WacoDream

Hope everyone is enjoying good weather and out flying their beautiful Wacos this weekend.



I have my panels marked out on my Pica Waco in progress. I drew them freehand from reference photos and past build shares. Not perfect but hopefully close. Next step is trace paper to make the templates. I picked up some 3 ply .4mm birch which I will use to cut the panels. It wraps nicely around the curves and should hold up with a few coats of paint. I think the thickness should be close to scale. We'll see how they turn out. If they don't look right I'll just use the pieces as templates for a thicker version.

The tricky part is the going to be the round cone at the front of the fuselage. I think spun aluminum is the only way to go.

acerc

Michael, I used the 1/64 ply on my Waco as well. It needed a couple more coats of prime and sand than what I did, the grain still shows. Now I just finished a Pitts where I used flashing aluminum and it turned out very well. In the long run the aluminum was easier and far less work. Here's a pic of the aluminum panels prior to primer. And the cool thing is they are installed with screws so they are removable. Just a though!

WacoDream

Thanks Robert.  That's good feedback.  Perhaps I'll go with Aluminum as well.  Any suggestions on where to buy?  Are there any known issues with 2.4htz receivers and Aluminum? 

Your Pitts build is looking great!

acerc

I get it at Home Depot. This, http://www.homedepot.com/p/Amerimax-...3#.UdCUnYzD9jo . It can also be glued in place with some contact cement, but I like the removability of screws. And I have two 2.4 recievers smack in the middle of aluminum with no issues at all.

WacoDream

OK great.  Thanks Robert!  Heading out to Home Depot right now.  Appreciate the tip! 

Aurelio Beroes

Hola apreciados amigos desde Venezuela les estoy haciendo seguimiento ya que estoy trabajando en un proyecto Waco YMF basado en un modelo PICA, y este foro me ha sido de gran ayuda. Soy un fanatico de la escala en aeromodelismo. Les pido disculpa porque mi inglés no es muy bueno, y necesito de la ayuda de un traductor Google para hacerles llegar mis experiencias en este, y otros trabajos a escala. Yo aún sigo fiel a mi sistema de transmisión Futaba en 72 Mgz, y en un trabajo realizado sobre un PT 19 de Dinaflite, utilize cobertura de aluminio, la cual fije con cemento de contacto el cual ha funcionado muy bien. La recomendación que me hicieron es que utilizara modulación PCM para evitar posibles interferencias con el aluminio, y les digo que funciona a la perfección. Igualmente me indicó el compañero Jack Diaz, que podÃ*a utilizar sistemas 2.4, porque tambien da buenos resultados.
Un gran abrazo con muchos saludos, y les continuaré dando seguimiento. Y en alguna ocasión les estaré colocando fotos de mi trabajo actual.
Aurelio

Hello dear friends from Venezuela I am following up since I'm working on a project Waco YMF PICA based on a model, and this forum has been very helpful. I am a fan of the scale model airplanes. I ask apology because my English is not very good, and I need the help of a translator Google to to extend my experience in this, and other work to scale. I'm still faithful to my Futaba transmission system in 72 Mgz, and work done on a PT 19 of Dinaflite, use aluminum cover, which attach with contact cement which has worked very well. The recommendation I made ​​is that PCM modulation used to avoid potential interference with aluminum, and tell them to work perfectly. Also I said mate Jack Diaz, who could use 2.4 systems because also gives good results.
A big hug with many greetings, and I will continue to monitor. And on occasion I will be putting pictures of my current job.
Aurelio

hopkimf

My Feedback: (56)

No comments, so I located the tail per the 2 degree positive incidence. hope it's right. Hard to change once built.

Mike Hopkins
Waco Brotherhood# 132

Dash7ATP

I can under your confusion... As for a lifting tail, I'm not so sure about that myself.. On the PICA kit, the zero degrees incidence for the bottom wing is being measured on the bottom of the sing where it's flat. Typically, the incidence is measured at the chord line, which is from the leading edge to the trailing edge. Considering the radius of the Clark Y airfoil, I think that's pretty close to two degrees above the angle of the flat bottom. That would mean that the incidence with respect to the bottom wing would be pretty close to zero - zero. This will no doubt get a few comments from the brothers.....Joe

FMBB

Hi Mike,

2 degrees is absolutely correct every thing else would not deliver any comparable good flight flight performance as the 2 degrees.

Peter

Waco Brother #170

hopkimf

My Feedback: (56)

Peter,

Thanks for comment. Glad that's right.

Added two photos below. I put the center section upside down on a level table and put a Robart gage on wing. With the wing box( that attaches to fuse) level. I got a plus one degree on wing. Maybe I did something wrong in build, but the Robart meas from LE to trailing edge gives that value. Checked both sides. They're close.

Mike Hopkins

Waco Brotherhood # 132

FMBB

Hi Mike,
never measured the center section this way. Just level the fuse and test install the center section and measure the angle again installed inside the fuse assuming the fuse is leveled it should be 0°. Check your incidence instrument first that it is correctly leveled, adjustment brackets are correctly centered to the wings leading- and trailing edge, if not it will obviously lead to wrong values. Difference in upper and lower trailing edge blanking thickness will also add to wrong values as leading edge blanking does.
But test install and measure again that is the value that should be correct 0°. If not we may have to have a closer look to your build.


Peter

hopkimf

My Feedback: (56)

Peter,

You are correct. I redid it and agree. Zero-Zero. I had to clamp two Robart bars together to cover the wing chord, and in the process, I somehow didn't have one of the Robart pieces that contact the wing seated right.
Not sure if technically correct, but I call the Robart measurement the mean chord line angle. If so, the mean chord line is zero for bottom wing.

