LesUyeda

Beautiful. Love your color scheme.

Les

Jaybird

Thanks Les, but I can't take credit for it as that's how it looks out of the box! I do like it though and I know it will be a hit when the other guys get to see it fly. Putting around at half throttle with the Saito 125 chugging away was great.

I'm thinking that the amount of up trim needed for level flight might mean I can remove some of the nose weight. Everything else is pretty much factory set and the incidences measured match those from plan built kits. i'll keep it the way it is for a few more flights and then start removing some of the lead weights I have mounted to a bracket off the engine mount.

We have lousy weather forcast for the weekend and into the weekend. There is an EAA full scale fly-in at t alocal airport planend for the weekend and the local club will be flying models there too. I've been invited to participate which would be fun but it all depends on the weather.

Jaybird

nine o nine

My Feedback: (1)

Balance is balance. Don't change it unless you really think it IS noseheavy ....sluggish elevator response in the landing flair for instance..... sometimes not enough elevator response for a good flair. The Waco really should have a sightly tail high look in level flight. Sounds like the manufacturer made the wing and tail incidences so as to achieve a level flight attitude. You can only change that by changing incidences. I'd say just go with it.
If you remove weight from the nose it won't change the attitude of the plane significantly but it may make it a little more agile. Waco's aren't supposed to be agile . Mitch

Jaybird

Thanks Mitch. I can't change the stabilizer incidence without a lot of cutting and refitting so I'll leave that alone too. It just seems a shame to fly with up elevator all time countering the stab incidence and adding to the drag. I'll try the dive test on the next flight and see if it holds a constant 45 dgree dive or tries to pull up (nose heavy) or tuck under (tail heavy) and then think about it some more. I love the sight of it in slow cruise...it reminds me of an large elegant lady.

Anyway, stocked up on glow fuel today ($$$ Yikes!) so I'm ready as soon the weather cooperates. I still have to finish my pilot adn i might look a few more details just for fun.

Jaybird

pimmnz

Just to add to what Mitch said, balance only affects pitch stability. Moving the balance point back to cure a TRIM 'problem' may result in the loss of the airplane. If you can't get enough elevator a low speeds, that may not mean a forward balance, simply not enough elevator angular movement. As for the 'drag' associated with a bit of up elevator trim, heck, it's a biplane, it won't notice that little bit. Yes, you could do the typical aerobatic trimming tests, but, again, it's a scaleish biplane, there are far too many other speed/drag related aerodynamic things going on for that stuff to ever clearly tell what is going on. If it flies nice, lands predictably, climbs on full power and descends at idle, it's probably perfectly in trim, and the balance is in just the right place.
Evan, WB #12.

Jaybird

That's reassuring to know, thanks. I tend to overthink how the different forces in flight interact with each other (or not) so I'll just leave it alone and enjoy. The first landing went very smoothly I might add and even on a hard tarred surface rather than the grass. I had plenty of elevator to get it to stall up high and it handled great on the ground. I'm sure my next take-off will be more of what I expected since the trim will already be there. I built an old Great Planes Super Skybolt biplane kit (1992 vintage) with very similar top, bottom and stab incidences and it flies level with about the same amount of constant up trim. I figured it was just how I built it and was surprised when this new ARF needed the same thing.

I know on a full size aircraft the stabilizer is actually producing a downward force behind the CG in flight to counteract the nose down tendancy when power is removed. The Beechcraft Sports that I fly have a full flying stab with an upside down airfoil. I've never been able to figure out if models are designed the same way especially when so many models have flat stabs (no airfoil) and have positive incidence (which would be an upward force with airflow?). I'd love to have a converstion with someone about this and see if I can get the concepts straight in my head.

The picture shows the trim position for level flight.

Anyway, looking forward to a lot of fun flights.

