Final mods and Trimming of the P-40

I haven't had to tweak flaps on anything, may have to on this Twister I am building.

I am really glad everything came together for you. Sounds like you have a good fleet to work with now.

Did you post a picture of it all built? If you did, I missed it.

Ron

Good Fun Rusty !! Its good you know how to tweak those baby's for performance !! Hers the thread Ron at the end of page two is the finished P40 . https://www.coxengineforum.com/t11037p25-what-s-that-big-box-by-the-back-door-or-the-p-40-assy-is-done

getback wrote:Good Fun Rusty !! Its good you know how to tweak those baby's for performance !! Hers the thread Ron at the end of page two is the finished P40 . https://www.coxengineforum.com/t11037p25-what-s-that-big-box-by-the-back-door-or-the-p-40-assy-is-done  

Thanks Eric.. I'd missed the finished-pics too. Pretty SWEET! Glad that she flew well for you Rus.! I'm always fascinated when you explain the trimming-steps applied to get the model on rails! Which "tweak" made more of a difference in this case? Did you reduce tip-weight first.. fly.. then tweak the flaps?

roddie wrote:...I'm always fascinated when you explain the trimming-steps applied to get the model on rails! Which "tweak" made more of a difference in this case? Did you reduce tip-weight first.. fly.. then tweak the flaps?

Okay, Rod, first come the pre-maiden checks: Fore-aft CG, of course. Since it was tail heavy, I added a large muffler and a 1 oz. aluminum spinner, which put it right on the recommended mark. I will re-adjust that to suit my preferences last of all, after all other trimming is done. E.g., I've only now got that set for good on the Twister. Turns out it's tail heavier than recommended.

Next hang by the neutral leadouts and check two balance points... first, one you are all familiar with, is to see that the fuse angles a degree or 3 nose-down from tail to nose. Mine was spot-on. Second is to view it from the front(or back) and see if the wing is perfectly vertical straight up and down, or if it rolls toward the bottom or top. This can sometimes be adjusted with LG and tail wheel weight. This would only be at all a concern for a PA ship, and then not critical unless badly out of line. Mine was rolling only very slightly toward the top, so heavier wheels or longer LG(which I'd opt for, as these gear are pretty short). I will not bother with it.

Pull test it from the handle to 10 G. Don't forget or omit this step!
If I had not pull tested the Twister when I recently re-maidened it, it would be a pile of rubbish now.

Now I fly it with a skilled observer. 5 laps upright and 5 laps inverted, both at observer's eye level.  Don't fly fast for this adjustment, or the Gees will cover the problem up. Mine flew upright with its outboard tip low... very much so. Then it flew inverted also tip-low, but not quite as low. This indicates too much tip-weight and the outboard flap pushing the wing up in relation to the inboard neutral. Usually, the outboard flap is adjusted so as not to interfere with the relationship between flap/elevator at neutral. In other words, inboard is your baseline. Realistically it could be the inboard flap but that's gonna complicate things... build straight! Lol. I knew the book had recommended too much tip weight, 1-1/2 ounces. I removed 1/2 ounce and then broke a cardinal rule... tweaked the flap slightly down to help lift the wing more for upright flight and opposite for inverted. It flew better, but still low upright and close to equally high inverted. That tells me I got the tip-weight closer, but the flap still needs tweaking downward. I'll keep playing with both until it's wings-level, no roll in either direction.

The observer must have good vision, and a contrasting background like trees helps me. As the plane flies toward you and away, look at the lines and trace their line going into the wing, and imagine them exiting the outboard wing and continuing the same straight line. The observer has to be standing where the sun illuminates them the best too. I also find that sometimes I can't detect any roll, but am just not 1000% sure, and I wonder if I am imagining a slight wing attitude. I usually call it good, but inform the pilot I'm having to force the conclusion. A second opinion should come from someone with a proven track record in watching this. I actually have a really good record on calling it right. Sometimes it's not an ideal background, or the wind is making it waver, or the pilot can't hold it steady. Or the engine is surging... that will roll the wings. And it will correct a bit when the engine leans out, so get it as early as possible. You can only guesstimate on a windy day.

