TXKflier

Have you flown yours yet? I plan to maiden mine tomorrow...

Tomorrow's forecast: Except for a few afternoon clouds, mainly sunny. Warm. High 88F. Winds S at 5 to 10 mph.

Perfect..

CrashPro

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Maiden day for me tomorrow too....good luck with yours TXKflier....tomorrows forecast here is high of 99[]...2 mph breeze right down the runway I should have a video up tomorrow eve...

vasek

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Damn that plane looks fine! I'm so tempted

V.

CrashPro

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Maiden flight was successful,...however, was cut short because the one-way air valve decided it wanted to be a two-way valve,...lost air pressure and the gear dropped. Sorry the video isn't all that great,..it was hard to keep the plane in the view finder.
http://home.dc.rr.com/maurie/F18%20Maiden.wmv

virtualvictum

Very nice flight for the first one Crash!! Keep it up. What do you think of the roll rate at the recommended cermark low rate settings? I think they are quite fast. I have not attempted a high rate roll yet for fear that the wings will be thrown!! Motor sounds good as well.

CrashPro

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Hi virtual

I haven't flown the plane yet,....I had one of the more experienced pilots at the field do the maiden,...as I'm the only guy that does any videoing,and I wanted to get the maiden flight on video.He only did one roll,....and I wasn't zoomed in at the time,...but he said it was extremely fast. He didn't try it on high rates, as the flight was cut short. I put 20% expo on the low rates and 40 on the high. I doubt if I'll ever hit the high rates switch tho. I'll order a new one way valve tomorrow,...suggestions?.....Robart?

virtualvictum

Hey Crash, glad all went well. I haven't had any problems with the one way valve on mine. Maybe you should try Cermark and see if they will warrnty the vavle. If they will replace it then why spend your money? If they won't then I believe you can get one from Tower Hobbiescfor a reasonable price. I would go with Robart or Century Jet. I have both and no problems with either.

TXKflier

Well, the weatherman missed the wind forecast a little bit. The wind was about 15 mph at about a 20 to 30 degree angle across the runway from the right. However, it was fairly steady.

The maiden flight went pretty well. I raised the gear on takeoff and flew around for what seemed like 10 minutes. I made a few approaches to check the low speed handling. Then I did a touch and go. I don't know if it was the wind or the plane, but my F-18 dropped like a rock and was difficult to keep from touching down too hard. The nose would get pretty high and the plane would sink pretty fast, but there was no sign of tip stall. I imagine I should have kept a little more power on it.

For the first flight, I had it balanced at about 6" from the root leading edge. When I rolled it inverted, it took an awful lot of down elevator to fly level. So, before the 2nd flight I added weight to the tail. This moved the C/G to the specified 7" from the root L/E. I refueled, cranked up, and headed out for flight #2.

As I climbed out after takeoff, the engine sounded like it might have sagged. So I throttled back a little, turned downwind, came around, and landed. I opened the needle a bit, checked the top end, and headed back out. On this takeoff run, the engine was a little too rich and I was having trouble keeping it straight. It drifted off the right edge of the runway and as I throttled back, it zigged back to the left, hit the edge of the asphalt, and jumped into the air. The airspeed was low and the nose was getting higher. I opened the throttle as I tried to lower the nose, hoping I'd be able to set it down without destroying it. However, as the engined revved up, I realized that the edge of the runway had shattered the blades on the Zinger wood prop. I had no choice but to throttle back and let it do whatever it was going to do. It was now about 10 feet high with the nose straight up and zero airspeed. It suddenly did a stall turn to the left and came straight down, hitting the asphalt runway squarely on the spinner. We could see the fuselage buckle from the engine back to the wing L/E. Then it fell backwards, coming to rest on the landing gear with the fuel tank and engine laying on pavement. Amazingly, the only airframe damage other than the shattered nose is a tiny ding in one wingtip.

It will fly again... but with more horsepower. The new OS .61 FX I had in it is marginal for this plane. I have a Jett .90L, but I don't want to feed it. I may try a Magnum .91 XLS in it next time..

CrashPro

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ooh.......bummer TXK......I assume you're just gonna buy a new fuse?

TXKflier

Nah, I'll tape it all back together with Scotch tape on the outside, then put glass cloth and epoxy on the inside..

CrashPro

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yeeeeeeah!!,...now you're talkin!!!.....thats exactly what I'd do!!

TXKflier

Then I'll remove the tape, sand, fill, sand, prime, sand, and paint it..

Did you notice the hardware on my elevator pushrods and how I drilled and tapped the arms for setscrews? I've never liked metal clevises on metal arms, even after the arrival of FM radios. And, I didn't trust the gripping power of the clamp on Cermark's arms. I didn't want them slipping on the flying stab shafts.

