Neil Guildford

I have just bought a second hand F-15 from greatplanes which I am going to recover, maybe spray paint, but can't decide what engine to put in. I fly from a grass strip and the model is currently fitted with an Irvine 53. The model has retracts and weighs 8lb 8oz.
I think that flaps may have to be installed.
The problem I have is the plane is nose heavy and a larger engine will enivitably be carrying more weight in the tail.
Has anyone got any experience with this model?

Neil

CRFlyer

I have one of the GP f-15's. Mine is built mostly stock except that I added a hatch up front to get at the nose wheel/steering mechanism. I have a o.s 46fx on mine and I can say it is not enough engine to pull the plane around IMHO. I also had problems with the bird being nose heavy. I solved the problem by moving the battery pack to the extreme tail of the fuselage.

My guess is you will need to add some weight to the tail to get it to balance correctly with a larger engine.

johntheroadie

My Feedback: (6)

I have a F-15 currently. Like CRFlyer, I also had problems with it being nose heavy. Matter of fact, I flew it all last year with a nose heavy condition. I even cut a hatch out in the tail of the airplane to fit my battery, but it still needs some more weight back there. Even with that issue, it flies predictably....it's not going to blow you away, rather, it's almost as docile as a trainer. Lands better than a trainer too, in my opinion. I have too much rudder throw on mine and it does strange things at full deflection, so keep them low. Conversely, mine requires a lot of elevator to rotate, but I think that's mostly due to the heavy nose. I have a Thunder tiger .46 pro on it and I think that it pulls it around okay, but it definately won't win any speed records.

I also fly from grass, and had a lot of problems with ground clearance and the grass beating my landing gear to death, so after the canopy parted company with the airplane on that last flight of the season, I intended to do a lot of revisions to it this year...namely to fix the nose heavy condition, fit larger wheels, longer/stronger landing gear, reinforce the nose gear former, and put a new canopy on. Unfortunately things have came up this year (namely a baby) and I haven't had a chance to finish working on it. So sadly, I can't report on how it flies right now with those problems (hopefully) corrected.

Neil, if you can, I'd like to see pictures of your retract setup in your airplane. The fixed gear looks goofy on mine!

Best wishes!

magnumeng

My Feedback: (8)

Would a tuned pipe help move the weight back some to help wout with the nose heaviness of the plane?

RANIERY

My Feedback: (3)

hello guys, i have i Gp f-15 to but in the building and moving process i lost all the wood for the wing so i'm stuck with the fuse.
anybody can help with a set of wing kit or something. tower don't sells them no more. thanks

Neil Guildford

I have put the battery and elevator servo in the tail. I did that last night while reducing slop in the movement.
Can someone please tell me where the CG is.
Neil

piper_chuck

My Feedback: (12)

You can download the manual here: http://www.greatplanes.com/manuals/discontinued.html

davbow

My Feedback: (6)

I had 2 of them... I thought they flew great.. Not a speed demon of course but landings were fun!!! and easy....
i had an os 46fx with tuned pipe.... problem is the fake inlets act like big speed brakes.....i always wondered if you opened them up and make a flow through ducting.... if it would make any difference... i did have to add weight to the back.... she did flat spins very well with the cg moved aft...
it was a great intro into delta wing flying.

Neil Guildford

Thanks for the link but it talks about relating to the plan. Can someone give me a measurment from the wing leading edge where it meets the fuz.
Thanks, Neil

hattend

My Feedback: (20)

Well, On page 47 it says the balance point is where the "main spar intersects rib #5" to start with and then plus or minus 1/2" after test flight. Find that junction and draw a line 90 degrees to the root rib to that point. Then balance on the line.

Don

piper_chuck

My Feedback: (12)

Oops, my bad. I forgot about that part. I looked up the measurements I did for someone on usenet in December. This is taken from the plans I have. It obviously assumes that your plane was built according to the plans. The CG range is 114-139 mm back from the where the wing contacts the fuse. From the rear of the wing, again, where it contacts the fuse, the CG range is 259-284 mm forward.

lenjr

My Feedback: (4)

Dear Sir:

Do you know where I might buy a Great Planes F/15 Eagle?

Here is my email address - [email protected]

Thank You
Leonard jr.

piper_chuck

My Feedback: (12)

Sent a PM to you Leonard.

Neil Guildford

Thanks Chuck. On my plane I can't feel the ribs.
I'll post a picture soon of the retracts.
Neil

vicman

My Feedback: (10)

Hey Chuck, are you holdin out on me?![X(]

Neil Guildford

I'm recovering it at the moment so I will show you a picture of the closing doors later.
Neil

piper_chuck

My Feedback: (12)

Vic, holdin out? Whatever would you mean?

johntheroadie

My Feedback: (6)

Thanks for the pics, Neil! It is very much appreciated!

I've never seen an GP F-15 with retracts, so I was wanting to see how it would be done. If I ever get ambitious, I'd like to retrofit retracts in mine as well...

f104g

Both of my GP F-15's flew with an OS 61SF. I put some additional weight in the tail area to balance it up to the correct place...

They both flew very well and lasted me for years.

Neil Guildford

Does anyone know of one fitted with flaps? I'm about to start on stripping the wing back and am considering putting some on. The only problem is it will more than likely make the plane around 9lb. On an Irvine 53 this may be a problem.
Neil

Neil Guildford

ok, this is really strange. I have removed over 6oz of lead from the tail and put the battery in the far back. I moved a servo back for the elevator and I have a plane now that is tail heavy, by a long way. Either the last owner was flying this thing tail heavy or my change in layout has made a huge difference.
Not that I don't beleive your CG measurment Chuck, but can someone else verify where their F15 is flying at, please?
What I'm considering is whether this plane can be flown way back on the CG, and maybe this helps for take-off from grass.

Neil

piper_chuck

My Feedback: (12)

No problem, I got the measurements from the plans for my unbuilt F-15 kit. I need to check out some other things in the kit, I'll double check my measurements while I do that. I may even be able to scan that part of the plans. If I haven't posted by tomorrow, send me a PM as a reminder.

Neil Guildford

Slowly getting there.

Neil Guildford

One with the wing. I've decided against flaps as the ailerons aren't big enough in my opinion to be split in half. Instead I will use 2 servos in the center of the wing to give flapperon movement when needed.

johntheroadie

My Feedback: (6)

Okay, I'll try something...

I dug out my old plans and scanned them on my home scanner to see how they'd come out. I didn't resize them or anything but here are the plan sections that show the CG range on the F-15... Maybe they can be of some help.
I'm sorry I can't give you a good CG measurement from my F-15. Given the recent changes, I wouldn't trust it until its has been flown and proven. []

I think adding a second aileron servo is a good idea. The F-15 is coming along very well, Neil! Looks good!