Jaybird

rcjunky67

CONGRATS JAYBIRD!!! Glad eveything went well. And I'm glad to know a little more about what to expect once I get mine built. Thanks

pimmnz

OK Jaybird, there is no 'nose down tendancy' when power is pulled off, nor does the tailplane have to be producing a downward force all the time, fact is it does not. Trim is not a 'force balance' as such, trim is an airplanes speed control. What happens is quite simple, the trim controls the AOA of the wing(s). Power controls the thrust, and therefore speed. At some point there will be a place where the speed and therefore thrust, is balanced by the drag, so the airplane no longer accelerates, and weight equals lift. This is good old 'Straight and Level'. The balance (not CG, please) is arranged so that the airplane remains at this trimmed condition so long as the thrust remains constant. For this nice thing to happen, much experiment and many years of flight has determined that the balance needs to be just a bit forward of the point where all the lift forces can be represented by one force. To do this there is, in 'S&L' flight, a small downward force generated by the tailplane. Consider now what happens if you change either the trim, or the thrust. If you change the trim, you change the 'S&L' speed of the airplane, up trim = slower 'trimmed speed', down trim = higher trimmed speed. This is because you changed the AOA of the wings in flight, and therefore the lift generated by the wings. To maintain 'S&L' you have to either increase or decrease the airspeed to maintain L=W. But what happens if you change the thrust and not the trim? This time the airplanes tries to maintain trimmed speed, speed does not change. If you increase thrust the airplane will try to increase speed, the wings will increase lift, and the plane will start to climb. The trim will not allow an increase in airspeed, so the extra thrust and lift is balanced by the airplane climbing, at a constant rate, at the same trimmed speed. Less power, less speed, and the trim tries to maintain the same speed, and does so by allowing the airplane to descend using gravity to help maintain trimmed speed, at the expense of height. All still nicely balanced, and with the balance forward of the lift, it is all automatic, no pilot action required, other than initiating the changes. If you consider just the tailplane, then you can see that the changes in speed change the forces on the tail, which changes the airplanes attitude, which restores the original speed and tail force. Changing the tailplane camber (elevator trim) changes the tail force, which changes trimmed speed, etc, etc.
Evan, WB #12.

nine o nine

My Feedback: (1)

Whew!!!! Exactly what I said. Nothing's changed since the twenties! Thanks Evan. You an instructor??? Mitch

nine o nine

My Feedback: (1)

What I said Evan!!! Great explanation of aerodynamics 101. Just shows that nothing's really changed to basic airplanes since the twenties. Mitch

nine o nine

My Feedback: (1)

Don't know why my post came out twice. Said the same thing though. Thyanks Evan. Mitch

LesUyeda

"The picture shows the trim position for level flight."

Is it really supposed to fly level. Sowhere I once read, that nose down allowed the pilot better visibility forward.

Les

Jaybird

"Tail high" may be the flight attitude, but for my model it took that much "up" trim to get hands off level flight under power and to keep it from diving towards the ground. I took off with the elevators set even with the fixed stabilizers and almost didn't get airborn. Once up in the air, if I relaxed back pressure on the stick it would start to descend, so I used the radio elevator trim until I could get level flight. Once that was set it flew very nicely. I've only had the one flight with it so there is a lot left to experiment with and experience. It did stay very responsive to control inputs during the stall test and was especially easy to handle on the landing approach.

I didn't mean to stir up the aerodynamic pot and I appreciate the information. I'll break out my Jeppsen Private Pilot manual and go through chapter 3 Aerodynamic principles again. Maybe it's unique to model biplanes that the horizontal stabilizer is "set" at 2-3 degrees positive relative to the bottom wing. More information is needed apparently.

Jaybird

Lins

Damn, with all this talk about flying I might have to start my 1/3 Genesis instead of waiting till fall... Guess it's time to get the jig started...

pimmnz

Sorry guys, I was trying to keep it simple...Full size the mnemonic at the top of the climb was 'PAT', Power, Attitude, Trim. Set cruise Power, push the stick forward and set Attitude (horizon on screen) and then Trim away the control forces. Every time you did that, when it all settled down the altitude didn't change, and the RPM and Airspeed was always same. Modellers can't feel the control forces, so we have to use other (visual) ways of setting the trim. Biplanes, with all those wings and wires and stuff are very sensitive to speed changes, and generally we don't use trimmable tailplanes, so you have to find a speed where visually it looks like a nice cruise, then trim with elevator to maintain height. Only rarely does this ever mean the the elevator and tailplane line up. And if you wish to change the cruise speed, then even if it did, it won't now. Jaybirds trim is tiny, given what is possible, and not really worth futzing with. Another thing to consider is that we rarely use trim correctly, full size set 'takeoff' trim, then fly at 'cruise trim' then set another trim for circuit and landing, and you just don't care what the elevator/stabiliser looks like on the ground, the elevator will be hanging down anyway. Only models, with their rigid control systems, show the last commanded elevator trim at rest, and how often do we re-trim for all phases of the flight? I know I'm generally too busy to worry about the elevator trim, once set for the general 'cruise' position. Anyway, enough.
Evan, WB #12.

