WACO YMF
11-18-2015, 03:13 AM
Thread Starter
Well, at least that means it's out there. I'm sure whoever runs Outerzone would be happy to add links to this thread, and to the AMA's offering of the newer edition of the plan, if informed of them. After all, they're already explaining where they got the material from, and, from their point of view, keeping something available that came from a now dead web site.
Ouch! I'm so sorry to learn that you're not well. Please accept my best wishes - and then pull yourself together and damn well stay alive until I've got my YMF-3 flying: I'm expecting to need good advice along the way, and do you really want to be responsible for what happens when someone else has to step in and offer it?
It's weird, you know: in my time line, reading the thread, you're just retiring today, and planning to move to Tennessee...
-tih
Ouch! I'm so sorry to learn that you're not well. Please accept my best wishes - and then pull yourself together and damn well stay alive until I've got my YMF-3 flying: I'm expecting to need good advice along the way, and do you really want to be responsible for what happens when someone else has to step in and offer it?
It's weird, you know: in my time line, reading the thread, you're just retiring today, and planning to move to Tennessee...
-tih
Bill, Waco Brother #1
11-18-2015, 01:10 PM
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Well, I'm caught up with this thread, now. Took quite a few hours, but was very much worth it. Lots of good information, and I've got a long list of bookmarks to reference while I'm building my YMF. (That won't be just yet, though: I've got two other projects on the bench, and need to finish them to make room for the WACO.)
The many discussions surrounding center of gravity and angles of attack were very interesting. As far as the latter goes, the drawings from Pica match the ones from Paul Matt, in that both sets agree on a datum line (the top stringer along the fuselage side), the thrust line (0⁰ to the datum), and the angle of the flat part of the bottom of the Clark Y wing profile for the wings (both at 0⁰ to the datum). Having a Clark Y profile with its flat underside parallell to the datum line means that its geometrical AOA (AOA of longest chord line) will be about 2.5⁰, while its aerodynamical (i.e. zero lift) chord will be found about 3.5⁰ from the datum line.
The stab, however, is drawn on the Matt plan as parallell to the datum line, and on the Pica plan at about 0.5⁰ positive to it. At the same time, the Pica plan claims that the stab AOA is +2⁰. This doesn't seem to make sense. Some thought is required.
It's been pointed out time and again how the WACO tends to fly a bit nose down at cruise speed. Well, the Clark Y airfoil has its optimal cruise AOA at about +1⁰. For the WACO, that would mean dipping the nose to about -1.5⁰. This would have the wings operating at their optimal +1⁰ geometrical AOA. At the same time, if the stab were trimmed to +2⁰ relative to the datum line, it would be flying at +0.5⁰ to the surrounding air flow. It is not unreasonable to guess that this would be a good trim angle for stable flight at cruise speeds with the Clark Y airfoil, which is known to produce a nose up pitching moment at speed, requiring a somewhat lifting tail. For slower flight, the stab on the full-size is trimmable to a negative AOA, of course.
At the same time, the CG indicated on the plan is obviously not good. There are several formulas for calculating suggested CG ranges for biplanes, and they all agree that the CG of the 1/5 scale WACO should lie between 5 and 5½ inches from the leading edge of the top wing, with a clear preference for the more forward balance point for early flights requiring docile behavior. Using the CG indicated on the 1/5 scale Pica plan will result in a ticklish model that is challenging to fly.
My tentative conclusion is that the AOA of the horizontal stabilizer on the Pica plan is wrong, and ought to be at +2⁰ to the datum line, as specified in the Pica text. The CG should be at, or very slightly behind, a point 5 inches behind the leading edge of the top wing.
Furthermore, I've decided that I want a properly adjustable stabilizer, and will be building it as previously suggested by, among others, Bill (Stickbuilder).
The many discussions surrounding center of gravity and angles of attack were very interesting. As far as the latter goes, the drawings from Pica match the ones from Paul Matt, in that both sets agree on a datum line (the top stringer along the fuselage side), the thrust line (0⁰ to the datum), and the angle of the flat part of the bottom of the Clark Y wing profile for the wings (both at 0⁰ to the datum). Having a Clark Y profile with its flat underside parallell to the datum line means that its geometrical AOA (AOA of longest chord line) will be about 2.5⁰, while its aerodynamical (i.e. zero lift) chord will be found about 3.5⁰ from the datum line.