That's the basic trimming for any good flying plane. For fun sport flying, a plane that goes where you aim it and lets you fly imaginative flights and amaze your friends and neighbors, there is every reason to do these things. You'll fly much more relaxed, more confidently in a stiff breeze, and crash a lot less... and be more proud of your builds. And learn what needs building better, what does and doesn't work. Learn what props fit your style and make the plane fly with the speed and line length that suits you best.

For PA, there is plenty of other stuff and it might take a lot of flights. And becomes much more arguable. It can become hard to delineate where or if preference and aerodynamics overlap... or sharply meet. That in itself can be arguable.

Hope that helps answer your curiosity.
Rusty

Yes Rusty.. and "thank you"! When you "tweak" the flaps.. how do you go about it? There's generally a joiner-wire connecting them. Do you grasp "both flaps" at the joiner-wire locations and slightly bend in the desired direction? I try to use flap-joiner wire that's not too heavy.. but heavy enough to drive "both flaps" equally with a minimum of flexing. Some of the old kit wire-joiners were pretty "stout".. and didn't look like they could be bent without damaging the flap(s). Maybe "todays" stunters use a lighter-gage wire for trimming? Are trim-"tabs" for when a flap-tweak can't correct a condition.. or are they used on wings that don't use flaps?

Thanks again for taking the time to explain these things.

Rusty, it's been difficult for me to get out lately. Shawn now working and my job has impacted my weekends. Somehow work in general feels that work is no longer a 5 day a week tradition. Lately, weekends have been given up to support Uncle Sam because it certainly doesn't benefit me. Today however, we both got out and put up a few patterns. I flew a few patterns on  the Oriental today, just for the record I haven't flown that plane since my debut of it at Huntersville a few years back. The old girl is developing some cracks where the bottom block meets the F-2 former. As much as I hate to do it, I may have to open the belly up and get in there and do some fiberglass work.

                     
                               Fox .35 powered
Fueled it, fired it, and it did exactly what it was supposed to do. No fussing even though it's been dormant for a while. Seeing the comments in regards to the L&J Fox .35's lately  we had a new AAC L&J Fox today to play with. I can say with hands down certainty that I won't be needing one of those. Very gutless and my 40th anniversary Fox outpowered the $200 Fox with ease. While the AAC engine was lighter it seemed to lack a lot of torque that the stock Fox offers. I can testify for it's smoothness but that didn't make up for it's lack of power. I find it a very unrealistic statement when the claims are much higher above stock.






We also took out the P-40's. Many P-40's are in the club. Dan uses a Tetra tank.

                 

Profiles are no strangers to bad vibrations and these ARF's are well noted for that. The Tetra tank is a hard tank with a bladder inside. If you look at the tank, you can see the pickup is on the front of the tank and not in the rear like a conventional hard tank. There's a vinyl like bag inside the hard tank similar to a balloon tank. The way were using this tank is opposite of it's intended purpose which is to deplete the inner bag ridding it of all air and then filling with fuel similar to the balloon tank setups. Instead, we suck all the air out of the inner bag and fill the tank itself with fuel. The inner bag is hooked to the muffler pressure nipple and as the engine is running, the bag inflates pushing outwards against the fuel. This setup is a bit problematic to get used to but it's not affected by vibrations.

       I have discovered that many of the ARF's were flying with a tip low attitude. In fact, the club is flying one currently with about 1/2 oz. of inboard tip weight . Even with all the weight out of the tip weight box the plane was falling hard outboard.

          Rusty, Dan has been in the lab once again making creations, while this isn't related I think you will find this impressive. Here's what will be the next twin on his HUGE P-47 currently flying the Fox .35 inline twin. He needed a bit more power and opted for these K&B .40 twin. Cool as all heck and I can't wait to see this in action. These are Dykes ringed engines one being a front rotor and one rear rotor. The center mill finished piece has the bearings to support the crank jointer. If anything it will certainly be entertaining.

Wow, he's quite the innovator. I guess he had to turn an L allen wrench into a stubby to tighten one set of bolts on the center housing.

I remember the green Oriental from 2013. That was the first contest I ever entered. With my old Shoestring... amazingly a survivor in a fleet that has very few old planes. Ron Cribbs has flown it more times than me over the last couple of years.

I cut a three blade Masterairscrew 12x6 down to 11" today. Once the P-40 is fully flight-trimmed, I'll try it. I hope it works if only for the cool factor.

Here's a new pic, Fleet 2017:

Looking good Rusto!!

