Bill W G S

I apologize if this seems to be a sophomoric question but it is an idea I would like to explore.

What are the pitfalls, aside from weight and cost that one would experience in creating a scale jet aircraft using scaled down versions of the same construction methods used to make the full sized item? Building the scaled version of the aircraft's airframe in detail as close as possible to the original. Using traditional materials i.e. aluminum and titanium where appropriate. Skinning the aircraft in a thin aluminum composite material and so on.

Thanks
Bill

DaveMatthews

Simply . . .TIME

seanreit

My Feedback: (60)

Yup, what he said:

http://www.youtube.com/watch?v=jg0k7zDsB8w

invertmast

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Weight possibly as well...

LGM Graphix

My Feedback: (22)

It's not a jet, but it is built exactly as teh full scale, just in miniature.
http://ca.youtube.com/watch?v=ncsaUNEzaTw

tothemax

I'm afraid for me it would be the $$$$$$$$$. A full scale fighter that costs taxpayers $50 mil would cost me $10 mil to build an exact model @ 1/5 scale.

Bill W G S

That video clip was quite inspiring! That was an awesome labor of love! Another fine example of why I appreciate this forum so much!

Bill W G S

I agree the cost of an exact duplicate in scale would be very high. There would be some cost savings in that the complex computer controled 4x redundant avionics that are harded against electronic warfare and the even costlier multi phase radar arays and comunication systems would be replaced by lighter and far less expensive RC gear. That said one might try to fashion the radio reciever to look like the radar array and so on. But you do make a very good point.

tothemax

I confess I am am guilty of making a feeble attempt a a little humor. That said I think it would be a noble and a worthwhile undertaking.

Bill W G S

You are perfectly correct in bringing up the issue of cost. Certainly when dealing with expensive materials like aluminum, titanium and composites. I can assure you that there will be no $50k toilet bowl covers budgeted into this project

rhallgarth

That ferrari is the most amazing piece of model engineering I have seen. Totally amazing but I have a little bad news for the guy. He could have bought a ferrari for what he spent on the model but then again modelers never think about that or we wouldn't have 10s of thousands of dollars sitting in turbine models.

mugenkidd

My Feedback: (94)

...

highhorse

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NEVERMIND the cost, time, etc...The real prblem is this:

Where tha heck are you gonna find someone SMALL enuff to crawl into the tailcone and buck those rivets?

DaveMatthews

it would be 343 times less in weight. Remember its cubed, so it would be only 192lbs which aint too bad . . . . . . . LOL (would fly like lead)

Woketman

My Feedback: (6)

There is another issue. On the propulsion lines for the Shuttle, we have certain thicknesses (one for aluminum and one for steels) that are not-to-exceed min thicknesses, as a function of line diameter and based on empirical experience, to prevent handling damage. Were you to scale down everything linearly, I suspect that the aluminum skin would be so thin that handling damage would become a big issue. Any grabbing or touching in a skin area would cause at least cosmetic damage. The airframe would only be able to be handled at the same load points ("lift here") that the full scale was handled at. If every time you needed to reposition the horizontal stab on your workbench you had to get a handling fixture, bolt it into it, move it around, then un-bolt to get access to something, I think we would all soon say to heck with it!!! [X(]

You could scale up certain thicknesses to relieve this concern, but then the weight starts to shoot up.

Ron S

My Feedback: (2)

Dave is correct - you would use the scale CUBED to figure out the final weight, if everything is scaled down correctly per the original poster. Thus, the model would be extremely heavy (relative to normal model construction). It would make a very nice display model though!

Gordon Mc

My Feedback: (11)

Or a miniature Merlin : http://www.dailymotion.com/video/x1y...miniature_tech

Vettdriver

I saw in a magazine several years ago a model of a zero being built by/for the owner of Saito or O.S. or something.
Does anyone remember it? It was being built "as per the blueprints"

Bill W G S

Ok, so let’s get specific, a full sized Sukhoi SU35 BM has a maximum takeoff weight of 76,059 lbs. At 1/5 scale using the cube formula that makes the model weigh 608 lbs. This assumes a fully fueled and weapons laden aircraft. A more normal weight would be 55,776 lbs and 446 lbs scale, 38,600 Lbs empty weight, scale 309 lbs.

While the model of the [link=http://www.youtube.com/watch?v=ncsaUNEzaTw]Ferrari[/link] is impressive there are many fundamental differences between a sports car and fighter jet. The fact that you can make a scale combustion engine that will run is not true of a turbofan jet engine. It is quite impossible to just scale down a turbine engine design and make it work. Even if I had detailed drawings of the AL-41 F1A turbofans they simply would not work in a scaled down format due to fluid dynamics. The amazingly dedicated and talented gentleman who made the car produced every component in scale to exacting detail; that is not exactly what I am proposing.

What I would like to do is produce the airframe, skin, landing gear, and the look of the cockpit in perfect scale detail. The engines would be produced as close as possible to scale dimension. The maximum diameter of the engines can be approximately 8 inches. The N035 Ibis Radar array and associated wiring will be eliminated. Many thousands of feet of wire with heavy couplings and electro magnetic shielding will be eliminated. Heavy hydraulic primary and redundant systems will be replaced with much lighter servos. No flares, rear facing radar, the IR sensor at the front will be replaced with a camera.

Overall I would guess a 20% weight savings from the empty weight, so let say 247.2 lbs Add 10 liters of fuel and that makes 269.2 lbs.

SDCrashmaster

So when you startin' the build thread?

I like Woketman's thoughts on what true downscaling would yield in tolerences. A 250 lb. model with a lithoplate skin would take pinpoint handling to prevent damage.
And I'm sure that lithoplate would even be too thick scale-wise.

Woketman

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One of the things they always say when giving a tour of the NASA Michoud Assembly Facility (MAF) where we build the Shuttle's External Tank is that if you scaled down the ET to the diameter of a Coke can, an aluminum Coke can would be far too thick.

Bill W G S

Right now I am in the research phase of my project. I am building a website dedicated to the model and I will be, for lack of a better word, relying on the collective knowledge and wisdom of those who wish to contribute intellectually. These contributions will influence how I will proceed. The wed site will be www.su35bmmodelproject.com, if you go there you will find it is still under construction.

Bill W G S

What is a reasonable thickness for a full scale aircrafts outer skin?

Woketman

My Feedback: (6)

I have been away from aircraft for far too long. I used to know the thickness of the C-5B's skin, but the Miller Light washed that away a decade ago!

Bill W G S

After some more research it seems that .3mm, .25mm and .2mm litho would be appropriate scale material. The next consideration would be stress fatigue on such thin material but being a scale aircraft fly time is usually limited to 15-20 minutes at a time.