Hueydriver

I maidened a FunAero Bookaty this weekend with a Texaco on the nose. Although I know it was designed to run at lower RPMs, there was initially just barely enuff oommph on a 7/3.5 to get the model to altitude. I changed to a 6/4 with slightly better results. The Bookaty has a draggy, big chord, low aspect ratio wing for a powered glider, but it sits nicely in the air and even picked a thermal for a few minutes (it's a bit pitch sensitive due to the short moment arm).

Question is, what would be your best prop/power choices for the Texaco on a machine like this? Would it be better to go back to a Black Widow as the kit was designed for?

SGC

A black Widow will produce more power than a Texaco. The Texaco has a small venturie to better suit low RPM's on a large prop, typically they use an 8X4, the aim is to get long run times not max power, this suits the 1/2A Old timmer models, but not much use on heavier sportier models.
Stewart

MJD

My Feedback: (1)

(1) the Black Widow would be a better choice, but you might be content with the Texaco if you get it propped better for the model.

(2) my suggestion is a 6-3 MAS or 5.7-3 APC. The 6-3 MAS has the benefit of a centered and proper sized prop screw hole, and is a decent performer on .049's. The 5.7-3 is a good performer too, but make sure it is properly bushed and centered. I have never seen a case where a 6-4 performed better than a 6-3 on .049's, usually the opposite. 6-4 is too much load IMHO, although yes, the Texaco will turn it without much grumbling. But for Black Widows etc., IMHO you are too far below the hp peak with a 6-4 to get decent performance.

MJD

BMatthews

What did your model come out to for overall weight?

If it's built to the 18 oz weight as mentioned at www.funaero.com then there's no reason why it won't climb with a 7 x 3.5 or even the 8x4. But you need to be PATIENT My own 19 oz Texaco old timer basically "glides uphill" when the engine is running and I need to use small control inputs to guide it into very gentle turns. Horsing the model around generate a lot of drag and the minimal power of a large proped Texaco or BW engine just won't stand for that.

The stubby wing will play a small part but not as much as you suspect. Also if it's pitch sensitive then just reduce the elevator throw. Pitch sensitivity comes from only two things, rearward CG's or too much elevator. The nose moment arm isn't a factor other than how it affects the CG.

Hueydriver

It came in at 18 ozs, and actually amazed the small electric guys on how light it was. I see what you say about climb gradient...it took a long time on the 7/3.5 prop to get to altitude, and having the Jr tank, just enuff fuel to do it. I hear what you're saying about the pitch sensitivity, but short tail moments always make for a "twitchy" pitch attitude (for a given control throw), specifically if there is monmentary increasing or decreasing performance windshear due to turbulence (it does happen, even if for only a split second). You're right about the drag in a turn, it falls off quite rapidly with subsequent altitude loss.

My error was probably flying in a 7 knot wind. The groundspeed was very low in the climb and if I wanted to keep it in the manouvre box of the flight line, I had to use too much rudder with the inevitable altitude loss. Next time, I'll use R/O techniques and use elevator for trim only. Sure looks pretty when the engine quits, tho'

It's a great little kit, IMHO!

Tim Wiltse-RCU

Huey,

For starters just screw on a 6x3 of your choice and see how it flies. Not knowing how many head gaskets you are using take out all but one or two if you are using more. With a 7x3.5 prop you are looking at only turning what 8/10,000rpm ? Let the little Texaco wind up and it should do ok or like you said pull it off and slap on you Black Widow with a Cox black 6x3 and call it a day.

Later,
Tim

hfenn

Tom Connor, the BooKaty designer, and I belonged to the same club when he first designed the airplane. We used to hold a 1/2A duration contest and the BooKaty came to dominate the event. I believe one year 5 of 10 pilots had one. I flew mine with a Texaco but I don't remember what weight it came out. BMatthews is correct, don't expect a steep climbout. Even so. I could get some loops and rolls out of mine. Many flew theirs on Black Widows with good success also, but they had to blast up to altitude in the three minutes that engine would run and hope to find some lift quick. Putting around with the Texaco with the Cox 7X3.5 gray gave me 5 minutes (sometimes a little less, sometimes a little more) to look for lift. By the way, I found that with mine and many others I flew (as well as the speed 400 powered version I built; I was the first to do that with the BooKaty) the airplane tends to turn away from lift when you encounter it. So, whichever wing went up, put in some rudder to make it turn the opposite way and you should be headed into the thermal. I got lots of 15 minute maxes with mine during contests and even longer flights when just playing around.

Hueydriver

I've been using a 7/3.5 wooden prop, but will shift to a Cox or carbon for the next flight....maybe I'm just being too impatient and fly for lift and keep the rudder as neutral as possible. Higher aspect ratio wings tend to just wobble when they hit lift. A right turn into it works for me.....does Tom still actively market the kit (his website is still shows it there)? I'd like to build another.

BMatthews

TAIL moment... DOH! Sorry I thought I'd read NOSE moment in the first post. Yeah, a short tail will give a more sensitive pitch all else being equal.

hfenn

You can get it here. http://www.funaero.com/products.htm
Tom sold the company, but I know these folks and they're great to deal with. Tell them Hollis sent you. The best 7X3.5 I found is the Cox gray. I think the wood props load the engine too much. Since the Cox props are hard to find, I've found Master Airscrew 7X3 and 7X4 work well too.

SST

My Feedback: (2)

You will definately lose performance with a wood prop...Been there, etc...The Cox is best, but I've heard that Graupner makes a 7x3.5 that's nearly as good as the Cox. The Cox props are hard to find. I've been trying to corner the market on 'em for the last 3 years...