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Finally got the batteries for the scale. Now I wish I hadn't. Final weight came in at a marginally obese 17lb 2oz. Double checked scale calibration. Still a heavy bird. Don't know where I picked up all that additional weight, but if anyone can get back with what their's weighed in at, I'd be interested to know. Items outside of the norm: 4500 mAh 6v battery, 1400 mAh 7.2 6c sub C ignition, Tony Howard exhaust, custom gun ports, Dave Brown 5" P-51 spinner (painted) H9 WWII pilot, additional balsa reinforcement in retract and firewall (with fiberglass/epoxy resin), extra 791 for choke, 3 oz lead in tail, and upgraded hardware throughout (used only 4-40 rods from package). As I've said before, I used the Evo 26GT(w/bisson inverted wrap) to SHAVE some weight. Now I'm overweight, underpowered, and thinking I better wear my brown pants for maiden. Gonna wade through the previous long thread and see if I can find some weights there. Let me know guys!
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Are the wheels supposed to fall off when you land? No? How about the engine?
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After running through the old post I came up with everything from 14.7 lb(w/Saito 180) to 17.3 lb(also a Saito 180). And these were on a 77" wing. Maybe I'm not too far off. Going to try a static thrust pull tomorrow morning. Running a Xoar 18x6 and getting about 8200 rpm on a brand new engine with three tanks through it. Post your weights if you can. May get interesting.
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Are the wheels supposed to fall off when you land? No? How about the engine?
I am thinking of using only one 6 volt battery pack to control everything and they just charging it back up after every flight. Would it be a problem running the retracts and all other servos with only 1 battery?
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Joined: 10/1/2006 From: Columbia City,
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Won't be a problem at all...unless evidently you're using the JR791 retract servos. The jury is still out on that . Just make sure you get a big enough battery to run your junk for a full day in the air! As I've already said, I'm all digital,(except retracts, throttle and choke) and with a gas engine potentially flying all day, I opted for a lead brick JR 4500 mAh 6v. May go with a couple of smaller batteries (or air retracts) if this retract servo issue doesn't go away.
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Are the wheels supposed to fall off when you land? No? How about the engine?
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Joined: 3/12/2005 From: Fort Collins,
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quote:
ORIGINAL: Jarrah
I am thinking of using only one 6 volt battery pack to control everything and they just charging it back up after every flight. Would it be a problem running the retracts and all other servos with only 1 battery?
cheers
Jarrah,
One battery pack can certainly run everything in a 6-channel plane. For example, I use one 1850 mAh AA 4.8 volt battery in my 60 size H9 P-51 for Rx, servos (including flaps) and retracts (one servo). Three 15 minute flights and the battery still doesn't drop below 5 volts (5.5 volt peak when charged).
Relatively light, AA-sized 4-cell (4.8 volt), or 5-cell (6.0 volt) battery packs rated up to 2700mAh are about $28 US each; plenty of juice for most applications. Large cell packs are, of course, available, but their weight is significantly higher.
The above being said, I have the following additional inputs:
1) if you are using JR791 servos for the retracts, you should power them with 4.8 volts, not 6.0 volts. (strong recommendation from Horizon Hobby on this!). Consider using a separate 4.8 volt battery for them, and use a 6.0 volt for the Rx and remaining servos.
2) in general, using a separate retract servo battery, regardless of the servo, will prevent a "hung" retract from draining the battery in flight from continuously trying to reach "end of travel". Dual battery wiring diagram is attached, courtesy of a "BigPlumbs" posting under another build thread, I believe.
3) my LHS owner also advised using a separate battery for big "stump pulling" servos like the JR791's because they draw so much current initially that they could cause a momentary, but large, voltage drop on an Rx-shared battery that could shut down the Rx down in flight. (Haven't heard or read about this one before...)
Bo
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quote:
ORIGINAL: reincarnate
You're the man Rip. Hope your legs don't get tired running all of these errands for the crowd. Already own all of the air junk, already bought the dang 791's, just don't want to add another dang battery to already fat bird (lots of scale detail. Gonna post an exact weight of mine later today). Asked Danny @ JR in radio thread, so if you want to follow what he says, check that. Here is why I'm still stalling on this. You can't adjust the travel or end points of gear channel/servo. So if you have your servo set up correctly, it will run to its end point and stop without overdriving. Just thinking out loud, not about to outguess the experts. Like you said, "It's only a $1500 airplane". Now stop messing with my head! How's the exhaust coming? I'm looking forward to seeing it. Keep up the great work.
OK, done with the scratch-built, dummy scale exhausts. Took about an hour a night for 5 nights (spread out over two weeks). Not sure I can claim they're as good as the Tony Howard kit, but they're close, and a darned site better than that molded plastic junk included with the plane!
"Spitpilot" helped me with dimensions on the manifold and pipes (thanks, again!). Was just going to post pics and be done with it, but figured some of you might want to know how I did it, so here goes.
I used 45-degree angle balsa 3/4" on a side (1" on the long side). I trimmed the bottom-side angle of the manifold (where the pipes come out) down a bit on thickness to more closely match real P-51 pics I found on the web. My trial set up with 3/8" diameter aluminum tubing didn't look quite right, so I used 5/16" tubing instead.
A Dremel sanding drum rounded the ends of the manifolds, followed by careful hand sanding with fine grit paper to get the rounded ends.
Then, knowing the hardest thing about drilling into odd shaped objects is "holding your work", I found a scrap piece of styrofoam, cut one side at 45-degrees, then V-notched it to take the two manifolds side by side with the exhaust-sides facing up.
