How do I determine 'max cruise airspeed'?

[wildirishtime]

So I have a Model 3 with the Bluehead 582. She seems to have endless
power - at a cruise RPM I can easily hit 90mph indicated, or more with
some extra throttle (lightly loaded)

We all want more speed out of our planes, so if it's calm air what
truely is a SAFE/SMART level flight 'cruise' speed for a model 3? in other words what would be the failure if you're going too fast, the fabric adhesion to the ribs?

Thanks for the insight...
~Wild

[t j]

Any time you get near Vne you are playing with fire. Flaperon flutter at near or exceeding Vne on the early kitfox models prompted the use of the mass balance weights.

[wildirishtime]

...true. I have the weights, I have the metal flaperon rib bearing reinforcements installed... I've never felt flutter (except that incorrect
rod end installation the prev owner did which I resolved).

So outside of feeling flutter and slowing down imediately, what else
should hold me back from doing 98mph?

I'm not asking for trouble, but if a plane can fly faster safely,
I want to do it too :) Cheaper than upgrading to a Kitfox 4!

~Wild

[szicree]

I'm not sure that flutter can be responded to before catastrophic failure occurs. By the time you feel it you might have fewer parts on your plane.

[Soarhead]

To answer the original question "max cruise airspeed" is determined by the manufacturer and set out in the pilot operating handbook under operating limitations. It's 100mph indicated for a Mark 3 (Vne) reduced to 75mph indicated with flap extended.

As far as I can recall from my principles of flight theory, aircraft are designed to Vne + 10% and test flown to Vne +5% so if you achieve anything more that 110mph you're the test pilot! The fabric most likely won't rip off - the wings will. These limitations assume flight in still air as turbulence will place additional loads on the wings. Age and hours of the aircraft will also have a bearing so all told, approaching 100mph is dangerous territory!

Hope this is helpful.

Safe flying!

soarhead
G-BTWB

[wildirishtime]

That's the best answer I've received - no I don't want to be a test pilot, but max speed (within reason) for the model3 in smooth air is easy for me to reach, and with a low hour airframe that's clean I'm excited to get max speed, as opposed to upgrading to a Model4 just for a few MPH gain!

~Wild