorance of current F2A flying - are they running crankcase or pipe pressure? I couldn't find anything in the sporting code saying what was required in that regard.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  16. #16
    aspeed's Avatar
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    F2A rules allow any pressure you want (no superchargers or turbo of course. I used pipe pressure but it would never be rich enough for a good run. The hot way was backplate pressure with a centrifugal fuel switch which would often leak. I never had that problem on mine. It was essentially a spring loaded weight that would open up when sufficient centrifugal force was achieved. It would basically open the fuel line. When on the ground and in the dolly, a set screw would lean it out enough to take off. Now they just use suction on I think a uniflow tank. It still needs to be richened a lot in the air, so the motor is mounted sideways which gives room to mount the tank significantly inboard, enough to richen itself enough to get a good run. The tank is adjustable in and out to calibrate this. I personally think a bigger venturi can be used with the old way, but hey they can go 200 mph now, and I never could. It often requires a good whipping to get the plane on the pipe with the suction. Oddly enough, the AMA rules don't allow whipping really at all, so the A speed class can be a bit harder to get a good run, and there is no shutoff with monoline so a burndown is more possible. A shutoff is manditory in F2A speed. I should mention I haven't flown FAI since 1980 when I quit because I couldn't run fast enough. They since lengthed the lines, but are faster now, so I still can't run that fast. (out of the pylon, I could fly it normally though) For an rc plane it will need to be richened a fair bit in the air, from the ground setting for a proper pipe setup.
    Last edited by aspeed; 12-27-2013 at 02:53 PM.

  17. #17
    MJD's Avatar
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    I would lean towards crankcase pressure + IMC. I believe the wee bit of extra real estate and ~15g weight is worth it for an IMC. A sub-micro servo is sufficient. That way you can lean a bit for launch then start opening up fuel flow in the air as needed. IMC + servo + fuel tank is lighter and roughly similar size to the lekkie ESC + battery combo.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  18. #18
    aspeed's Avatar
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    I think the IMC is only needed if you use the piped one. I suppose it is extra insurance against a lean run on an unpiped one too. You could also richen it up like crazy for a kind of throttle if you get in big trouble too.

  19. #19
    MJD's Avatar
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    Yeah, I meant with a piped speed .15 in the nose, definitely IMC. Better than launching staggering rich and hoping you got it right, or some kind of richening mechanism. Just use a tiny IMC and servo - voila. Set it up on the ground using a bench prop.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  20. #20
    combatpigg's Avatar
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    A back plate mounted, diaphram actuated pressure regulator would allow surplus fuel pressure from a latex bladder delivered to the engine in perfectly timed shots. You could launch "on the pipe" and have it set close enough on the ground to allow for decent launch rpm and unloading afterwards.
    I have a few for .36 sized engines and they are pretty intricate, so building one for a .15 might take a Swiss watch maker's skill to do it right.
    Last edited by combatpigg; 12-27-2013 at 10:14 PM.
    WHO GUNNA FEED MAW KEEEIDS..???

  21. #21
    MJD's Avatar
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    I need to move the engine back, with the engine forward of the stock firewall the CG can't be adjusted correctly with battery shift. So I can either move it back to submerge the engine lugs in the fuselage and leave the forward end out, and blend the fuselage down to prop hub diameter and run spinner nuts. Or, move it back a bit more and run a Brodak 1" Al spinner, locating the engine so that the fuselage lines can be smoothly extended forward to meet with the spinner. . So I lean towards the KISS route and blend the fuselage into the prop hub, and just run the spinner nut. Not sure how fond I am of the idea of running a spinner on this little fellow, wish there was a 3/4". Any comments/advice from experience?
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  22. #22
    combatpigg's Avatar
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    I've never used a hollow spinner on Cyclon or Fora powered planes. The cowls can still look pretty cool if you simply neck them down in front but leave a gap for air entry past the spinner nut.
    On the G&Z speed engine, the spinner ran perfectly. I think it was about 3/4 in diameter but the backplate would most likely need to be adapted to other brands of engines..
    WHO GUNNA FEED MAW KEEEIDS..???

  23. #23
    MJD's Avatar
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    I posted this in the wrong thread.. but nobody noticed anyways .

    For the sake of continuity I copied it over here where it belongs.

    Let the butchering begin. The engine looks a lot bigger when I place it in the mount, that's encouraging. The airframe seems more and more suitable the more I putz with it.

    Attachment 1954032Attachment 1954033

    I have to get out the epoxy filler and very slightly blister out the sides to accommodate the mounting lugs. Then to form the half cowl underside the engine, then an exhaust tunnel, then time to get out the profile plates and plasticine to form the plug for the top cowl. Should look like something in about 6 weeks..

    Update: this morning, said a bad word or two, then scraped out all the semi-cured epoxy filler and backshelfed the containers - too much settling and crystallization so it ended up off-ratio. Should have reconstituted it properly first. Cleaned off with solvent and sandpaper and started again. Mixed up a different batch of lite epoxy filler and redid it. It's curing suspended over the woodstove at the moment, it's overnight cure rate stuff so now to patiently wait until the morning to break out the sanding block.


    Click image for larger version. 

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    It was very evident from this placement that mounting to the stock firewall would have resulted in a forward CG even with the battery and elevator servos stuffed as far back as possible. So a bit of extra work is worth it. Net I'll cut a ply profile plate to screw to the mount, that tapers parabolically to the prop driver OD, screw it down and use it to shape the lower section of the cowl from lite balsa. No need to go silly with composite for this part, I'll just hollow it and apply 3/4oz glass.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  24. #24
    MJD's Avatar
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    I posted this in the wrong thread.. but nobody noticed anyways .

    For the sake of continuity I copied it over here where it belongs.

    Let the butchering begin. The engine looks a lot bigger when I place it in the mount, that's encouraging. The airframe seems more and more suitable the more I putz with it.

    Attachment 1954032Attachment 1954033

    I have to get out the epoxy filler and very slightly blister out the sides to accommodate the mounting lugs. Then to form the half cowl underside the engine, then an exhaust tunnel, then time to get out the profile plates and plasticine to form the plug for the top cowl. Should look like something in about 6 weeks..

    Update: this morning, said a bad word or two, then scraped out all the semi-cured epoxy filler and backshelfed the containers - too much settling and crystallization so it ended up off-ratio. Should have reconstituted it properly first. Cleaned off with solvent and sandpaper and started again. Mixed up a different batch of lite epoxy filler and redid it. It's curing suspended over the woodstove at the moment, it's overnight cure rate stuff so now to patiently wait until the morning to break out the sanding block.


    Click image for larger version. 

Name:	MM2.jpg 
Views:	17 
Size:	128.0 KB 
ID:	1954298 Hurry up...!

    It was very evident from this placement that mounting to the stock firewall would have resulted in a forward CG even with the battery and elevator servos stuffed as far back as possible. So a bit of extra work is worth it. Net I'll cut a ply profile plate to screw to the mount, that tapers parabolically to the prop driver OD, screw it down and use it to shape the lower section of the cowl from lite balsa. No need to go silly with composite for this part, I'll just hollow it and apply 3/4oz glass.

    I still think a very small Al spinner would be better, but the smallest I can find is the 1" from Brodak. For 3.8"-4.2" dia this is a bit big I think.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231


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