Scratch build turbine trainer
 

Hello all,

I want to scratch build a turbine trainer for my Simjet,
Don't want to be cheap, but I got so much balsa and ply in stock, master most building techniques and above all enjoy scratch building that I don't want to buy a kit.

I would like some basic measurements to start with, based on the facet 1200 as I like that concept.
Complete drawings would be nice, but I don't mind drawing something up myself.

My wishlist:

-Wing profile
-Dihedral amount
-Plan or basic sketches suited for taking standard measurements
as tail planforms, distances etc.

Would really appreciate any help
Thanks in advance,
G.J.

Scratch build turbine trainer
 

Not even a wing cross section (profile) of the wing root?

C'mon guys, I won't say anything bad about any manufacturer, I promise. I think they are all good.
Not a bad word about BVM either, does that help?
Come on, some help for a creative fellow modeler...

Scratch build turbine trainer
 

Well, here is my advice...

There are some excellent books out on the market for designing model aircraft. Just because one chooses to use a turbine for propulsion, the basic concept of airframe design and of course aerodynamics remains the same as that for a propellor driven craft.

I like the book onmodel aircraft design by Andy Lennon, a Canadian, who also wrote a ton of technical stuff for Model Airplane News magazine. I believe it is no longer in print, however, and my copy I bought 15 years ago will remain a favourite. One good book, I just picked up in the last few years, is published by Traplet publishing, and is excellent also, allthough not quite as thorough. Look on the Traplet website to order...

Now, for the meat and potatoes of designing your own craft: for the most part, it depends upon what you are looking for in a plane. For a good sport plane, with moderate top end speed but good aerobatic and low speed flight go with a nice thick symmetrical section, I like 16% or even 18% thickness. As for diherdral, again for good aerobatics a flat wing is totally acceptable. I have built 3 large scale planes of my own design (two large gassers and one a turbine) and all three had no dihedral, ie, perfectly flat wings. With ailerons, you dont need any. If you do want some try 2 or 3 degrees.

I like to start off by designing the wing, ie wingspan and chord, and then the fuse length which then allows calculating the tail surface areas. These formulae are all pretty basic, and in the books I described above.

My advice is just go for it! It isnt as hard as some would have you believe to design your own model and have it fly great. I have done 7 or 8 of my own and if you are following a traditional layout you cant really go "wrong" unless you have something way out of whack.

here is the link to the Traplet book:

https://www.traplet.com/pages/nonmag...&id=31&-search

As far as actual construction goes, it is really dependant upon how much experience you have building kits and such, to know what size materials to use where, etc. Good luck and best of all enjoy the process!

AJC

Scratch build turbine trainer
 

Viper1,

I concur with AJC... Check out Thomas Kamps books, particularly "Radio Controlled Jet Model Guide". There are a lot of ideas in there and he covers installation considerations.

Good luck!!

Scratch build turbine trainer
 

As I understand it the Facet is a short kit anyway, the builder must supply some of the wood for the kit (I'm not sure exactly how much).
It looks like a great flying jet trainer and it is very reasonably priced.
Unless you are just dead set on designing your own turbine trainer it sounds to me like the facet kit might be just what you need, so why re-invent the wheel?

Scratch build turbine trainer
 

Thanks for your help guys !!

Any airfoil in mind? how does NACA 65(2)215 look ?

14.996 % thickness, camber 1.926 %

Regards,
G.J.

Scratch build turbine trainer
 

If you're designing a trainer then why the laminar flow airfoil?

The whole point in building a turbine trainer IMHO is to build something that doesn't go that fast and allows you to learn the quirks of flying turbines. You want something that handles well at slow speeds and doesn't allow the speed to build up.

The NACA 65(2)215 airfoil seems unsuitable to me for a couple of reasons:
1) Sharp stall.
2) Good for higher speeds. Not so for lower speeds... At high AoA laminar airfoils really suck.
4) Low drag at high speeds. You don't have a prop slowing you down, you don't want it to get away from you.
3) Difficult to build. Hey, a trainer should b simple to build.

I would go with a simple semi-symmetrical/fully-symmetrical airfoil with a large LE radius. Something that is designed for slow speeds (Maybe S3016? S2027?)

15% thickness seems o.k. to me. You could go up to 18%. Just remember that slow for a turbine is still a 3 figure number in mph...

Scratch build turbine trainer
 

I just used something like a NACA 0018 or 0016, full symetric with a nice blunt LE.

Why not just "borrow" a nice wing rib design from any other plane you have, my first own design giant scale gasser I enlarged the Sig Astrohog rib 160% and it works awesome!

Now I prefer full symetric and no dihedral, for flying inverted as well as upright.

AJC