Stickbuilder

Trust me on this. Just jack up the tail until the model is level. Place a framing square on the table and against the leading edge of the top wing. Make a mark on the at the point of the square. Move the square to the trailing edge of the bottom wing, and again make a mark on the table. Measure the distance between the two marks. This is the Mean aerodynamic chord measurement. Do some simple math to find 26 - 28% of that figure. That is your correct center of balance.

Bill, Waco Brother #1

reyn3545

That sounds simple enough, even for a sales guy. I guess it's 26-28%, measured back from the leading edge?

mrdhud

My Feedback: (48)

Bill, I forgot to tell you I sure missed two old scale guys this month.[&o] Hope it not permanent.

Stickbuilder

You got it.

Bill, Waco Brother #1

Stickbuilder

Dan,

I don't know why it is not in there. I heard from Gordon Banks (used to be the editor and publisher) and they have told him that they don't require any more articles or columns from him. Maybe we are next. Why not contact them and gripe about it not being there.

Bill, Waco Brother #1

WacoNut

My plans are the same, I was going off of memory and it isn't what it used to be[&o]. I have my wings set at "0" on the bottom and +1 on the top. I set the Stab to +2 and I also made the incidence adjustable on the top wing of my Pepino Waco. I haven't flown it yet but it will take flight this spring before my 33% gets a go.

Later!!
Anthony

mrdhud

My Feedback: (48)

Call out to all Brothers

If you’re a reader of RC Report you’ve seen that Dick & Bill’s column Two old scale guys was missing this month. I hope it was just a mistake and not a permanent thing. I emailed this letter to them and ask the rest of you to do the same in hopes the column won’t be canceled.


I missed two old scale guys this month. I hope youv'e not canceled this column it is the first one I go to and quite frankly the only reason I subscribe to RC Report. The combination of Dick & Bill makes for great reading and I will hate to see there column cut. Please respond with an explanation on the disappearance of these two old scale guys.

Thank you
Dan Hudson
WB 45

reyn3545

OK... I'm going to show how much I don't know again...

I assumed that the bottom wing was always set at zero. There's not another line on the Waco that can be used go measure the others against. There's a downward slope from the cockpit to the cowl, and again from the rear cockpit to the tail. If you were going to set the bottom wing to -1, what would you use as a zero line?

WacoNut

The Pepino Waco has an internal box structure and that should be "0", unfortunately you cannot gain access to that now. You can always check the relationship between the top and bottom wing. If the top wing checks +2 and the bottom checks "0" then shim the bottom wing and block the plane up so the top wing checks +2 and recheck the bottom wing and it should read whatever you shimmed it to. Mind you your struts may no longer fit correctly and may induce warp. My "N" struts are adjustable as well
Anthony

reyn3545

A guy can learn a lot here!

I don't know how the bottom wing relates to the box, but the top does have +1 degree incidence. I haven't checked the stab, maybe I'll do that this afternoon.

I have to fly to Orlando on Monday night for a sales meeting that's going to last until Thursday. If it's not raining or 20 degrees outside, I may sneak out during the day on Monday for a little flying time.

Cricklewood

I sent a comment to RC Report about the article from the Two Old Scale Guys not being in the last issue and the response I got from Julia was that their article missed the deadline. She did indicate that it would be in the next issue. We'll see.

Chris Kerrigan

WB #133

reyn3545

I got tired of watching pre-Super Bowl hype, so I went down to the basement, put the plane together on the pool table and got the angle meter out....

The lower wings and stabs are in line with each other, and the upper wing has +1 degree of incidence. Should be close enough.

Stickbuilder

Missed the deadline indeed. They keep changing the so-called deadline.

Bill, Waco Brother #1

Cricklewood

Bill,

Sorry, I didn't mean to sound like I was judging you just passing on the response I got from RC Report. And yes it is hard to meet the deadline if they keep on changing it. I look forward to, hopefully, seeing your joint article in the next RC Report.

Chris,

WB #133

mrdhud

My Feedback: (48)

Bill, I got the same response from Julia I got the feeling she didn’t appreciate my email to much. Guess I griped to much.

aminiet

Apologize for the delay in posting the picture. I was having my hair done.

SuperCub Man

Hey - They did a nice job with the hair!! But barbering aside, I am close to finishing the wings on my Waco ARE and am trying to decide my next step. The wings are sheeted over ribs so I thought I'd glass them with some 1/2OZ or 3/4OZ cloth. They are very strong with carbon fiber strips on the main spar so the glass is not to add any strength, just create a paint surface. I will be covering the open framework with Sig Koverall and applying a dope finish - or at this point nitrate dope to fill the cloth prior to painting with something! Dope or acrylic or latex or Krylon - still deciding. Others in the club suggest I should skip the FG and just cover the wing with the Koverall cloth and dope, since the strength is already in the wing, and save myself some mess!
Do my brothers have any thoughts on the pros and cons of this??
Thanx

lazyace

My Feedback: (126)

koverall and dope are all you need

WacoNut

Jim,
If you don't want to smell all that dope try Polycrylic to fill the weave, I am using that on my 33% and it's working out good. I am give you some tips if you want to go that route.
Later!!
Anthony

SuperCub Man

Thanks for the info Anthony. Here's another little puzzler I just ran into on the Waco ARE build. For years I've been using the Robarts incidence meter to check the wing incidences as I build my models. The wing incidences on the plans say that both wings are to be set at Zero degrees to the Thrust/L with the stab at 1 1/2 degrees. So I carefully blocked the inverted fuse up level and set the wing in the saddle and slapped on my incidence meter. Horror of horrors it was 2 1/2 degrees out!! This meant I would have to carve 1/4" out of the rear of the saddle or raise the LE 1/4" to acheive zero degrees. This area is all ply and hardwood and not something I want to contemplate and my wing fit to fuse would be ruined!!.

I was sure I built it accurately so I checked the plans again and I noticed that the line through the side view of the wing was parallel to both the thrust line and the "bottom" of the Clark Y wing, but did not pass through the wing trailing edge. On putting a level on the bottom of the wing, I was indeed at Zero!!

So which is right? Dario built and flew this aircraft many times with great success so I don't think the plans are wrong and I will go with the setup as built. But what about the difference in the readings? Dario was too good a designer to make an error in this regard so what's up??

I've tried to copy the plans to illustrate my problem and I'd appreciate your points of view?

Stickbuilder

Where is the wing saddle relative to the datum line?

Bill, Waco Brother #1

SuperCub Man

Don't quite understand your question Bill. I posted the plan section above and it shows the wing saddle, wing outline and datum (center) line. Am I missing something or do I not get what you're driving at?

Phlip

I think it's a common mistake to use the flat bottom of an airfoil as the datum line. Ithink Dario erred in this regard.

A plane that is set up with zero wing incidence and positive stab incidence won't fly very well as there's no decalage. If you use thrust as zero, then plus 2 1/2, plus 1 1/2 degrees makes sense; although I'd state it as 2 1/2 degrees down thrust, zero wing incidence, negative 1 degree stab incidence.

But I'm definitely not an expert!

Jim Henley

Jim,
I am a relative new comer to building a biplane, but I would think checking the incidence with the plane upside down would give you some odd readings, since the Clark Y is not semitrical, wouldn't that throw your incidence off?

WacoNut

Jim it looks like you have a flat bottom airfoil, if so then you should be getting a positive incidnce reading like you are getting. There is no way you should be that far off with the saddle cut per the plans. If you measure the incidence of a flat bottom airfoil you will get a positive incidence reading with the bottom of the airfoil at "0" to the datum line.
I would go with what you have.
Anthony