You ought to take out the classics once and a while, just to get back to your roots. The Shoestring will do a pattern, just not with really tight turns.

The P-40 is dwarfing everything!

Thanks, Jamie. Still a little trimming, but this time it'll be over grass. I was flying over the pavement in H'ville.
I didn't know you were a member here, a fellow CEFer. Hope to see ya on the show tonight.

Yeah, Ron, you're absolutely right. Actually that SS will turn pretty tight. We'll fly them in December, and I might take it and the Yak out and loosen them up for you before December.
I didn't realize how big that P-40 was till I loaded it into Big Red Saturday.
Rusto

I just completed a Brodak Shoestring. I built it for racing so I made a lot of changes in regards to structure. I flew the plane to see how it would fly at our stunt field and was quite surprised. It's fully capable and flies quite gracefully. It doesn't slide through the maneuvers like a Ringmaster and isn't jerky at all. Powered by Fox.35 and it gets the job done quite well.

Remember the Brodak P-40 ARF does not have any dihedral and the wing is low mount

the camp that sez add diheadral and the camp that sez build and fly it as designed, are mostly staying with flat wing and doing the compromise trimmings to get rid of most bad habits for the over head maneuvers or hinging in the tight corners

I am in final stages of engine mounting (OS LA 40) and bench trimming a Brodak Oriental ARC right now

I expect the Fox is a great match for the SS. Mine has the Max-S .35 and I love the way it runs too. Fred, I look forward to your Oriental. That's a great flying ship.

I don't know how long it's been since I posted, but just for a fun refresher, listen to the Max-S chewing up the air with a 10x6 prop. I think it's a 10", surely not an 11", but has a pretty 4-2 break. Skip the Cardinal part of the movie.

Rusty, the Fox is indeed a good match. The MAX-S does offer a bit more power. The Fox though is more tolerant of burn down screaming runs. The machining and overall quality of the MAX is far better but the MAX does suffer from a few issues with it's design. The weight between both were pretty similar. The Max tolerates a muffler superior to a Fox. The Max doesn't seem to cater to too many prop choices as it prefers 10" props generally paddle bladed styles. I never knew why Duke didn't take a page from OS and upgrade a few things. Anyone in this hobby should own both in my opinion. I have a MAX .40 which is really a jewel. Not much mention of it, it did gain popularity in the 70's with both the r/c crowd and control line flyers enjoyed it. It seemed that when OS moved into the 80's the baffle piston engines went to the wayside and the FP's were introduced. The Shoestring is a very capable plane. It's timid enough to be flown as a trainer, it stunts superior to a Ringmaster and it works very well for racing. The main flaw with the Shoestring was in the design of the wing. The double ribs under the fuse while it seems like a terrific idea actually concentrated vibrations directly into the wing and nose of the plane. This acted like a tuning fork and while some of them worked terrifically without issue, many did not. The cowlings of the Goldberg designs worked well to stiffen the noses, but it transpired those vibes directly into the area I mentioned. Cracks would form quickly in and around the cowling area where it met the sheeting and also where the fuse and the leading edges formed regardless of glue types or reinforcement.

Any idea what "FP" stands for? Or for that matter, "LA?"

I hope to go fly and trim the P-40 some more about 4-5:00 this afternoon. I hope so, but the wind will have to abate. Still haven't seen the maiden video from Saturday that Will shot.

Boy, I had a really fun show tonight on the live Google Hangouts/"Stunt Hangar" 'Tube channel. We covered a lot of topics and had a good Show-and-Tell too. It ran from 9:40 to 12:40 or so. Mondays and Fridays(or sometimes Thursday).

Rusty

Will posted his video of the P-40 on his 'Tube channel. Not much but it sounds cool. Not too bad of a takeoff either.


Btw, for those of you who can come to Huntersville for the October contest, the aging circles will have the cracks filled and sealed with a fresh blacktop. That's October 20, 21, and 22.
Rusty

[quote="RknRusty"]Any idea what "FP" stands for? Or for that matter, "LA?"

Hi Rusty
I believe the FP stands for Front Induction Schnuerle Porting but I can't help on the LA

I must apologize, I've been flying more than reporting. Mostly each outing has been a couple of trim flights on the P-40 and a couple for big grins on the Twister. I have a little video of the pits and field from Sunday, and maybe a flight that I'll get back to. That handle adjustment I wrote about a couple of weeks ago has made me look like a whole 'nother pilot with the Twister, and each day I've got the P-40 dialed in as far as she gets without a mod. I did the mod tonight and will fly it tomorrow, hopefully with no more tweaking, just fun and practice now.

