Hey everyone,

I am working on a design for a small aerobatic model to be powered by my PAW .19 R/C diesel. This may be kind of a long shot, but I don't suppose anyone here would know what kind of static thrust to expect from this engine? Even a ball park figure would be helpful for design purposes, and for choosing gear to go in the model. I do not have the necessary equipment to perform the static thrust measurements myself.

Thanks for your help,
Chris

Chris,

There are spreadsheets around the 'net that use several input parameters and adjustments for predicting prop thrust.

I just checked in one of those, specifying a 9-6 APC prop at 11,500 RPM, and found about 2.25 lb static thrust, about 2.5 lb possible, unloaded, in flight. Those are reasonable prop and RPM conditions for a PAW19 RC, and it sounds about right to me...

For several years, I flew in CL Old Time Stunt with a Sterling Ringmaster on a 19BR (no throttle, of course) and often did the most basic static thrust check:- nose straight up, did it lift the 32 oz model? It did, with several ounces to spare. So, that's 2 lb+ static thrust in my own hands.

The net choke area on R/C PAWs compares closely with that of the non-throttle CL/FF versions, so I'd hazard a guess that you should expect somewhere just over 2 lb, static thrust...

with a 9x6 prop the engine will run at about 9500 rpm, so expect a thrust of nearly 2 lbs. A 3 lbs plane will be nicely powered by a .15 diesel. A 2 lbs plane will zip.

Thanks for the advice guys. Lou - do you have a particular spreadsheet link you can recommend? I will try a few different props and measure RPM and make some more approximations, but sounds like in the neighborhood of ~2lbs is what I can expect. Will have to weigh the engine, and see how likely it will be to make a model with a thrust to weight ratio greater than 1:1 (perhaps not too likely).
Thanks
Chris

you can use mine for free [8D]
It can be found at www.mvvs.nl , propellor section.

I've got a PAW 15 (non-RC) in a 590g model (ie about 1.3 lb). This has comfortably more than 1:1 thrust/weight, although I don't know exactly what thrust it's putting out. It turns an APC 9x4 at about 11000.

I wouldn't really want the model any heavier than this (the wing loading is already a bit high with only 250 sq.in.)

Are you sure? 3 lbs is 48 oz! I'm not really happy with a 15 in a stunter weighing more than about 20-22 oz. Maybe my engines just aren't cutting it!

I'm currently building a design for a Tiger replica, which turns a 9x4 at 12000 having just been run in. Target weight is 500g/18oz, with a wing area of 310 sq in and span of 40in. A PAW 19 would fly something like that beautifully.

Shouldn't be a problem!

Right on, will see what I can come up with! I am scaling down and lightening some existing plans for a .25 sized profile type model, so will post some pictures and info on this forum when I get building.

Cheers
Chris

Chris,

Pe provided you the link to the one I consulted...

Thanks, Pe!

Steve111,

You used the word stunter - may I presume CL stunter? If so, I agree about weight and displacement concerns. We NEED to be comfortably overpowered...

For RC, however, the models use a bigger sky, and can take time and distance to spool-up some V. Only in out-of-sight-verticals and hover-type-3D is deadweight and prop thrust a concern.

Pe, by the way, my 30+ year old PAW 19BR did turn 11,000+ on an APC 9-6. Maybe I finally got it run-in?

U/C models have to drag those control lines round and round. R/C models do not. I flew a Ringmaster with a Super Tigre G-30 2.5 cc diesel in the late 1950's into the early 1960's. Full size Ringmaster but construction lightened up some. Top and bottom wing spars at the high point and much smaller leading edge. Fuse also lightened up. Later a full size flite Streak on an O. S. 15 diesel. Still later a Flite Streak Jr. with a Wbra Mach II diesel. The Webra was also used in one of the Veco U/C models. I do not remember which one. All flew well. Jack

Are we suddenly talking aerobatic control line here?
If so, a .15 will power a 2 lbs plane nicely.

@ Lou,
I always keep my numbers conservative.
In CL, I know my diesels vastly outperformed glow engines of the time. I was dearly disappointed by the performances of the OS engines I obtained in the 60-ies. They needed a load of nitro to perform anywhere near my trusty diesels, and then still would not pull a decent sized prop.

Sorry guys - kinda forgot what forum I was on. Came here straight from the CL forum and had CL on the brain![sm=red_smile.gif]

I'll just go and put on my big shoes and red nose now.

U/C, R/C or free flight we are still talking about diesels. Jack

Steve111, re: yr #12.

DON'T YOU DARE apologize for flying CL!!!

We use engines, too, and we often have to pay for throttles we won't use and mufflers we don't want. ...AND, thereby, prove that only R/C engines sell... CL fliers never have enough altitude to fly even ONE mistake high... We are always in ground chop, never in the clear upper air... We are never outside the middle of the aircraft's path in flight, never off to one side, wondering what the air is like way over there.

I've tried RC, and - not knocking it for those who enjoy it - it was not for me. NO tactile feedback. Eye control, not reflex and learned reflex to physical feedback. I had to look, make a move, wait for the response, re-evaluate, etc... For those it works for, enjoy! For us others, we can enjoy what is enjoyable for us, most of the time...

And, if things go wrong, the wreckage is (usually) closer...

Lou: [sm=thumbup.gif][sm=thumbup.gif][sm=thumbup.gif]

A framed copy of that ought to sit above every CLer's workbench.

(Although you might be surprised just how far away some of my wreckage has ended up...)

At least I made a tidy pile in one place!

(Ok, its not a diesel).

Regarding Steve's "Tiger device" C/L stunter he posted about before - I'm going to build one too, and am tossing up between powering it with one of my plain bearing PAW 19s, or a MARZ.