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ZIROLI 96" F6F HELLCAT BUILD

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Old 06-23-2011, 03:14 PM
  #176
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Default RE: ZIROLI 96

Engine testing:

Good new: elevator flutter gone.
Bad news: with stock mufflers, I'm only getting 5500 rpm's.
I've got a new magneto GT-80 for the dauntless that I can try for a bench mark.
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Old 06-26-2011, 04:26 PM
  #177
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Default RE: ZIROLI 96

Engine test (cont)

My buddy suggested a hole in the fire wall to get more air to the carb so I used a 1 5/8" forstner bit to drill a hole in the fire wall behind the carb.
For a 'bench test', I then put the SBD's magneto GT-80 on the hellcat and got about 5600 rpm's.
I then put the original electronic GT-80 on with box weight, muffler, etc.
One nice result of the hole in the fire wall was to run the fuel line plus ignition wire through the hole as now they are not running directly behind the exhaust O ring and eliminate the possibility of contacting each other.
This also resulted in about 6" less fuel tubing to the carb.
After routing and securing all wires/hoses, I tested the engine and
cold: got 5970 rpm's but it dropped to 5800 on subsequent 'runups'.
I then mounted the cowl and tested again and getting a respectable 5900 rpm's.
I was thinking that I should try adjusting the sensor to see if I can get more rpm's: do that, tomorrow.
That should be good enough for flying ( I may buy a 20X12 3-blade prop).
I took a video but it will be posted after the upload.
The cowl flaps need to be adjusted as they stick out too far.
They are on the same lever as the choke so I'll know when the choke is closed plus the cowl flaps are functional in that they will help cool the engine as this is the only exit for air.

I also tested the retracts in the UP position for 30 minutes to insure they are operational in both modes. I did find a small leak in one of the canopy air cylinder connections: amazing how such a small leak, quickly drains the air tank. I used soapy water and a cheap, small brush to find it.


engine, cowl flaps, canopy test:
http://www.youtube.com/watch?v=1NtXytICcn8
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Old 06-27-2011, 06:06 PM
  #178
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Default RE: ZIROLI 96

Miscellaneous

I did a CG check at 5.5" behind LE, with gear up (and the wings attached) and she is several ounces nose heavy.
With the heavy scale exhaust and the weight box over the engine, my 'guestimate' was pretty close.
I'm hoping to maiden her on Sunday.
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Old 06-27-2011, 07:01 PM
  #179
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Default RE: ZIROLI 96

Great job! Good luck. Looking forward to the report
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Old 06-28-2011, 05:09 AM
  #180
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Default RE: ZIROLI 96

WOW...Just unbelievable....What a great job....B7
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Old 06-28-2011, 07:38 PM
  #181
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Default RE: ZIROLI 96

Thanks, guys.

==================
Engine testing (cont)

I think the ignition battery was the problem for low rpm's as the 3000 ma was dead, this morning.
It was an older battery so I put a new 3000 ma battery in.
I got 5850-6030 rpm's: much better.
I got some 93 octane gas to test on the engine and the idle was about 500 rpm's faster but the high end only got around 5500 rpm's: probably needs the sensor advanced but I'm not moving it.
In trying to make the carb gas line as short as possible, the line got kinked on the edge of the hole in the fire wall and kept the engine from advancing from idle. The T going to the fill line was too close to the hole so I just added about 3 more inches to form a half loop inside the metal engine mount.
Yesterday, I forgot to mention when I was bench testing the GT-80 (new engine) with a magneto and it wouldn't start due to someone put the vacuum hose from the engine block to the fuel inlet: It took me about an hour to figure out that my fuel line was going into the wrong inlet.

I also adjusted the cowl flaps so they don't open too wide.
The scale exhaust is giving some scale weathering!
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Old 06-29-2011, 06:16 AM
  #182
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Default RE: ZIROLI 96

Looking good and sounds good too and keep up the good work. Got to keep them cats in the air…. Just getting mine back in service. New cowl and moved servos up front to get some lead out of it.
Will be using Jeff’s RCS 150 back in it for a few shows we hope. Todd
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Old 06-29-2011, 12:26 PM
  #183
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Default RE: ZIROLI 96

Hey guys, I am looking for one of these to purchase. Rarely see them for sale on RCU. Anyone who has one interested in selling? Thanks. Mark.
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Old 06-29-2011, 04:01 PM
  #184
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Default RE: ZIROLI 96

Todd,
She should sound sweet with a radial: I wish I had the bucks to put radials in all my planes.
Got some details/pictures on your center tank and bombs!

Mark,
Don't see too many at the field, either, along with the C-45, P-61 and SBD.

=====================
Miscellaneous stuff.

I made an antenna wire from some straight pins, a spring from a pen, a fishing swivel and some brass wire. It's not scale but I put three white balls from straight pins so pilots wouldn't hit the wire so what do I do, I removed the wire while testing the engine but snapped off the front mast.
I drilled out a hole on each part and put a brass rod in: will bend the next time!

