Big bipe aero

[ebetancourt]

Some of you may remember my talking about the Basic in my Waco almost two years ago. A lot intervened from work to a new knee, but the interest is still there. The challenge is the altitude loss when building speed. I have a fixed pitch prop, and although in my Citabria that was never an issue, in this thing, either the prop is a lot more efficient, the engine redline is more of an issue or the whole thing is complicated by drag. So I have been considering alternatives. I can convert to a constant speed prop, but it would be an expensive proposition, sell my plane and buy a Waco with a constant speed prop, or just enjoy myself with what is possible.

Anyway as part of my search for knowledge I picked up a book on the Waco Taperwings. This was the first commercial airplane to do an outside loop and the airplane in which the Cuban 8 was first performed. It apparently was a real favorite of the barnstormers in late 20s early 30s. One of the many questions I had was, "how do you do an outside loop in an airplane without inverted systems?"

In a letter to the head of sales for Waco, dated September 29, 1929 one R.W. Mackie explains that on August 27th at the National Air Races he was on vacation and the outside loops (7) were done "solely for the pleasure involved." Some relevant quotes:

"the speed attained, sometimes in excess of 300 m.p.h."

"the motor would quit before even a vertical diving position had been attained"

From the description of the first successful outside loop in a Taperwing by Freddie Lund, the technique apparently was to build speed, level off, roll inverted and push!!! In that first one, BTW, Freddie climbed all the way to 2,600 feet then dove 1,800 feet to build up speed. Which sounds like he started at 800 feet to do a maneuver that had never been done before. I concede that I am a wimp.

Ernie

 

[whifferdill]

...or the whole thing is complicated by drag.

In a biplane? No way.

One of the many questions I had was, "how do you do an outside loop in an airplane without inverted systems?"

Deadstick.

If you're still trying to be competitive flying the Primary Sequence, remember that you've got between 3500' and 1500' AGL to do six basic figures. The Waco is a big airplane. It'll show up fine at the top of the box. Plenty of altitude to gain speed for each figure before reaching bottom of the box. A stock Stearman can score decent in Sportsman in the right hands. Your Waco would do fine. Ironically, the sequence that was specifically designed for low-perforrmance airplanes doesn't flow that well from an energy standpoint through the whole thing. Doing a turn before the roll isn't good energy management for a low HP, draggy airplane.

IMO, you should fly the Waco for what it is. Modifying it for more aerobatic performance seems kinda like wondering how you can mod a Hummer for better fuel economy when you can pick up a Honda Civic for a fraction of the price...and keep both cars.

Below is from an email I recently wrote to a buddy with a Citabria who wants to fly Primary. Applies just the same to the Waco. Maybe more info than you care to know, but I had already written it, so copied it all, FWIW:

Something to keep in mind as you're putting the Primary sequence together - The last figure is the roll, which is preceded by the turn. At a min. 60 degrees of bank required for this level turn, you're gonna scrub speed and exit without a lot of energy for a good looking roll. A good looking level roll is hard enough to do in the Citabria without having to start from a reduced airspeed. You are not allowed to dive for airspeed between figures. I think the roll will look better and be easier to perform from as high an airspeed as you are comfortable with. So this is what I would recommend doing - fly the whole sequence up to the roll, and then wing wag and take an interruption. You can then reset your position in the box, dive as needed for any airspeed you like before pulling level for the roll. You will take a 5 point penalty for this interruption, but it's worth it if you can make the roll look significantly better from a high airspeed rather than a low one.

If you take a look at Form A of the Primary Sequence (the scoresheet and the one that lists the catalogue #'s and K-values for all the figures in the sequence), you'll see that the total K-value for the Primary Sequence plus presentation score is 63. Each individual figure has a K value listed. Each figure is given a score from zero to 10 by the judges. Figure 1 is a 45 upline which has a K-value of 7. If you received a 10 from all judges on this figure, you would gain 70 points (7x10). Total possible points for the sequence is 630 (63x10).

Let's say you score an 8 from each judge on each figure, and get a presentation score of 8. This would give you a total of 504 points out of a possible 630. 504/630= an 80% flight score total. Remember the interruption is 5 points. If you interrupted, your point total would be reduced to 499, which divided by 630 = a 79.2% score. Not much difference.

