YA P-38 Build
08-21-2014, 07:15 PM
#78
My Feedback: (24)
Looking good Chris
I did the nose on the NP-38 with magnets. Four small dowels keep it positioned in place, magnets top and bottom hold it on. Had initially thought it would have batteries in the nose, but plane came out nose heavy....go figure
The Gun barrel as a screw is a pretty cool idea
I did the nose on the NP-38 with magnets. Four small dowels keep it positioned in place, magnets top and bottom hold it on. Had initially thought it would have batteries in the nose, but plane came out nose heavy....go figure
The Gun barrel as a screw is a pretty cool idea
08-21-2014, 07:26 PM
#79
Thanks, yeah I wanted a very secure design on the nose cone and not knowing for sure if the fuse is pressurized in flight or not I wanted to avoid magnets.
Next up is finishing the guns and the spinners then balance it and run up engines one more time. Maiden soon to follow as weather permits.
Next up is finishing the guns and the spinners then balance it and run up engines one more time. Maiden soon to follow as weather permits.
08-23-2014, 03:28 PM
#80
O-ring inside of the mount then captured on each side with retainers. This will act like a damper and prevent the barrel from loosening.
This is a flanged retainer from a washer thats soldered on the tube then cut to length and soldered over the barrel tube.
08-23-2014, 03:39 PM
#82
Receiving blind nut and bulkhead in place and added epoxy fillet afterwards.
Turned down a hex head screw and soldered into the tube end. Now you just use an Allen key to tighten the nose on the fuse. The o-ring retains the barrel so its all together and easy to manage.
08-23-2014, 05:34 PM
#84
Lol, Im at the staring stage.
Its balancing on the spar but needs 6oz in the radiators to balance out or 3oz on the stab. So for ease of use Im going with the aft radiator location so the lead strips can be changed later if need be. I made 4 1.5oz lead strips so these can be flattened and stuck to the skin easily with silicone.
Its balancing on the spar but needs 6oz in the radiators to balance out or 3oz on the stab. So for ease of use Im going with the aft radiator location so the lead strips can be changed later if need be. I made 4 1.5oz lead strips so these can be flattened and stuck to the skin easily with silicone.
08-23-2014, 10:59 PM
#87
Both spinners are cut now so the next step is tapping and threading the backplates. This is a delicate operation and I dont have a nice vice or mill. So that will be done by my friend at his machine shop.
I got the elevator counter balances mounted and epoxied in place too. Pretty simple, just drilled and epoxied a brass tube on the balsa rib first. Then I epoxied a steel rod in each part. Finally put the balance in each tube and epoxied them.
I got the elevator counter balances mounted and epoxied in place too. Pretty simple, just drilled and epoxied a brass tube on the balsa rib first. Then I epoxied a steel rod in each part. Finally put the balance in each tube and epoxied them.
08-24-2014, 06:37 PM
#90
Anybody having problems with the DLE / RC Excel remote cut off swithes?
A buddy of mine has had two go out this season alone. He was there today giving me a hand and said the symptoms we were having seem just like what had to deal with.
1) sputtering at any RPM
2) not starting after having run just fine
3) shutting off
So... In order to get these out I have to take apart everything and disconnect the leads which are shrink tubed. Basically they are buried in the center wing.
Otherwise the engines seemed to run strong and idle was around 1300 and up to 6250RPM. They turn over in two flips at low idle right now... when they run!
A buddy of mine has had two go out this season alone. He was there today giving me a hand and said the symptoms we were having seem just like what had to deal with.
1) sputtering at any RPM
2) not starting after having run just fine
3) shutting off
So... In order to get these out I have to take apart everything and disconnect the leads which are shrink tubed. Basically they are buried in the center wing.
Otherwise the engines seemed to run strong and idle was around 1300 and up to 6250RPM. They turn over in two flips at low idle right now... when they run!
08-25-2014, 04:40 PM
#94
It was cool taking it out on the runway to taxi test. Man this thing has power! Just a little jab and it leaps forward and crabs to the left. Good to see some of its character before the first flight though. Im going to reprogram the throttle curve because I can feel the response has changed with the addition of the velocity stacks. The low range feels normal and then it quickly feels like your at full throttle but there is a lot of stick travel left. Half TH is at about quarter TH so Ill smooth that out.
