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1/2A THRUST-O-METER

Old 09-11-2009, 05:27 AM
  #51  
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Default RE: 1/2A THRUST-O-METER

ORIGINAL: BTerry

CP, is there a Master Airscrew prop that works on the Norvel .074? I know the APC 7x3 seems perfect, but I want something a bit more durable.

One of these days I will build something, put this engine in it, and bring it over to your side of the Sound for show and tell!

MA makes a 7X3. In fact, I prefer it to the APC in that size only. It gets more thrust on the .074. In all other sizes on all other engines, I prefer APC.

I see you're in Silverdale, WA - I'm in Silverdale, BC.
Old 09-11-2009, 10:33 AM
  #52  
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Default RE: 1/2A THRUST-O-METER

I agree that the MAS is the better choice here. There's other examples where the MAS seems better than APC. I swear that right now the MAS 6x4 cut down to 4.2" pulls better than the APC 4.2x4. I was "making" MAS 4.2x4s before I knew about the APC product, but then flocked to APC like a good little lamb until recently. In the last few outings I've compared the 2 props 1 flight after the other and like the cutdown MAS slightly better. On a different airframe, different rpm regime, who knows?
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Old 09-11-2009, 10:47 AM
  #53  
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Default RE: 1/2A THRUST-O-METER

What if I do not need high speed. Instead I would like to have better low speed authority. Is MAS 6x4 or cut down MAS 6x4 will be suitable for 061?
Old 09-11-2009, 11:03 AM
  #54  
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Default RE: 1/2A THRUST-O-METER

If you don't want speed, stay away from 4 pitch props. Go with a 6x3 and the average plane will do no more than 40 mph in a dive. If you have no choice and only have a 6x4 available, it will run on a .061 engine and you would NOT see much of a speed difference, except maybe less speed if the engine is weak. The biggest difference is that a 6x4 will wear out that engine sooner than a 6x3 with hotter runs and less of a "happy place" to set the needle valve.
The best prop for going slow would be the 6x2 or 5.5x2. I learned how to fly control line planes with a 6x2 on a Cox .049. The 2 pitch props should keep any model in the 30 mph zone.
Old 09-11-2009, 11:39 AM
  #55  
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Default RE: 1/2A THRUST-O-METER

Thanks for advice. I'm going to build and fly Tiger Sport with it. I have BigMig 061 and BigMig 074, both new. I do not have any props yet except MAS 8x4 which is too big of course. I'm going to order bunch of different props so please clarify, are you talking about MAS or any brand (Cox, TopFlight, Zinger, APC)? I can't buy 1-2 prop at once because delivery cost and time. Can you give me preposed list of which props to get in advance?
Do you know someone who flown TigerSport?
Thanks,
Kostya
Old 09-11-2009, 12:05 PM
  #56  
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Default RE: 1/2A THRUST-O-METER

For the .074, buy MAS 7x3s. APC would be your 2nd choice. If you can find a soft nylon Tornado 7x3, it will never break and the performance is OK.

For the .061, buy Cox 5x3s and 6x3s from Xenalook...buy the rubber props. 2 of each should last you a lifetime. If you crash, just straighten the prop out.

The APC 5.7x3 might be the best for .061s, but they are fragile. Think of this prop after you refine your taste.

The soft flexible props I suggest are practical so that you will not need to constantly order new ones.

The local pylon racing record is held by a rubber 5x3 on a AME .061, not the hard plastic prop.
The thinking is that the blades flatten when the airplane turns [keeping the rpms up]. With a typical .049 engine, you will not have to worry about setting speed records with a 5x3, but as you gain experience flying, you will like the 5x3.
Old 09-11-2009, 12:41 PM
  #57  
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Default RE: 1/2A THRUST-O-METER


ORIGINAL: combatpigg
I agree that the MAS is the better choice here. There's other examples where the MAS seems better than APC. I swear that right now the MAS 6x4 cut down to 4.2'' pulls better than the APC 4.2x4. I was ''making'' MAS 4.2x4s before I knew about the APC product, but then flocked to APC like a good little lamb until recently. In the last few outings I've compared the 2 props 1 flight after the other and like the cutdown MAS slightly better. On a different airframe, different rpm regime, who knows?
CP,

The performance of the cut down MAS compared to the APC is probably all in the tip shape. APC has narrow little tips with reduced pitch, while your cut down MAS has big old paint stirrer tips at more or less full pitch. So larger effective prop chord and higher pitch out at the tip wins.

