Thrust requirement for model
 

Hi All

I am going to starting building a BAC Jet Provost from scratch and will be using the KJ-66 engine to power it. I was going to build the model with a 2m span and hopefully around the 20-25lbs mark.

What I want to know is will this model be too big for a KJ-66 or just about right?

Thanks

RE: Thrust requirement for model
 

Hi.

I can't say for certain, but i can safely say that a lot of gents here would have thrust rating somewhere between 1:1
or 0.9:1. Some are having more thrust than these figures in their planes. I don't know enough about it, but i remember
someone here had flown a model weight in about 25lbs with 13 lbs pusher. It still sounded so cool that people still scratch
build their models. Good luck with your project

RE: Thrust requirement for model
 

Over my years of building and flying turbine powered models I use the following general rule of thumb:

conventional designs ie : Panther, F84, MB339, Sport planes, T33, P80, F86, Tutor, L1011 etc
0.6 - 1.0 thrust to dry weight

delta configurations / bifurcated / F15, F16, F 5, Eurofighter, Rafale,
1.0 - 1.5 thrust to dry weight

Speed is another thing though...with good flow through ducting some aircraft can attain incredible speeds with smaller thrust engines
ie ARF Bandit ( P70 ).

D.W.

RE: Thrust requirement for model
 

I think it will be plenty...
Some are flying the big 1:4,5 2,56 meter span Jetwelt BAC Strikemaster with a P80. That model weighs around 18 to 20 kilos.
http://www.jetwelt.de/2-jetwelt_9.html

RE: Thrust requirement for model
 

Hello Foofydoo

Rene's Bluntie was 84" span and flew really good on a KJ66 running at 120K and 25lbs. The engine had the double preload upgrade to go up to 120K. It would be very scale with a standard KJ

http://www.galtechmodels.com/Turbine...ikeM-Kit.shtml

We are in the process of building the next one with a bunch of upgrades.

Cheers
Tarquin

RE: Thrust requirement for model
 

For give my ignorance, but is there a website which shows all the upgrades for the KJ-66, 25lbs sounds like a lot of thrust for the KJ-66. I thought 16lbs was about the maximum.

RE: Thrust requirement for model
 

This Jet Model Products T-33 was flown for years with a JetCat Hammer. I think the Hammer was generously rated at about 17 lbs. The T-33 weighed around 28 pounds.

RE: Thrust requirement for model
 

I flew A Fei Bao MB 339 with a Ram 1000 for about 2 years. The plane weighed 52lbs wet and the engine produce aboout 28lbs thrust on a good day. Performance was decent.[8D]

RE: Thrust requirement for model
 

I suppose what I have to remember is the Fullsize BAC didn't have vertical performance and took 15 mins to climb to 15,000ft, so KJ66 seems ample for a 20lb model if I get it under that weight.

CHeers

RE: Thrust requirement for model
 

remeber ..the wings fly the aircraft...the engine is there to overcome drag...the thrust difference between say a 20lb turbine and a 30lb turbine will manifest itself as slower acceleration...remember force = mass x acceleration....in our case thrust is force.....remeber aircraft like the big yellow twin hornet flew on ducted fan my friend;)

RE: Thrust requirement for model
 

Before all the "big" engines were around, planes flew, and as NUNU pointed out; before that, they flew on ducted fans!

My first Hot Spot flew at just under 0.5:1, 0.45:1 to be exact and that was a delta wing.

Good luck with your project, you will be fine.

RE: Thrust requirement for model
 

Does this mean i can fly my skymaster F-15 on a P-70? my idea was to keep it as light as possible, use only elevons and rudders, glue the ailerons and flaps so they dont move, use lipo's and try get it in the 20lb range dry, add 3-4 lb of fuel? anyone tried this? do you think it will work?

RE: Thrust requirement for model
 

.7-.8 to 1 is very doable for all planes. We were lucky to have that with DF's of ald. Most of the planes flown now a days are powered by the stuff the biggest engine in that will fit rule. GMHO