715mm blades on Align 700N wideframe

[choppaholic]

wondering if anyone as used 715mm on their original align 700n not the newer ones, mine is a 700 LE manual says 690-710 and got some 715mm but wondering if I am too close to a tail strike, tails are 105's. did a good search but cant find anyone using them on the net? would appreciate if anyone can shed light if you used this size.

[Si Goodchild]

I haven't tried this but my gut feeling is that the heli will bog terribly, even with an 105 engine. I have 710s on a very powerful Raptor 90SE e-conversion and I have to feed in the collective steadily to avoid bogging. And that's with over twice the power of a standard 90-size nitro engine! Expereince on other helis suggests that even a relatively small change in blade length can have a dramatic effect on handling and power consumption. My old Align 550e really struggled with 555mm blades but was superb with 520s. My raptor 50 with 620mm blades bogged badly but was fine with 600s.

Your concerns about tail blade strikes are valid, but to be honest I don't think that will be the limiting factor.

Si G

[choppaholic]

thanks, i know what you mean i usually use the smallest recommended blade size on all my helis,know what you mean specially on the 550 when I had one, 550mm were also a battery killer.

these blades are mainly for test flying, i have lost two sets of edge blades now trying to sort engine and vibration issues, cant afford to put good blades on until its sorted. these are some really old blades so perfect to be test blades and not too fussed if it boggs the heli just dont want them causing a tail strike and causing another unnecessary crash.

[trillian]

What I do for estimating the tailrotor to main blade is measure the distance from the main grips to the tail grips, or from the tip of a tail blade and just see what the clearance is like. If you rotate the head to where you get as close as possible an imaginary straight line from one of the tail grips to the blade grip and measure from approx the centre of the grip at the blade bolt (centre of the bolt as well) to the same place on the tail grip, you can at least see what you have to work with. A couple of my 700 helis have a bolt to bolt distance of 820mm, so I know that 710 mains and 105 tails have a little separation. (and actually drawing a straight line with a tape measure is being conservative because the blade cannot actually make a straight line toward the tail, it will only ever be able to flex a little and in a curved fashion, so there will actually be a few mm more space in real life.)

A boom strike is a different issue.

Regarding the issue of power required for longer blades, I would think it's mainly a matter of how much pitch you run. With longer blades you should be able to compensate by reducing the pitch range a little bit. You can get both more punch (due to higher tip speeds) and more stability with longer blades but obviously there's a price to pay in power. But the F3C guys used to run 720s with .91 engines for years (not with a Trex but just in general, and usually heavier helis) -obviously flying style is a big factor as well.