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Old Dec 16, 2006, 04:14 PM
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Joined Nov 2006
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Help!
Thunder Tiger V Bat Wing

I have a v bat with an AXI 2208 26 out runner with 8x4 prop.

Every time I rev the motor the wing pitches down.

I have tryed down thrust, but it not seem to help.

I have also tryed up thrust.

It did fly when I launched it from a dolly.

The motor is on a plyon.

Any ideas what to do about thrust?

Jim
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Old Dec 16, 2006, 11:34 PM
Mum is the word!
Joined Jun 2003
6,791 Posts
Try a smaller prop and a few more volts.
What is the wingspan and airfoil?
Is your cg correct?
Ck
Quote:
Originally Posted by James Carney
I have a v bat with an AXI 2208 26 out runner with 8x4 prop.

Every time I rev the motor the wing pitches down.

I have tryed down thrust, but it not seem to help.

I have also tryed up thrust.

It did fly when I launched it from a dolly.

The motor is on a plyon.

Any ideas what to do about thrust?

Jim
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Old Dec 17, 2006, 01:07 AM
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meadowvale N.S Canada
Joined Feb 2006
207 Posts
sounds like lever action... try moving the cg aft a little might help shorten the moment of the lever action
~shawn
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Old Dec 17, 2006, 07:06 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by James Carney
I have a v bat with an AXI 2208 26 out runner with 8x4 prop.

Every time I rev the motor the wing pitches down.

I have tryed down thrust, but it not seem to help.

I have also tryed up thrust.

It did fly when I launched it from a dolly.

The motor is on a plyon.

Any ideas what to do about thrust?

Jim
James, that is a very nice looking wing at an awesome price too, BUT it looks like the motor was added on as an afterthought. Your problem is definately a thrust line problem. That pylon pod put the thrust line way above the centerline of the wing and the resulting lever is forcing the nose down. As well, that motor pod probably produces as much drag as the entire rest of the wing.

Solution? There is likely not enough trim range in that pod design to compensate so... ditch the pod completely! Mount the motor to the nose of the wing and I think you'll see your thrust problems disappear. Your mount could be as simple as mounting the motor on a 1/2" square spruce stick and rubber banding it to the underside of the wing or you could work on a more integal mount system. My two cents!

Tony
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Old Jan 06, 2007, 10:27 PM
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Orlando Int, Florida, United States
Joined Oct 2004
2,195 Posts
i just picked one of these up in san jose for $35!!! the hobby shop (sheldons) ws having a moving sale, EVERYTHING in the store was 50% off... so i figured what the hey, why not

id never heard of the v-bat but it looked neat anyway, and thunder tiger is a good brand

as for your pitch problem, ya id say the motor pod was more of an afterthought indeed... neat idea on their part by making it removeable though...

for mine i plan on recovering it (already stripped it; nice construction BTW) with clear (just because...)

as for the motor thing i think ill jsut leave it as is for now... but if and when i do put a power system on it i think ill mount it in a pusher configuration behind the fuselage pod, with a streamlined nose fairing for the battery

should be a sweet plane i bet... must be awesome on the slopes... too bad i live in florida

-David
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Old Jan 17, 2007, 09:50 PM
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Joined Jan 2007
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Hi,
I am new to this site but I too am the owner of a V-Bat. I know the power pod is set up for a 10 glow engine but I also wanted to try and convert the V-BAT to electric. I did plan to try to use the pod setup however after reading about the problems with the thrust line I tend to agree. I think I am going to use a setup similar to my zagi. You can buy zagi replacement parts (motor try and cover) for about 12 dollars. I will kepp you posted on my project when completed.
Best Regards,
GBMIKO
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Old Jan 18, 2007, 10:41 AM
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United States, OH, Tipp City
Joined Jun 2002
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Dave from Radical RC here, I've got some problem with high motor models as I fly Seaplanes. You did not specify if the nose down was speed related or is it just doing this in the initial micro second you advance the throttle?

If it does it the instant you advance then it's the high thrust line. If you advance the throttle slowly and it stays in trim (and does not pitch down) then it's the high thrust line NOT the angle of the thrust line. Nicer radio's like Futaba 8U and 9C (certainly some JR also) have a setting called throttle delay. In a pylon mount seaplane often just 10 or 15% delay will cure this problem and prevent you from moving the servo too quickly. What this does is alow the model to speed up so the stabilzing force (your reflex) effect increases with speed right along with the motors forward pitching moment that is increasing with RPM.

Note, "throttle delay" is a bad name, it actually is a system by which the speed of the servo is slowed down. It adjusts how abrubtly you can advance from idle to full speed. Futaba should call it "Speed Adjust" or something similar as it's more descriptive. You won't really notice the delay to responce in flight up to about 20%. Over that it starts to be a safety hazard as it works both ways, on the way up and down. So, be aware of all the effects. It would be nice if they allowed setting this on the up side only but not the retard side of the throttle. I think some of the $1000 plus radios allow this modification.

