Wing Loading P51, Too Heavy??
 

Hello all, Wondering if my P51 is going to fly and survive its first landing. I Found a old Pica 1/6 P51, super detailed, never had engine mounted. Plane alone weighs around 13 lbs, have a Evolution 33GX Gas engine fitted, all up empty weight is around 16 1/2 lbs. Wing area is 950 sq inches which calculates out to about 40 oz/ft wing loading. Taking off and flying I don't think will be of issue as the 33 will make power to weight ratio better than 1:1 but my wonder is how hot are landings going to be?

Full flaps, robart gear, never started yet

Opinions???

Don't the plans say that plane comes in at around 14lbs? If so, I'd say you are a little on the heavy side but not way out of the ballpark. With full flaps it should not be a problem. Just be sure to fly it in under a little bit of power and then cut the throttle after you are on the ground. How tricky that will be depends on the length of your runway I guess. :D

Nice Bird!! just remember to fly it like a warbird and you will be fine. You might tinker with flap setting with gear down about halfway through the first flight. Just get 100' up and go gear down and flaps with 1/3 power. Some will pitch up and some will pitch down. But that should give you a sense of how it will feel on final.

David

Don't really know weight from plans, bird was built when I bought it and no plans or even discussion with the person who built it could be had, anyone know where I can find a set of plans?

But THANK YOU for your insight and suggestions, YES, on first flights I will find the most open longest runway I can fly from :)

ALL thoughts and suggestions are welcome, even repeat advice so no one be shy.

The exhaust is custom as I could not find a muffler to fit under the cowl and the model is too nice hack a big muffler out the side or bottom, not done welding it together yet, here is what it looks like cowl off, right side will be functional also

My opinion, 40 oz/square foot is well within acceptable limits on a 1/6 scale P-51 and the model will fly just fine. Assuming it's built nice and straight of course and properly balanced.

You are a craftsman sir. That exhaust work is top notch. There are some videos of P-51s with the Keleo exhaust on you tube. They are much like yours and have a unique sound.

David

The P51 has been a favorite for a long time. And this version appears nicer than many

The wing loading is a bit high tho. Take offs are not going to be too bad. Just need more speed than normal. Landing too need more speed and that could prove more of a problem even with flaps. You will have to learn it's habits and if it will tend to tip stall easily if slowed even a little too much.

Years ago I built a Midwest extra 300 with almost 1150 squares that was more porky than I wanted at 16.5 lbs. That one would snap in on landings all the time until I increased landing speed. Good luck with the flying

Yeah, the exhaust is very cool. Super nice work!

The wing loading on my KMP Bearcat is sky-high, no pun intended. (47+ oz/ft) It flies just fine. As long as you carry a bit of power on final, you'll be fine.

One thing that is recommended with all new planes is to check the stall with some altitude. Slowly reduce throttle to idle, and add up elevator until you reach the stall. This will tell show you how slow you can get the aircraft for your landings. It will also tell you which wing will drop, or if it will just fall forward. This important step, is overlooked by most.
The key to good landings is getting the wing stalled at the right time. Most pilots, at least at my field land way to fast. This generally results in ripped out retracts.

My old Pica T-28 ended up around 45 oz/sq foot and I was worried it was too heavy as well. It flew fine but it did take a while to tune the CG to get it to slow down as the build ended up quite nose heavy. Slow flight at altitude is a good suggestion as well so you know how to slow it down rather than just flying it in hot. Beautiful Mustang there and I am sure it will fly great.

I don't understand the exhaust. It looks like the vertical tube isn't sealed. Is there a seal inside that we can't see that's between the horizontal stack and the highest part?

Also, I know it is too late really to make any adjustments, but washout will be your friend. If you have an incidence meter, it would be easy to check. A couple of degrees will help greatly with your stall if the wing loading is high. Learned this big time when I first started flying the 1/12th scale combat models, that all suffered from a high wing loading as well, and had to be hand launched.

http://www.rcuniverse.com/forum/atta...mentid=2039206My favorite weekend "beater" has a wing loading of 53 oz/sq ft, of course being a bit bigger helps due to the fact that everything is a bit more efficent as you get bigger. You won't have any problems as long as your P-51 is straight and the CG is good. If anything set it up a tad on the nose heavy side, then when you pull off the power it should establish a nice glide which will help on landing. Best of luck, it's a pretty model.