I also balanced my horizontal stabs. I set up my Dubro prop balancer in the over/under mode and added weight at the root L/E until they sat level. It took about 0.65 ounce to balance each one. For weights, I cut two pieces of 5/16" all-thread about 2" long and made a slot in one end of them using a hacksaw. I drilled about a 9/32" hole in the stab root just behind and parallel to the leading edge. I mixed up a little 5 minute epoxy and screwed them into the stabs until the ends were just below the root surface. It seems to me that 1.3 ounces is a small price to pay to know that my horizontal stabs won't be trying to fly through the air backwards.

Yes, I've read everything I could find on RCU about balancing control surfaces and saw where many folks don't think flying stabs need to be balanced. It's my personal belief that every individual flying surface that could possibly come off an airplane must have its C/G at or in front of its center of pressure. Visualize an aileron that has been removed from the back of a wing. By itself, it kinda resembles a wing, doesn't it? So does a rudder or an elevator. They each have their own center of pressure and center of gravity. What happens if the C/G is behind the center of pressure? They'll want to swap ends when travelling thru the air. An improperly balanced control surface may never flutter, but it would like to. The only thing stopping it from doing so is a tight linkage. And that's just not good enough..

cutter-nj

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Hey TXKflier sorry to see your plane damaged like that, I had some minor damage to the nose that I was going to fix in the same way. I am contemplating if I should try to paint it, do you have matching paint or are you going to repaint the entire plane. I e-mailed Cermark to ask for touch paint but have not gotten a response.
Please post some picture of the repair.
Good luck.

Sparhawk

The jury is still out on whether or not stabs should be mass balanced. On an All Flying Tail (AFT), having the cg behind the center of pressure is bad, however, when the pressure is behind the cg, the stab will always want to weather vane into the wind, much like a flag. This is good! This greatly relieves the stress on the servo setup when the plane is at speed, and of course becomes a little greater as the speed comes down. The real F18 does not have balanced stabs and drop like bricks once the hydrualic pressure comes off them.

Personnaly, I have never balanced an AFT and have never had any problems with them. It is too easy to install digital servos that are overkill for the required torque. Hitec 5645's on 6v are more than plenty to fly this plane. The mechanical setup should always favour the mechanical advantage side, ie: in on the servo horn, out on the control surface. Of course, if tail weight is needed, why not add it to some place that will do a little good, like the stabs? I just would be cautious as to how much you add. You always want them to drop aft, rather than have them closer to neutral.

Spar

funflyerf4

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Don't know what all the fuss is about?I have the F-16 with over 400 flights and no problems with the Cermark controll linkages no slipping or problems.Blancing the aft.Why?I am over 50 flights with the F-18,The roll rate is great about 2-3 on the stick movment It is a quick roll rate I love it.It lands great and flys great.It has been radared at 118 but there is more speed in it.I feel it is quicker than the F-16 which has been clocked at 126.

TXKflier

I don't have paint for it yet. Cermark says it's covered with Oracover. Some people say Oracover is the same as Ultracote. There are matching paints for Ultracote. Perhaps it'll match Oracover. It appears to me that Ultracote Deep Blue is a close match to the F-18, but I don't know for sure. If I can't find matching paint, I'll probably get some blue and some white or black and mix my own. I'm not planning on painting the whole fuselage, but I may end up having to. I wish I could go to the auto parts store and buy acrylic lacquer like I could in the good old days..

Lynn

vasek

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funflyer,

what size prop are you using on the LX 90?

Thanx, V.

funflyerf4

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I use an 11-8 and tachs at 14,800-15,00 on the ground.

TXKflier

I finally started repairing the broken nose on my Cermark F-18P. The first photo shows the half of the firewall that remained in the nose. I broke the firewall out using needle nose pliers. I then ground out all the epoxy and microballoons using my Dremel grinder. It was fairly easy to tell when I got down to the fiberglass. Occasionally I'd rinse the nose out with water to remove the white dust so I could see things better. Fortunately, the other half of the firewall came out easily, mostly during the crash. I ground the epoxy off of it using my bench grinder to get the big stuff and then my Dremel and a sanding drum to finish it off. Now I can use it as a template to make a new one.