If you advance slowly and it goes out of trim to the downside and stays out of trim to the downside then you need to angle the motor downwards slightly.

If the model randomly pitches downward or is very very sensitive to slight down elevator input at high speeds then your CG is too far aft.

I've had a number of radio sets over the years. Once I got my first Super 7 then to the 8U then the 9C, I just can't make myself purchase any of the simpler radio's anymore. It's nice to have the features on hand to fix problems with models. I can remember a model where I had every extra mix in the 8U utilized to get it flying perfect. Made the modest extra money for a radio in this class seem like a bargain. It seems like you start to find some of these more interesting features at the $300+ level. Can't bring myself to buy a 10 or 12 or 14mz however.

I've recently started using a Tracker II for the shop models, it's an interesting radio for the money. I'm not sure if it has this feature or not however.

Dave
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Old Jan 21, 2007, 08:23 AM
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Joined Nov 2006
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Hey, I too just bought this wing at a bargan. I had intended to use the Pylon and convert to electric. I was going to just attach a hardwood stick to the pylon. I was a little nervous about getting the thrust right. This thread has solved my problem, ditch the Pylon, BRILLIANT!! I'll just use the hardwood stick to mount the motor on the front (or maybe the rear). I actually thought about sloping this wing (I live in St. Thomas USVI, great area for sloping) but our slopefly areas are tight and I'm sure I couldn't land the thing without breaking it. Anyway, thanks for the input guys.
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Old May 05, 2009, 08:26 AM
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Joined Sep 2006
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'V-Bat' from Thunder Tiger wanted.

I want to buy the V-Bat from Thunder Tiger too because they have foolishly discontinued the lovely 'Velocity 2' flying wing here in Europe anyway. I popped 'V-Bat' into Google with no result except from a website: www.greatmodeldeals.com which has no leads to actual shops. I will try Sheldon Models as I got stuff from him before. But I would appreciate it if anyone knows another supplier too.

No one in Ireland (me) or the UK (accross the water from me) has even heard of the V-Bat but it sounds good as a 5 foot span model. As to problem with the pod causing a nose-down couple, it is simply that the the pod is too high for a tail-less model. The suggestion to mount the motor on the nose (or at the trailing edge as a pusher) is correct as the Law of the Lever applies! The thrustline is too far above the centre of drag, the wing.

I look forward to any replies and now I am going back to adding lightweight wing extensions, and a tailplane mid-way up the fins, to my Phase 3 'Fantom' flying wing to try and tame it.

Harry Lime, Dublin.
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Old May 05, 2009, 05:23 PM
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raleigh, NC usa
Joined Aug 2001
1,954 Posts
vbat pylon blues

hey all

chuck those pylons and mount your motor on a long stick out the back or on the nose to solve your pivot problems . . . .

I use to see these planes often, great slopers but terrible powered planes - - only because everyone insisted on using those stinkingly poor designed pylons - enough pitch change to make you take up tequila

If you are recovering it and have the wings apart, just draw the CL on the root and inbed a stick mount, a nice 30-45 gr outrunner and a 1500 mah pack would about balance out real nice . . . . .. as you get to ditch the 4 cell RX pack and use the esc as he radio power supply!

Enjoy . . .and if anyone wants to dump theirs for 35 bucks or trade for a HP wild wing. . . Id be willing to take it off your hands!

Phil
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Old Jun 28, 2009, 03:07 AM
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Joined Sep 2006
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V-Bat - the solution

First of all, you can still get the V-Bat from www.rcgraves.com tell Brittany I sent you. Here is the solution:

When I got the kit I saw this rather chunky and heavy centre-section pod designed to take the engine pylon and the little tow-hook! Throw it out, it weighs a ton and the the too-high aluminium engine holder doesn't work anyway. I put the pod on my scales and saw that it weighs the same as a small geared in-runner and 3S Lipo pack of about 1,500 Mah and size 3 x 1.5 x 1 inch.

Make a 2 inch longer plywood wing-joiner than the one supplied and glue it in place of the original one. You now have a wondereful 2 inch gap between the wing roots that you can fill with a shaped nose-block to take the motor and a tail-block to keep the trailing edge in place. I then glued a rectangle of paper-thin 1/32nd plywood on the underside, overlapping onto the covered part of the wing by 1/2 inch.

You must devise a similar way to make a removable cover for the top-side of the new centre-section. Now just think what you have done: You have got a proper power unit for no increase in weight AND you have increased the wing area free of charge too!

Just one more important thing to do before you fly. You have to double the area of those inadequate wing-tiplets. They are just too small in area. I replaced mine with new ones made from a sandwich of 1/8th soft balsa and my aforementioned thin plywood. Job done. Comments welcome.

PS: Happy with your V-Bat? Now for a REAL flying wing try the Albatros XXL from www.kuestenflieger.de. Your life will never be the same again.

Harry Lime, Dublin.
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