hooaa

My Feedback: (1)

I'm throwing together a Predator. The firewall looks frail. I want to use either my Nelson Q500 or Jett 50 FIRE. After I pin the firewall and glass behind it can I expect it to hold up for a few dozen sport flights? Is the wing strong enough for pylon snap turns? I'd like to hear from anyone who has been down this road. I'm at the engine mounting phase of construction. I ordered a Jett CG tank which will likely be a snug fit but will keep out the bubbles. I plan to use the Hitec 225's for the tail feathers. Anyone using these in this application? I hope so because they re in the mail.

combatpigg

My Feedback: (3)

Every chance I get, I like to tell people about the POS ARF PREDATOR. I have seen the firewalls dettach, so pinning and glassing is a good idea. The wing incidence is way off. The covering seams on some parts has either no overlap, or it faces into the wind. I have at least never seen a wing hold down failure. The 225s are used by many guys for the tail. Get yourself familiar with high rate / low rate flying, because those tiny, inboard mounted ailerons don't have much control at landing approach speed. I think it is a nice design that I have copied to build my own Q500s from, but the ARF is a substandard POS.

hooaa

My Feedback: (1)

I haven't glued the tail feathers on yet so I will use my incidence gauge to zero out any vs. the wing. I'm used to low/high rate birds like the Whip so that's no problem. Is the rudder function useful at landing/gliding speeds? If not then I'll just set up the mixer for the Elevator function.
So the question remains will the firewall remain intact with the Nelson Q500 hanging on it?

Mike Connor

My Feedback: (5)

I havn't had a Predator but have built a couple other Q-500 planes with Jett 50 engines. I have seen a couple of firewalls come loose from prop strikes and bad landings so I reinforce mine. Along with pinning I use triangle stock and light glass on the inside. I also use two strips of light glass in a cross pattern on the front outside. Even with a fuel tank hatch the fire wall joint is intact after a crash. Again I am not familiar with the predator but Q-500 wings are generally very strong when glassed on the center section.

I remember daven and other Q-500 guys talk highly of the Hitec 225's. I used them in my second Jett powered Dust and really liked them. They are strong, fast and center well. Daven may chime in here with his vast knowledge and experence.

combatpigg

My Feedback: (3)

I don't know if they [LANIER] ever corrected the wing saddles or not, but I first set the engine on the plane with a 90 degree plate bolted to the crank [and clamped to the table] that sets the thrust line, [relative to the table], then wrestled with the wing and tail angles. If I remember correctly, the tail checked out close enough, with respect to the thrust line, it was the wing that needed to be jacked up quite a bit in back to set straight. The plane was impossible to trim hands off as it was delivered. Good design, poor execution.

hooaa

My Feedback: (1)

I imagine that I could use a level on the firewall to set it vertical, and following that check the wing and tail for zero incidence.
Since the Nelson doesn't have a throttle I'll need to to trim it very well before flight. Sorry now that it is a POS, I could have put my buck thirty towards a composite like the Shotgun.

hooaa

My Feedback: (1)

CombatPigg,
Lanier must have heard from customers because the firewall is 90 degrees from the wing, and the tail feathers are within 1 degree. I just had to rock them slightly toward the left to align them with the wing.
So I guess I'll bolt on the Nelson and hang on, praying that the 2 minutes of fuel will pass quickly (for the 1st flight).

combatpigg

My Feedback: (3)

HOOAA, that's good, they sent you a straight plane. You might consider using a fuel line pinch for a shut off, or at least a fixed fuel tank pick up that would allow you to kill the engine when you roll inverted. That's the way we run our .15 powered combat planes, and they perform everything very well, except extended inverted flight. It is interesting though, you can do a huge, flat loop, and as long as you maintain some g force to hold fuel on the pickup side of the tank, you can fly inverted for a little while. A simple fuel line pinch is to have a hole in the firewall that a wire passes through. The servo controlled wire is looped around the fuel line, and the servo just pulls the doubled over fuel line through the hole in the firewall to kill the engine. Good luck with your project![8D]

bob27s

My Feedback: (19)

The current version of the Pred are GOOD aircraft.
Flown and set up pleanty of them. Everything lines up straight. They go togther quickly and properly.

Most were set up for 424 racing with a TT40, but there is nothing extraordinary needed for flying with a 428 engine (or Jett .50). Others may have had a bad experience, but I believe the Predator is an outstanding Q-500 aircraft as it comes from the box. Many 424 pilots fly them. Good value, good straight plane, and its quick too. Excellent way for folks to get started in the sport.

The firewalls SHOULD be glassed from the factory (on the outside). I was pretty sure they made that modification well over a year ago. Glassing inside does little good - has to wrap around the firewall and attach to the fuselage sides. If yours is not glassed, you may have an older plane. If so, remove the covering around the front 1.5" of fuselage and firewall, and add a layer of 2oz glass cloth and epoxy.

The HS225 servos are just fine. I use them quite often on the 428 Q-500 aircraft. Pleanty strong, and reliable. With the 424 engines, smaller 80/85 series servos are ok. Horizon sells some Expert digitals that are inexpensive, and work very well - same size as 225, and look like clones of JR servos.