I also epoxied small magnets to the two doors and screwed in some #1 flat head screws to the service panel: this worked great as no measuring was involved, just keep adjusting the screws until the door seated properly.

I'm getting some good weathering on the bottom exhausts stacks!

I used my corsair CG stand for the hellcat, measuring back 5.5" from the LE.
I'm glad that I put the expansion foam in the belly pan as that was a lot of weight concentrated in one spot!
The balance gave me problems as when I balanced the plane with the gear up, the plane was way nose heavy with the gear down. I think I've reached a happy medium: I filled the tank and balanced the plane with the gear up (initial flying): Then removed 2/3 of the fuel and balanced her with the gear down (landing). On the maiden, my backup is to fly with the gear down, should the plane be tail heavy.

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Old 06-29-2011, 05:48 PM
  #185
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Default RE: ZIROLI 96

Here are a few of the bombs and tank I took when the 150 was on it the first time.Todd
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Old 06-29-2011, 06:03 PM
  #186
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Default RE: ZIROLI 96

some more.
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Old 06-29-2011, 06:22 PM
  #187
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Default RE: ZIROLI 96

One thing on the dead ignition battery, if your engine has an optic kill, some of them will drain the battery if there is not a switch installed. But then I heard you mention a magneto so not sure if you need one? For a while I would always have to unplug my ignition battery to the otic kill till I got a switch installed.
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Old 06-29-2011, 06:33 PM
  #188
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Default RE: ZIROLI 96

no optic switch.
The magneto GT-80 is for the SBD but I mounted it on the hellcat to see if I get the same readings as with the electronic ignition GT-80.
I use a servo operated choke as my 'kill switch', in addition to a manual one on the surface for magneto engines.
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Old 06-29-2011, 06:39 PM
  #189
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Default RE: ZIROLI 96

Todd,
Looks like you have releasable bomb drops: one of these days, I'm going to have to that.
Looks like you had to put a huge lead block on the fire wall, even with a big radial.
With my scale muffler and weight box, my 'up front' weight is 'no slouch' either.
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Old 06-29-2011, 06:57 PM
  #190
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Default RE: ZIROLI 96

Yes it is a heavy radial but the weight is way back with the long prop shaft. The chunk of lead on the firewall is 9 pounds.

Todd
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Old 06-30-2011, 08:33 PM
  #191
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Default RE: ZIROLI 96

More engine problems (good that they are on the ground!)

I had a fuel T in back of the engine mount and the engine shaft sticking out the back rubbed against the fuel lines: I think this is why I was getting such erratic reading fluctuations.
Initially, I put hard nylon wrap around the lines but that didn't look like the 'best' solution to the problem. I decided to remove the tank and re-do the lines so the T is inside the fuse.
I drilled an additional hole in the fire wall just behind the carb fuel nipple for a direct line to the carb.
I'm now consistently, getting 5910 rpms.

After putting the cowl on, I had trouble starting the engine.
Once the engine started, no problem.
I found that the magneto wire moved by the choke butterfly and was blocking complete closure.
It's a 'catch 22' with the O ring exhaust: run the wires outside the engine box and there is little room to get by the hot O ring; go inside and you have carb and engine crank shaft issues.
A regular ol' wrap around muffler would have been a lot easier.

I also checked engine temp with the cowl on and the right cylinder reached 280 degrees (without cowl, 190). Too hot even if it will be cooler when flying, so I quickly attached a robart dummy radial to the cowl with holes cut for each cylinder to force air over only the cylinders.
I've got to work on my daughter's house the next two days so I did a 'quick and dirty' fix, just functional. Some wood was epoxied to the cowl and the plastic radial was screwed to the wood.
Later, I can 'dress it up'.

"if warbirds were easy, everybody would be flying them!"
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Old 07-03-2011, 05:22 PM
  #192
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Default RE: ZIROLI 96

Maiden:

Almost lost her!
Did the usual 360 degree range test, surface movements and RPM's at 5900: all looks good!
I used about all the runway I could and slowly gave up elevator; only the plane barely got off the ground and the tail was drooping. It didn't 'look good' so at about 10', I leveled the plane so she would gain some speed and then slowly gave elevator to get some altitude; just enough to be above the trees on the 'down leg'.
I left the gear down and on the first lap, I landed her without flaps: a little hot but a smooth landing.
The runway splits into two directions and I was heading for the center rough so I veered left and went into the soy bean field but only about 6' and no damage done.

After I got home I tried several of my props:
Mejzlik 3-blade 22X12 CF 5880 rpms (original prop set up as a 'bench mark')
Xoar 2-blade 24X12 wood 5850 rpms (nothing scientific but the 2 blade seemed to pull better than the above prop when holding the horizontal stab).
Mejzlik 2 blade 24X15 CF 6450 rpms (now we're talking some serious rpms!)
Mejzlik 3-blade 21X11.5N CF 6990 rpms (needless to say I was ecstatic: same prop that I use to power the P-61 with G-62 that give me 6300)
Bolly 22X12: didn't even test it after the above results!

