roydefiant

New video of gear mods with nose gear hooked up

sysiek

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F900

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Nearly 15 years in the making to me to buy an AirWorld Gripen, ever since Kevin W sold me a PMP Gripen with an inverted OS91 DF motor for thrust I've loved how it flew. I remember reading this thread back in 2006 and others after with a lot of going back and fourth how could I justify the cost in buying this Gripen, but I always said I would own one and now I do. Weighing in a 25lbs (minus Turbine, Batteries, fuel and RX) it will be powered by a 220 and I'll use a Cortex pro gyro.

Since there is not many around any further tips or recommendations are welcome although Hans at Airworld has been A+ and has given me a lot of good information.

Dave Wilshere

I still have my kit ‘waiting for time’ it’s sat on my office since 2006 with bits done. I was just thinking recently the new JetCat P-250Pro would be an ideal turbine for it.

The main thing is getting it to unstick, the canards really need to be live to lift the nose.

Dave

F900

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So I've watched many videos that seem to work around the 200N range without any issues taking off, I've read not to use full power until in the air lol, so it has me slightly confused. I could install a 300N but it's est to weigh around 45-47lbs (20.4kg), having 65+lbs of thrust seems to be taking it well more than I need. Thomas Gleissner flew this Gripen so there should no surprises as long as I'm making that CG and I get my rates and flightmodes set up correctly.

On my Gripen you can see where the CG is marked.

yeahbaby

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Robert,
I bet you could save weight installing a 180-220 size motor in there and still have plenty of push, even at Denver density altitude. Also, taking off at less than full power relieves the downward pressure on the nose wheel during takeoff acceleration. I’ve been taking off at half power on my swim 190 powered UBevo and recently started using reduced thrust on both my PNP hornet and my SM F4. Both The F18 & F4 are powered by the big block AMT engines. The reduced thrust gives a nice smooth rotation and usually elicits a “ is there something wrong with the engine “ question from a spotter. Give it a try.

Pull Up Now!

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You have down-locks on the main gear struts? That has been a problem in the past.

Dave Wilshere

When this model was introduced there were no gyros as good as now. Plus you said in your post a 220N turbine, perfect as it will be lighter than the original use P-200 unit and a bit more thrust.
the combination of gear behind the ‘model’ balance point, the full scale will have a balance point back from where we have to fly as they have super computers...and we don’t!

You will get on fine, the post at the beginning of this page lays out just about everything.

F900

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Thanks Dave, I've read all of the above and will use that as for reference 220N, Cortex Pro and trying to keep it as light as possible. I'll update one everything is installed and we will see what the weight comes out.

Thanks Buck - Rafael will be in the air very soon Just adding some front gear lights.

alasdair

I had the Jetlegend Gripen. The only teeny problem was that on take off a little gentle up elevator didn't work, a bit more didn't work.
FULL up elevator got it off the ground and into a very steep climb. After a few hairy takeoffs the system of full up and almost immediately going back to a third gave a decent take off and climb.

The problem was as Dave described, the model CG is way ahead of the full size CG so there is a lot of weight on the nose. Enough up elevator to lift the nose to a flying angle gives a very steep climb. Too steep.
Have Airworld moved the main gear forward a bit to help with this? Or some other solution? Or do you just need to be careful?

Dave Wilshere

It’s only a tiny bit forward of the scale position. What you want is the canard on a spring loaded switch, so blipping it puts full up on the canard for a split second to get the nose flying or like I did on the F-35...cheat and drop the nose gear enough to get an AOA

alasdair

Thanks Dave.
I never had the problem on the CARF Eurosport.
Yes, I know it's a sport model, but do you know how the main gear position compares to the Eurofighter?

Dave Wilshere

The ES sits at a positive angle of attack, so less affected by the relationship.But also the ES was designed as a model from the start and not really a scale jet.

Anyway...Gripen thread

sysiek

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this setup should make every gripen fly perfect

sysiek

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so bad the aviation design never finished with production of this 1:6 scale gripen , this is before the maiden flight

sysiek

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and the maiden flight way too much expo on the canard

F900

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So what your really telling me is hold on and I'm in for a nice ride lol

If you at 90% of real Gripen landings on landing they always have the canards in a pitch up configuration in the below video. ... I hate these unknowns since you never get these types of flight profiles setup correctly until your a few flights into flying it, but that is a good suggestion by using the flap switch to configure the canard for landing, only concern is how much down elevator needs to be mixed in if any at all.

sysiek

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alasdair

Good takeoff, like one of my better ones, with a little jump off the ground and a nice controlled climbout. Same colours as mine, stand out well. What engine? Mine had Wren 80.
I too noticed that the elevators (all moving foreplane) were much less powerful than the elevons.
F900 Thanks for the airshow video. Shows off the full size well. I had my foreplane rigged like that (on Eurosport too) to go up to a stalled angle on approach for drag (as airbrake) but with some lift to reduce stalling speed. But I found I didn't need it. With the throttle low and nose high both Gripen and Eurosport come down just fine without messing around with the foreplane.

sysiek

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That was the second flight, and my stirring cable has a little problem , but after some flying and changing some settings the jet was flying like eurofighter with slow landings, on this video the jet has p-120 and after super eagle but on the end the p-80 and this was the best setup for sport flying. The aviation design has k-140 f much bigger jet but very light.

F900

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Pull up - Do you have a direct contact for Gear Bunker? I'd like to buy the landing gear mod. I am not on facebook so I have no way in contacting them.

I've started getting the Gripen ready for flying and your right that gear lockdown mod would be welcome.

Also any idea of what Hydraulic fluid is used? As you can see in the picture below mine is well below the black line, I'm assuming it will need a topup.

I plan to install the new ACEx 240 turbine, Cortex pro gyro and for now just use the JR servos that are installed.

F900

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So chatting with some people appears that the AW Gripen can be very challanging to takeoff and land.

Any assistance on who I need to contact to purchase the hydraulic locking mechanism?

And if anyone knows who flying this Gripen in this video below would be helpful that I can find out what GC they are using and flight modes .. thanks.

Dave Wilshere

I would say you can see it’s sitting at a positive angle of attack and that’s all you need for a smooth take off. I don’t believe it’s difficult to land.

F900

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Thanks Dave, I see that, a lot of money has gone into this Gripen (as we all do in these jets) and want do to everything I can not get into a tricky situation, take off's should be easy and a non event. For the size its a light jet so maybe I am just been over cautious ..

Dave Wilshere

I remember seeing Tommy from AW fly the prototype at JetPower- he has no issues but I don’t remember his radio set up. Ali had one a few years ago and it tore down the runway before leaping into the air. I would put some Tygon in the nose leg spring to stop it compressing under acceleration and set the canards positive AOA to lift the nose. Playing with the old CARF Rookie you could have the canards set at 45 degrees and it was still flyable.
Caution is good, but I think it’s going to be fine. One day I’ll find time to build mine!