I cut a 2" length of the same aluminum exhaust pipe, and spent 10 minutes with my Dremel tool notching one end of it to create little cutting teeth, like a hole saw. Slipped a smaller 1" piece of brass inside the other end of the hole saw and CA'd it in to strengthen the aluminum for the drill press chuck.
The pencil marks on the centerline drawn down each manifold show where the front and rear edges of the tubing should come out of the balsa, when placed at the 45-degree swept back angle. On the drill press, I carefully brought the cutting tube down to the rear (higher) mark for each tube, and cut down into the balsa until the front (lower) mark was reached with the hole saw. Repeat 11 more times!
Epoxied in the pre-cut exhaust tubes into the angled holes, primed the whole thing, then painted the manifold "aluminum plate" and the exhaust pipes "flat black."
Positioned, and traced the manifold on the 'Stang, and cut away the covering. I hogged out the center of the curved balsa sheeting in the top cowl area with my Dremel sanding drum. The balsa sheeting was plenty thick to handle the depth, is non-structural in that area, and is even stronger now with the manifold epoxied into the notch.
I think it came out looking pretty good. Put the static spinner up front for the final shots: my DB spinner was still drying in my paint booth...
Bo
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Joined: 10/1/2005 From: Lund, SWEDEN Status: offline
Hi,
The wiring diagram for separate retract servo power was excellent! I´ll for sure implement that!!
I don´t have a proper kitchen scale so I went down to the local convenience store and borrowed their digital scale for a minute (had a big laugh about it with the clerk on duty!). Mr "Donald Moore" weighs in at 276g with parachute and all. Is that about 0.6 lbs? It all adds up fast doesn´t it... I also posted some pictures of him in my gallery.
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Joined: 9/26/2002 From: Evans,
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The 77" version flies very light on the wing and the new version has a bigger span. If anything a couple of extra pounds may make the plane easier to land by giving it more sink. So I wouldn't worry about the weight much.
Walt
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Rip... You did a great job on the exhaust manifolds! Looks great and you have the pride of doing it yourself. Now I feel lazy. On a separate note, as promised, I did my static thrust check this morning. Temp in the garage was 45 deg (outdoor 16. Freakin winter...) and still on 30:1 mix fuel for break-in. Tached prop again and still running about 8150-8200 steady with the 18x6. End result was 15.9 lbs static thrust. Trimmed weight down by removing pylons and bombs from wings, and ended up right at 17 lbs. Should be able to get another 550-600 RPM out of the Evo, by the time she's all broke in, so I'll keep hoping. The 18x6 is the only prop I've got in this range right now (haven't bolted up the Zinger Pro to see if a difference exists). Waddaya think guys? Just because I know how to test the thrust doesn't mean I know what the results mean! Ski pilot: Don needs to trim his mustache. Outside the corners of the mouth will never pass muster! He looks great. Do you have a full cockpit, or his he due for surgery? I see by the Far Side calender to Don's right that you also favor the finer things! Monday, Rusty makes his move!
< Message edited by reincarnate -- 2/11/2007 4:01:54 PM >
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Are the wheels supposed to fall off when you land? No? How about the engine?
Posts: 70
Joined: 11/12/2002 From: Newcastle, WA, USA Status: offline
Bo, you did a great job on the exhaust system - the forum you started is helping many on this model world wide and is certainly bringing many ideas on building to the table - keep up the good work.
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Bo...Another idea from Tony Howard is to paint a small (1/32 to 1/16) black line around exhaust shroud. Provides a "relief" around shroud, making it appear to to be protruding from inside of fuse, instead of on it. Not easy to get even line around shroud, but makes a great effect.
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Are the wheels supposed to fall off when you land? No? How about the engine?
Posts: 437
Joined: 3/12/2005 From: Fort Collins,
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quote:
ORIGINAL: reincarnate
Rip... You did a great job on the exhaust manifolds! Looks great and you have the pride of doing it yourself. Now I feel lazy. On a separate note, as promised, I did my static thrust check this morning. Temp in the garage was 45 deg (outdoor 16. Freakin winter...) and still on 30:1 mix fuel for break-in. Tached prop again and still running about 8150-8200 steady with the 18x6. End result was 15.9 lbs static thrust. Trimmed weight down by removing pylons and bombs from wings, and ended up right at 17 lbs. Should be able to get another 550-600 RPM out of the Evo, by the time she's all broke in, so I'll keep hoping. The 18x6 is the only prop I've got in this range right now (haven't bolted up the Zinger Pro to see if a difference exists). Waddaya think guys? Just because I know how to test the thrust doesn't mean I know what the results mean! Ski pilot: Don needs to trim his mustache. Outside the corners of the mouth will never pass muster! He looks great. Do you have a full cockpit, or his he due for surgery? I see by the Far Side calender to Don's right that you also favor the finer things! Monday, Rusty makes his move!
Thanks for the compliment, Rein. Hah! I don't think you should feel lazy building your exhaust from a "kit"! Now, if it had been completely pre-made....
I had already decided not to fly my 'Stang with the wing bombs. Don't want the weight or the drag, and "ground strike role" isn't my favorite historical deployment of this fighter, anyway. Hmmm, now if I were to set them up for in-flight release (joking: they're too heavy and would hurt like hell if they hit someone. Probably wouldn't survive ground impact, anyway!)
Don't know if your static thrust is "right on". There's a number of threads on this topic, on similar engines, over on the "Engine" side of RCU. I'll scan over there again to see what I find.
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All Forums >> RC Airplanes >> RC Warbirds and Warplanes >> RE: New Hangar 9 1.50 P-51 Build 
RE: New Hangar 9 1.50 P-51 Build - 
Gonna wade through the previous long thread and see if I can find some weights there. Let me know guys!
. Just make sure you get a big enough 
