POWER.. P-60E OR P-70??[]

P100?

Z

Minimum of a 70 but the new p one hunskie would be best. 60 ok if it is real light and you maintain your energy well.

Keep it light...P-60SE with the rpm turned up to 170k.
Vin...

Thanks for info. What is the thrust when P-60SE is turned up??

What is P 1 HUSKY??

Having flown a scooter with a P60 and P70 I would go with a P100 all day long!
Regards Al

P100

1-Husky is Douglish for 100

I have over 100 flights on the Tam A-4 with a P-70. That is marginally enough power for my liking. Like the others have said P-100. To me it's the only option.

About 14.5lbs of thrust. The jet doesnt need more power, it needs to be lighter to fly right. You can have all the power you want but it will be flying like a picnic bench.
Vin...

The weight of the motor is not the whole story though. The way a 60 absolutely eats gas, you have to carry more of it. A 100 might well be just as light with 7 or 8 minutes of fuel on board. I'm sertain that a Wren SS, Merlin 90, or Rabbit would.

Check out the comparison table in RCJI for specifics.

Don.

Yup. Keep the weight DOWN and put in a light weight engine with at least 18 pounds of thrust if you have the luxury. The P-100 is not that much heavier than the P-60 but it has some serious thrust. The P-70, I believe, is a fair bit heavier than the P-100 and drinks more gas than the -100 has a slower accel speed - it's not the perfect engine for this jet IMHO though it has been proven to work OK. The key to long flights and happy aerobatic routines on the A-4 is a punchy engine that is light and efficient, not a big engine that needs more fuel.

Vincent is the master of the whipped P-60 in the A-4 though, I would trust his advice if I were you. If you have to pick from a P-60 or a P-70, upgrade the P-60 to a SE model and whip it to the boosted specs. Just set the timer to 5 minutes or add a 12 ounce aux header tank between the saddle tanks (plumbed just down stream of the main) to deal with the excess fuel burn on the whipped P-60SE for a 6 minute timer.

I fly mine with a Wren SuperSport and the 12 ounce aux header tank. At 18 pounds of thrust, never do I really long for more power - it seems it has the perfect balance of strong vertical, assertive takeoff and low fuel use. I set my timer for 7 minutes and always land with the full aux tank plus a few ounces in the main. Sometimes I take off with half saddle tanks and set the timer for 6 minutes and land a lot closer to half aux tank, the 6 to 7 minute flights are fine with me and the lighter weight is more fun in the first few minutes of flight. But the big thing about the Supersport is it really can sip fuel for the thrust you get.

I've flown Tam's A-4 on electric power at 3 pounds lighter weight. In the pattern it makes all the difference. This thing is so easy to fly when light, though it can't compete with speed and vertical, the EDF shows what a heavy bird is missing in delightful handling and scale speeds on approach.

You also want to watch the speed on the A-4. I don't think you want to take her too fast, limit it to 190-200 (of course 200!) - but for real. The tail can wag a little in gusts, I'm not sure what that airframe is really stressed to do but I beefed up my tail a little in the rudder hinge area just to be safe. I'd hate to see what would happen on that big A-4 rudder if you over sped and got some flutter. It could be extremely ugly and dangerous in about 0.002 seconds, but plenty of guys are running it safely and repeatedly at legal speeds on fast P-60's, Supersports, P-70's, etc. A stock P-60 is not going to take this A-4 above 160 straight and level IMHO so you are safe there, but getting to that speed is gonna take 1/3 of your tank!

Thanks .Any secrets to keeping it light? looks like wren MW-54-ss,, is the best combo. Just missed one for sale ,cheap.. I had a kingteck for it . Great engine. Ithought it was to heavy and used to much fuel. What is "max" sport flying weight? I seen 17.5 to 20 lbs. 18.5 seems most comon.. thanks

I wouldn't say the SS is the best bar none... even though I'm happy with mine, there are some nice engines out there. The P-100 looks very promising. There are other 18-20 pound thrust engines too. Look at total installed weight. The P-100 doesn't have all the extra stuff like fuel and gas solenoids, everything has really been cleaned up and the kero start is probably worth a few ounces of weight hit in convenience. Make an engine choice for this model primarily but also look at your next jet too, it's not super critical. Don't sweat a few ounces here and there as long as fuel burn is good.

