Flight Times

[Hamtown009]

Our plane flew a 1:46 in a gym that is about 24 feet tall. Hit the ceiling and continued... Are there any tricks to maximize times in a plane? Our weight is 7.6 grams. We used the Freedom Flight Models 2010 kit. Any suggestions?

[jander14indoor]

Good progress so far. 1:46 is pretty good, your plane flys. Key to longer times becomes planned experimentaion and is where your flight log is critical to sort out what works, what doesn't.

No tricks though. Need to adjust trim to minimize drag vs lift (typically this means flying on edge of stall, with minimum difference between wing and tail angle of attack and rearward cg that's still stable). Need to match rubber to prop to maximize motor duration. Winding to torque vs turns is an advantage.

Of course losing that extra .6 grams will help, but there is more time in your current plane.

Give us some details of your current trim, prop and rubber and we can give some directional things to work on.

Jeff Anderson
Livonia, MI

[Draylon Fogg]

YAY PLANES ARE WORKING NOW!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Hamtown009]

Here are some specific details--- PROP: widest width - 3.5 cm length - 19.9 cm RUBBER: our best time was with a .095 rubber band at 80 winds after a dewind of two, trying to experiment with others too. What do you mean by asking us to measure the trim?

[jander14indoor]

That sounds like one of those fat, high pitch, Ikara props. The true experts (trust me, there are folks who outfly me consistently, but not by a lot) like them. But I've found fat, high pitch props to require real expertise to get the best out of them, and I don't use them without lowering the pitch significantly. When coaching students I find much faster progress with a lower pitch prop and longer thinner rubber. You might try that.

What's the multiplication of your winder? I don't know if 90 cranks is a lot or under wound for a 0.095 motor. Do you measure torque? How close is that to breaking your motor? As I've said in the past, I often see otherwise very good planes underperform because the students don't WIND their motors. The motor is your fuel tank as well as your engine. This is a duration event, if you don't put every bit of energy in that it can store and then get it all back out, someone who does will beat you everytime.

Trim. Where's your cg with respect to your wing (either leading or trailing edge)? What angle of attack are your wing and tail at? Prop offsets? Wing offsets? Wing twist? Tail offset? Etc. In flight, is your plane on the edge of a stall, or over stabil? Dutch roll? Flight attitude (nose or tail high, wings level, rolled into or out of turn). Also, etc.

Hope that helps,

Jeff Anderson
Livonia, MI

[germinator]

What jander said is completely true, but I think that if you are significantly over weight, you are using way too much of something. I personally don't find the densities of my pieces (though I know I should) and my most recent plane, including bass for the wing posts and a few other components, came out to 6.93 grams (but do NOT use bass until you can build light, then you probably still don't want to). I think that if you use "regular" sizes of balsa; about 1/8x1/4 for MS, 1/8x1/8 for boom, and 1/16x1/16 for your wing and stabs, and don't go crazy on the glue, your plane should come out under 7 grams. I'm not trying to disregard what jander said, I just feel that it is very easy to build to 7g and making a bill of materials might be better when you are a bit more experienced and can start worrying about consistency.

I am using wood from a kit that is pre cut and came out to 7.4 grams. Does the fact that is is pre cut matter in the weight?

[WrightStuffMonster]

I am using wood from a kit that is pre cut and came out to 7.4 grams. Does the fact that is is pre cut matter in the weight?

It depends on the kit. Sometimes kit wood is laser cut, which incurs a very slight weight penalty. (much less than .4 g)

[leetx]

I would like to share with others the flight times of our airplanes. I share them with the purpose of establishing an achievable benchmark based on the new 2010 rules and encouraging others to maximize their performance. These times have been made with the Freedom Flight kit and are achieved with dedication, hard work, and probably a bit of luck.

all times are no-touch

20': 3:15
25': 3:25
30': 3:40

[WrightStuffMonster]

20': 3:15
25': 3:25
30': 3:40

Nice work! Those are very respectable times for a kit plane.

[leetx]

Jeff,

I actually went through your table! I found a discrepancy in the weight of the stab fins:

wing fins 2 7 0.0625 0.0625 0.0547 6 0.086
stab fins 2 4.5 0.313 0.188 0.527 6 0.831

Your table was very helpful.

The following table is cut from my Excel spreadsheet where its MUCH easier to play with the numbers and adjust. Its for a particular design, so don't use it blindly as a guide.
Not, I don't weigh parts to thousandths, only hundredths. And I only measure to thousands of an inch. And I mix units TERRIBLY, sorry, I grew up with the english system and engineer in metric, deal with it.

Finny 09 by Bill Gowen
PLANNING DATA
Part Name qty length width thickness volume (in3) rec density (lb/ft3) wt (grams)
wing spars 2 15.5 0.0938 0.0625 0.182 8 0.382
wing ribs 7 4 0.0625 0.0625 0.109 8 0.230
stab spars 2 7.75 0.0312 0.0313 0.0151 5 0.020
stab ribs 5 2.25 0.0312 0.0313 0.0110 5 0.014
wing fins 2 7 0.0625 0.0625 0.0547 6 0.086
stab fins 2 4.5 0.313 0.188 0.527 6 0.831
motor stick 1 10 0.375 0.25 0.938 8 1.970
tail boom 1 12 0.188 0.125 0.281 5 0.369
wire prop hook 1 1.5 0.02 0.000471 489.6 0.061
rubber hook,wire 1 0.75 0.02 0.000236 489.6 0.030
wing posts 2 4 0.0625 0.0625 0.0313 10 0.082
prop 1.750
groc bag covering, wing 1 15.5 4 62 8 0.320 gm/m2
groc bag covering, horz stab 1 7.75 2.31 17.9 8 0.092 gm/m2
groc bag covering, wing fin 2 4 2 16 8 0.083 gm/m2
groc bag covering, stab fin 2 2.25 1.5 6.75 8 0.035 gm/m2
glue, tissue tubes, etc(est) 0.500
total wt estimate 6.856

ARGGHH, the columns look right in edit, but bunches in preview, oh well, I'll post now and try to sort it out later.
Double ARGGHH..., even after I post, when I pull back up to reedit the spacing is right, is there a tab command I'm missing????

Jeff Anderson
Livonia, MI