08-26-2014, 09:31 PM
#95
Made some progress today. Tom finished the spinners and I took out the cut off switches. We ran the engines again and they ran ok but still had some hesitation. Basically long story short I changed out the prop on one engine to an 18x10 just to see if the engine would respond better and it did. I had been running 20x8 then cut and balanced them down to 19x8. The props blades were still too wide and the engines were still over loaded. The motor tached out at 6300RPM but when fitted with the 18x10 it did 7300RPM and cleared out and ran better. The idle RPM is as low as 1350RPM and I can cycle the throttle stick aggressively with no hesitation. Now were getting somewhere.
Another interesting point. The low end needle HAD TO BE set to more than 2 turns to run at all with the previous prop plus keep in mind these are fully cowled engines. Now with the 18x10 prop AND the cowl back on plus the low speed needle reset to 1 turn out the engine ran well and was responsive. Plus the temps are in the 150-170F range.
Why did I run the bigger props? The thinking was to get the idle RPM to settle down with a little more load and also less idle thrust. Ive had planes before where the prop is great for the engine but with a clean plane the idle thrust makes the landings faster. I wanted more thrust and less pitch speed.
We have the same engine and an 18x10 prop on a TF Stinson Reliant and at low idle this plane is tough to land, it just floats and putts along in ground effect. I have to take a long approach to get it to settle down and let the engine get to low idle.
I also fly a World Models Zero for Tom with the same DLE 35 RA with an 18x10 and same thing the idle thrust is a factor when landing. In the Zero's case though I can slow it down better and land with a higher angle of attack than the Stinson.
So now double the effect and put that on a pretty slick plane like the P-38 and you see my concerns. But I cant argue with what works and these engines really like 18x10 props so Im setting up a pair of these and were going set the carbs one more time to these props.
One other thing that seems to be working in our favor is the weight of the spinners.They are acting like flywheels and helping to lower the idle RPM so this might be the perfect combo in the end.
The DLE manual states the engine will handle 20x8 and 19x8 props but Im seriously doubting that based on what we have seen on the tachymeter. The engine needs to spin up or it bogs and needs a lot a fuel to run. Also less fuel and higher velocities in the carb seem to be better for this engine carb combo.
Last but not least, the left engine throttle servo horn screw backed out during testing the other day. Thats why the darn engine quit! The carb shut and killed it. Couldnt see it because the wing and cowl were on and I could hear the servo work so I didnt look any further.
More to come, were planning on going out by Thursday. Fast taxiing and checking engines then if its good were going to fly her.
Another interesting point. The low end needle HAD TO BE set to more than 2 turns to run at all with the previous prop plus keep in mind these are fully cowled engines. Now with the 18x10 prop AND the cowl back on plus the low speed needle reset to 1 turn out the engine ran well and was responsive. Plus the temps are in the 150-170F range.
Why did I run the bigger props? The thinking was to get the idle RPM to settle down with a little more load and also less idle thrust. Ive had planes before where the prop is great for the engine but with a clean plane the idle thrust makes the landings faster. I wanted more thrust and less pitch speed.
We have the same engine and an 18x10 prop on a TF Stinson Reliant and at low idle this plane is tough to land, it just floats and putts along in ground effect. I have to take a long approach to get it to settle down and let the engine get to low idle.
I also fly a World Models Zero for Tom with the same DLE 35 RA with an 18x10 and same thing the idle thrust is a factor when landing. In the Zero's case though I can slow it down better and land with a higher angle of attack than the Stinson.
So now double the effect and put that on a pretty slick plane like the P-38 and you see my concerns. But I cant argue with what works and these engines really like 18x10 props so Im setting up a pair of these and were going set the carbs one more time to these props.
One other thing that seems to be working in our favor is the weight of the spinners.They are acting like flywheels and helping to lower the idle RPM so this might be the perfect combo in the end.
The DLE manual states the engine will handle 20x8 and 19x8 props but Im seriously doubting that based on what we have seen on the tachymeter. The engine needs to spin up or it bogs and needs a lot a fuel to run. Also less fuel and higher velocities in the carb seem to be better for this engine carb combo.
Last but not least, the left engine throttle servo horn screw backed out during testing the other day. Thats why the darn engine quit! The carb shut and killed it. Couldnt see it because the wing and cowl were on and I could hear the servo work so I didnt look any further.
More to come, were planning on going out by Thursday. Fast taxiing and checking engines then if its good were going to fly her.
09-07-2014, 07:44 PM
#96
Success!
Maiden flight today, went well no issues finally.
I replaced one engine because of a suspected bad ignition so since we had the same set up in the Zero we just swapped. The Zero tached over 7700rpm and the good P38 engine tached about the same hence the reason to swap them. Installed though we lost a few hundred rpm from the Zero engine which I cant explain yet. The good engine tached today up around 8100rpm!! You could hear the difference between them but since both ran well I decided to dial back the good engine close to the same rpm as the Zero engine. That worked and you could hear the engines in sync as well as on tach.
