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Top Flite 1/7 P-51 Build

Old 01-28-2009, 11:27 PM
  #1876  
Corsair 29
 
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Default RE: Top Flite 1/7 P-51 Build


ORIGINAL: jdunstan

Hi:

Where did you find a suitable pilot figure of the correct size?

Thanks,

Jim
Jim,

Dont know if you've seen these from Century Jet:

[link=http://centuryjet.com/product_info.php/cPath/46_38_36_31/products_id/39]http://centuryjet.com/product_info.php/cPath/46_38_36_31/products_id/39[/link]
Old 01-30-2009, 07:17 PM
  #1877  
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Default RE: Top Flite 1/7 P-51 Build

Corsair:

I finally clicked on that link you provided. These units look like a great idea. I wish I'd known about them before I did mine.

Old 01-31-2009, 08:31 AM
  #1878  
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Default RE: Top Flite 1/7 P-51 Build

They seem like they've been around for a while now, but haven't seen a build thread on them. I believe most of the High Speed gliders folks use them to reduce drag.
I plan to get the most of the other wing panel servos installed today, and start joing the wings.
Old 02-09-2009, 04:39 PM
  #1879  
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Default RE: Top Flite 1/7 P-51 Build

Corsair 9:

Thanks for the suggestion on the Century Jet 1/7 scale pilot figure. I ordered one and was very disappointed when I received it. It is made of some sort of rigid resin that looks like paper mache. It is crudely made and crudely painted. But the main reason I have to send it back is that since it is rigid I cannot position it to fit in my Bob Dively cockpit.

I would appreciate any other suggestions on a fill figure pilot for my 1/7 scale Mustang.

Jim
Old 02-12-2009, 01:14 AM
  #1880  
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Default RE: Top Flite 1/7 P-51 Build

I understand your problem. There are not too many good figures available. I am building a 1/6th Corsair, and there IS a lot of options in that scale with moveable limbs, e.t.c.. One must plan on grinding away a lot of plastic to get the weight down with a Dremel. Keep searching, but realize the best figures are in 1/6th and not your smaller scale. It is one of the reasons I chose the scale for my Corsair. Perhaps you could get away with a larger out of scale figure? Good luck, Eric
Old 02-12-2009, 12:15 PM
  #1881  
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Default RE: Top Flite 1/7 P-51 Build

I am going with the Aces of Iron bust for mine. I only hope I can paint it as well as they do. [link=http://www.acesofiron.com/page/AOIW2P5117.htm]Aces of Iron Pilot Bust[/link]
Old 02-16-2009, 10:51 AM
  #1882  
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Default RE: Top Flite 1/7 P-51 Build

I'm gettin excited.

We'll be going to near Charlottesville, VA on the 25th, and the weather is looking good for a maiden.

I joined the Rivanna RC club early this year, and took my pilot's test in January when we were there helping my daughter to move.

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Old 02-16-2009, 10:59 AM
  #1883  
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Default RE: Top Flite 1/7 P-51 Build

Congratulations Bob. Also, good luck on your maiden. Looking forward to the pictures. I will try to post more of my build today.
Old 02-16-2009, 12:09 PM
  #1884  
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Default RE: Top Flite 1/7 P-51 Build

OK, it has been a while for pictures. So, here they are. I included some of my landing gear mount customization, and some silly ones of adding the wing to the fuse to remind me that I am building a copy of the greatest warbird of all time.

The landing gear blocks were made from 2 pieces of 1/8" ply epoxied together with carbon fiber in between. I just didn't feel that the two 1/4" strips would provide enough stability and distribution of force (in case of hard landing, which never happens, right?). Plus, with these units, I felt that it was easier to match the installation in the two wings.

Well, back to work. Will post more after I sheet the top of the wing. Meanwhile, back under the weights for the wing.

-Ray

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Old 02-16-2009, 12:58 PM
  #1885  
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Default RE: Top Flite 1/7 P-51 Build

Hey Bob,
Your daughter at UVA? I must have missed that post. I'll PM you my phone number. I live about 45 minutes from Charlottesville. I fly at the Staunton / Augusta club which is about 20 minutes from Charlottesville. I'll make the trip over to see the maiden!!!!!

sean
Old 02-16-2009, 02:10 PM
  #1886  
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Default RE: Top Flite 1/7 P-51 Build

All right, Sean! Yeah, my daughter is a lab rat for a doctor at UVA.

