stunthanger.com
Engine basics => Engine set up tips => Topic started by: RknRusty on August 20, 2017, 12:26:50 AM
-
It's a Brodak profile P-40 ARF that I'm just finishing up. Sorry, I forgot to weigh it before leaving the shop tonight, but I think most people's are in the 40s. I always used an APC 12x4 when the same LA.46 was on my 52 oz. Cardinal. I haven't used a 3-blade prop on anything since I was 12 and flying my plastic Stuka.
I just now went eBay shopping and didn't see an APC 11x5 3-blade, so I dropped a Master Airscrew 11x5 and 11x6 in my shopping cart. I haven't clicked the Buy button yet.
Any thoughts on my 3-blade prop choice would be appreciated.
Thanks,
Rusty
-
Hello Rusty
I bought a 12x6 3 blade Master Airscrew to replace the 13x6 APC on my old Enya 60 MkII but when it arrived found it was a narrow blade prop and did not feel keen to try it.
When I have used 3 blade props in the past they were Tornado Greys or the Glass filled Magnum wide blade props which looked the part but are not as efficient as a good two bladder so used them on scale models. Wonder if the LA 46 will run away with the extra pitch but you have less choice with 3 bladders. Realism and prop clearance still seem a good reason to use them on semi-scale stunters. Good to hear your P40 is nearly ready to fly.
Regards Gerald
-
I've got a 3 blade prop on my Brodak P-40 ARF, although electric. If nothing else it looks so much better than a 2 blade. good luck.
-
I tried several of the JZ 3 blade props back in my RC days.
My opinion,while they look good,just won't pull as good as a 2 blade.
Mike
-
Hello Rusty! Generally I try to avoid sharing my experiences / opinions because there are so many variables between models, environments, equipment and even modelers themselves but I can say "give it a try", you may be pleasantly surprised. A few years ago and even until now, I have been building a Claus Maikis model called the Big Tiger. Honestly I endorse the design without question. One of mine uses an OS 40FP with a 2-blade 11x6 and two of them used Fox 40's r/c, with the throttles locked open, and Master Airscrew 10x7 props with greater than expected performance. Recently, because I accidentally broke one of the props and subsequently I mounted an APC 11x6 four blade prop. I was pleasantly surprised and have not regretted the change. Now, that's my experience, for what it's worth. So, in conclusion, my suggestion is try it ;D!!
-
Rusty I asked the same question a while back
Here is the thread with some same and other opinions
https://stunthanger.com/smf/open-forum/excuse-the-assault-please-i-desire-a-three-blade-prop-recommendation/msg486132/#msg486132
On a dare I bought 2 of the very low cost ($6.50) Hobby King Turnigy 3 blade wood 12x5
They are beautiful props but the center sandwich method scares the hell out of me
Description quote "The Turnigy 3 blade Propeller has an Aluminium reinforcing hub in the centre and studs securing the blades together. This is a three piece built up unit and is factory finished to a high standard. Its is lightweight and very strong for use in glow and electric applications."
I do not see the aluminum just looks like grey Epoxy to me
-
It's a Brodak profile P-40 ARF that I'm just finishing up. Sorry, I forgot to weigh it before leaving the shop tonight, but I think most people's are in the 40s. I always used an APC 12x4 when the same LA.46 was on my 52 oz. Cardinal. I haven't used a 3-blade prop on anything since I was 12 and flying my plastic Stuka.
I just now went eBay shopping and didn't see an APC 11x5 3-blade, so I dropped a Master Airscrew 11x5 and 11x6 in my shopping cart. I haven't clicked the Buy button yet.
Any thoughts on my 3-blade prop choice would be appreciated.
How many blades it has is probably less important than the pitch, and you are adding 25% more pitch (with a corresponding drop in the RPM and horsepower). It's an open question whether it will draw fuel sufficiently at the much lower revs. The only thing you have going for you is the reduced diameter, which will cut the efficiency and maybe permit you to run it faster than the difference in pitch would suggest. If you end up flying the airplane faster, that will certainly increase the line tension in level flight.
I would be a bit surprised if this was better (assuming you match airspeeds) but there's only one sure way to find out. It is a pretty drastic change, so you might have to make other changes, too (like a narrower tank, a smaller venturi, or many more layers of pantyhose to recover some fuel draw). I would strongly discourage you from adding head gaskets or other modifications, like the people who will descend upon you to change the exhaust duration and/or "drop the liner".
If you can get it working otherwise, and then you find that you are running a 4-2 break, and the power change at the break is excessive, THEN, add a head gasket about .005 at a time, and reevaluate.
If it was me, I would try about an 11.5-3.75 "flat back" Eather three-blade, specifically, the prop I ground down in the flyoff in 2006, since it's already about 11 7/8 and fuzzy! That would maintain the RPM at near the current value, so fuel draw would be unaffected.
Brett
-
They are beautiful props but the center sandwich method scares the hell out of me
I do not see the aluminum just looks like grey Epoxy to me
You can trust them, the center part is really strong (see picture) and yes, there is aluminum inside.
