How many G's ????
 

Alright guys. Let's talk G forces. For those with logging instruments, how many G's have you recorded. Which planes are pulling the most? Just thought it would be fun to hear.

RE: How many G's ????
 

Using the RCATs data system which measures G's with an accelerometer (not GPS), we've recorded readings around 6 or 7 G's in normal flying and as high as 10 G's on a KingCat when we were "trying" to rack up higher G's...

Bob

RE: How many G's ????
 

With an Eagle Tree system in my TopCat I was seeing 2 to 3 g's in normal level turns, up to 4 in hard turns, and 6 to 7 out of the bottom of loops. Indicated airspeeds were 180 - 185 mph on the bottom of the loops/dives.

RE: How many G's ????
 

I have recorded up to 16 on my last BobCat Composite. I know I have other times pushed the plane a lot harder ( when i was no measuring with the Eagletree system ) and would not be surprised if it was not significantly over 20 ( all in the confines of 200MPH .. I try to avoid pulling too hard when pushing significantly past 200 ) .. I know that kind of abuse in the long run is not healthy for an airframe ( you can see the wings bend at over 16Gs , which is like loading the wings with 2 large persons on the little plane !! ) and have only tried some manouvers a few times ;) The BobCat loos great doing a "wall" or a 100MPH snap roll :D.. I think a good question would also be how do the turbines physically handle this kind of stress also ? ...


Wojtek

RE: How many G's ????
 

So Wojtek,

Is your pretty bobcat still in one piece with that kind of flying???


Mike

RE: How many G's ????
 

Makes you wonder what BVM and the others are designing their airframes to!?!?

RE: How many G's ????
 

the plane had no issues with this kind of flying .. ( this is not regulary ) no cracks, bends , or any signs of fatigue.. even wings slid on and off the wing tubes same after many flights as when the plane was new. The airplane did eventually have issues with a failsafe lockout that caused its demise however which was not related to the stress it took ... As for the BobCat, BVM states it can "handle all the Gs you can throw at it" within the 200MPH top speed ... as per the recomended controll throws, that a lot of G's , and i would never even feel comfortable pulling full deflection on the elevator at anything near 200 ... Ask anyone who saw the first flight i had on my last BobCat at LiberyBell jet rally last year about how many Gs that plane can do .. I think BV was even relieved when he saw it land in one piece :D ... I would be more concerned about the stresses on the turbine wheel, and bearings, that about the airframe on this one ...

RE: How many G's ????
 

I was searching for info on "eagle tree" when I found this thread.

Not a jet, but using RCATs on our GT 80 powered F1 pylon racer 12 to 14 g's and the 280cc Herb Branson engine in a Miss Ashley unlimited pylon racer 17 to 19 g's

Does anybody know what type of thermocouple eagle tree uses for their egt?

RE: How many G's ????
 

Found it, type K

RE: How many G's ????
 

I have seen 14-16 G's on my balsa Bob cat with P120 while doing a circle and in a very large loop. This was measured with the jetcat GPS system about two years ago. The plane has now over 300 flights and no problems. I do not normally fly above 10-12 G's according to my gps.

The bandit can pull more than that since I had a couple but I never had the equipment to measure it at the time.

I have to say that I am confidant in pulling high G's on ONLY BVM BC, KC and the bandits...

RE: How many G's ????
 

Here's some G data from one of Tam's Viperjets taken in 2003. About a 600ft diameter loop, entry at ~180 mph IAS. About 8 g's on the initial pull and 7 on the bottom of the loop. G's relaxed to around 3 at the top. V^2/R gives you a reasonable indication of g's if you were flying a constant radius and velocity.

Michael

RE: How many G's ????
 

well, I finally pulled enough G's on my Composite BVM BobCat that it broke [X(] ... I started dropping down to low rates on my elevator ( around 65% and a lot of expo) for high speed low to the ground passes .. 1' off the ground or less and there is not a lot of margin for error there .. I also got used to pulling out hard vertical while still on the low rates ... well, I did not switch to low rates for a few passes, and when going vertical , I yanked as if I was on low .... uh oh :D .. the plane was 90 deg vertical in an eye blink, and I immediately felt it give and it spiraled upwards.. I killed the engine , and figured its a goner .. I ended up feeling the plane out and brought it in with a significant amount of aileron compensation ... i figured the wing tubes bent, or maybe I stripped an aileron servo .. all I found was a small 1/2" long crack in the upper skin ! inside the plane, the root rib plywood separated ( delaminated) and one of the small balsa ribs gave up also. I am amazed how the BobCat held up, and that the wing did not just tear right off !! I will only admit to 199.9 MPH on the pull up , and based on what others saw, and what I figured, the turn radius through the 90 degrees ( lateral distance traveled from horizontal when elevator was pulled up to 90deg vertical when the elevator was released) looked to be AT MOST 50 feet .... this translated to over 50 Gs !!! at an estimated 25 lbs with 1/2 tank of fuel that’s over a 1300 lbs loading !

http://www.rcpro.org/rccalc/GForce.aspx


The wing is in the process of being repaired, and should now be even stronger than ever [8D] ... no more dual rates for me ... just asking for too much trouble. The 50 G climb out was a true testament to how well engineered the BVM Composite BobCat's are. I feel i really got what I paid for and then some ... also add to the formula that the damage happened to the wing on the 83rd flight, with most if not all prior flights beating up the plane pretty badly and regularly exposing it to high G forces ... I am going over the whole plane and now that i know where the one wing failed, I will make reinforcements in the other as well ..

on the other hand, while flying this past weekend, i saw a Rookie 2 have it's wing burst and blow apart in the air, and it was no where near pushing any serious Gs ....



Voy

RE: How many G's ????
 

Voy
These guys might think your Blowing Smoke. :D I wittnessed the smile on BV face as the mains contacted the runway at Liberty bell. BTW
I know know why you use the "Alien" as a pilot. Fly like your Hair is on Fire......... :D:D:D
Semper Fi
joe