Did you ever get the engine running right in your Stik? If not, I still have my old OS 65LA which I'm not planning on using any more. You're welcome to it if you think you can use it. The LAs are good engines, but I don't care for them as the mid range is very difficult to get right, due to the low speed adjustment being an air bleed rather than a needle valve. Let me know if you want it, and I'll go clean the dirt off it from when it went in on the front of a Sig Cub.

Bring your Stik with you, you can fly as my guest.

Right now, we're planning on arriving the afternoon of the 24th, so I'll be at the field everyday at noon unless it's raining.

Old 02-17-2009, 04:10 AM
  #1887  
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Default RE: Top Flite 1/7 P-51 Build

Ray-E Man, I just thought I'd say that carbon fiber in the middle of a sandwich is not so effective. The material works in tension (like steel). Putting it in the middle of a sandwich has almost a null effect. Not to be too critical, just want us all to learn and understand best uses of material. -Eric

As an edit, I should say that you will get some benefit out of the carbon fiber for sure, and I wish I had made stronger rails (i'll find out). I think it is not so bad an idea for the screwing down of the units to be a weak link, such that a bad landing pulls out screws and doesn't destroy internal structure. This is important. Easier to fix a scraped up bottom and buy a new prop, then to rebuild the wing where the mounts are tearing the entire wing to pieces! One just needs to figure how much stress required to pull out the gear screws before damaging the whole wing, yet still be strong enough for regular good landings (just old school advice for those who haven't done this for decades)! -Eric
Old 02-17-2009, 10:06 AM
  #1888  
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Default RE: Top Flite 1/7 P-51 Build

Yes. In this instance, I was looking for tensile strength. I want to be able to distribute some of the force to the surrounding structure, but not so much to break it. I hope, if I hit too hard, it breaks where I have circled on the attached photo. Then, I only have to build a new mounting block, repair the ribs and the skin, then ready to go. I think, if you make this area too solid, then more important things will break on a hard landing (leading edge, main spar, etc.).

Of course, I hope I don't hit that hard.
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Old 02-27-2009, 06:53 PM
  #1889  
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Default RE: Top Flite 1/7 P-51 Build

Hey Bob,
How did that maiden go? Will you be flying tomorrow? Saturday? I may bring the DUS over tomorrow morn if you are.

sean
Old 02-28-2009, 06:35 PM
  #1890  
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Default RE: Top Flite 1/7 P-51 Build

Hey, Sean

My daughter has no internet access so I didn't get this until just now, in New Jersey at my son's. (Saturday evening) We got out of there before the ice storm hit. Did it?

For the last six months, I have spent some sleepless nights over that Mustang, wondering if I'd managed to assemble a $1200 eisenschwein. The maiden was such a non event. I fed in a little power, it rolled straight about 15 feet, the tail came up, I added a little more power, it started getting light on its wheels, I gave it a little more, and it started climbing out. It flies beautifully with the gear up, and needed about 1/16" of down trim for level flight. I never did get anywhere near using full throttle. I'll save that for another time. I dropped the gear and the flaps and trimmed it, made one missed approach, and set it down. It slows down really nice with those barn door flaps and the gear hanging down. I just blipped the throttle now and then throughout final approach to keep the speed from falling off too much, and set it on the mains. She rolled about 15 feet and stopped.

The 1.20 AX is an amazing engine. It was turning 8400 rpm on the ground at 600 feet above sea level, on 10%, one click off peak, with a 15x10 APC. I put one 12 oz tank through it before the flight, a mix of full throttle, half and idle, and it ran for 21 minutes.

I'm pretty happy with this one. The only bug that popped up was the tail wheel assembly. With the weight of the plane on it, that silly setscrew is not enough to prevent the wire strut from pushing up so far that it blocks the retract mechanism and the thing won't retract. I put a stack of washers between the bushing and the mount, to make sure it stayed where it belonged, and all was cool. I also could not get the engine to even spit by hand, so ended up using a starter and messing up the paint on the spinner, but what the hey, flying is the important part. It's why we're all in this.

Old 02-28-2009, 07:19 PM
  #1891  
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Default RE: Top Flite 1/7 P-51 Build

Congrats on your maiden! Sounds like you built a good one.
Old 02-28-2009, 07:19 PM
  #1892  
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Default RE: Top Flite 1/7 P-51 Build

Great to hear Bob!
Wish I had made it over there. The ice hasn't hit as of yet. It's 7:15 PM. We just got in from fund raiser and as I'm typing my son just ran across the room saying it's snowing it's snowing! We'll see what she brings.

