exocet-RCU

My Feedback: (1)

Yeah, MJD, I kind of figured that. But I can't find any 7X3 molded props right now. I've looked at the three main hobby shops in the Twin Cities and no one has them. I''m thinking an 8X3 won't be any better than the 7X4s I have now.

Tim

Mr Cox

I don't quite understand why you would want 7x3.5 props instead of the 7x4?
That would give you a low load and just require higher revs to get some speed. The engines are perhaps more happy on higher loads actually, with the 7x4 being the lowest suitable load. So can you not use the throttle instead?

The best 7x3.5 props I know of are perhaps the cox ones but they are becoming very rare now...
The wooden Rev-up 7x3.5 props are very nice though, very thin blades compared to e.g. MAS props, and are sold by Brodak (or at least used to be).

1QwkSport2.5r

Have you tried Hobby Warehouse in Richfield? They have by far the best prop selection in the cities. I've gotten 7x3 MA Scimitar and 8x3 MA combat props there when nobody else had them. Hub and Sky hobby have a good selection but only in the bigger sizes.

exocet-RCU

My Feedback: (1)

MR Cox, I was concerned that the 7X4s were too much load so was thinking of the 7X3s. I don't want to overheat the engines. I see a previous post from you stating that (as you did in the last post) that 7X5s might be a better option. I think I will try that as well. QwkSport, that's the place I usually go. They didn't have any. Maybe they've got some in now.

Thanks all.

MJD

My Feedback: (1)

7x4 is totally cool on the .09's. I concur with 7x4 or 7x5. Hard to say sometimes, that is a lot of airframe for the engines,

exocet-RCU

My Feedback: (1)

Flew the Skylark on Saturday on the 7x4s again. It flies but is underpowered for sure. Not sure if the 7x5s will help that or if it is just going to be underpowered. Thing is, I don't think anything bigger will fit in it and, with 2 ounce tanks in the nacelles, I can't go much bigger. Maybe a .15?

MJD

My Feedback: (1)

Is it airspeed or climb that tells you it is under-powered? A pair of mild-mannered .09's might never get you much in the may of vertical.

4” pitch props at 14k or so are going to produce a top speed of around 50mph at best – if the power is there to do 50mph. If the aircraft is significantly slower than that then perhaps the slippage indicates the problem is disc area, not pitch speed. In which case what are you gonna do – fit 8-3’s, they will pull harder at lower airspeed but might get you in the 40mph range at best if those engines can get them up close to the mid-teen’s.

If it is flying around now at 45-50 mph now, then maybe you do have the power to go faster, so the 7-5's might give you a bump in performance.

Or I'm off my rocker and you should just try the 7-5's and 8-3's if you can find them and see what happens, it's all voodoo

By the way how much does it weigh and what are the wing dimensions?

gcb

IMHO the prop(s) should be chosen to match the airframe, then the fuel and plug should be chosen to adjust firing time in the engine for maximum power. You can adjust prop, fuel, and plug for best results for a given day (temp, humidity) at your location. Fortunately, our engines can perform under a wide range of parameters. The more high-performance your engine, the narrower the range for peak performance.

I would suggest trying several props, including your wood 7x3.5's. Don't overlook trying 8x3's.

George

Pond Skipper

Maybe prop design will make all things better

The MA have a lot more cord area and wont let the engines unload once your at speed and the throttle response
will be slower.

APC 6.5 x 3.7 with 25% nitro.

MJD

My Feedback: (1)

I wasn't going to comment on MA props - haven't used them since I can remember. I recall checking like for like against each other (i.e. MA vs APC 10-6) and always getting the impression the APC's performed a little better, so was left with the opinion that APC are generally more efficient. Plus, they have about 100 more choices.

If (harnessed) power, not airspeed, is the issue, then 8-3's might work well. If you're sucking for airspeed and feel there is more to be had, then I'd be fooling with 7-5, 6.5x3.7, 7x3.5, i.e. various combos that have same or similar diameter and a bit more pitch speed could be the answer. Will be interesting to hear. Or a pair of good .15's.. but 2oz fuel will leave you wanting 3 or 4 oz when you spend a lot of time over half throttle. Bindur Dundat with an FP .15 on a small model.

exocet-RCU

My Feedback: (1)

So the current MA props (7X4) are the Scimitars, not the regular style. I have some APC 7x5s and some MA 8x3s (combat props) so I think I will just have to try those. The plane is really stable but it has a very slow climb rate and top speed is definitely below 50 MPH. Unfortunately I will be going on vacation Friday for a week so won't have time to test any of these theories until I get back. I will keep you all posted, though.

Thanks.

