Kit sacrelige.. Bad Baby Birdie mutant
03-08-2017, 08:21 PM
#126
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This isn't a real coat of primer on the cowl. Well, ok, it's real primer, but not a real coat,. 
it's whatever you call a coat of primer you shoot on just to show up all the surface defects. Couple of divots her and there, the nose ring needs interior filling at the top and a bit of recontouring. The back plate is the integral unit for the speed spinner, the 1-1/4" spinner I'll use is a hair bigger and matches the nose ring well.
Oh yeah and I made apple strudel.
it's whatever you call a coat of primer you shoot on just to show up all the surface defects. Couple of divots her and there, the nose ring needs interior filling at the top and a bit of recontouring. The back plate is the integral unit for the speed spinner, the 1-1/4" spinner I'll use is a hair bigger and matches the nose ring well.Oh yeah and I made apple strudel.
03-09-2017, 05:58 AM
#128
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That pipe will never look pristine - I do have a brand new Profi pipe too. This one was used, looked decent enough, but when I did the ice trick to bend the header section I was a total spaz and filled it too far.. and split the seam at the convergent-divergent section joint. After inventing yet another two foul words, I massaged it into shape and joined it with glass and high temp epoxy. Holds great, works perfectly, but looks like it slipped out back end of a stray dog. I'll paint this one, and might suck it up and buy one more new pipe.. I think they are friggin' $95 though. At least I finished the strudel.
03-09-2017, 07:58 AM
#129
That's a new Profi F2A pipe, the one that came with the Profi. I have a used Profi pipe, the same maybe 2 years older, that I bent the header to fit etc, and it looks uglier than this.. but it is the pipe I will end up using. It gives a big performance boost over the stock pipe - took the bench prop from IIRC about 27k to 30k.
The new pipe looks sexier in pictures. I'll probably do something odd like paint the old pipe in high temp or something to pass visual inspection.
The cowl is a standard old school FG speed top, probably used on dozens and dozens of .15 - .21 speed models. The original shape is what - predictably - got people cursing the model's ugliness. It has been systematically whittled down to this. I trimmed about 3/8 off the top of the cylinder section and capped it with ply before reshaping with epoxy filler etc. It's still quite light, well, will be again once I grind and sand a bunch of this outta here. But I'll try to keep a cool intake look.
So the possibility of committing to SMALL this year has a bit to do with the motivation on this, or vice versa, and the Scat Cat etc. Nothing like some pressure. Finances and holiday time are on the opposite side of the scale, but it has definite promise. I miss events, so much independent, local flying here.
If this all works out, it ought to move along okay. Reckon it may be a bit quicker than a TD. The F2A trainer here with all its exposed parts and two lines, does 200kph on the same engine. It's pretty safe to say a small RC model will have no trouble topping that.
Skipper - you giving SMALL any serious thought? Is there an incentive program brewing here?
The new pipe looks sexier in pictures. I'll probably do something odd like paint the old pipe in high temp or something to pass visual inspection.
The cowl is a standard old school FG speed top, probably used on dozens and dozens of .15 - .21 speed models. The original shape is what - predictably - got people cursing the model's ugliness. It has been systematically whittled down to this. I trimmed about 3/8 off the top of the cylinder section and capped it with ply before reshaping with epoxy filler etc. It's still quite light, well, will be again once I grind and sand a bunch of this outta here. But I'll try to keep a cool intake look.
So the possibility of committing to SMALL this year has a bit to do with the motivation on this, or vice versa, and the Scat Cat etc. Nothing like some pressure. Finances and holiday time are on the opposite side of the scale, but it has definite promise. I miss events, so much independent, local flying here.
If this all works out, it ought to move along okay. Reckon it may be a bit quicker than a TD. The F2A trainer here with all its exposed parts and two lines, does 200kph on the same engine. It's pretty safe to say a small RC model will have no trouble topping that.
Skipper - you giving SMALL any serious thought? Is there an incentive program brewing here?