The 2 biggest things I can say that will save weight is 1) the engine choice and how you mount the engine, and 2) careful planning to mount as much stuff in the nose as humanly possible. I mounted my engine very far forward. Not just forward on the rails, but I modified the forward engine mount rail rail bulkhead to accept the engine stuffed very far forward, much more so than an unmodified bulkhead will allow. I also modded the ducting to accept the starter housing and FOD screen. I had to have Tam make me a custom pipe for this though - the P-60 pipe isn't big enough for the higher thrust first off and second the length had to be longer to accept the forward position so the P-70 pipe wasn't long enough either. You may ask, "how is that going to save me weight if I use a heavier engine and just mount it forward; the engine is still aft of the CG isn't it?" Because the stock position for the P-60 vs. the modded position of my heavier engine actually favors my heavier engine as far as CG moment arm and counter weight required in the nose to attain CG. It will help. Do not be tempted to put your UAT in the nose though. If you somehow get air bubbles in it you are going to crash and not know why (major aft CG if you get air bubbles). My UAT is part of CG ballast but it's not so critical, it's located on the right side just aft of the canopy opening and equipment tray.

Make your nose equipment tray permanently mounted to the airframe. The nose cone will just be a fairing that is removable to service the batteries, fuel pump, etc. The permanent mount forward tray makes it possible to stuff a lot more equipment up there; it really moves installed weight forward. I use twin A123 2200mah battery packs for the Smart Fly battery bus. My FADEC battery is in there too. Even my solenoids are in the nose. I don't have an on-board starting gas tank, I have an off-board one. I use a festo quick disconnect and a manual on-off valve that arms the tank for the normal engine auto start. This saves space and reduce crash fire risk (debatable). That also saves me about 5 ounces of tubing, tank and mounting equipment. It all adds up. The biggest weight saving for me is I have absolutely zero lead in the nose. Some guys have nearly a pound of dead weight in the nose. My install is not quite as pretty, because it's really crowded in the front end. But it's effective - where it counts is when the engine is running. I also am using Tam's personal CG position of dead center on the forward wing tube. That's just a little aft of the normal CG position Tam shows. I find it suits me but I'm not telling you to use it, you'll have to make that choice. But that allowed me to take out all ballast I originally had (a couple ounces only).

+1, it's real easy to push this airframe past the limit, p-70 + left stick in the ON position too long = folded wing (all my fault, not the airframe)




this airframe is also VERY sensitive to CG changes, a 1/4" can make all the difference in the world of a great flier and a brick.

Dang KC, sorry to see that. Thank you very much for posting. I hadn't really considered that part of the wing as an "inspection" point, but I will now. Another great point about airframe speed. Did you get a chance to look at the break inside - did it show any clues that might give guys with good wings something to look for? Did you have hard points on the underside? (some I've seen thought compromised the wing a little).

Raptor, since we are showing pics, here are a couple in regard to what I had mentioned before. These were early in the build, I changed a few things for final installation but it's the same idea.

the wing was built great, the aileron hinge blocks weren't glued the best in the world, but that didn't cause the problem (even tho they let loose during the event), i just pushed it way too hard and the wing folded (in level flight, it hadn't had hard G's), fortunately the airframe was the only loss as i was able to belly her in at a reasonably slow speed.

GONNA DO A P100 J/C /.FITS ALL MY MODELS NEEDS. I DONT KNOW HOW MUCH FUEL IT WILL USE YET.. THANKS FOR IN FO. I WOULD BUY A 54SS IF ANY FOR SALE.. NOW ITS A WREN 00.