Just out of curiosity, how fast can something like a Tiger 2 with a .46 go?

Well, I'm certain you will most likely get a better answer than mine. But here goes my guess. IF a 46 turns 12k revs and the pitch of the prop is 6 inches. 100 % effeciency would give you about 6000 ft per minute or about 68 mph.

It's hard to say giving all of the variables, but 50 - 60 mph is a good estimate

Well I'm not too technical on this... But I would say fast enough to hit
the ground and cause big damage if your not careful:-)

I did this for a math project in school about a month ago. Going with a 15 mile an hour wind we calculated that my LT-40 was doing about 83 km/h with a .46 FX and 10x6 prop on it. Against the wind we were going about 53 Km/h. So the average speed or the normal speed (without wind) would be about 68 Km/h just as kingwoodbarney said.

junior, I am sure that you are overestimating the speed on the LT40! That large flat bottom wing produces a lot of drag which keeps the speed down. The LT0 is more of a 40 mph type plane which is one of the reasons that it makes such a great trainer. The Tiger2 has a symetrical wing and the fuselage is a more aerodynamic design. Its more of a 60 mph plane with a bushing engine and around 80 mph with a good engine such as an OS 46 AX. It will turn over a 11-6 prop at around 14.2 k!

I just remembered something I heard during the 100 birthday of the Wright Brothers. I think they said the best prop ever designed was about 88% effecient. I would imagine a typical production prop is in the low to mid 80's. So 80 % gives you about 54.4 mph and 85 % would give you 58 mph. Lets call it 56 mph. That is my final answer. No lifeline.

And that is just an ideal. As someone stated earlier, the airframe and wing have thier say so.

Well, heck, Junior Flyer has the test data !! What the heck is 68 km/h ? Hmmm, hang on......fooie, thats 42mph !!!

WOW, that is only 62% effeciency !!!

Fastsky, did you not see that Junior said kilometers/hour not miles/hour?

Yes, he was using Kilometers,

So if I remember my High School standard/metric conversions, 68 Km/h equals...


Lemme see....

... Carry the two....

150 Bushels!

it would be.... ummm.... 42mph, dead on for an lt-40

_amn metric! Your right. Plese accept my apologies!

That's alright, up here in canada we use kilometers. Just went out today and flew off snow for the first time. Made some skis for the LT-40 works great.

So how many liters are in a yard? I gotta learn this metric stuff.

27

I have a Tiger II with a .46, I don't know how fast it goes. I do know that at full speed you can't pull the wings off of it, I tried! A full throttle snap-roll doesn't hurt it either.

I have an LT-40 with a TT .46 Pro, and have thuroughly "stress tested" that airframe... I cant break it !

oh, but my garage door can

but thats a different story altogether.

Fastsky -- are you suggesting that flat bottomed wings are inherently slower than wings with symetrical airfoils?

I'd say it actually has more to do with the wing's thickness than the fact that it's flat bottomed. Fast planes have thin airfoils to reduce drag. A Tiger 2 isn't all that fast (regardless of engine) simply because the airfoil is relatively thick.
Dennis-

DB you are correct about thickness being the critical dimension.

There is also more to the story --- in the case of model aircraft, & for a given thickness, plan form, section taper & aspect ratio, flat bottomed wings are inherently faster than symetrical or semi-symetrical wings. They provide the necessary lift to support the model at a lower angle of attack & require less nose-up trim force than is required for a sym or semi-sym airfoil. In some cases, flat bottomed airfoils can actually provide all the necessary lift at zero AOA, or even 1 or 2 deg of negative AOA, depending on speed. Fully sym sections are the worst choice for speed, as they require a significant AOA to provide adequate lift & require substantial nose-up trim forces.

Trainer wings are usually slow because they have a large span, have a low aspect ratio, a large wetted area & are often relatively thick -- none of that has to do with the airfoil section