03-09-2017, 09:23 AM
#130
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I first tested the engine on the Uctkam pipe, and while it ran fine, the power jump switching to the Profi pipe was impressive. Static rpm on the bench jumped from about 27k to 30k just from this switch. That was with the old Profi pipe pictured above that has half a coat of white paint and scars. IIRC it was hitting 27 and change on the UCTkam pipe and was heading for 31 before I backed off the needle on the Profi.
The Uctkam pipe has less expansion/smaller max diameter with a large stinger outlet diameter - definitely a trainer pipe. It will likely end up coupled to the header on some sport .15.
They ended up using a Rossi pipe on the Uctkam .15 F2A trainer and picked up some speed. The 5" pitch prop is understandable with the open draggy airframe and lines:
http://www.f2aspeed.org/node/17
The Uctkam pipe has less expansion/smaller max diameter with a large stinger outlet diameter - definitely a trainer pipe. It will likely end up coupled to the header on some sport .15.
They ended up using a Rossi pipe on the Uctkam .15 F2A trainer and picked up some speed. The 5" pitch prop is understandable with the open draggy airframe and lines:
- Tuned pipe. We operated the engine with the stock ЦСТКАМ pipe and with a Rossi pipe. The latter produced faster speed and allowed the engine to pipe-up easier but broke on one of the flights.
- Propeller. The best speed was achieved with a Master Airscrew 7x5 S-2 G/F Nylon Gray Propeller cut to 140 mm (5.5 inches) diameter. With this prop the engine was turning about 30,000 rpm in the air. I suggest starting with 6 inch diameter and cutting the prop until the engine pipes up. Too small propeller will turn a lot of rpm with no thrust. We also tried more pitch (up to 6.5 inches) but this did not result in faster speed.
- With these modifications and settings the system performed quite well. The fastest time achieved in a practice session was just over 200 kph, which is excellent considering the exposed lines, landing gear and no engine cowling. The airplane routinely did around 160-180 kph with a Rossi pipe and slowed down to 150 kph on the stock pipe (on FAI 80/20 fuel).
http://www.f2aspeed.org/node/17
03-09-2017, 06:19 PM
#132
I wonder if the Ucktam pipe is a bit longer than the others? The old Rossi pipes from the 1970s were adjustable for length. Some of the F2A pipes are adjustable with tailpipe sleeves. Those APs are so cool. I just picked up a couple more at a swap meet. An .09 and a .15. I think I got three of each now. My first .15 started to wear the con rod bushing at 25,000 rpm, so I keep it less now. That was on an F2D combat prop. unpiped. The .09 has a lighter piston and may last better. The profile trainer was with no nitro, so no lines and a bit of nitro could get some nice speed. Nitro means more pitch on the prop. More speed!!!
03-09-2017, 07:01 PM
#133
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Mac 1110 with shortened inlet header (went on OPS with SE header)
Uctkam 2.5 pipe
Profi F2A pipe
In same vertical order.
Yes the tuning length of the Uctkam looks longer, also longer fat section, less aggressive profile and large stinger ID.
The beat up Profi on the model is very close to the bottom pipe but an earlier version.
03-14-2017, 06:15 PM
#134
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Almost ready for the paint shop. The cowl is one last spot glaze here and there away from primer. I just need to bolt a sacrificial 1-1/4" disk to the engine backplate and blend in the lower half of the spinner ring, then the fuse is ready for prime. Wing is ready. I polished up the pipe, even the JB Weld on the Dr. Frankenstein repair job shined up a bit. Chucked the stinger in a cordless drill, and with a wad of 4/0 steel wool in the other hand it shined up in no time.
Shoulda taken a picture up the back of the cowl.. the opening forms a crude annular cooliing air outlet with suitably more area than the inlet. With the inner baffling I think it ought to run nice and cool, the air is funneled and squeezed to force it through the cylinder fins like Andy Lennon's book says.
