krammer

Hi I have a VMAR ARROW TIGER 40-52 ARF plane and took it for a test flight today

I found that there was no lift on the low rate setup of (8mm)and lift on the high rate (12mm) was done at nearly top speed of the plane on the runway,

In the air when you go to do a vertical climb it starts for about 2sec then just stalls very quickly and makes a dive for the ground but does come back resonably good.

Does any one have any sugestions that may help me,it would be much appreciated

Thank You

spad

Hi Krammer
what motor do you have and is the CG in exactly the right place according to the instructions?
cheers
Rick

krammer

Hi Rick,
I have the vmax 46 engine in the plane and yes the G.C (80-85mm from leading edge) is as per instruction manual but it doesn`t say to do it upright or upside down.

krammer

Mind you thou I had to put 200grams of weight on the front of the plane??

tIANci

Krammer - I know the VMARs are not that great a plane but I have never heard of them being tail heavy. You have to hold the plane upside down to test the CG. For such type of planes I would have about 15mm on low rates and about 25mm on high, I usually go for almost whatever is mechanically possible to high rates.

When you say go vertical for 2 secs then it comes back down it may mean your engine is not powerful enough to hold the plane in a vertical, what prop are you using and what RPM are you getting?

krammer

Hi tIANci ,

I`m using a 10.5x7 ARC prop and the motor has just been run in,
When i say go vertical you will be flying at a level path and then you pull up the elevator to go vertical the plane will raise the front by only about 100mm - 200mm then it drops back down?

jrf

My Feedback: (551)

What you are describing sounds like a wing stall caused by too much elevator travel, applied too quickly. Try applying the up elevator slowly and see if the problem goes away.

You should not have to add 7 ounces of lead to the nose to balance this airplane. An extremely nose-heavy condition could account for the difficulty in getting off the ground and also the stall at full elevator travel.

I suspect something is wrong with your balancing method. What do you use as a balancer?

Jim

krammer

Hi

As per attachment above is the rates for the plane and the C.G for it as well,Thats what i set it up to,

They way i did the C.G for the plane was to use my pointer fingers as i don`t have a Great Planes C.G Balancer as yet

Is there another better way to do so untill i get a C.G Balancer??

The C.G on th plane beforew i added any weight was 125mm from the leading edge,

In saying that i found this site wich states a printing error in the instruction manual fro the C.G for this plane

[link]http://142.179.114.175/novo/default.asp?id=382&Lang=1&SID=[/link]

Thank`s

jrf

My Feedback: (551)

Well, there you go. Moving it back should solve your problems.

(Don't ya just love VMAR quality?)

Jim

krammer

Hi Jim,

I still had to add 200grams to get it to balance at the 3-3/4" mark?

JS615

jrf

I have 7 vmar planes and there just as good as any of my other planes from other companys!!
i dont know how good or bad they were in the past but the ones i have bought in the past 6 months are built very well and fly just fine,,so lets not let this thread
turn into a vmar bashing party!!!!

krammer

Hi jrf,

do you have a arrow tiger,

I`m not bashing vmar in any way ,I just want to fly it but as you can see i`m having problems with the C.G and want to get it right before going in the sky with it again as the first flight I had with it the way it took off and handled, I think i was lucky to land it again in one peice

tIANci

Krammer - I have been flying and balancing using my fingers for a long time now its decently ok but you really need to balance the Arrow inverted. What I always do is to trim the plane up and then go at about 75% to 85% throttle and then roll inverted. If the plane is pretty nose heavy you will need to input a fair amount of DOWN ELEVATOR. If the CG is spot on the plane needs no ELEVATOR input when inverted. It all depends on how you like it. For me I like a little nose heavy, just a bit for my aerobatic and sport planes.

Like what JRF says your plane is probably too nose heavy hence the plane does not want to lift off easily. The so called stall may be because of the motor/prop. The motor is not the best around. What sort of RPM you getting with the prop?

Also you may check the following:

Low end too lean, when its too lean the engine will loose power as you climb
High end too rich, same problem as the above
Too much prop for the motor, get a tach, you should be taching in the 13,000 region on 15% nitro

Some people have noted that the VMAX Engine runs nicely on 5% nitro and not 15%, it happens here in Malaysia. Maybe its more humid and hotter here.

JS615

dont run more then 10% nitro in the vmax engines,
also krammer i was not saying that you were bashing vmar,,and no i dont have the arrow tiger yet, i was thinking of getting one,
it does sound like your plane may be nose heavy,,also have you tried a 11x6 prop yet,,, i have the vmar aero subaru and it has the .46 vmax with a 11x6 and it kicks ass,, no problems at all with it,,
also you said you got 7 oz of wgt in the nose,, man thats alot for that plane???

JS615

krammer i have the great planes c g balancer, and its a must, i too use to finger balance my planes but its hard to get the c g dead on that way, especially the larger planes that are out there.
are the elevator and rudder servos in the tail of the arrow tiger, or are they in the center of the fuselage???

JS615

also where did you put your receiver battery???

krammer

7oz of weight is a lot ,but that was what it took to balance the plane,

I run 10% in all my engines without any problems(touch wood)

but i just don`t get it the plane is balanced (with 7oz lead up front)

All the thro rates as per instructions

new run in motor as per motor manual and sounds sweet as from idle to full rev`s with the 10.5x7 prop that will pull the plane from hand when holding in the vertical position

BUT IT JUST WON`T FLY PROPERLY[:@]

Will try a 11x6 prop but don`t like my chances as i wouldn`t think coming down one pitch size will mack a difference(will it?)

krammer

I put the battery on the top of the fuel tank and the reciever right behind the fuel tank

JS615

have you tried the richmondrc web site for info??
they have a knowledge base that has some things about every plane they sell,, and some times you can catch them live,,on there new live chat site they have,, ive used it and its great, very informative, they are not on live all the time though...
but im sure they could help you..

krammer

The elevator and rudder and throttle servos are in the middle of the fuselage

JS615

you said you had a hard time getting the plane to lift off, after running the length of the runway????
if so then there is no doubt you are nose heavy.

JS615

i would pull some of the lead out of the nose and try again..
go with 100 grams and see what happens,,..

jrf

My Feedback: (551)

So you are saying that you moved the CG from 3 1/4" to 3 3/4" and it took the same amount of nose weight? Not possible. Something is very wrong with your method of measuring the CG.

Turn the airplane upside down and measure back 3 3/4" from the leading edge at both sides of the fuselage and make marks on the bottom of the wing. Transfer this point to the center of the wing by drawing a line between the marks. Now drill a hole into the wing at the center and screw in a big screw-eye. Lift the plane by the screw eye.

You can remove the screw eye after you are done and cover the hole with tape.

I think you will find that you are still way too nose-heavy.


Jim

magnusji

I have a Tiger with an ASP 52 and i have placed the battery behind the fueltank and no extra weight up front.Replaced the aluminium motor mount with a plastic one to reduce weight up front,flies inverted with very little down elevator.Can`t remember were i have cg on my Tiger but it lifts off in about 10 meters.
Magnus//

krammer

OK JIM,

I mentioned earlier The C.G on th plane before i added any weight was 125mm from the leading edge,


I did as you said as you will see in the pictures below,

I measured back from the leading edge 3 3/4" and drew the lines,inserted hook screw and hang the plane upside down,
It is level (with the 200gramms of weight in it)

I have 100 gramms of lead with the battery pack witch is on the top of the fuel tank,and the other 100 gramms lead melted and formed in the engine cowl as in pictures.

Krammer