Sound's like a fine bird you got there! I was down looking mine over today. I just don't know what to do with it. It's not in any shape to fly. I just keep kicking around weather it's worth working on or not. It seems like so much work to get it flyable. I could just build another one! But then again, this one has never been flown..............decisions decisions!

Sean
Old 03-02-2009, 04:53 AM
  #1893  
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Default RE: Top Flite 1/7 P-51 Build

Bob...nice to here the details on your flight! I know you are a fellow "old schooler" which is a tired expression, but nice to here just the same. I hope we will all find some solace in this great hobby during the coming months of concern. I won't hesitate to continue to spend some money on this hobby as possible, during this hard time. Damn them all if they think we'll stop our beloved hobby, Bob! I'll share, if I maiden my stang this summer, friends. -Eric
Old 03-02-2009, 07:26 AM
  #1894  
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Default RE: Top Flite 1/7 P-51 Build

Thanks, guys. This wouldn't have happened without all the support and encouragement I got from this forum.
Old 03-10-2009, 02:20 AM
  #1895  
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Default RE: Top Flite 1/7 P-51 Build

Hey all,

Makin progress here. Just curious what muffler you used with the 120 AX. Seems like having to pay 50 bucks or so to put a pitts muffler would make a 4 stroke more appealing. Also anyone use a saito 115 or 125? Never used a Saito only OS and Magnum 4 strokes. Also for a 2 stroke are you sid emounting or inverted mounting the engine. Always planned for an inverted megnum or OS 120 but thinking now about the 75 or 120 AX. Let me know what you think. Finishing the retacts and then hopefully closing the wing up this week.

Pilotman520
Old 03-10-2009, 08:20 AM
  #1896  
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Default RE: Top Flite 1/7 P-51 Build

Pilotman: This is a long one, but it's information you'll need if you decide to go this route.

I was going to go with the Saito 150, as its performance is what I felt was needed for this bird: the ability to turn a 15x10 or a 16x8 APC prop in the neighborhood of 8400-9000 rpm on the ground.
This calculates out to over 10 pounds of static thrust and between 75-85 mph. I ended up going with the OS 120 AX because the various RPM posts on the engine indicated its performance is almost identical to the Saito 150. The advantage of course being that it costs a little more than half what the Saito does.

One of the best things about the 120 is that it can be purchased without a muffler for $30 less than with. http://www3.towerhobbies.com/cgi-bin...&I=LXLGH9&P=ML

That's great because the standard OS "power box" muffler is one ugly sob, [:'(] and it weighs a lot- over 7 oz.

I went with the 120, mounted inverted, and I used a Macs muffler stuck out the left side, and I used the OS aluminum engine mount. http://www3.towerhobbies.com/cgi-bin...?&P=8&I=LXSXF2 Jtec makes a wrap around, inverted pitts muffler for the 120, but I didn't find out about that until after I had purchased the Macs. There's not a lot of difference in price between the two, so if you're going with the 120 choose your preference. I might switch over to the Jtec in the future, as it would require very little modification to my cowl- just filling in the Macs hole on the left, as I already have a big cooling outlet on the bottom near the firewall. I think the Jtec will fit in there without cutting another hole on the left side but I'm not sure on that. I do know that anything other than a factory style muffler is going to be restrictive and will cost some rpm.

The 120 and the Macs did two things I was looking for: 1. The performance I wanted 2. A fairly large weight savings over a four stroke as the OS is 8 oz less than the Saito, and the Macs muffler can't weigh more than an oz or two. (Someday I'll put it on my powder scale.) This was important, as I was able to balance the plane by putting a 4 oz, 1450 milli amp battery in the tail wheel well. No lead required.

The system won't let me upload any pictures right now, but if you go back to page 70 there are some on the 6th post down from the top.


As I found out during my first flight, this setup gives a comfortable margin. There's no need to use full throttle except for aerobatics. Easing the throttle in resulted in a very scale like take off, and I can cruise around all day at 50% power or a bit more.