(or at least it sounds good)

Got an APC 7x3 on the .074 for the little yak I built, need to grub around in the box for a MAS 7x3 and see how that does.

Duke
Old 09-11-2009, 12:44 PM
  #58  
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Default RE: 1/2A THRUST-O-METER

I'm not sure what you mean by "rubber". Are they really rubber? Are you talking about these : http://cgi.ebay.com/Cox-049-051-Mode...4.c0.m14.l1262 ?
I have some of these 3 blades http://cgi.ebay.com/12-K-B-4-X-3-3-B...d=p3911.c0.m14
Are they good? (I wouldn't call them rubber...)
Thank you,
Kostya
Old 09-11-2009, 01:59 PM
  #59  
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Default RE: 1/2A THRUST-O-METER

The only blanket statement I think you can say about props is that you will never know until you try. When you go up and down the entire list, APC has done an incredible job of doing their homework. Each and every size of their props has a real time application or they will phase it out.
I like the way they have the web site set up now, you can either browse by category or just go up and down the list in order of size.
Old 09-11-2009, 02:05 PM
  #60  
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Default RE: 1/2A THRUST-O-METER

Salat, I am not sure what he means by "medium stiff". You should contact him.
I have never tried K&B props, I have not ever seen one.
Old 09-11-2009, 02:49 PM
  #61  
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Default RE: 1/2A THRUST-O-METER

How you would comment on 4-¾ X 3 3-blade prop at all? Can I break in with it?
About APC. They have many props which are looks suitable for IC but marked as E or SF. Is it safe to run them on IC?
Old 09-11-2009, 03:47 PM
  #62  
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Default RE: 1/2A THRUST-O-METER

I'll bet it works good on a model that is aerodynamically clean and light, like a 200 square inch [or smaller] plane. It wont pull a larger plane as well, but it should work to some degree. Give it a try if you already have it..
Old 09-11-2009, 04:41 PM
  #63  
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Default RE: 1/2A THRUST-O-METER

Ok, so you confirm that it will be safe to break in both size Norvels with it? Excuse me my stupid questions. I have not started engine almost 20 years. And even so that were of diesel type.
Thank you,
Kostya
Old 09-11-2009, 05:47 PM
  #64  
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Default RE: 1/2A THRUST-O-METER

Yes, go ahead and use that prop on either engine. Make sure you use fuel with castor oil and make sure that the total oil content is at least 20%. 25% oil would be better if you are not very experienced with tuning.
Old 09-12-2009, 01:46 AM
  #65  
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Default RE: 1/2A THRUST-O-METER

Do I need nitro for break-in?
Old 09-12-2009, 02:03 AM
  #66  
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Default RE: 1/2A THRUST-O-METER

No, those engines will run without it just fine......but less power. The head shims will probably need to be removed for the best performance and with no nitro the engines will not have as much torque for spinning larger props. You will see the truth soon enough. After 1 day of using 0% nitro fuel, you will know more about it than I do. I have only tried 0% with 1/2A engines a few times..
Old 09-15-2009, 12:39 PM
  #67  
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Default RE: 1/2A THRUST-O-METER

CP;
MAS has a few sizes that are not as well known, or talked about. One is a 6x3.5", with this one I regular cut down to 5 1/4", where it really runs well(IMO). Have you checked this prop out for pull, or RPM?

Another is the 5.5 x 4-1/2" , a real unusual size. Any data you have about these, like to know what data you can perhaps add ?
Old 09-15-2009, 01:41 PM
  #68  
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Default RE: 1/2A THRUST-O-METER

I have been using the MAS 5.5x4.5 and 5.5x4 on an AP wasp. The 5.5x4.5 was a little to high load for the engine, at least in my plane (old school pylon style with a thick wing) and using 10% Nitro. The 5.5x4 was a better match and that's what I've been using mainly.

For comparison the load of the MAS 5.5x4.5 is slightly higher than for a cox gray 5.5x4.

Here are some rpm numbers I get on my JB welded CS on 10% Nitro (no thrust data though):

APC 5.7x3 18200 rpm (nice scream to it)
Graupner 6x3 17400 rpm (good match, nice idle at 3000 rpm)
Cox (gray) 6x3 16000-16400 rpm (unstable, seemed like a too high load)
Cox (gray) 5.5x4 16400-16600 rpm (unstable, seemed like a too high load)
MAS 5.5x4.5 16000-16200 (unstable, seemed like a too high load)

(This should/could fly something, I just don't know what yet...)

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