The drawing in the background is a Brodak L'il Satan plan, I'm doodling it up for an RC version on an idiotic urge. (hey why not)
Shoulda taken a picture up the back of the cowl.. the opening forms a crude annular cooliing air outlet with suitably more area than the inlet. With the inner baffling I think it ought to run nice and cool, the air is funneled and squeezed to force it through the cylinder fins like Andy Lennon's book says.
The drawing in the background is a Brodak L'il Satan plan, I'm doodling it up for an RC version on an idiotic urge. (hey why not)
Last edited by MJD; 03-14-2017 at 06:20 PM.
03-15-2017, 05:12 AM
#136
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As they say in England - the first flight ought to be a trouser-clip affair. Maybe I'll skip breakfast that day.
Although I've been fussing with the cowl in spits and spurts for a while, it's been fun, and the first time I've gone to these lengths on the cowl baffling. We'll see how all this goes by the sound of the engine about 30 seconds into the flight I guess.
Although I've been fussing with the cowl in spits and spurts for a while, it's been fun, and the first time I've gone to these lengths on the cowl baffling. We'll see how all this goes by the sound of the engine about 30 seconds into the flight I guess.
03-15-2017, 10:00 AM
#137
Welp hope you vid the maiden the best flight of all flights is the one you remember
and marvel over the big mystery the big heart thumper the wonder the challenge the
soiled shorts hehe... best wishes and happy happy Mike.
and marvel over the big mystery the big heart thumper the wonder the challenge the
soiled shorts hehe... best wishes and happy happy Mike.
03-15-2017, 10:43 AM
#138
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And fyi I just decided not to mess around with the Scat Cat wing covering and stop being such an AR wingnut.. fly the dang thing. So I'll get off the pot and finish off the last few details over the next couple of weeks or so.. no panic, it is still a miserable frozen wasteland up here for the time being.
I can test the Birdie with the Uctkam pipe and a finer pitch prop if I think I need training wheels.
I can test the Birdie with the Uctkam pipe and a finer pitch prop if I think I need training wheels.
03-16-2017, 04:22 AM
#139
At 30000rpm one needs to worry a little about the strength of the props too. Even the Graupner speed props are "only" rated for about 160000/diameter (in inches).
Has anyone seen any max rpm numbers for the MAS scimitar props?
Has anyone seen any max rpm numbers for the MAS scimitar props?
03-16-2017, 05:19 AM
#140
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No I haven't seen info on the MAS. A Graupner speed 6x5.5 prop cut down to 5.5 or 5.25 diameter should hold up fine - they run these over 30k regularly at Speedcup. But aside from that choice, I would be using CF props. Once I get it trimmed out and things seem to be working - the eventual goal is to run a 3x6 single blade or in that size range. Both for the fun factor and for function.
03-18-2017, 11:13 AM
#142
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This is the last step before prime and paint - hooray! I've blathered up the engine compartment with epoxy, and set the motor mount in semi-permanently with epoxy/microballoon/Cab-o-sil paste all around, to homogenize it with the 1/16" ply sides and bottom fuse structure. Don't need anything vibrating loose or just buzzing in situ from play. The engine/prop was pretty smooth on the test stand actually.
So if tomorrow pans out it's prime and base colour time. Klasskote white primer, probably predominantly red and white then some bright neon or gaudy color accents later or something TBD. Maybe find some local kid who's high and hand him some spray bombs, whatever.
I assure you, that is 30 minute epoxy and microballoons you see in there...
So if tomorrow pans out it's prime and base colour time. Klasskote white primer, probably predominantly red and white then some bright neon or gaudy color accents later or something TBD. Maybe find some local kid who's high and hand him some spray bombs, whatever.
I assure you, that is 30 minute epoxy and microballoons you see in there...
03-23-2017, 11:44 AM
#143
Found an rpm limit on the MAS S2 now, there is a fine print in the box that says 165000/diameter (in inch) so quite similar to the Graupner speed props then. The S2 seems flimsier than the older Scimitar props I have from MAS though...