The jett bubble tank will provide enough fuel for 3.5 minutes of run time with the Nelson/Jett 428 engine at full throttle.

I would not recommend using a fuel line pinch on the Q-500 engine. The nice thing about the Nelson and Jett engines is the air valve carb gives you the ability to 'flood off' the engine at the end of a flight. Helps avoid a temperature spike, and makes plugs last a good long time.


Photo attached is just one of many Predator's flying for sport use with Jett .50 engines (with a black muffler, and Q-500 APC D serise prop).

(pilot Doug Allen)

Bob

happyal

Hi,

I’m at about the same stage as you when you started this thread, i.e. deciding if it will stand up to a Jett engine. My Predator’s firewall is glassed outside and on the inside; also you can see there is glassing where the wings join too. Guess they've beefed it up since the first version.

I’ve deceived to fit my Jett 40 Super Sport engine, just waiting for the back mount and tank from Jett. I’m going to fit HiTec 85MG servo’s for the tail, as I belie that they centre better than the 225’s.

Looking forward to starting a Pylon class in my local area with this airframe. Let me know how you get on with yours.

hooaa

My Feedback: (1)

Bob,
Thank you for your timely suggestions. Upon closer inspection I found 1/2 oz (approx) glass, wrapping from side to side, covering about 1" on each side. There is also a wrap side to side inside. So they paid attention to the modeler's complaints. I will do as you suggest and place 2oz glass on top of theirs. I was going to wrap it inside but after I think about it the outside make a lot more sense.
I have been using the Nelson air valve carb to shut off in the past and it works well. Same with the Jett50, I just close the venturi completely.
I am at the engine decision stage. My Jett50 does not have a backplate mount as it was on a Whip. The Nelson does have a backplate but the muffler would end up on the bottom making it vulnerable to getting whacked by a myriad of items in our cow pasture. I think I'll order a backplate for the Jett50. It turns an 8.8x8.75 at nearly 19K. It won't break any AMA records it but it will keep the adrenaline flowing.

hooaa

My Feedback: (1)

Flashman,
Mine was wrapped inside and out also, but with very thin glass. I'm going to cover it with 2 oz as Bob27 suggested. Now I must order a Jett backplate. I let you know how the initial flights go. Good luck.

happyal

Hi hooaa,

Thanks for that, I think I'll put a little bit of glass on it too.

You should be getting into the 140mph range with that engine, that sounds like a good time to me

daven

My Feedback: (1)

Sorry, but I was out on a little R&R the past few days.

The predator is a decent plane. The early ones had several issues: Firewalls that did not stay in, warped wings, weak wings, bad wing bolt plates, bad incidence, etc....

Going fast is quite a bit different than your average sport plane, and it takes a little more attention to detail. Most of the issues have been fixed that I am aware of. I would still check for wing warping, reinforce the bottom of the wing hold down plates, add a little glass to the firewall area, and definately beef up the wing with either glass or Carbon Fiber strips on the botttom at the high point.

Despite its issues, this plane has done a lot for local beginner pylon racing classes, but is still a hair short of what is needed for high performance engines like the Jetts or Nelsons.

hooaa

My Feedback: (1)

I appreciate all the tips on the Predator and will strengthen it in various places. I'm using the Jett50 FIRE. The backplate mount places the exhaust so close to the 2-1/4" firewall that it appears that I must cut into the left side substantially to clear a 15-degree manifold. I didn't see one in either Mac's, Jett, or Cady catalogs. Is there a more elegant solution?

bob27s

My Feedback: (19)

If all else fails, use a good-ole sport mount. Dub's aluminum beam mount has a 3 hole pattern that matches the 3 hole backplate mount. Just like the QM40 engine mounts.

http://www.jettengineering.com/accy/mounts.html

Moves the engine fwd about 3/8" from where it would be with a backplate, and should allow a riser-header to clear the firewall.

With the rear pipe, CG should not be an issue.

Try spacing it out, see if that will work.

Bob

hooaa

My Feedback: (1)

In haste I ordered a Jett backplate from Cady yesterday. I'm sure it will be in the mail today. Should I order the "light" or the "sport" beam mount?

Ed Smith

Metal geared servos are bad news in a Pylon Racer. There is always some vibration present. The gears will wear and the control surfaces will get sloppy, centering will not be improved.

Ed S

bob27s

My Feedback: (19)

Backplate wont go to waste over time

Sport mount. The light mount will position the engine in the same place as the backplate mount.

Also, as Ed noted, stick with nylon gears. Metal gears do not last long on the 225 or 85 servos.

I have about 20 HS225 servos. Love them for Q-500 ! Very reliable, lots of power.

jaka

Hi!
HS 85 with metal gears are not recommended on the elevators (metal gears will fast wear out, go with nylon gears) and Hs 225 servos are much sturdier than those small Hs 85 servos. Hs 85 better centering than Hs 225...No way!
I have used Hs 225 (on elevators) for many years in both Q-500 and F3D pylon here in Sweden and they have performed flawlessly.
Regards!
Jan K
Sweden