F-18
 

I have now owned two F-18 singles from yellow and in comparing them to many other DF planes I have flown, they don't perform as well in the takeoff/landing configuration. They need more speed to lift off and don't slow down as well in the pattern. Is this the observation those that have owned and flown them would have?

F-18
 

Hi,

You said 'in comparing them to other planes...' Which planes are you comparing them to? Most DF planes I've owned can take off in a shorter distance than the F-18, much like you said, but getting it slowed down in the pattern seems very easy. In fact, the F-18 single probably has the shortest landing/rollout distance of any of the DF planes (including sport planes) I've ever flown.

F-18
 

I was always afraid to let my f-18s slow down too much on final until I was told how to correctly. Proper use of the flaps and throttle control and the jet will come in nose high and slow enough to make you think, "That looks too slow!"

Planes
 

Shaun

I started flying byron many years ago with the MIG, F-16 and F-86. I've flown F-15's from Top Gun, Avonds. F-4's from yellow and Miller. BVMs include a couple of Maverick Pros and an F-86.

I won't argue about the landings, but these all seemed to get airborne much easier than the 18s, and many seemed to provide more natural lift on approach.

I was just trying to see if maybe I had a couple of problem planes, or if this is just the nature of this model.

F-18
 

Hi,

Well, with the exception of the Miller F-4, you named a whole bunch of planes that get airborne faster than the F-18! Now that I know what you're comparing them to, I can pretty much agree with you. Part of the reason is the aft point-of-contact of the main wheels (because of the joint in the main gear). You'll notice a substantially shorter takeoff roll if you use flaps on takeoff.

I don't think you have problem planes--it's just the nature of the beast. Do you use flaps on takeoff? If so, how much?


Thanks

Re: F-18
 

Actually.. the F-18's that I've seen are very solid in the landing phase. Very few scale airplanes this size are as good as the F-18 in landing.

More Info
 

Thanks for the reply Shaun.

Yes, I use 10 degrees of flaps. More info: Runway is paved 600 feet, really by the time you get rolling and pull up, about 500. I was taking off into a 10 MPH breeze right down the runway, straight take-off roll (no weaving around), engine was running very well (in-flight mixture set to max rpm takeoff), 10 degrees of flaps. The only negative is that it was a hot florida day, so density altitude was probably in the 1 to 2k area. Plane weighed in at 15 pounds on the button, flown clean. Single tank up front, balanced at 12 3/4 inches from the trailing edge with the gear up and the tank empty. Used all the gear and struts from the kit, with a slight positive incidence on the main wing, but not much.

Plane could be horsed off, but wouldn't continue to fly as the flying speed really couldn't be effectively reached with this setup. Spot anything wrong?

BTW, the miller kit with the byron fan set up was not bad at getting airborne. I flew it off grass.

Thanks, Keith.

F-18
 

I had the 24oz tank in front of the fan on my first y/a f-18. Take off was always a fight because adding that much fuel to the front of the plane after setting the cg made it very nose heavy. My new f-18 has the conformal cells which place almost all of the fuel over the cg point. You actually set the cg with the tanks full. The new plane comes off the ground with much less takeoff roll and flies much more consistently throughout the flight due to the cg staying more consistent. The conformal cells also give you more fuel, 31oz compared to 24oz. During climb out the 24oz tank is lifted way above the motor creating a rich mixture which could also effect climb out power.
I usually use 20 deg. of flaps on takeoff. Shaun may have more info for you. I was just trying to give you what I know from past experience, and from what Shaun has told me.

F-18
 

Keith,

Yes! I spot something wrong. In your inflight mixture, are you setting it up for 110% on the deck, then richening it up in the sky? You'd kinda need to if you're using the single tank up front. Try this: Set up your engine to takeoff RPM, then lift the nose up until the tailcones hit the deck. You'll probably notice a richening up of the engine due to the 'gravity feed' happening now with your fuel. Use of the conformal tanks will drastically improve that situation, basically eliminating the use of the remote mixture. With them, you can turn the plane in whatever attitude you want, and the RPMs won't change.

My first one was using the single tank, but never since. The conformals can be a pain (especiall if you use a Ramtec), but they're worth it as far as engine reliability goes. Hope this helps.