The biggest concern I felt about these props after I bought few was because of unequal angles between blades. I was afraid about possible excessive vibrations, but in practice they performed just fine. They all came balanced quite well.
Another issue - hubs are not flat and require sanding.
So they are not perfect, but for the such ridiculous price they are totally fine props. I use them on my electric stunt ship.
And.. I think 12x5 would be too much for a LA46, so perhaps try to cut it to 11".
-
Thanks for the replies, guys. I'll let you know what I finally choose.
I'd planned to maiden it today, but we'd have had to use the mild morning time to mow, and then fly in the heat. So we blew it off till Thursday. I would've had to pull an all-nighter to get it ready anyway, so it's just as well. I think I have another thread on it, so I'll do a show and tell over there.
I've never tried the wood Master Airscrews, so I might try one.
Hi Gerald, good to hear from you, I don't believe I've ever seen you post before. Gerald is one of my regular
Video Hangout guests. I'd love it if some of you other guys would drop in or just watch.
That's a cool looking prop you posted, Fred. Cool is low on my list, but it's my first Warbird pattern ship, so... I do like Cool. I'll read that link. Got another couple of replies on it, so I'm interested.
Brett, weakening fuel draw is something that hadn't occurred to me, good tip. As you said, I'll just try and see. I usually use muffler pressure, mainly to close the loop and keep grass seeds and debris out of the tank, so maybe that'll help boost it. Randy says pressure makes them stupid, but I seem to get along with it... give or take a half second.
I plan to use the new Sullivan 6 oz. clunk I bought for my Cardinal kit. I do have a couple of narrower metal tanks, but they're only 4 oz., and maybe a 4.5. Not enough since it might be cool in Huntersville in October. Probably not enough in the summer either. I donated my other good 6 oz. tank to my club's plane, a really old Tutor I flew so successfully this spring and also fixed up before returning it.
With the LA(or any other engine that wasn't originally meant to) I don't care to run a significant 4-2 break. When I plant and pull up for that first wingover, I like knowing it's got the authority to power up and over without worrying if it's going to delay breaking and flutter in the wind.
If I try a few 3-bladers and am still not happy with it, I'll bolt my old reliable 2-blade on it and never look back. Cool be-damned, I'm here to fly, not look good. I just like looking good when it works out.
I'll report back after its maiden flights.
Rusty
-
Three blade? Run a bladder and swing an 8x8 single blade. That should pull it.
Oh and ditch the venturi. Just run the nva right through.......
-
& dont forget 60% nitro .
-
& dont forget 60% nitro .
Still sold by those RC car guys I believe....
-
Lol, y'all don't tempt me, I have all the stuff to slap a bladder on it.
-
The past few flying sessions I have been experimenting with an inexpensive Master Airscrew 10x7 3 blade prop on my LA46. These props pitch out at around 5.5-ish or so on my Prather pitch gauge. The 10x5 Master Airscrew 3 blade pitches out at around 3.8. The MA props are said to be quite easy to repitch using a heat gun or 200+ degree water.
My current airplane is 56oz, 55" span, 600 sq. in., and the LA46 is equipped with a OS LA25 (.257") venturi with the OS NVA, and a lightweight tube muffler. Plastic Sullivan 4oz clunk tank on muffler pressure. 62.75ft, .015 lines (center of plane to the handle) It holds the needle setting nicely and yields a very steady wet 2 run launching a little under 10k on the ground. Pulls consistent and strong throughout the pattern and it does not hesitate or lose any tension overhead. I'm quite pleased with the performance. Note, though, the 3-blade does require quite a bit more fuel to run as opposed to a 2 blade, which should be considered if you are tank limited.
Previously, I was using a 2 blade APC 11.5x4 which also ran well in this plane. Overall, I prefer the better corner of the smaller diameter MA three blade and its run characteristics, so for the near future, it's staying on the plane. I'm quite sure a lightweight carbon prop would be better in every regard, but the MA price sure is nice...
$.02
-
Thanks, Brent. My LA has the same venturi/NV as yours. I have heard the same about MA's pitch.
-
A local flier beats me regularly in Classic with an overweight USA-1 powered by an LA-46. He uses a 12x7 Master Airscrew 3 blade cut down to 11 inches. As stated above, MA props are underpitched. He runs a fast 2 stroke, not a 4 x 2 run. Just FYI and might be worth a try. 8)
-
A local flier beats me regularly in Classic with an overweight USA-1 powered by an LA-46. He uses a 12x7 Master Airscrew 3 blade cut down to 11 inches. As stated above, MA props are underpitched. He runs a fast 2 stroke, not a 4 x 2 run. Just FYI and might be worth a try. 8)
Yeah, that sounds worth trying. I probably don't need all that pitch for my 40something oz. plane, but at their price I can try an assortment. I need one for my Yak-9 Fox.35 too. I have a 10x5 or thereabouts for it but haven't ever bolted it on.