TXKflier

Tonight I cleaned the outside of all the pieces with alcohol and the inside with lacquer thinner. Then I taped the nose back in place using Scotch magic tape. It wasn't too difficult to put it back together. The matte finish tape helped me see when the pieces weren't level with each other. Occasionally I had to run an Exacto blade along a crack to make a little clearance so that the pieces would line up. Once it was all back together, I started putting fiberglass inside. I'm not sure what weight of glass cloth I used since it was some old stuff I had laying around. It was probably 2 ounce stuff. I used Z-Poxy finishing resin to glue it in. The first piece I installed was about 6 by 8 inches. It covered the bottom half of the fuselage and went in pretty easy. The next piece was much more difficult, mainly because I tried to get too fancy and also because it was going in the top half of the fuselage where it's harder to work. I cut it large enough to cover a little more than the upper half of the fuselage. I also cut a slit in it so I could install it on either side of the motor mount. This made its placement fairly critical. While trying to position it, it became saturated with epoxy and then I couldn't do anything at all with it. It kept sticking to my fingers and the brush. I trashed that piece and cut a smaller one. I put it into position dry and then brushed Z-Poxy into it. I cut another piece and installed it on the opposite side. It took about 4 hours to install the fiberglass. This is the first fiberglass fuselage I've repaired. Now if the epoxy will just cure and hold..

CrashPro

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wow...looking good TXKflier.....your building/repairing skills far surpass mine

TXKflier

Thanks, CrashPro. You -do- know that photos tend to make things look better than they do in person?

Yesterday, I took a Magnum .91A XLS, a ringed SuperTigre .90, and a Jett .90L to a friend's house to do some break-in and prop testing. The first engine we mounted up was the Magnum. After running 3 fairly rich tanks through it at 3/4 to full throttle with at least a 10 minute break between each one, we made some quick rpm checks with various props. I say quick because I left the main needle set a little on the rich side and leaned the motor by carefully pinching the fuel line with my fingers. A remote needle would have been a big help. Here are the results:

Zinger 12 x 6 = 12,500
Zinger 11 x 8 = 13,000
Zinger 11 x 7 = 13,700
APC 12 x 6 = 13,000
APC 11 x 7 = 13,600

I didn't have a 12x7 or 12x8, but I'd like to try some. The fuel had 10% nitro, but I don't remember what brand. The temperature was about 90 degrees with about 55% R.H.

Next we ran the SuperTigre 90. I could tell from the first tank of fuel that it couldn't compete with the Magnum 91, which didn't surprise me. I had compared the carburetor bores earlier and had a feeling that the 'Tigre wouldn't be able to breathe as well. One thing I noticed about the Magnum was that as I leaned it out near the peak, it started to make a sort of sputtering sound. I imagine this was caused by detonation or pre-ignition. I haven't done any research yet to see what I need to do to prevent it other than running it on the rich side. I was happy enough with the Magnum that I decided I wouldn't run the Jett. I might sell it and buy 3 more Magnums (or a bunch of spare parts)..

The Jett is a great motor, but I just don't want to feed that monster. I also want to fly more than 5 minutes at a time. I think I'd rather fly an EDF than it..

I made a couple of interesting discoveries today. The first was that a Magnum .91A XLS has the same mounting lug dimensions as an O.S. 61FX. Then I checked to see what I'd have to do to put my Jett .90L in the F-18. It also dropped right in and bolted up, except that its larger carburetor would require a little trimming of the fuselage ahead of it. While I had the Jett out playing with it, I got to wondering if the Jett 90L muffler would fit the Magnum. Sure enough, it bolted right up. There are three threaded holes in my Jett muffler - two of them line up with the Jett .90 and two line up with the Magnum. So, no need to buy an Ultrathrust muffler just yet. I can't wait to see how it runs..

CrashPro

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Hey TXK

My 90LX mounted up without having to trim the fuse up any.
Has only flown twice.....first flight with a 12X6.....had about 3 minutes running on the ground....and a 4 1/2 minute flight.....and it took 25 cranks on the fuel pump to empty the tank,.. (50 to fill it).....2nd flight was with a 11X9....2 minutes running on the ground,...and a 5 minute flight,..still had half a tank.

TXKflier

A friend of mine has a Jett 90L in a Cermark F-16P. When he was running it in on the bench, I think he said it took about 5 minutes to suck down 12 oz of fuel. I made the test flight and a few other flights and his plane was on fumes after 5-7 minutes. He's running a MA 11x7 on his and it's turning 16 grand on the ground. Personally, I don't think he has enough prop on it. I'd rather it have a 12x7 or 12x8; however, that's a guess because we've never tried one. When you go vertical with his F-16, it runs out of steam fairly quickly and falls over. I don't think that 11" disk up front is big enough to support the weight. However, when you dive at the runway and make a high speed pass, it sounds a lot like an Indy car going by.

phjoker

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I have the 90Lx with an APC 11X8 Turning 15,000RPM on the ground on the F-16 with the stock tank wich I believe is a 12 oz tank. My flights are about 5 min
Now thats full throttle from take off to Landing. and I still have a little left in the tank to spare.