F-18
 

Shaun, sent you a pm

Mixture
 

Shaun

Yes I am right on the edge of lean when on the ground. I am using a hopper tank set off to the right at carb level, so I don't think the angle of attack should make a huge difference. The engine doesn't seem to be going rich when I try to rotate. The real issue is, I can't get enough speed to generate lift in the 500 feet I have to work with.

From experience, I can tell you the fan is turning up OK and the jet moves down the runway just as well as anything else I fly. I guess I need more runway, particularly here in Florida, to get the speed/lift ratio where it needs to be. I think I'll wait for a cooler day, maybe at a jet meet where I have 1000 feet or so to try it.

I can't take much weight out of this airframe, as I didn't build it. I'm sure at 13.5 or 14 pounds, I would see a difference.

I do have a set of conformal tanks, but they won't go in without tearing out the fan mounts, and I don't want to do that.

Thanks for the prompt messages. Keith.

F-18
 

Keith,

Well, interesting. Are you using the scale wheels and brakes? Are they spinning freely? The older ones had brass bushings, and they could stick. That could be something to look into.

Try that test I mentioned. I think you'll see that the use of a hopper won't make any difference as far as what I'm talking about goes. If your hopper is plumbed to your fuel system, then it's all in the same loop. Though the carb is drawing from your hopper, the hopper is drawing from your main tank, so if gravity suddenly helps out the hopper to get fuel, your carb will react accordingly.

500' says something is wrong, big time. There's no reason you shouldn't have that bird off in 350', in St. George, without flaps, in relatively high heat.

Wheels and brakes
 

I'm using the scale wheels, and they do spin freely. As I mentioned, the jet was making good speed down the runway. I'm flying a maverick pro most often right now and the speed is similar, yet the F-18 doesn't want to fly. My last one did the same thing. I'm puzzled.

Anyone else out there flying the F-18 with better results?

F18
 

Keith's sounds exactly like mine with the exception of the landings. Mine slows to a crawl on landing. All I have is about 500' and then it slopes down about 3' at the end. I taxi all the way to one end and let it run on the ground all the way off the other end. But then again I am at around 2K' altitude and the temps were in the high 90's. Sounds like our all up weights are similar. I did not build mine either. The first flight on it was very intersting. it was tail heavy and the engine kept cutting in and out. The slightest elevator input at slower speeds cause a wild nose high rotation. I barely got it down in one piece. I will have to check those tanks.

Thanks Shaun

Ted

F-18
 

Hi,

Hmmm. Well, I guess I'm out of ideas. I do think you should check out that 'raise the nose at full throttle' thing. You might be surprized. So far, it's had the same results on each one I've tried it on. It's the main reason they made those conformal tanks....

There are several videos that feature that airplane taking off in short order. I was flying a Blue Angel ARF in the Arizona Jet Ralley '99, and the takeoff is in less than 300' with DF. We must solve this mystery.....

F-18
 

I would check your CG 1st, and ensure your airplane is sitting slightly nose high on the ground. With the CG ahead of the main gear, you'll need a fair amount of elevator to unstick. Shaun's idea of using flaps on takeoff is good too since that gives you positive angle of attack without any other changes.

Re: Mixture
 

I'm not sure how you have your hopper tank plumbed, but if you have it setup with one inlet from the main tank and one outlet to the engine, with no other connections to the hopper tank, then the hopper tank DOES NOT effect the relationship between the main tank and the carb - all it does is act as a bubble trap. This has been discussed ad. neausium (sp?) in the heli. ranks and if your hopper is plumbed as I described, all it is, is a "fat fuel line." Raising the main tank above and below the carb line with a hopper like this will still richen and lean the mixture just as if the hopper wasn't there.

If, however, the hopper is vented to the outside air pressure and the fuel is pumped into the hopper (this would require some type of valve to regulate the level in the hopper, I would think), then the position of the hopper would influence the mixture at the carb.

Bob

F-18
 

Is it possible to have to much toe in on the wheels. I know the F-18 takes alot of toe in but could there be to much. Are the landing gear in the right place? Would the surface of the runway affect the distance of the take off run.

Just my thoughts.