I concur with everyone else's comments, 40oz/lb should fly great. Will fly more like a scale bird than sport, but not by much. Mustang flaps are pretty effective, so keep some power on all the way to the field, cutting it when your just about to touch down. Don't try to slow it down too much on the approach. Just let it come in and land on the mains, don't try to three point it right off the bat

That is a beautiful muffler(manifold) you are building and I do not mean to be critical about it but you are putting a tremendous load on the exhaust screws. There is a long cantilever going aft and another crossing over. There is going to be a lot of weight exposed to the usual vibration. Do you plan on supporting it some where? If so, that support has to be the engine. You can’t strap it to the fuselage. Dan.

Hi,
I have flown quite a few P51's including the Dave Platt 81" model, but I have no experience of the 1/6 scale Pica. However, I think the most important thing to check is the amount of washout in the wing. Even a heavily loaded model will be ok with washout ( within reason ). Check that the wing has at least 2degrees washout and fly it with authority. Good luck, a nice looking model by the way.

Cheers,
Merlin man.

THANKS everyone for their suggestions, comments and compliments.

Cafeenman your confusion on the exhaust system is because it is not finished yet. There is plugs for the tube ends and the right side manifold is on the table under the model, there is MUCH tedious tig welding to do yet. I would have rather had purchase a bolt on scale exhaust from the guy mentioned who makes them but he was too busy to talk to me even, wouldn't even sell me just the manifolds so I was left with 2 choices, hack the cowl with a big ugly muffler or make my own, so if I have to make it it at least should look the part, luckily I have the skills and equipment to do such just not the time lately, all this work was done last winter, just getting back into it now again and hoping for some time:(

I am glad to hear it is sounding like it is not going to be a flying brick and wing loading is not too high, I want a fun model to fly not a headache. I'm hoping to have it completed for spring, I will post some pictures of the exhaust system once completed, each manifold will be iso mounted to the fire wall with tabs to help support it all. I will definitly stall test on first flight, 16 oz of gasoline should give 20+ minutes of air time for a long unhurried first flight.

More suggestions and comments welcome. Anyone possibly have the original plans and reccommended CG point or better yet flying one of these??

http://www.rcuniverse.com/forum/rc-w...fications.html This should tell you what you need to know.

Hey Merlin Man there is a gentleman who has posted regarding the Platt Mustang over on RC Groups who I'm sure would be very interested in your experienced input. Check out the link below if you have a few minutes to spare.

http://www.rcgroups.com/forums/showthread.php?t=1627678

Hi,

Thanks Chad. I briefly checked the post you mentioned and the gentleman seems to be doing a good job. I didn't reply to his post ( can't remember my p/word!) but would be happy to help if I can. I don't mind if you point him in my direction if he needs specific help.
Cheers,
Merlin Man.

Sounds good Merlin Man, I will send him your way if he wishes to pursue speaking with you. Somewhere near the end of his thread he was asking for some input from somebody who had actually flown the Platt airplane. Thanks for checking it out and stay tuned...

Welding time!!
 

First pictures were of prototype to test welding on, here is the actual pieces to be welded together after getting the welder set up for this thin .040" tube, now the hard tideous part comes, TIG welding it together. Only thing missing in the pictures is the end plugs for the manifolds, they are a press fit and once in won't be easy to get out. This is the step I have been dreading, TIG welding thin aluminum is no easy task

Thanks guys for doing this, its Corey user name cportelli the one building the Platt Mustang
Hi Merlin man i was wondering how the Platt Mustang flys, and handles at slower speeds.

You haven't tried to balance it yet have you? The final weight is going to depend on that.

Please consider balancing it right where suggested by the plans or one of the online apps that considers the measurements including the horizontal tail. When you balance them nose heavy for safety and they're porkers, you're cutting your own throat. Nose heavy handles slower because it's reducing the ability of the tail to control the airplane. It's really not a good idea with a heavy plane. You're already going to have a wing struggling with a lot of weight. That reduces the AOA available before the wing stalls. That reduces the AOA the tail has to work with. Add in the extra weight the tail has to control from the nose heavy condition and the tail is risking stall too. You really don't want to reduce it's capability with excess nose weight that's really not making the plane easier to fly and certainly not safer to fly. Want it to feel safer? Dial in some exponential. But keep the recommended throws and the recommended balance point.