nrad2000

Use those rate earth magnets. They are very strong. I built a removable hatch in front of the canopy and is held with 2the magnets. I'll take pictures this weekend. Finished covering my plane. Stupid me, I put one of the stars up side down. Hopefully no one will notice.

acdii

I got back into the '51 last night after putting the wing on my Dewey and adjusting the controls. I think I still have linkage work to do before I fly it, not happy with the throws. 

nrad2000

tonight is the fuel tank and lines, throttle linkage, drop in the servo's, connect the push rods, and balance. My final step is: mount the battery and receiver so that the plane will balance.

I think I read somewhere on this thread that it is best to CG it 1/4" towards the leading edge from 3 7/8". I guess it's better to be nose heavy then tail heavy.

nrad2000

I didn't get much done today. But just to see what the plane looks like I bolted the wings on, retracts lowered, and placed it on the ground - my first initial response was - COOL!! Then my son walked by and pointed out that my star on the side of the fuse was up side down. Oh, crap!! Too make things worse - viewing from the top of the plane for the very first time I noticed that the plane did not look straight. I measured the ends of the wings and they are on straight. took a yard stick and the fuse is straight. then I measured the distance of the stab from the wings and they were OFF. Almost 1" inch off. the left side of the stab is 1" further than the right. That is HUGE!! don't know how that happened. must have happened during epoxy curing. I think she will fly but she won't fly straight and true. but I don't know - it is just the stab - maybe it won't really affect the flight.

what do you guys think?

acdii

It will be squirrely.  When you say off, are you meaning the stab has more on the left of the fuse than the right, or its crooked?  Better post a picture of it, but either way, the plane will fly like crap if the symmetry is off.   If you have more elevator on one side than the other it will tend to turn in the direction of the lessor elevator, and you would have to compensate with rudder and aileron.

nrad2000

It's just crooked - it has the same length on both sides.

nrad2000

nrad2000

Electronics are in. I still need to glue the canopy and toe in the wheels 2 deg or so. I weighed the plane and at dry weight she weighs 9.6lbs. I'll do a photo shoot tomorrow. Next weekend I'll fly her with video.

Mike_Jones

I did a complete dry fit today to check the CG before covering. Turns out the main battery can not go up front liked I planned. It's way too nose heavy. It will have to go in the spcae normally used for the gas tank. So that alleviates my problem of attaching the front cowl with easy access. Looks like I will have to remove the wing every time I want to change the battery. Or I will have to build another access hatch from the top. I'll have to think about this for awhile.

nrad2000

I put a 11.1v 1800mAh battery all the way in the back - behind the servo tray. that balanced the plane 1/4" forward. I built a forward hatch that is held with magnets - just in front of the canopy - for easy access to refueling, deans plug, and easy viewing of the fuel tank. I'm glad I did that.

I took the plane today to the field and started the engine. With a 16x6 MAS I got 8500RPM. Plenty of pull. I then changed the prop to a 14x6 and got 10900 RPM. equal amount of pull. I didn't have a 14x7 on hand but I think that is the ticket for my OS FS 91S engine. it may have been the 16x6 prop and the load it produced but the exhaust valve spring broke in two. suddenly lost power. I'm going to change out both springs just incase. I'll attempt to maiden her this Saturday morning. Hope all goes well.

capriman

when you install the new valve springs, set the valve lash very carefully !! watch for spring bind, you should have a couple of thousandths between each coil of the spring.. ( I build race engines also )

nrad2000

Capriman, I have the OS Valve adjustment tool - I use it to adjust all my OS 4 strokes. I still don't know why the spring would break. I tried looking looking online and some said over reving, another said over heating, and another said - just a bad spring.

what is spring bind? is that twisting of the spring?

I'm hoping the springs get delivered by friday so that I can get them installed and maiden the P-51.

capriman

Spring bind happens when the amount the valve is moved by the camshaft is a distance that is greater than the total distance of the space between each coil of the spring...something has to give. Take a spring out of a ball point pen and compress it on a table until it is fully compressed, and then go further, this is what is happening. You might need to buy a few feeler gauges in the .001 to .009 range to make this check with the valve fully open. Look for clearence between each coil from top to bottom.

nrad2000

Will do. UPS scheduled for Monday.

raptureboy

You normally setthe stab to the center line of the fuselage, then set the wing to the stab. Have you checked to see if it is the stab that is crooked or the wing instead? Check the stab against the center of the fuselage. Good luck on the maiden.

acdii

Pics to come, the landing gear is finally in correctly, and the wheel doors are on. Other than the timing of the retracts, that part is done, now I jut need to work on how to get the doors to open and close, still haven't quite figured out how to link them up to work.

nrad2000

raptureboy, the wing is straight and my stab is crooked.

Tonight I'm going to pull out one of my other engines out from another plane and put it into the mustang while waiting for the valve spring. I really want to see how this plane flys.

acdii

Well here are the pics of the landing gear after I pulled them out and reset them. Now the doors close fully. Next is to reskin the areas I removed, and figure out how the hell to make the doors work.

nrad2000

She flies!!

Throttled up - tracked fairly straight - used lot of Right Rudder - tail came up - 30 feet the plane pulled up on her own. made my first turn and noticed it was wanting to climb - got up to 200 feet - started putting trims. I put couple Left aileron clicks - but I had to put a lot of down trim to keep her level. I flew with the retracts down - maybe that had something to do with the ballooning. Couple circuits and she flys hands off level but after I exit out of a turn she begins to climb. I don't think I am flying fast enough. powering it with an OS FS 91P w/ 14x6 MAS at full throttle I can't point the plane up. Loses speed fast and just falls. Tried a loop but just fell out of it at the top. After 5 minutes of flying I decided to bring her in. Used half flaps - started high - cut throttle - and she glided in but continued to keep gliding - touched the ground - had only 30 feet to stop on hard dirt - I gunned the throttle and went back around - same thing but at a lower approach. Glides really nice with wings level at half flaps. touched down at last 1/4 runway. just enough runway to turn around.

My impression: I need more speed or I need to pitch up the prop. I'll try a 14x8 - the biggest the OS manual states it can use. Truely, it does not fly like a stunt plane, does not fly like my sport planes. my setup felt more like a way under powered trainer.

fastp51

 Congrats on that nrad.What material is the robostrut steel or brass? I also am building this kit and may have some questions.Thanks for the great posts.

nrad2000

It's brass like - soft metal - easy to drill thru.

I'm gonna try a 14x8 MAS Sunday morning. Need more Air Speed.

acdii

Sounds like it will climb even more with added power. You can try moving the weight a touch forward and see if it flies better. You might be a touch tail heavy.  When I maidened the T-34 she was tail heavy and would balloon like you described. It would also glide a long way.  I have the balance a touch forward and it flies more normal, no flaps at all.

capriman

When your knees stop shaking and your hands stop sweating, pat yerself on the back...job well done.

Riddle4U

Nice job and congratulations on bringing it back for another shot! The P-51 was not a stunt plane originally, and the model....with a similar high wing loading will not be an acrobat. It is a scale model of a plane that flew large sweeping maneuvers at between 200 and 400+ mph! Expect similar flying style with the model....it is NOT a Pitts Special! It certainly is a demanding model I imagine, and I have yet to maiden mine (75% finished). Fly it with the mindset of the real P-51 pilot, and enjoy!

Mike_Jones

Congrats Nrad. I'd say you set the record for building time to flight. Nice job. My P51 is just ready to start covering. Flying season doesn't begin here until mid April.