Hello,

I have a World Model Super Chipmunk 90s ( Flaps and Retracts) going to be powered by an OS 91 Four Stroke with the Pump. I am trying to figure out what prop size would be best for speed and/or as much speed I can get from the .91 FS and best prop for the *Plane*.

Is a 13X10 size too small for this plane? Or is this fine?

another prop is a 14x8 or 14x10?

Please advise.
(It would help if you have or had this size engine and a pretty close setup)


Thank you very Much

Go with the 14x6 or 14x8, 13x10 is a lot for that sort of flying. If you wanna fly slow big loops then try a 15x4W ... Mine was with a G90 turning a 14x6, it was good.

If you want speed then you need a smaller diameter, higher pitch prop. I have flown this plane with 12x10W APC prop on an OS 91 with good results. You will need to get your idle down good and low or it will land fast. This is a great airplane and a knock off of the Goldberg Chipmunk and both fly extremely well. I currently am flying mine with a Saito 1.00 and a 14x8 prop with good speed and vertical performance. Whatever prop you choose, keep the tach reading up in the mid 9000 range.

Thanks guys, I will try all those sizes and I will post my rpms

Is the 14x8 ok for the .91 fs, will it be too much load?

Hi all i have WM super Chipmunk 90s and i have 2 brand new engine 1 75 tower hobby and the other one is OS 61 FX what should i install and what prop size should i use please help thanx

The tower 75 with a 13x6 prop is the best choice for the WM chipmunk. The os 60 leaves a little to be desired on the vertical

cooleto - i'd go with the FX with a 13 x 6 and not go through the potential trauma of dealing with the TH75. i'm not saying it's a bad engine, but it does have more quality issues than the O.S. line of FX engines.

14 x 8 is fine for the 91. I was running a master 14 x 6 and seemed as if it had some power to spare. Mine was not pumped.

I used a Graupner 13x6 3-blade on my OS .91 FS Chippy. Good pull and didn't load up the engine.

CJ

Use a Master regular black 14x6 it will give you PLENTY of power but also makes the most *****in howl on flybys, it'll give you the shivers!

MA prop? Hmmmm ... don't flame me but I think they are one of the worst props available. I still find APC and Bolly props to be much better than MA props.

tIANci - you are just plain EVIL. how could you say such dastardly words!!! LOL. i agree. masters are not the best props out there but their scimitars are okay. i have their props for my scale planes because, while nothing beats the apc in terms of performance, apcs just look oh-so-radio-control. haven't used a bolly prop before.

A lot of people consider a 14x6, or any size with similar load, to be ideal for the OS 91 four stroke
14x6, 13x8, and 12x11 would all put a similar load on the engine.
I don't know if the 12x11 would give the overall performance you need but in theory it would be fast.

Fore - what evil ... hehehehe ... yeah APC props do not have the look and the Scimitars are nice esp the wood ones. I guess you are a poser and you do not fly much!!! Hahahahaaha ...

p/s I did just purchase a MA 12x6 wood for my coming AgWagon ... tried it out on a flattie and it has less bite/performance than an APC 12x4

tIANci - hey... i fly APC for those planes that demand it. but why buy a cub and put on a nasty grey twisted peice of hard plastic in front? keep that nastiness away from scale planes. my P40 that i'm prepping for tomorrow's flight is getting a nice master 14 x 6 and a brand spanking new 91 SII pumped. woo hoo!

Forestroke - let's not highjack the thread ... hehehe ... I am getting my new WM Chippie at the end of this month, it may have my YS110 since the weight is the same as the G90 I used last time and the TT91 4C that I have. Not sure if I want to go EP with this plane. I got a nice AXI 4120 that will fly it scale. The YS110 will give me like 15 lbs thrust and the plane will only be 7.5 lbs!!!

ooooo...sounds good, tIANci. if i get a chippie, though, my saito twin's going in!

Saito 90 Twin? That baby sounds ever so sweeeeeeeeeeeet! I envy you ... I will have unlimted vertical with the YS110 for sure! Wanna see a 3D Chippie? I know the ELE/RUD is definately big enough. Hahaahahaaa ...

THANX for all the reply's but still didn't help for the engine choice thank you all[&o]

i think my votes for the 61FX over the TH75. i have the 75 and it's given me troubles since day one. i wouldn't wish it (my particular one) on even my enemies. i finally decided to retire it and replace it with an O.S. Surpass 91, which is a great engine.

if you already have both, and the 75 runs reliably, then i'd go with the 75 for the power. if you haven't bought either, then i'd spend my money on a fourstroke engine like the:

(listed from most economical to most amazing)
magnum FS 91
thundertiger FS 91
o.s. surpass 91
saito 91
ys 110 (that's the only one in the area)

the surpass and saito are about equals in price but saito's love high nitro fuel so you're looking at higher running costs with higher performance. the surpass is happy sipping 5~10%

personally, i'd go for the magnum FS 91 since it offers decent power, good reliability and great 4-stroke sound that, at a price of 199.99 at tower, is only $30 more than the 61FX

if you must go 2-stroker, i heard good things about the supertiger g-75 ringed engine.