With the tail drooping, I'm now not sure if the plane is tail heavy or just the plane was going to slow. To be safe, I'm adding some more weight to the nose and will be 'rocketing' with the Mejzlik 3-blade 21X11.5N prop.

Video of the flight:
http://www.youtube.com/watch?v=mPSaD6xTSZw
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Old 07-03-2011, 05:58 PM
  #193
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Default RE: ZIROLI 96

Pretty scary. Great job getting her back on the ground in one piece. Looks very tail heavy or just not enough power coming off the prop. Was the CG checked and verified before the maiden? Good news is that you get to try again real soon. I'm sure the next flight will be perfect. Good luck .
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Old 07-03-2011, 06:10 PM
  #194
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Default RE: ZIROLI 96

Your dilemma sounds identical to my experience with my Dauntless a few year's back.
The GT-80 must spin @ 7000 +RPM's to fly that model and its weight.
I use a Bolly 2-blade 24" x 8" and get 7200 revs.
Don't know if Ralph Cunningham is still in the game, but he is the authority on these engines and may provide additional insight.

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Old 07-03-2011, 06:39 PM
  #195
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Default RE: ZIROLI 96

Mark,
Yep, did the CG check (see post #184)

Nick,
If Ralph was C&H ignitions, I think he retired.
I'm partial to 10 or 12 pitch on my WW II warbirds and 8's for the WW I so I'm going to get less rpm's.
I think that I do have a 24X8 but it may be a Zinger: never hurts to try it out!
Been thinking about the 21X11.5 getting the 6990 rpms, I may have to make some kind of 'pull' meter to see which prop has the most pull: The Mejzlik 22X12 2-blade may be the best choice as 2-blades usually seem more efficient than 3-blades (at least on our models): more research.
The 21X11.5 3-blade is only an inch shorter and 1/2 a pitch less than the 22X12 3-blade but, as seen in the above posted (192) picture, the mass appears to be about 60 percent.
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Old 07-03-2011, 08:38 PM
  #196
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Default RE: ZIROLI 96

Honestly, from the video it did not appear to be tail heavy. I know pitch is good for speed, but disc is much more efficient thrust. Two blades are especially more effective. If It were me, I would go down in pitch and up in diameter until that magic RPM number is reached. Early flights are knee knockers already even without prop issues.
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Old 07-04-2011, 02:43 AM
  #197
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Default RE: ZIROLI 96

Look here, post 559...

http://www.rcuniverse.com/forum/m_37...3/key_/tm.htm#
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Old 07-04-2011, 07:02 AM
  #198
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Default RE: ZIROLI 96

Thanks for emailing me and giving me a lot of helpful solutions.
It's always good to get lots of input.

===================

First, I re-balanced the plane.
To save some dead weight, I filled the tank and balanced her with the gear up.
The picture shows how much extra was needed: several more ounces.
My logic with the full tank of gas is the gear will be down on landing with about a 1/3 tank so no problems on being tail heavy.
I ran out of room in the weight box so I bolted two large chunks of lead to the cover.

I think that I've narrowed the prop selection to the Mejzlik 2-blade 24X12 or the 3-blade 21X11.5N as those two give the best rpm's. Later, I will give each prop a 'pull' test: I'm thinking that I can attach a bungee cord to the tail and see which one pulls the farthest.
I'm going to stick with the scale exhaust: it probably reduces power but it also provides valuable weight: plus it looks cool!

I found out why the plane zigzaged after landing as the brass tubing holding one pull wire came loose on the tail wheel and the pull/pull on the rudder were also loose: for me, I can never get those wires tight enough where they won't be loose after a few maiden flights!
While on her back, it was good anyway to check out all the 'innerds' to make sure all is secure.
I remove the cowl to protect it and let all the front end weight rest on the 'weight' box while upside down.
Also, I checked out the clunk to make sure it didn't come off or bend on that 'sudden stop', after landing.
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Old 07-04-2011, 07:20 AM
  #199
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Default RE: ZIROLI 96

A few buddies also were at the field.
Yellow P-40
balsausa nieuport.
Didn't get pictures of the 1/3 Fokker D-6 and 1/4 D-7.
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Old 07-04-2011, 11:22 AM
  #200
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Default RE: ZIROLI 96

Prop thrust test.

I used my 'scientific measuring device' and attached a bungee cord to the tail wheel and a safety backup of a rope tied to the fence.
The results are in the picture:
Mejzlik 2-blade 24X12 CF at 6360 about 2" past the next prop.
Mejzlik 3-blade 21X11.5N CF at 6980.

I pulled the plane to these locations and the bungee cord is about maxed out telling me that:
1. like a tractor pull, that last 2" farther may be a lot more thrust.
2. a 2-blade at 6360 is more efficient than a 3-blade at 6980
3. the lower max rpm's will also be easier on the engine.

Can't keep the engine at max too long as the cylinder head ran up to 218 degrees very quickly (less than 15 seconds).
Probably best to do ground tests with the cowl off.
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