Thanks again,

Mike Hopkins

Waco Brotherhood # 132

tmac48

Peter and Mike, I would like to add some comment if I may. If you plug the outer wing panels to the center sections ( top and bottom wings ) and then do your incidence measurements ,do you get the same values on the outer panels compared to the centre sections? I believe this is what led to my values being out of kilter when setting up my model, has meant that I have had to accept what is not a perfect set of numbers. I would marry the wings to the center sections and then do the whole decalege thing from there if I started over again. What I believe is that if you measure from centre of leading edge to centre of trailing edge on the centre section, you will get a different value if you take the same measurements from the outer panels. Regarding the 2 deg positive on the stab, this is pretty common on most of the models that I have built, even precision aerobatic models.
Regards tmac.

hopkimf

My Feedback: (56)

tmac,

Good question. I am not an expert modeler and retired from mechanical engineering, so I do not have expertise in aircraft design/analysis. I will try plugging in both top and bottom outer wing sections and check.

I can imagine a situation where I want to set up the top wing for incidence and dihedral. Both are built in and should remain constant except for the effect of weight. Maybe the wing droops a bit at the outer end. I can get the droop out with the struts and maintain the incidence as well. That's assuming the opposite end of strut is fixed. Unfortunately it is not, but is tied to lower wing. So the reaction of the strut on the upper wing is equal and opposite on the lower wing. It's a matter of elastic deflection. So how do you keep the lower wing where it should be? Wires. Looks to me that the wires from fuse to outer lower wings are critical for keeping it where it must be. Likewise for upper wing wires. You can get pretty deep into this in no time and gain an appreciation for what the old boys had to consider when building the full scale versions.

I think most models are over designed to the point that static deflections don't really come into play and simply building and screwing together results in an adequate design.

I welcome comments and challenges to my unofficial thoughts. Comments from experts welcome of course!

Mike Hopkins

Waco Brotherhood # 132

tmac48

hopkimf, The dihedral of the wings is pretty much set by the joining tubes and the final adjustment can be made with the landing and flying wires. The point I was trying to make was concerning the difference of the angle of attack of the center sections compared to the outer panels measured from the leading edge to trailing edge. I went to the trouble of making a jig to set the top centre section at the desired 2 deg neg angle of attack only to discover that this was way wrong when the outer panels were attached.This comes about because the cord of the center section is shorter than the outer panels, thus giving a different reading. I would be interested to see what your readings are of the center section compared to the outer panels measuring from leading edge to trailing edge.
Regards tmac.

hopkimf

My Feedback: (56)

TMAC,

I need to make a sketch to understand. Attached is a quick one of constant chord. Will create a blend to go from center section chord to full wing chord and see what the picture tells us.

M Hopkins

tmac48

hopkimf, The cord at the second last station of the center section is a lot shorter and therefore at a different angle of attack than say half way out on outer wing panel. ( measuring from leading edge to trailing edge )

tmac. Trying to load some pics. Nop can't upload.

tmac48

Will have another go at pics. Ok seems to have worked. Photos show my next attempt at the fuel lines, now to duplicate this on the other side and run the servo wires through them. The decals on the cowl blisters are finished, not perfect but as good as I can get them.

tmac.

hopkimf

My Feedback: (56)

TMAC,

I went down and looked at upper center section. Agree. Looking at it from rear it's obvious the outer ribs on either side are at a greater incidence than those at the center. I put a straightedge on bottom of TE and it and it is fairly flat until the second station from the ends. So this begs the question on setting up the upper center section. If you pick a station in the middle for your reference, it's going to be off at the ends and so are both wings.

If you really need minus two, my inclination (pardon the pun) is to use the end ribs on center station. If you pick the center, you will have too much in the wings.

Making the 3 D drawing takes more effort than I want to go thru. I'm going to set mine up off the end rib unless someone has a better answer.

Back when I started this project i asked about an adjustment means. Got several comments, but nothing looked easy. Would be nice to have if it needs tweaking.



Mike Hopkins

Waco # 132

tmac48

hopkimf, glad it is not just me that can see what I was on about. I found that by using the center section my setup ended up with not enough neg incidence. Peter will chime in here i'am sure and he will know the correct way to do the setup on the top wing using only the center section.


Regards tmac.

hopkimf

My Feedback: (56)

Gorgeous Model!

tmac48

Thanks.

tmac48

Thanks.

nine o nine

My Feedback: (1)

For the chance that I'm sounding ignorant......The fixed root ribs, top and bottom, are at a fixed angle of incidence. The chord line would be parallel regardless of the total length of the ribs. By having a different AOI toward the tips, but at the last full chord wing station of the wings means you are warping the wings. If it's intentional I.E. washout it's ok I guess. The wing tips of the YMF are designed with built in washout however. My AMR measures the same AOI from the fuselage root ribs out to the last full rib before the tip taper. Mitch

tmac48

Nine o nine,I wish I could draw it for you. the top center section on the Barth Waco is very different to the top center section of the AMR rendition, I have noticed this from the various posts on this and other sites. the back 1/3 of the middle part of the center section on the Barth model drops down appreciatively to meet the trailing edge so a direct line drawn from leading edge to trailing edge is at a greater angle of attack than a line drawn from the leading edge to trailing edge of the outer panels , there is not any warping or wash out involved. IF I could borrow a couple of incidence metres I could better show just what is happening- I am sure I am not going crazy, but then again?

Regards tmac.