The stab, however, is drawn on the Matt plan as parallell to the datum line, and on the Pica plan at about 0.5⁰ positive to it. At the same time, the Pica plan claims that the stab AOA is +2⁰. This doesn't seem to make sense. Some thought is required.
It's been pointed out time and again how the WACO tends to fly a bit nose down at cruise speed. Well, the Clark Y airfoil has its optimal cruise AOA at about +1⁰. For the WACO, that would mean dipping the nose to about -1.5⁰. This would have the wings operating at their optimal +1⁰ geometrical AOA. At the same time, if the stab were trimmed to +2⁰ relative to the datum line, it would be flying at +0.5⁰ to the surrounding air flow. It is not unreasonable to guess that this would be a good trim angle for stable flight at cruise speeds with the Clark Y airfoil, which is known to produce a nose up pitching moment at speed, requiring a somewhat lifting tail. For slower flight, the stab on the full-size is trimmable to a negative AOA, of course.
At the same time, the CG indicated on the plan is obviously not good. There are several formulas for calculating suggested CG ranges for biplanes, and they all agree that the CG of the 1/5 scale WACO should lie between 5 and 5½ inches from the leading edge of the top wing, with a clear preference for the more forward balance point for early flights requiring docile behavior. Using the CG indicated on the 1/5 scale Pica plan will result in a ticklish model that is challenging to fly.
My tentative conclusion is that the AOA of the horizontal stabilizer on the Pica plan is wrong, and ought to be at +2⁰ to the datum line, as specified in the Pica text. The CG should be at, or very slightly behind, a point 5 inches behind the leading edge of the top wing.
Furthermore, I've decided that I want a properly adjustable stabilizer, and will be building it as previously suggested by, among others, Bill (Stickbuilder).
Last edited by tih; 11-18-2015 at 02:07 PM.
11-18-2015, 03:15 PM
Thread Starter
I think that you will find 2.5 degrees positive on the stab is perfect. If you follow the text for finding the mean average chord and set your balance point at 28-30%, you'll end up with a great flying model. Several of us also set the top wing at -1 degree. That allows the top wing to stall later than the bottom.
Bill, Waco Brother #1
Bill, Waco Brother #1
11-19-2015, 07:36 AM
Thread Starter
Bill, Waco Brother #1
11-21-2015, 03:23 AM
Thread Starter
Now, someone has started a thread about looking for parts or templates for the Pica YMF. Is this thread invisible? I sent the guy here. No response from him though.
Bill, Waco Brother #1
Bill, Waco Brother #1
11-21-2015, 04:04 AM
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Incidentally, I just ordered the Pica 1/5 scale plans from the AMA. Greg Prater, their plans coordinator, was very helpful and quick to answer. Even including postage, the cost of a set of plans from the AMA is less than half what the local copy shop would charge me to duplicate my original plans from the kit.
11-21-2015, 04:08 AM
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Bill, Sorry I can't be of help with the gear. When you mentioned scale gear and plane my brain started to work and I remember you had mentioned that to Dan and I at 12 o'clock High.
11-21-2015, 11:33 AM
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Took a good look at my kit tonight. It's almost so I just have to leave the wood in the box, and cut new parts: everything is so perfect, and the die cutting is clean enough that I have to hold the sheets of balsa up to the light at the right angle to properly see the part outlines. The stacks of sheets that were paper wrapped from the factory still are, but I've been able to inspect individual sheets anyway, because the paper holding them has crumbled and come apart at the folds.
Really looking forward to building this model! I'm actually wondering whether to put off finishing the two projects currently being built to do this one first...
Really looking forward to building this model! I'm actually wondering whether to put off finishing the two projects currently being built to do this one first...
