iflynething

Just go to thinking and you know how you can have too much of a prop. Well, I know that that has soemthing to do with the weight and not just the diameter of the prop.

Anyways, you know how APC prop are heavy..well, wouldn't the weight of a 11x7 Master Airscrew prop be about the same as a APC 10x6..I mean you know that APC props are pretty heavy....but I just thought that I might point this out and see what others think.

I hope that you know what I'm talking about!!.....I can't really find a good way to word what I'm trying to say[8D]

ChuckN

Aside from the location of your plane's CG, the only thing a heavier prop will do is cause the engine to accelerate and decelerate a little slower provided the props are the same dia and pitch. A heavier prop is just like a heavier flywheel. It won't have any effect on top speed.

FWIW: I weighed the two props you mentioned. The Master Airscrew 11 x 7 weighs 28 grams and the APC 10 x 6 weighs 31 grams. The APC will still spin up quicker and to a higher RPM on the same engine due to it's overall size. Is this what you were pondering about?

JoeAirPort

My Feedback: (41)

An APC 18-6W weighs 4.5 ounces. A Bambula 18-8 wood prop weighs 2.5 ounces. The APC is almost double the weight of the Bambula.

ZAGNUT

My Feedback: (1)

problem is that there are no good wood props in the smaller sizes anymore....unless of course you have your own private stash of REV-UPS


dave

der_steuermann

My Feedback: (2)

And we should not forget the centrifugal forces loading our props on high performance engines in particular. A lightweight prop sure is beneficial here.

Personally I do hesitate to mount APCs on speed engines. Even the APC props belonging to the D1 pylon series aren't my first choice. I personally prefer carbon fiber props featuring superior torsional stiffness and tensile strength combined with very low weight.

downunder

A heavier prop only has one benefit and that's to act as a better flywheel for idling. A lighter prop will rev up faster (I don't like the term "spool up" cos that's usually reserved for gas turbines...just being picky ) but not necessarily so. It really depends on the polar moment of inertia (a lighter prop could have the CG of each blade further out to the tip).

One area where the lighter prop has an advantage comes from the fact it's a flywheel so it causes gyroscopic precession in a turn. Usually this isn't noticeable except in exceptional circumstances but it swings the nose left or right depending on up or down elevator. Apart from that, prop weight has no real affect.

ZAGNUT

My Feedback: (1)

how about when it hits your fingers?


dave

iflynething

WOW, thanks guys for the very quick response. Ummm.....Lemmme see here.

Say I had a 11x7 Master Airscrew prop on a .40 LA (which I did becuase that's the only prop that I have)....Well, I finally got to go to the LHS and go me a APC 10x6 prop...What I was thining was that wouldn't the weight of the 10x6 APC be about the same weight as a MA 11x7 and counteracts what you were trying to do with gettin less prop for the engine. I hope you unserstand that...But, like many of you guys said, that [weight] really has nothing to do with how much power the engine has.

Oh, do I know that the APC's have that flywheel effect. I can have a very low throttle on my Somthin' Extra....I just don't like that I don't have the throttle response that I would like to have....the APC kinda bogs the engine down a little bit and takes it a while for it to "spool up" (that was for you downunder)....

But anyways, thanks alot for the many responses in such a short a mount of time.


That always has an affect!!

britbrat

Actually, you will find that the APC 10-6 will greatly benefit your Superstar/.40LA combo & it wont be from anything to do with weight. Your engine just can't spin that 11-7 prop at anywhere near its (engine) optimal rpm. You may think that it is running just fine, but it isn't -- and you are hurting the engine by using it. An 11-4 will benefit your plane even more -- either APC or MA.

With the engine/plane combo that you are flying, propeller weight simply isn't an issue -- but pitch & dia are very real issues.

daven

My Feedback: (1)

Actually, on an LA .40 I would suggest the APC 10x5

Let her spin.

iflynething

Oh yeah...I knew that the 11x7 was way too much....I just had that one for when I first got my Somethin' Extra's OS 46 engine and I just had that one......But I do have a 10x6 APC.....I have had others that suggest that I use a 10x5...I might try that sometime....I liked the 10x6 when I first was flying the Superstar too, though.

Thanks Alot though,

~Michael~

JoeAirPort

My Feedback: (41)

Try an APC 11-4 or 11.5-4.

Joe

iflynething

On the .40LA??.......That seem alot, but again, I'll keep that in mind, and try it out....get one from a buddy at the flying field if one of them have one..and see how I like it!!

Thanks,

~Michael~

JoeAirPort

My Feedback: (41)

Yeah I run them on my 40FP. The 11-4 is perfect, the 11.5-4 is a little lower RPM's but is great for hovering. They both work fine but I prefer the 11.5-4. Also I'm running Omega 15% nitro.

jaka

Hi!
If the engine is going in a high winged trainer (type Kyosho "Calmato" )and if you fly at sea level and if you want your airplane to fly real nice and have good climbing performance and be real quiet......then a 11x5 or 11x6 APC would be best!
An 11x4 is too small an so is a 10x6 at least for the OS .40 LA and at least compared to the above props I mentioned.