Now let's say you didn't take an interruption and did the roll from low airspeed. Let's say you scored a 6 on the roll rather than an 8. It doesn't take much to lose 2 points on the judge score. Since the roll has a K-value of 10, you'd get 60 points rather than 80. That 20 point loss from the lower score would reduce your total flight score to 76.8%. You would have to be between half a point on the judges score to make the interruption choice a tossup...as in getting a 7.5 rather than an 8 (5 points on a 10K figure). Another nice thing about the interruption is that aside from being able to select your entry airspeed, you can place the roll perfectly in the box, right in front of the judges for best presentation. Interruptions are rarely taken in any category for airspeed issues - they're usually taken when you accidently exit a figure going the wrong direction, get too low to complete the sequence, or realize you are about the go out of the box. But in Primary, in a plane like the Citabria, I think it makes sense to take one only for the roll. The rest of the sequence flows pretty well from an energy standpoint.

 

[ebetancourt]

Thanks for the feedback. I really don't want to be competitive, just have fun and learn. And it is really not a mod of the Waco, they come with constant speed props, I just didn't buy one of those.

In a biplane? No way.



Deadstick.

If you're still trying to be competitive flying the Primary Sequence, remember that you've got between 3500' and 1500' AGL to do six basic figures. The Waco is a big airplane. It'll show up fine at the top of the box. Plenty of altitude to gain speed for each figure before reaching bottom of the box. A stock Stearman can score decent in Sportsman in the right hands. Your Waco would do fine. Ironically, the sequence that was specifically designed for low-perforrmance airplanes doesn't flow that well from an energy standpoint through the whole thing. Doing a turn before the roll isn't good energy management for a low HP, draggy airplane.

IMO, you should fly the Waco for what it is. Modifying it for more aerobatic performance seems kinda like wondering how you can mod a Hummer for better fuel economy when you can pick up a Honda Civic for a fraction of the price...and keep both cars.

Below is from an email I recently wrote to a buddy with a Citabria who wants to fly Primary. Applies just the same to the Waco. Maybe more info than you care to know, but I had already written it, so copied it all, FWIW:

Something to keep in mind as you're putting the Primary sequence together - The last figure is the roll, which is preceded by the turn. At a min. 60 degrees of bank required for this level turn, you're gonna scrub speed and exit without a lot of energy for a good looking roll. A good looking level roll is hard enough to do in the Citabria without having to start from a reduced airspeed. You are not allowed to dive for airspeed between figures. I think the roll will look better and be easier to perform from as high an airspeed as you are comfortable with. So this is what I would recommend doing - fly the whole sequence up to the roll, and then wing wag and take an interruption. You can then reset your position in the box, dive as needed for any airspeed you like before pulling level for the roll. You will take a 5 point penalty for this interruption, but it's worth it if you can make the roll look significantly better from a high airspeed rather than a low one.

If you take a look at Form A of the Primary Sequence (the scoresheet and the one that lists the catalogue #'s and K-values for all the figures in the sequence), you'll see that the total K-value for the Primary Sequence plus presentation score is 63. Each individual figure has a K value listed. Each figure is given a score from zero to 10 by the judges. Figure 1 is a 45 upline which has a K-value of 7. If you received a 10 from all judges on this figure, you would gain 70 points (7x10). Total possible points for the sequence is 630 (63x10).

Let's say you score an 8 from each judge on each figure, and get a presentation score of 8. This would give you a total of 504 points out of a possible 630. 504/630= an 80% flight score total. Remember the interruption is 5 points. If you interrupted, your point total would be reduced to 499, which divided by 630 = a 79.2% score. Not much difference.

Now let's say you didn't take an interruption and did the roll from low airspeed. Let's say you scored a 6 on the roll rather than an 8. It doesn't take much to lose 2 points on the judge score. Since the roll has a K-value of 10, you'd get 60 points rather than 80. That 20 point loss from the lower score would reduce your total flight score to 76.8%. You would have to be between half a point on the judges score to make the interruption choice a tossup...as in getting a 7.5 rather than an 8 (5 points on a 10K figure). Another nice thing about the interruption is that aside from being able to select your entry airspeed, you can place the roll perfectly in the box, right in front of the judges for best presentation. Interruptions are rarely taken in any category for airspeed issues - they're usually taken when you accidently exit a figure going the wrong direction, get too low to complete the sequence, or realize you are about the go out of the box. But in Primary, in a plane like the Citabria, I think it makes sense to take one only for the roll. The rest of the sequence flows pretty well from an energy standpoint.