Building techniques

[carneyf1d]

I know im not jeff, but id like to answer this.
People often confuse density with stiffness Yes usually a spar with heavier density is stiffer. However, through the length of a spar, a stick of balsa can have weak spots and low Stiffness Coefficients. It is more important to find a spar that is stiff, not dense. You want to limit the amount of upward flex in the wing as much as possible. So look for balsa that has low deflection numbers. To test deflection hold the spar where around 6 inches hang off the edge of a table. Take a 1 gram test weight and hang it on the end of the spar, measure the amount the balsa bends downward at the tip. Use the spar with the least amount of bend.

[jander14indoor]

I know im not jeff, but id like to answer this. <SNIP>

Hey, I'm not god or anything, nor do I actually know everything, not even close, answer away!

How can you make a mortise and tenon joint?
<SNIP>

Carefully? Actually its a by-product of past experience and the motor stick I've been using the last few years. I tried using a big tissue tube on the stick and a plug in tail boom. I could make it work, but had to pay close attention to angle of the tail. I found it too much of a challenge for most beginning div B students so dropped it. When I made my rectangular hollow motor stick, it naturally had a socket at the back. I just trim the tail boom to a rectangle to fit tightly.

Jeff Anderson
Livonia, MI

[danyalukin]

And with the new rules (draft can be found here: http://www.pjmcelligottcom.com/wrightstuff.pdf) Going for the bonus is the way to go, right?
I mean, its 40% for a 6cm wing...

[jander14indoor]

Careful with draft rules, get a real copy as soon as possible because these can mislead you!

That said, to a brief look, looks pretty close to the final published in the rule book. Just don't base a protest on it.

As to bonus, only data can answer that question, but it may be close this year, it wasn't even close last year.

Just remember, there is NO bonus at regionals, so don't fly with a narrow wing if you want to win a regional, the wide wing will blow it away.
At states I doubt the 30% for a 7 cm wing is enough, but its at least close.
The 40% for a 6 cm wing has interesting possibilities.

Jeff Anderson
Livonia, MI

[danyalukin]

At states I doubt the 30% for a 7 cm wing is enough, but its at least close.
The 40% for a 6 cm wing has interesting possibilities.

Jeff Anderson
Livonia, MI

Were ordering rules soon. But, the ting is, if use the big wing for states and small for nats, its difficult to switch from one to the other... no time to practice...i hate that, nothing to do about it... What if compensate by a big (28cm by idk, 20cm) stab, far from the wing? that would help?

[andrewwski]

Doesn't seem worth it to me. 6 cm is narrow. Really narrow. The last two years of WS in C, they made it 7.5, and that seemed narrow.

First you're going to have to fly at regionals. Flying on a 6 cm chord wing with no bonus is going to be extremely difficult. You won't be able get anywhere near the times you could with a wider wing.

Then, if you go on to states, you'll be flying a 6 cm wing when the maximum is 7 cm for the 30% bonus - not going to be worth it. Flying with a bigger wing should give you more than a 30% increase in time. If you were flying 7 cm, it may go either way, but at 6 cm it's definitely not practical.

Now, if you go on to nationals, the 6 cm wing may work out to your advantage. 40% is a lot. But again, it's going to be a small wing, and you probably can get that much of an increase with a bigger wing.

Doesn't make sense to go with a 6 cm chord wing to me in that circumstance. It's going to cost you at regionals and states. And 6 cm is narrow. Really narrow. I hated 7.5 cm wings enough when I was used to at least 10. 6 just sounds crazy.

[jander14indoor]

OK, lets be careful here, we're doing engineering here, not a popularity poll.

We can speculate all day long based on theory which approach is best. That might be useful in throwing out really bad cases, but in the end it comes down to building BOTH and testing. Make your final decision based on DATA, not opinion. This whole event is about test an analysis, it cannot be won without putting in the time to gather the data.

And remember, every minute you spend learning how to make a wide wing fly well, contributes to your ability to make the narrow wing fly. And vice versa. You aren't wasting time flying one and not the other. Based on anecdotal (but fairly broad) experience, if it takes you 10 hours practice to get your first plane flying well, it will take far less, say 5 hr to get the second optimized. And so on. Now, it then takes hours getting the final ounce of performance out of any given design, but that's good enough to tell gross differences.

But have no doubt, your 6 cm wing will get blown away at regionals by a 10 cm wing, and even more by a 12 to 15 cm wing. Don't forget, the other guy can build a giant tail too.

Jeff Anderson
Livonia, MI

[danyalukin]

But have no doubt, your 6 cm wing will get blown away at regionals by a 10 cm wing, and even more by a 12 to 15 cm wing. Don't forget, the other guy can build a giant tail too.

Jeff Anderson
Livonia, MI

Well, i never planned to do the same for each competition, just said taht it will be very hard to switch and test 2 types of planes. Second, our regional is not running it... ;(
And so i will start building 2 types of planes, 6cms for nats and big elliptical 15cms for states.. hope that will get me somewhere.
And another question, what do you think of the proportions of tailboom to motorstick in the freedom flight model of last year? I have a feeling the tailboom is too long...

[swimmerdude5]

can someone please help me on how to adjust my wings with the verticle posts i attached?

[carneyf1d]

adjust the the wing as in angle of attack?