In our last episode, remember I'd put an unsatisfactory 2-56 snap-together ball link(R/C stuff, I do believe). That worried me even though it was copper wire wrapped and JB Welded together including a threaded solder coupler. But the ball link interfered with the linkage to the long rod resulting in more flap that elevator throw. There were half dozen ways to fix it, so tonight I got down to it.

Here's a pic of that impotent ball link. If the thru-bolt had been longer I could have just put the the long-rod's ball link on the opposite side of the horn and had them both connected to the same hole/same bolt... but not possible.


I did try to L bend the crank wire during assembly, but missed the bend by a 16th inch. That's a problem when it's attached inside the wing. That's why I got in this mess. So here's my fix. An L-bent wire wrapped with copper wire and soldered while the leadouts, flaps, and elevator were all clamped to neutral. Now the long-rod and its ball link can go in the intended hole with no interference or binding. I now have equal or more elevator than flap, and neutral is neutral at all points in the system.
Dang, it looks a lot neater in real life than in this picture. But it's stronger and the rod is less flexible.



Sunday I tried my 25° trim-tab to lift the outboard wing along with 1/2 oz. of tip weight removed after the Huntersville maiden. The result was wings level in both directions. Engine runs were good, but for some reason it was still wimpy in the wind and overheads were impossible. The lap time was inexplicably slow, over 6 seconds. It made no sense... Until Wayne asked me what length my lines were. 60' I insisted. The measuring tape solved that problem. It was my old Cardinal lines and I'd forgotten they were 62' i2i. DUH!

Tomorrow I'll be armed with a set of 60' and 58' i2i lines and I fully expect to be busting out full patterns with authority. All I have to learn now is if my tank is big enough. If not, I have a clunk that'll bring it up from 4-1/2 oz. to 6 oz. Thanks again to my friend Roger Altizer from West VA for giving me this cool plane. Hope we get to fly together at H'ville in a few weeks.

Unfortunately, I may not fly the Twister tomorrow. It keeps running out of gas earlier and earlier. Wayne noticed fuel spewing out of the venturi area and I've not had time to investigate it. I hope it's just a split fuel line and not the gasket. Or the needle or spraybar. It's a brand new short needle, so the threads should be okay. Maybe I'll fix it at the field.

And I'll report with some video if I get to the camera.
Rusty

Rusty, that notch in the flap is quite questionable. A lot of stress in that area and now that it's notched it could be twisting in flight. That could really use some 1/64" ply under it extending outboard a bit. Even if it seems fine now you have nothing under the horn offering enough footprint. While your rods might not be flexing, the load is now concentrated directly there. In regards to your line length, 62' and greater is not out of the question. That's pretty much spot on for that plane. In the course of flying, did you sweep the leadouts forward as this may help in the overheads. I would sweep them as far forward as possible until line tension down low starts becoming compromised.

Yeah, I'm a little concerned about that too. I think I'll go ahead and reinforce it since you've reinforced my concern.
I took it out to Congaree today and put four flights on it if you count Wayne's turn at it. I'm in the process of making that movie now, and a report will follow in the next couple of hours. We flew till dark and got the good outta the day... and now I'm outta gas. I have a couple of quarts of Sig on the way to hold me over until Huntersville
Rusty

Rusty, did you receive my message? I sent it the other day and I was curious to see if you received it. Our current fuel were using is nearing $30 a gallon. Ken

Ken Cook wrote:Rusty, did you receive my message? I sent it the other day and I was curious to see if you received it. Our current fuel were using is nearing $30 a gallon. Ken

Oh! "PHILLY FLIERS PICNIC TODAY"
I did, Ken, and I apologize. I meant to reply the evening after you sent it to me. I'm calling it a night right now, but I will post back tomorrow afternoon or evening. That can happen when I read a PM before sunrise and I'm in a minor rush to get to my tri-weekly treatment.
Rushty

Ken $30 a gallon? We have VP fuels stations (gasoline) in OKC and have a deal with a distributor to provide our little group with cases at a discount. Have you any VP fuel stations in Philly?