Selcuk

Hi,
I am from Ankara, Turkey. Love to scracth-building and currently working on a f 15. I used Pavel Bosak's f15 plans for air frames which is originally for pusher prop engines of 46-60. BUt I modified to ducted to fan by using RK 740 from Kress jets without retracts. Actually the airframe is about 3.5 lbs and expecting to be around 6 lbs. We do not have any ducted fan plane in our club and even I have not seen anyone.So I need your help... Problems are

1. How can I do the inlets and outlets?

2. I will order the engine in next week and planning to buy os 46 vxdf. Do you have any advice?

3. planning to put one steering servo, battery and receiver under the cockpit area, two servos for ailerons under the wings one servo for throttle. Elevators are the main problem. How can I control two elevators with one servo? Where do I place it?

4.Where do I put extra tank?

5. CG is planned to put which is shown in the plans. Do you have any advice for cg of f 15 airframe?

6. Any valuable suggestion?

Thanks in advance

Selcuk

Selcuk

three more pictures for f15 fans...

Johng

My Feedback: (4)

I suggest reposting this in the Scratch Building forum, since there are alot more hackers in there. Folks here tend towards more prefabricated kits. Anyway, I'll say what I know.

First, if that orange bit is the fan, it is located too far forward, both for aerodynamic and CG purposes It needs to go back amidships. AS it is, it is too close to the forebody to allow the air to smoothly enter.

Once you get the engine located, you can make the ducting out of paper at first. THis is only to get the shape. Then you need to fiberglass the paper shapes with very light fiberglass to give it stiffness and fuelproofing. Another way would be to get pieces of foam and carve them to the shape of the ducts you need. THen fiberglass them and melt the foam out with acetone or gasoline. Either way, you need to plan ahead to make the pieces small enough to fit into the plane then fit back together.

The OS 46 is a good motor from what I have seen, but I haven't used it. However, almost no one uses the Kress fan. The Turbax 1 fan is most widely used with that engine.

Use 2 servos for elevator. Standard servos should be fine, so it won't cost much money and will not be any heavier than all the gizmos you would need to run the controls from one servo.

You say you won't use retracts, will it have fixed gear or no gear? You might want gear at first, but it's weight and drag. I would recommend making the gear removable or even making a launch dolly so that you don't have to lug wheels around during flight.

Fuel tanks - put them at the CG, close to the fan. Sullivan has saddle tanks that will carry 22 oz of fuel a pair, a good amount for a 46. Look here - http://www.sullivanproducts.com/Fueltanks2MainFrame.htm

Follow the plans for the location of the CG. THe overall shape of the airplane hasn't changed, so the CG location won't either.

Turbulence

My Feedback: (76)

Selcuk

You are off to a great start; let's begin with some of the problems you need to address. Below are some general ideas but will require to test and make sure they work for you.

How will you start the engine? Will you make a hatch and can you get a starting wand to the engine?
Since you want to use ONE servo for elevators, then you will need to place the servo somewhere in the front or middle of the plane. Then run TWO rods to the elevators. This can be done with Ny-rods if the servo is in the nose or if closer then you can use some 4-40 rods. What ever you choose, they have to form a " Y " when they come out of the servo.

If you select the option of placing the servo in the middle of the plane (if you can do it without getting in the way of the ducting you will make later). Then your main focus should be that BOTH rods travel are set in way that they move exactly the same. You can connect one to the servo and then solder the other rod to that one. If you go the ny-rod way in the nose, then you would do the same (referring to the Y ) then make sure that the outer sleeve is secure in the way that when you move the elevators, there is no flex in the line.

Ducting: Since I don't know what material you have to work with, here are two. If you can find some thin Lexan (plastic) then you can roll that up to make you ducting. The other option which would probably work better for you since you are doing the twin exhaust would be thin plywood. You can soak the ply in water for a couple of minutes so it can soften, then slowly roll it into what ever shape you want. (I think some people have even used vinegar to soften the wood, but I have not tried it, too smelly).

Fuel tanks. Well if once you make your ducting you will see what space you have left to work with. The tank DOES NOT have to be a ducted fan tank, but saddle tanks where popular because they would fit where other would not. Any tank will do as long as it fits in the airplane. I think you should make the ducting first, then worry about the tanks after that.

Last if not least, let me know if you need pictures of the servo set up, I will try to make whatever I described and take pictures of it, if you need them.

Turbulence

volkan

Hello
this is a bit off the subject, but i am from turkey to (but i live in London) i got to turkey v.often, but i want to fly there. any shops you know of in istambul (erankoy side)

thanks

Volkan

sidgates

My Feedback: (2)

Did you happen to go to school in Denver, Co. USA at one time. I helped Selcuk Gucheri (spelling ??) When he lived in Denver.

Selcuk

Thank you very much for your responses. I carried back the ducted fan system about 1 inch, found thin (250 Microns) Lexan and now building the ducts. What is your opinion about changing the ducted fan system with dynamax fan, os 91 vrdf and standart tune pipe. I calculated the wing loading as 41 ounce per sqfeet. Is it to much?

Volkan,
There are two model hobby shops at the Anatolian site of the Ä°stanbul.

Sidgates
I am not Selcuk Guceri. I've heard his name, asked to my club members. If I found him I will give your name.

Thanks.

MDSCUSTOMS

Hi Selcuk,

Firstly I would forget the OS46 engine for this one as it is not going to give enough thrust for you - This Plane was designed for .60 engines using a normal prop. Normal props give far more thrust than a ducted fan. So if you can get that OS.91 with the dynamax unit in there I would opt for this. You will get better thrust from it and better performance.

Also with the extra power of the OS91 - You should really consider fitting a set of retracts on this plane - the extra weight of them is not a lot.

Keep the centre of gravity where it is marked on the plan - this is marked at this point for a reason - You may need to move components inside to keep on the balance point.

Keep any ducts / airflow to the fan unit as smooth as possible.

I have these plans too - nice to see someone actually attempting a D/F Conversion

Good Luck

Mark

FalconWings

My Feedback: (57)

.........only that it was 7 years ago.

MDSCUSTOMS

Oops - I looked at date of last log in rather than date the thread was started - The advice still stands true though - anyone know if this one was ever finished..??

Mark.