Guys (and Gals)....

I just happen to be in possession of 2 evoJet 90's and they need a home....so I was thinking twin F-4 but my buddy Ozie slapped me about the head and shoulders for even thinking the thought.... Then I thought A-10, yeah that would be cool.... and then it hit me, why not do a model of one of the jets I actually work on? Hey now there's a thought! So, I sized them up and made my choice (sorry BBJ, maybe next time!).

That brings me to, building a model of a Gulfstream G550...but ALAS there is no commercial model of said airframe...So I guess it is scratch build time! Now I am a fairly good builder but I am by nobody's description a "scratch" builder, so I come to you with hat in hand and ask for assistance.

I know what I want but I have no idea where to start. I have two turbines and an idea.

This is what I know: 2 engines, about the same physical size as a P-70 and they put out a conservative 19 pounds of blow. (See I told you I don't know much!)

Anyone care to suggest on how to proceed?

Some pictures of the intended subject:

Well, great project !

First, you have to imagine the size of your future plane. You know the thrust of your engines, so, lets take a thrust/weight ratio of 0.5, that is a good value for a liner jet.

So you have twice 19 pounds of thrust, that should make a plane of 76 pounds. Now you have to found the scale that produce a plane of 76 pound of final weight approximatively.

For exemple, have a look at Aviation Design Falcon 7X here : [link]http://adjets.free.fr/adjetsv6GB/falcon/falcon.htm[/link] This plane is 69 Lbs weight for a single Jetcat P160SX turbine. That's near your though...

EDIT : The AD Falcon 7X should be a good subject for a twin turbine conversion with twin "90 size"...

A model of similar layout (Lear 35) is on my to do list but to a much smaller size so it will be interesting to see where your project leads.

Step 1, pick other people's brains.

Sean McHale is building a Frankel Learjet on RC Scale builder:

http://www.rcscalebuilder.com/forum/...638&PN=1&TPN=1

It's an EDF conversion of a model that's been ICDF & turbine powered, many problems will
be similar to what you have to solve.

Good luck! - John.

Inbound - About 5 years ago I was where you are now. I wanted a jet model of a plane that I could not buy as a kit or ARF. I had no experience with making molds. After hours & hours of research and study on mold making and consulting with two friends I started.

I used some ideas I came up with that I feel worked very well for me. You can see the basics on my web site at: http://www.sidgates.us

Look under "Models" then "F-94C" If you have any questions call me 303-757-7019

WARNING - It takes a lot of dedication to finish a project like this. I am finally close to my first test flight.

It is all dependant on you engine choice... Physical size is what I'm talking about. The engine Diameter determines the Nacelle diameter and the rest of the airplane has to be scaled from that. It is what is is... It's the only way to build any type of aircraft with engine nacelle's wheather on the fuse or on the wing.


Good luck !!!

Danno

P.S. If you need some assist with this project, P.M. me, I might be able to help you.

I have documented a lot of my scratchbuild in my A-6 thread on how I got formers and such. Might find some useful info in there.

Mark Frankel has a Gulfstream IV on the way. Fuse and gear are complete.

Thanks fir the replys guys! I guess I need to get some drawings for measurements. The engines dictate nacell size and that determines the size overall. So, a few basic questions....

How do I calculate the nacelle size for scale? I know the size of the evo 90 and I can get the full scale measurements.....

Westwind two, you have any details on the GIV, a link perhaps?

On my large multi-engine project, i increased the size of the plans until i had a good size nacelle/cowl. The rest of the jet followed suit....Good luck, i love the 550-may look to fly them here in a few years!

modelspecialties.com

Dave,

How close are you to Vegas ??

How does Las Vegas Blvd and Tropicana work for you? Actually at this moment I am sitting on the ramp at KLAS.... Why do we ask?

I was gonna look you up next trip out... Like to talk to you about your project. No worries...

Danno

UPdate:

I have some professional help on the project! A flying friend of mine is skilled at CAD and has offered to assist me on this. He also has some CNC equipment that will aid in making bulkheads and other parts...

I am on my way!

Dave,

Are you building one plane only, or are you doing plugs and molds for multiple kits??

Danno

Plugs and molds, plugs and molds! Or shoot, if your doing cad work, do some wood fuselage bulkheads, foam wings and a fiberglass tail section of the fuse, fin and nacelles

As this is my first attempt at a project of the magnitude I am planning on traditional building techniques. I will be making a plug for the nacelles.

If she flys I will use that as a prototype for a plug and molds( kits). Stand by to stand by....

Dave, I like what I see my man! This will be a fun project for you and for us to watch happen. There can't really be any substitute for being by the airplane you will model and having the chance to see the airframe up close on a daily basis. The best scale models have been based on engineering drawings and more importantly many personal aircraft visits where the naked eye can take in details as well as quality original pictures meant to help get the lines just right and that do not distort the purportions (easier said than done).

There was a G-IV EDF model made of foam that was released in 1999 or 2000 from a German source. As I recall it had about a 72" wing span and was designed for contemporary fans at the time that would deliver about 2 pounds of thrust each and it had a total weight of about 8 pounds, and was bungee launched of course in typical EDF European fashion at the time. I've seen several videos of it flying and it flew wonderfully on modest power when throttled back. The wing is so naturally efficient that it doesn't even need .5 thrust to weight, but for a model with landing gear, at least .5 or .6 would be nice to have. I have a feeling you may want to demonstrate what a nice, clean and efficient G550 could do without the limits of guys worrying about ther licences (aerobatics)

Good luck, and please do it!