Jaybird

Actually that last bit was very helpful to me Evan, thanks. I have experienced all of those changes and adjustments from inside the plane and it all makes sense. Trim away the stick forces for the speed and attitude you want and there you are. When it's time to climb or descend or add flaps you adjust the trim to suit. I just couldn't get it through my head why my model plane would would act differently. Which of course it doesn't, we as ground pilots just fly them differently and use the trim as you noted. And, inside the plane you never see what the relative position of the surface is, you just know when it's in the right place.

There, I'm happy and ready to fly again!

I have my pilot permanently installed now (he wasn't sure about that first test flight) and he's wearing a "Great Planes" logo on the back of his shirt. I added the headphone wires and microphone boom...so yes he holes in his head now.

Jaybird

miltac

Hello from a new PICA WACO owner.

I have searched all the prior post and these are the questions I still have.

1. What is the best way to remove the wing struts without breaking the balls off of the plastic tabs.

2. The plane came with a beam mounted Magnum 1.20 and I would like to mount a Zenoah G26. is the firewall strong enough to mount a gas motor directly to it?

thanks for your help
John

LesUyeda

" Maybe it's unique to model biplanes that the horizontal stabilizer is "set" at 2-3 degrees positive relative to the bottom wing. More information is needed apparently."

Its a stretch for my memory, but I seem to remember that it compensates for the positive attack on the bottom wing, putting the bottom wing at esentially zero in normal flight.

Les

rccrasher65

My Feedback: (35)

John, if your firewall is 1/4 inch thick, it will be sufficient for the engine.

Jaybird

Got in three more flights this evening after work with several take offs and landings. The Saito 125 has a lot of power and still is not fully broken in yet. The plane lifts off easily at half to 3/4 throttle and climbs out nicely. I have left the elevator trim from the first flight and it works great throughout the speed envelope. Rolls are very crisp at the reccomended high rates and more scale like at the low rates but still quick for a large biplane. Loops are big and fun and just cruising around the pattern is a joy. It carries a fair amount of speed if I don't throttle back soon enough on landing. This field in South Portland doesn't have the obstacles like at the KVMA field, but the grass surface has a lot of humps and bumps. I seemed to find a new one each take off and landing.

I'm really glad I sealed up the landing gear center cover and the front and back of the wing saddle area as the rich exhaust collects all along the bottom of the plane and gets up into the saddle from the trailing edge of the wing. The balsa would be pretty fuel soaked the way it came from the factory with bare wood.

A lot of fun. Unfortunately rain is forcast for the weekend, darn.

Jaybird

Blackwidow

ceije

mogman, Dave, good to see you on line, just a note, hope all is well and you and your bird are getting ready for Monster Planes, i'm looking forward to seeing you and the Waco, till later

Chris melhus, ceije 196

WacoNut

Tom,
I would fix the top wing incidence and fly the Waco and see how it performs before cutting the stab loose. That is alot of work.

You should be able to trim the plane out with the radio trim adjustment with it only being 2 deg off.
Later!!
Anthony

Wolflord

Hello Waco lovers....

I am going to be starting a 60" wingspan 1/6th Pica Waco.

I am wondering what other people have put in for a power plant. I was thinking of a Saito 91 4 stroke, or a 15cc gas engine. Would these be too big. The plans call for a 40-60 2 stroke engine. Also I was thinking of using a sullivan Tail wheel for 7-12lb model, has anyone used one? Where is the best place to locate it?


Thanks for your input.

Geoff

cannonball200

My Feedback: (36)

Jaybird,
I used a super fine line ink marker to make the lines for the door and cargo lid on my GP Waco along with the handles and hinges supplied in the decal sheet. The door pattern outlines are in one of the back pages in your manual. I just used the measurements and used a bendable plastic ruler to hold in place to do the lines. I first made a small ink dot at the end points and drew from dot to dot without stopping for a nice straight line. If you mess up, you can take it off with alcohol and start over. When finished don't mess with it until it dries. It will still come off if you rub on it, so I just try to keep from cleaning close to those lines.

Thanks,
Eddie