Regards!
Jan K
Sweden

JoeAirPort

My Feedback: (41)

Do you have RPM readings and at what Nitro % ?

Joe

AnthonyH

My Feedback: (16)

Just thought I would add something about the construction of the two props. The APC has most of its mass around the hub and the tips are very thin and sharp resulting in less weight. A wood prop has its mass distributed more evenly over the entire length of the blade and results in more weight at the tip. Think of a fugure skater doing spins. With arms out they spin slow. When they bring their arms in close to their body they speed up. Therefore, even though an APC may weigh more the engine may not 'see' that weight, and it is able to spin it at the same RPM as a lighter wood prop. APC is also more efficient than wood and you will see better performance from an APC. Try an 11x4 APC on your .40, 11.5x4 on a .46 or even a 12.25x3.75 and you will be happy with the results, if you are wanting torque and not speed.

downunder

The weight of a prop has no affect at all on how fast the engine can turn it. Max revs is determined purely on how much drag the prop has. The drag comes from the area of the blade, the pitch, diameter, airfoil cross section, shape etc. But I'm beginning to wonder if the original question comes from confusion caused when people say to use a heavier prop when what they really mean is use a bigger prop (in either pitch or diameter).

seanychen

My Feedback: (4)

A heavy prop also has the benefit of better inducing torque rolls. An extreme example would be helicopter.

britbrat

Sorry jaka, you are not correct -- this is an LA, not an FX -- it just can't pull an 11-6 effectively at any altitude. Like the 11-7, an 11-6 will overload the engine -- there will be increased side-loads on the piston, increased radial loads on the crank journal bearing, increased bending/shear loads on the crankpin, increased cyl pressures & increased cyl temp -- none of it good, or effective for that matter -- hp & thrust will be lower & engine life will be shorter.

Shortman

My Feedback: (21)

Basically,

wood props are generally (for big planes) like for 3D. They spool up much quicker then a composite prop

composite props are generally (again for bigger planes) liked for IMAC and pattern, the do not spool up as quick but are but how do I say it smoother?

for these small planes the APC's are just the best props, the master airscrews are good if you prop strike a lot I guess bescause they dont break as much, but they have no thrust.


Thats my experience with them.

50+AirYears

I liked an article on prop/engine combinations some years back in RCM. It said to match the prop to the airplane, then select an engine to turn that prop at the correct speed.

iflynething

Well ya know......I have heard alot of things about the APC's having ALOT of thrust.....Well more than any others....and I think that I have seen that on my OS46AX on my Somethin' Extra. I have been wanting to really try a 12.25x3.75....I just want to find someone who has that size before I buy it...I know that props don't cost that much, but that's about $3 that I wouldn't have to spend. It's just too much trouble for the LHS to order that special prop (the certainly won't have that size in stock) and then me not like it....Anyways, the Somethin' Extra is just too low....I think that I just might buy some aftermarket landing gear to go on it to get that larger prop. I have talked to a guy that would hover with the SE on a 46 with a 11x4 prop...I don't know how.....

I really don't want speed on either one of the planes...Especially the Somethin' Extra...that's not made to go fast.

Really, I went from a APC on the SE to a wood one...I like the throttle response with wood. Don't have to "wait" on anything!!

Thanks alot for the posts....They've showed me alot....Keep em coming, but I will really try out the props and see what I like.....(I'm not buying them first....going to ask someone to try them out first before I get anything bought)

Thanks Again

~Michael~

Shortman

My Feedback: (21)

Hey Michael, I had a Sig Somethin Extra a couple years ago and sold it and its still flying today (I think[8D]). You can get the aftermarket landing gear from TNT. It will give you much better clearence and with my OS 70 I needed every inch. The APC props will make more thrust then a small wood prop will and the spool up wont make a difference because the extra thrust coming from the apc will pull it harder then a wood prop will.

If you think an APC prop is expensive wait till you see giant scale props. $40-200 EACH! Not something cheap when you want to experiment.

The 12.25 x 3.75 will slow down the sig se a lot!

iflynething

Yes, I have heard of the TNT aftermarket landing gear....Could you please show me a website where I can look at a picture of the gear....or maybe post a picture on here??...Thanks.

I know that I'm gonna hate it when I get a larger plane, and I have to spend money on the huge props. I was at the field with a friend watching him fly, and I was looking at a Cap that a guy had in the back of his truck. I noticed the prop....It ws like a Menz Carbon Fiber....well I don't know about the Menz, but I know it was Carbon Fiber....but I told the guy that I'm sure that prop cost about as much as the plane....I was just kidding though...

Next time I'm at the field, there's a guy that has a CG Extreme 330 or something that he uses a 12.25x3.75....I'll ask him if I can use that...see how I like it!!