Pitts-SPS

I am thinking of buying a JetLegend JAS-39 Gripen and putting a Jetcat 120 in it.
Do you think it will be over powered?
Will it it?

Thanks

lov2flyrc

My Feedback: (24)

Slightly [sm=surprised.gif]

Big Tony

Do you have a stick thingy on your transmitter that isn't spring loaded well thats the throttle just keep it down the bottom half of the travel after take off and you'll be fine. Alternatively turn the max rpm down to give you 18-20lb (rpm / thrust chart is on the Jetcat USA website I think).

All the best

Ant

Laura H

Ant,
Thats like having a V8 car...If you can't use it to its potential then whats the point in having it.

Laura

Ps: Extra Weight and Extra fuel your carrying....

Big Tony

When your ready for the bigger car take the down rated big engine out of the little car uprate then put in the bigger car TA DA you don't have to buy a bigger engine.

A P80 fits in nice 120 is the same size so if he has the money for the 120 use that, while he's enjoying the gripen he can save for a bigger plane build it by then he maybe bored with it sell without the engine - put that in the bigger plane --- WINNER

Selling the engine and plane together you loose more money = bigger dent in wallet for new plane.

Just my opinion but I am the bloke who's stuffed a simjet 3000 in a starjet.

All the best

Ant

Laura H

A V8 doing 50mph and a 1.1 doing 50mph....The v8 still burns more fuel.....

Laura

Big Tony

1.1 - 80 bhp vs V8 550bhp is a bit of a difference between a p80 - 20lb vs p120 27lb

The fuel difference between a p80 and p120 at 20lb is about 5% - 5% on 2lt = .1lt = who cares. Looked into this loads when I was buying my last 2 engines thrust vs fuel burnt between more/less powerfull engines at the same thrust and concluded its not worth worrying about to much, if you can afford the bigger engine at the time buy it as it may save you money when going to a large airfame in the future.

But as my wife tell me a woman is always right so that means I'm wrong I'm just entitled to an opinion if I'm lucky

All the best


Ant

Laura see you at abingdon also what is santa bring you and your dad

Laura H

The 120 is alot heavier than a Supersport though...The P80 aint made no more thats old hat I thought!

Your Missus is right - women are always right!!!!!!

Abingdon always freeze ya bits off..

Me dad has just bought a Hawk - for his Mercury. So he is busy building that.

Laura
Ps When you asked my dad what he wants for xmas you always get the comment a Bandit or a S Class Merc...He is yet to get both. He stands no chance..

james love

My Feedback: (2)

I's been my experience the jets fly better using the size enginge they are designed to use.

James Love

Laura H

James your right.....

Laura

james love

My Feedback: (2)

Jetcat web site shows the P80 forsale at $2795

James Love

Big Tony

Thought he was wanting 66 size engine many more airframes available for 20lb+ engines.

Super sport - I have one slapping it in an AMD hawk at the moment - brill engine but knowing what I know now it would not be my first buy a 30lb er would be as bigger airfames always fly better (don't the ladies say bigger is better?? well than also applies to jets) as they have a lower wing loading GENERALLY = slower landings compared to smaller ones (unless its ali's old euro - always look mmmmmm on the wing loading to me) so surely thats the way to go (if no please refer back to what my missus says in my previous comment).

All the best

Ant

Whats santa bringing you.

siclick33

Supersport in an AMD Hawk[X(][X(][X(]

Laura H

I thought I heard the P60 & 70 were taking place of 80...Hey im not a Jetcat bum.

Xmas for myself...There is nothing I want..I'd like the money to put towards changing my car...

Laura

Laura H

Why not put a P120 in a Savex L39.......Ill be reading this next in a post....How do I fit my P120 in my Savex L39!!!!!!

Laura

Big Tony

All wrong they said a starjet couldn't take a 3000 well it flies great.

Colchester A1 Models the importers and mod designers for the hawk to take turbine tested the prototype with what engine??????

I'll tell you a SUPERSPORT ring and ask them.

So there

And as for the savex and 120 laura your being a bit silly now aint ya.

Here you are 20lb plane with a p80 would fly exactly the same as the same 20lb plane with a p120 rated to 20lb thrust as they are virtually the same weight you just might have to land 30 - 40 second earlier with the 120 plane. But with the 120 you can put that in a bigger plane and uprate. The P80 your stuck with 20lb weight planes unless you don't mind limited vertical.

All the best

Ant

cairoman

Bottomline....would the Gripen fly better powered by a Wren Supersport type (17Lbs) rather than a KJ66 size engine of, say 27 Lbs thrust?

Chris

lov2flyrc

My Feedback: (24)

From my experience with this airframe, that is correct Chris.

cairoman

Thanks Todd,

That's what I thought too.

Chris

Speedbird66

Hi there,
I think you could argue for a 120N turbine as well (I'm going to use 130N) :

If you are an experienced pilot who whish to push the Gripen to the limit a thrust to weight ratio of 1:1 is what you need direct after take off. The kind of high alpha tight turns the full size Gripen does will slow the model down if there isn't power enough particularly if you are in a climb.

Yes, the weight of the model and the wing loading will increase but a take off weight of 12,5kg including 3 litres of fuel doesn't ruin the models behavour. (Confirmed by at least two people flying this model with 120N of thrust). The idle thrust of a bigger turbine could be the biggest problem during landing if you don't get used to enter the high alfa flight mode on the final (or on the last turn in to the final).

On the other hand, off course, the model will be easier to fly with a take off weight of 11,0kg - but that's not always what you are looking for. Because it's lighter it will probably float longer on the final.

/Johan

cairoman

I 've got a question for those who built/flew the Gripen....truly a stupid question, but when you lack instructions.....

Are the canards dihedralled or anhedralled???? I know the canards on the full size Gripen are dihedralled, is the same concept followed in the kit?


Chris

Speedbird66

Hi Chris!
The Gripen has dihedral on the canard (like a normal wing).

Laura H

Looks strange though on canards for some reason

Aero65

My Feedback: (2)

Hi Chris

Flew the SM Gripen with these turbines.

PST600R http://www.hawaiijets.com/aircraft/G...Tim-Gripen.wmv 14 lbs thrust minimum

P-70 http://www.hawaiijets.com/aircraft/G...n-p70title.wmv Good combo. Good on fuel

Simjet 1700 sp 20 lbs of thrust. Flew well good combo

Artes Super Eagle 30 lbs of thrust. Awesome, had to be careful on take off and accelerate slowly. Also area above turbine can get too hot if your starter fails to go into cool down, and or tailpipe into the wind at idle for extended periods. Suggest heat blanket or BV heat shield.

Peter A

My Feedback: (34)

I am flying my Gripen with the P120. The plane is overpowered, and at full power is a rocket.
However, I never fly it at full power. The reason I used a P120 is because I had the engine and did not want to buy a new one for the Gripen.

The beauty is in the takeoff, effortless. Also on landing, residual thrust is higher than the typical 60N-80N and as such, reduce power early. Beyond that, have fun.