I have a K&B .65 engine. What size prop should I be looking to use?

Dave...

Interesting... K&B manual recommends 11x7.

See at http://www.mecoa.com/kb/58/5800.htm

Interesting because many .46 engines can drive an 11x7, but you could also drive a 12x7 or maybe a 13x4ish.

gus

2-Stroke Engines

.049 - .051 = 5.5x4, 5.5x4.5, 6x3, 6x3.5, 6x4

.09 - .10 = 7x3, 7x4, 7x5, 7x6

.15 = 7x6, 8x3, 8x4, 8x5, 8x6, 8x7

.20 - .25 = 8x6, 8x7, 9x4, 9x5

.29 - .35 = 9x6, 9x7, 9x8, 9.5x6, 10x4, 10x5, 10x6

.40 = 9.5x6, 10x4, 10x5, 10x6, 10x7, 10x8, 10x9

.45 - .50 = 10x7, 10x8, 11x4, 11x5, 11x6, 11x7, 11x7.5

.60 = 11x5, 11x6, 11x7, 11x7.5, 11x8, 11x9, 11x10

.71 - .80 = 12x6, 12x8, 13x6, 13x8, 13x10, 14x8

.90 = 13x6, 13x8, 13x10, 14x6, 14x8

1.08 = 14x8, 15x8, 16x6

1.20 = 14x8, 15x8, 16x6

1.5 = 16x8, 16x10, 18x6, 18x8

1.8 = 18x8, 18x10, 20x6, 20x8

2.1 = 20x8, 20x10

2.7 - 3.5 = 22x8, 22x10, 22x12, 24x8, 24x10, 24x12

4-Stroke Engines

.20 - .25 = 9x4, 9x5, 9x6, 9x7

.40 = 11x6, 12x6

.60 = 11x8, 11x9, 12x6, 13x6

.90 = 12x8, 13x8, 14x6

2.10 = 14x8, 15x8, 15x10, 16x8

From the Master Airscrew website. These are good guesses as to what will work.
I broke in my Super Tigre 75 with a 12x6, and the plane flies with it (Tiger 60). A 13x8 is too fast for my field, I put on a 13x4, but I have yet to check it out.
Good luck.

Guys ... try this ... its pretty easy to use.

While the charts are somewhat usefull, they are very generalized & make no distinction for engine characteristics or airframe types -- prop selection is not that straighforward. In addition to the type & size of engine, it also very much depends on the type of aircraft in use & the nature of the in-flight activities that you want to enhance or suppress.


For example, a TT .61 Pro or FX .61 will pull a lot more prop than an LA .65 -- and a 12-5 on an LA .65 & a big trainer would work OK, but could be a really poor choice for a TT Pro on a clean, speed-oriented sport flier.

You need to tell us what specific K&B motor you have, what the model is & what kind of flying that you expect to do with it.

The K&B .65 is made to spin big lumber at reasonable RPMs. I'm using a MA 12X6 with real good results on my .61, which leads me to believe I'd start with a 13X6, 13X7 if I was using a .65, as it's not made for the RPM the .61 is.

I get over 12000 RPM with an MDS .58 and a 12X6 wood prop.[sm=redface.gif]
It does fine on a Cap 232 40 size.

Putting the .65 on a U Can Do 46. I think its the sportster engine. It didn't have any papers with it.
Now, I don't plan on doing the 3D thing with it yet, I'd like to get used to the plane first. Then, I can go to
a different prop for the really crazy stuff.

Dave...

Hi Lucky. Start with a 13-6 and go up from there. The Sportster 65 is a serious lugger. Kinda like the big block of the 60 series. It spins a big, long prop at lower rpm's. A wood 14-5 or 6 would be within this motor's capabilities. Just check the rpm's. You want it to max out at 9200 or so rpm's. Anything over 10 grand is just abusing this engine. It is timed and ported to run around 9 grand max. I have one, it will spin a MAS black 13-6 all day effortlessly. With say a 14-4 or 5 this thing will make that UCD a ballistic missile. It will pull that thing verticaly like it has no plane behind it. And don't worry about weight. It is actually a very light engine for it's size. Go ahead and use it, you will love it.

Mark Shuman

Thanx everyone for the replies! Will try the 13x6 foist and then maybe move up to 14x4 next.
I still have to get a couple of 12 inch servo extensions for this plane. I am gonna compare it
to my Twist which flies really well when the Evo aint acting up or, like I did today, landed and promptly turned
the wrong way and smacked the runway fence. Damage is loosened throttle servo tray, wing dowel pin unglued
and a small dent in the wing LE. At least I got in one flight today!

Dave..