Tim

MJD

My Feedback: (1)

Well, it flies don't it? So that's a good start. Who knows, maybe two Enya .09's busting their balls on the best prop simply aren't going to knock you out on this airframe? You have two good prop candidates, will be interesting to find out what flight tests have to say about it when you get the chance.

exocet-RCU

My Feedback: (1)

Agreed. I don't expect a rocket but am hopeful I can get a bit more of a gap between full speed and stall speed. Now its just a bit close for comfort. But man does it turn heads when you fire it up. I suppose the other thing I could do would be to put a couple of those old "torpedo" style mufflers on it, which are basically made for looks anyway. Not only would it be louder but probably gain a few hundred RPM as the muffler doesn't actually DO anything


Tim

1QwkSport2.5r

They usually do wake up sans muffler, but these days noise is a problem at many club fields. I'm sure the day I show up with one of my Jett's will get me in hot water with someone. They are not exactly subtle in the noise department.

Tim - it seems we have a mutual flying friend. I'm Todd's other buddy Tim.

exocet-RCU

My Feedback: (1)

Tim, I have heard Todd talk about you. Glad to meet you. Where do you normally fly?

Tim

1QwkSport2.5r

Wherever Todd flies. Haha. I am not a member of a club yet - I'm still getting my feet wet learning to fly. A few weeks ago we flew his ultra micro T-28 and his little Blade Heli at the park by his house. He and I flew some planes at TCRC a couple years ago too. We buddy boxed on his Skyraider which was the first time I actually flew a plane. I picked up a T-28 myself to learn on but haven't had time to get out to fly it yet.

Good to make your acquaintance as well. One of these days we'll have to get together and hang out. He's talked a lot about you too.

exocet-RCU

My Feedback: (1)

Well, 8X3s aren't the answer. They caused the engine to run way to hot and hard. May just have to do some more significant mods to the nacelles to accommodate .15s. Well, live and learn.

Pond Skipper

APC 6.5 x 3.7 with 25% nitro.

MJD

My Feedback: (1)

My personal experience with .15's is that I can live with a 3oz tank if i have to concede on fuselage space - if the airplane is also fun to fly at half throttle part of the time. At 2oz it goes over the line and becomes annoying.. I would use a 2oz tank only where it is the obvious choice - a motor glider, flight to altitude and shut off for example. Or some over powered little fun thing where you want and expect a shorter but more intense/stressful flight for laughs.

My thoughts here is that this airplane is obviously underpowered with those .09's, so it won't be a rocket on .15's but it will be adequately powered for sport flight. At 3oz you'll certainly notice the capacity if you spend all the time at full throttle, but the compromise isn't a big deal I find, just don't get low slow and messed up 5 minutes into the flight.

1QwkSport2.5r

I'm not so sure those little Enyas are going to tolerate 25% nitro without shimming the heads a bunch. I've run 15% in my .15s on the ground, but I'm not sure they'd behave in the air without a shim or two under the head. Most Enya's don't like much nitro usually.

Tim - bummer the 8x3s didn't pan out. Do you have a pair of Schnürle ported .15s? The Schnürle engines edge the crossflow/baffle piston engines (like the Enya .09s) out on power usually, unless you're crafty and can do some DIY Perry Directional Porting on them. The liners are thick and incredibly hard so you'd need a small horde of cutting bits to do the work. Probably not the most economical route to go if you have stronger engines already.

MJD

My Feedback: (1)

I think the 7-4's are probably close to the best prop for those .09's, but the engines are just at the lower limit for the airframe. The total hp is what it is.

So far the Magnum .15 XLS I got recently is turning out to be a good sport engine, it powers the 2lb Mini Contender really well (longggg vertical and it will hover though I am a spaz at it) and seems okay on fuel consumption too. In fact I use a Hayes 3oz on this airplane and the capacity doesn't bother me because it's fun at 1/2 throttle and full bore. Mix it up and flight time is fine.

exocet-RCU

My Feedback: (1)

Thanks, MJD. That might be an option to consider. Also thought of finding some gently used or NIB OS .15 FPs. They seem to run nice right out of the box, transition well and would have enough power. I'll look at the Magnums too.

Tim

MJD

My Feedback: (1)

If they were in production I definitely would have suggested two FP .15's. Great little engine. I have one very well used and loved, and one recently snagged mint NIB.

BTW - I have a buddy who for some time has wanted to find a pair of .09's or .10's for a Catalina twin.. .15's too big he says. So.. are you keeping or ditching them? If letting them go I can contact him.

049flyer

My Feedback: (18)

I would use the OS FP or LA series of engines, they may not have quite as much power as the Magnum but they are much lighter. I would guess that the OS .15 is about the same weight as the Enya .09, I love Enya engines but some of them are a bit on the heavy side.

I also find OS and Enya carbs to be the best in the industry, easy to tune and reliable. The Magnum carbs can be inconsistent, some OK and some horrible.

I gave up on a recently purchased Magnum .15, never could get a reliable idle. Only the second or third engine in my 50 year modeling career that I can ever remember giving up on. Sold it on Ebay and yes I mentioned my problems in the sales listing.

exocet-RCU

My Feedback: (1)

MJD, If he's interested, I'd let them go. I have 5 of them sitting around. I think. These were fully broke in but, I must say, running them with the 8x3s got them pretty hot and discolored the heads a little. Not sure if he cares about that. They ran fine on the 7x4s again when I switched back to them so I don't think the heat damaged them. Let me know he wants them and we can talk. I'm always interested in trades, too.