Taxied out to the end of the runway and the winds were variable speed crosswinds and about 20 degrees or more off center. I ran up the engines a bit to get some speed up and noticed immediately the plane wants to wander a bit left or right so I had to compensate rudder as needed. Turned around and added power to see if it would settle with speed and it did. I added more power and pulled back lightly and the 38 rotated then slowly came off the ground no problem, it was on the wing and power was good. Pulled up and around nicely and retracted the gear, I figure they either work or not so lets see, sure thing they worked just fine.
I flew several circuits around the field to get a feel and it didnt need any trim, perfect! Thanks Greg for the CG advice it flew nice.
Decided it was time to land so I dropped the gear, came down just fine, flew a gear pass and proceeded to fly around for final. The P38 was feeling really good to me and although I didnt perform my usual stall test I got the impression from the relatively low speed departure that the stall was going to be pretty slow. I wasnt going to chance a flame out during a stall test. Anyway, made the approach and compensated for the cross winds but I got a little further off center than my usual landings. Brought the power back and held off then slight flare and it touched one main first then the next for a little bump but the suspension soaked it up fine. I was very confident with this plane right away and being able to land it on the first attempt speaks for itself I think. Compared to the CARF Gee Bee with a 250 Moki this thing was a breeze! That one took me 3 tries to land the first time.
I didnt take any photos or video because I have a thing about that, its bad luck for me. So next time out there will be some pics and video probably.
Now its time to paint it! Woohoo we made the milestone!
Maiden flight today, went well no issues finally.
I replaced one engine because of a suspected bad ignition so since we had the same set up in the Zero we just swapped. The Zero tached over 7700rpm and the good P38 engine tached about the same hence the reason to swap them. Installed though we lost a few hundred rpm from the Zero engine which I cant explain yet. The good engine tached today up around 8100rpm!! You could hear the difference between them but since both ran well I decided to dial back the good engine close to the same rpm as the Zero engine. That worked and you could hear the engines in sync as well as on tach.
Taxied out to the end of the runway and the winds were variable speed crosswinds and about 20 degrees or more off center. I ran up the engines a bit to get some speed up and noticed immediately the plane wants to wander a bit left or right so I had to compensate rudder as needed. Turned around and added power to see if it would settle with speed and it did. I added more power and pulled back lightly and the 38 rotated then slowly came off the ground no problem, it was on the wing and power was good. Pulled up and around nicely and retracted the gear, I figure they either work or not so lets see, sure thing they worked just fine.
I flew several circuits around the field to get a feel and it didnt need any trim, perfect! Thanks Greg for the CG advice it flew nice.
Decided it was time to land so I dropped the gear, came down just fine, flew a gear pass and proceeded to fly around for final. The P38 was feeling really good to me and although I didnt perform my usual stall test I got the impression from the relatively low speed departure that the stall was going to be pretty slow. I wasnt going to chance a flame out during a stall test. Anyway, made the approach and compensated for the cross winds but I got a little further off center than my usual landings. Brought the power back and held off then slight flare and it touched one main first then the next for a little bump but the suspension soaked it up fine. I was very confident with this plane right away and being able to land it on the first attempt speaks for itself I think. Compared to the CARF Gee Bee with a 250 Moki this thing was a breeze! That one took me 3 tries to land the first time.
I didnt take any photos or video because I have a thing about that, its bad luck for me. So next time out there will be some pics and video probably.
Now its time to paint it! Woohoo we made the milestone!
09-08-2014, 08:10 PM
#100
Bought paint today and as luck would have it there was a price increase since I got my shopping list from the paint store. They just did it on the 25th and wouldnt discount my order. Awesome...
Anyway, I picked up PPG Omni M125 Aluminum paint and the respective kit plus flattener for a satin clear coat. Its automotive paint and its catalized so it will be durable.
The painting plan is for an all aluminum look thats weathered. The scheme is like the photo but Im still looking for one that has invasion stripes for better visibility. Im less worried about the scheme right now since we know the base is a bare metal.
Anyway, I picked up PPG Omni M125 Aluminum paint and the respective kit plus flattener for a satin clear coat. Its automotive paint and its catalized so it will be durable.
The painting plan is for an all aluminum look thats weathered. The scheme is like the photo but Im still looking for one that has invasion stripes for better visibility. Im less worried about the scheme right now since we know the base is a bare metal.