F-18
 

Recheck wing incidence as slight up when sitting on the ground and check elevator incidence to main wing. Make sure your elevator has enough throw and the elevator servo has enough torque. I had two df F-18s (approx. 14 lbs each)and they both took off in 300 ft and landed in 100 ft. My turbine F18 at 22 lbs. wet will also take off & land in the same distances.

18
 

A couple of simple things to make the small 18 a bit easier to handle.

First, use a notch of flaps for take off. About 15 deg would be about right.

Second, you need ot use a dual rate on the elevator. About 1.5 inches of up for take off maybe even a bit more. After you ahve cleaned it up, to fly and land you only need about 1/2 - 3/4 inch. Electronis softening of the center is also reccommended. Futaba - neg expo, JR - expo. 30% or so would be good number.

Good luck.

18
 

A couple of additional points.

CG is importand and this plane, maybe more so than most other of the smaller df's and it was not designed to have a single tank in the front. The conformal tanks are very close to the CG making fuel not much of an issue. That may be where some of your problems are. You may want ot balance it half full. I believe the plane is to be balanced wit the gear up as well.

Here in Florida a 85 - 90 deg Summer days with lots of Humidity gives you a density altitude of 5 - 6 K and sometimes higher maybe as much as 8K, that is pretty high.

Maybe as high as 20 deg of flap for TO.

JB

Thanks
 

Thanks to all for the feedback.

While I hear you on the tank situation, the problem isn't that it goes rich when it leaves the ground, the problem is, it won't leave the ground. Leads me to believe I need to check the wing incidence, which I will do. I also think the high Density Altitude has something to do with the reluctance to fly.

I am using a notch of flaps. As I said, I can horse it off, but we all know what comes of that. Nose job.

The airplane is smooth on the runway -- speed doesn't seem to be the issue -- it moves along just fine.

The CG is right on, based on the data I was given. I'm sure with the forward tank location, it tends to be a little nose heavy on takeoff which can't help. The instructions I got said balance it with the tank empty, which means full on takeoff, the CG has got to be somewhat forward. I would guess most of the guys who gave me feedback are using the conformal tanks.

Based on all the feedback, it sounds like the plane has a narrow band of performance for takeoff, which means one or more factors on my bird leave it outside the acceptable envelope. My guess is they include the forward CG with the single tank configuration, possible incidence problems, the somewhat heavier weight, and my high DA issue with summer Florida flying. Sound about right Shaun? K.

F-18
 

I have been reading this thread & following it from its start & its more the reason I am turbininzing mine.I just bought a new YA F18 single & shes slated for a sweet lil' Wren54.The all up weight wont be much more than its DF counterpart & I dont think I will have any issues of takeoff dilemas.The thing I love about the Wrens is that they are fuel sippers(approx. 5 1/2 ounces a minute)and they are very light!A wren w/o autostart is just over a LB & I will only need 50 ounces on board and my UAT.The amazing thing is that a complete DF powerplant is heavy,I never realized just how heavy they really are!I after all this time decided to recently weigh one of mine along with a bvm pipe-it was 4.8 lbs,I was like woahh.Compare that to a light lil' Wren and bifricated Tam pipe & tell me just how sweet this 18 is gonna be.I dont think I will have any concerns whatsoever with mine.I plan to even load mine up with sidewinders , wing tanks & still dont think it will pose any issues .Everyone I have talked to about the YA F18/Wren combo thinks it will be very awesome.We dont have takeoff distance restrictions either so the takeoff roll no matter how great or small wont be an issue @ 8000 feet of smooth pavement-thanks US NAVY :D


regards Steve

New Approach
 

Shaun, I think Steve has it right.

Your first reply should have been "I'll give you a great price on the twin kit, stick a P160 in it, and performance won't be an issue."

f-18 help
 

I have the same yellow f-18 single and I had a problem
with mine on take off,it would take all of the runway before
it would rotate and when it did it barely had enough airspeed
to keep flying I had many hair raising take offs and could not
figue out why it would not rotate.I was told by a club member
that I bought the plane from to make sure that the plane had
a nose high attitude when sitting on the ground,I extended the
nose gear out about an 1/8 inch just enough to get the nose
a slight up attitude.And wouldnt you know it worked it rotates
with or without flaps in alot less runway than before.try it