11-21-2015, 02:04 PM
Thread Starter
Stickbuilder, I just noticed you were in Leesburg. I was just down there a couple of weeks ago to bury my mother. Her and my grandparents are buried at Lone Oak Cemetery. Leesburg is where I lived when I first started flying R/C airplanes, though the field where I flew is long gone, turned into a subdivision. I was stunned at how much it's changed, The Villages seem to have grown into it's own town. It was nothing but a small retirement community when I lived in the area.
Bill, Waco Brother #1
Last edited by Stickbuilder; 11-21-2015 at 02:09 PM.
11-21-2015, 07:57 PM
Thread Starter
My family hadn't lived in Leesburg since the early 90's, mom had lived with my wife and I for the last 5 years, she wanted to be buried by my grandparents. I took my first flights at the field in Fruitland Park and was a member of the club in Belleview when it was on Baseline Rd., sub-division there now. Crashed my first bi-plane there, a Smith Mini Plane, 4 times before I gave up and swore off bi-planes. It wasn't until 3 years ago that I went back to bi-planes and the first one was a Smith Mini Plane, I just couldn't give up on the SMP. I've got 6 bi-planes now, my favorites being the WACO and a H9 Christen Eagle. Took the Waco to the field today. Don't fly the SMP much anymore but it's still around.
Many good memories from Leesburg.
Many good memories from Leesburg.
Bill, Waco Brother #1
11-22-2015, 09:18 AM
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11-23-2015, 07:00 PM
11-23-2015, 08:03 PM
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Subscribed I just recently picked up a kit built PICA 1/5 scale Waco that I will power with a saito 150. The guy that I bought it from was a master builder and the construction proves it. Can't wait to get this one in the air. Thanks for this thread, there is a wealth of information here.
11-26-2015, 05:12 PM
Read page 2 and realized I'm in the wrong place, my WACO is an ARF. Apparently it's not enough to just love a WACO, you have to build them from a kit or scratch as well. Sorry to muddy up your thread.
Last edited by KaP2011; 11-30-2015 at 02:30 PM.
11-30-2015, 09:20 PM
I went back and read page 2. There are many in this thread vary passionate about the Waco. I spent three years building mine and I recently purchased the great planes Waco and enjoy flying it so if you have a passion for this classic that’s all that’s needed to become a Brother. Ask and it will happen.
12-01-2015, 04:05 AM
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Well, if that's the case, then I will qualify. I have a Pica 1/5 scale Waco YMF 5 that I picked up from a guy in the western part of NC. Although in my 36 years of flying I have built many balsa kits, this one I picked up already built. Great job done by the builder as he was very experienced and had several builds under his belt. He had powered this one with a saito 150 and designed the cowl around that engine. I've mounted the same engine in it but after reading the posts from "stickbuilder" I am wondering if the OS 160 twin four stroke might be a better engine. Anyway, I will have some time to decide on this before the spring flying season. I am officially making my request to be a member of the WACO Brotherhood. Thanks for the forum.
12-01-2015, 04:35 PM
O/K, have a question: received a set of 46" scale floats yesterday and wanted to know if they are perhaps just a bit too big for the 1/5 WACO. A tad over the 75% rule and seem to spec for something a couple of pounds heavier, (not sure if those specs include the floats).
No manufacturer info other than fabbed from thin ply and look a lot like Seamaster profile with rounded tops.
I do have a line on a pair of 44" Seamasters.
No manufacturer info other than fabbed from thin ply and look a lot like Seamaster profile with rounded tops.
I do have a line on a pair of 44" Seamasters.
12-01-2015, 09:36 PM
George,
This is what I did for my slave rods. I got some 1/8” toggle bolts and broke them apart and used to mount to the ailerons the 4-40 ball links fit in the toggles and screwed in place. Using a short piece of 4-40 rod in the ball link I JB welded them into a carbon arrow I got at wall mart. I think they look scale like. Hope this helps.
This is what I did for my slave rods. I got some 1/8” toggle bolts and broke them apart and used to mount to the ailerons the 4-40 ball links fit in the toggles and screwed in place. Using a short piece of 4-40 rod in the ball link I JB welded them into a carbon arrow I got at wall mart. I think they look scale like. Hope this helps.