Don't let the idea of an inverted two stroke scare you away- properly setup, the 120 doesn't know it's upside down. There are just a few things you have to pay attention to:
1. Use a Hayes Slimline 12oz tank http://www3.towerhobbies.com/cgi-bin...?&I=LXK835&P=7 12oz is what OS recommends, and there's no need to use anything bigger. This tank is skinny enough that you can mount it on a 3/16 ply or balsa floor that rests on the bottom of the former openings, and the center of the tank (top/bottom) will come out exactly on the center line of the spray bar in the carb.
2. Break the engine in on a test stand mounted inverted. After you've run a tank through it at slobbering rich full throttle, lean it to a few clicks off peak, then idle it down and start adjusting the low speed screw. This is the real secret to inverted mounting- proper carb adjustment. The nice thing about the new OS carbs is you can adjust the low speed needle with the engine running, safely.
The critical thing is to use a tach and get the engine down to its specified idle speed before you start adjusting the low needle. (1800 rpm or less) If you idle it down and it loads up and quits, which it probably will, turn the screw in half a turn and try again. It will probably keep running. Then, pinch off the fuel line and wait a bit. The engine should speed up just very slightly. If it speeds up a lot, it's still too rich, if it slows down immediately or dies, it's too lean. Play with it until you're happy, then go back to wide open and do the pinch test. (If the engine wants to die or won't speed up, you closed the low speed needle too much- back out 1/4 turn.) You want the same results- a slight increase in rpms. Play with the high speed till you get it, then go back and check the idle adjustment, followed by the high speed, then you should be ok. After this process, I can idle my 120 down to 1800 for 2 or 3 minutes, smoothly open the throttle wide and it will go right back to full power with no spitting or coughing. Inverted.

The temptation with most builds is to use a tank that is too large for the engine. The exhaust system can only supply so much pressure. If the tank volume is too big, the feed pressure to the carb will not build up quickly enough after running at idle, and the engine tends to starve during acceleration. I'm convinced that this and failure to properly adjust the low speed needle are the cause of most of the dead stick landings you read about on RCU on a daily basis. With the 12oz tank, my engine will run over 20 minutes at a combination of 1/3 full, 1/3 half, and 1/3 idle speeds. I made a 7 or 8 minute maiden flight and had more than half a tank left.
Old 03-10-2009, 04:28 PM
  #1897  
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Default RE: Top Flite 1/7 P-51 Build

Got the second flight in today (at my club in NJ) and it was a bit eventful. The tail wheel assembly disintegrated as I was about half way into the takeoff roll, and she went quickly left and ran into a fence before I could do anything except chop the throttle. She hit on the spinner, so no damage at all except to the Robart plastic retractable tail wheel, which is coming out as soon as I get home.

I epoxied the tail wheel back into place, cut the steering cables so it could castor, and plugged off the "retract" line to the T/W air cylinder, and went flying.

This flight I concentrated on the final trims with gear and flaps up. With gear and flaps down, there's no change. With gear only down, she wants to drop the nose, but that's easy to compensate for, so I'm not going to play with the trim on that. I did a go around on the first approach, leaving gear and flaps down, and the landing was one of the best I've ever done. Just slightly tail low at touchdown, the oleos absorbing the shock and no bouncing at all. Just settled down and rolled straight out.

I cannot believe how this airplane sounds. With the Macs muffler, there is very little exhaust noise at about 55% power, and she sounds like she's got a Merlin in the nose, as the prop kind of whines, especially in a shallow dive. It is awesome and has to be experienced. Maybe I can get someone to video her one of these days.

Looks and sounds better in the air than any warbird I've ever had, or seen. Four strokes and gassers don't come close to the right sound. I got lucky on this one.
Old 03-10-2009, 04:33 PM
  #1898  
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Default RE: Top Flite 1/7 P-51 Build

Your making me wanna build one!!!!
When you coming back down to Char'ville? I'll be glad to do some video for you.

Sean
Old 03-10-2009, 04:39 PM
  #1899  
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Default RE: Top Flite 1/7 P-51 Build

Sean:

I'm trying to convince the wife that we should come back the first week of May, but it might not happen until June.

Old 03-11-2009, 02:46 PM
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Default RE: Top Flite 1/7 P-51 Build

I was thinking again last night how docile this airplane is, and I think it is partially due to the way I make leading edges on everything. (Not entirely, because I think TopFlite's choice of airfoils and the tip washout have a lot to do with it.)

I can't remember what the plans called out for leading edge shape, and in any event, I didn't pay any attention. I always do a "shoe shine" sanding job on leading edges. After I do the basic shaping, I take a long piece of 120 grit paper that will wrap around the LE from spar to spar and pull it back and forth like a shoe shine cloth as I work from tip to root and back. The idea is to get a very round, almost blunt leading edge. I read a long time ago that this costs some speed and agility, but that it prolongs the onset of a stall, and makes the stall much gentler when it does arrive.

Seems to work. There is no need to be above idle on this bird from a 100' base leg entry all the way to touch down, no wind with the flaps down. If I add power at any point on the glide, I end up having to go around because she's too high and fast.

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