Wright Stuff B

[JasperKota]

If your plane does not meet a requirement (e.g. rubber motor is over 1.5 grams), will you be given some time (like three minutes) to attempt and fix it? I'm a bit paranoid that the scale I have isn't accurate and that my plane is actually under 7.5 grams despite the scale saying it's around 7.55. It would be an easy fix to just add some clay, but will I be allowed to do so at competition?

[bjt4888]

Jasper's,

I advise my teams to have three broken in motors ready that weigh between 1.49 and 1.495 grams and two more motors ready that weigh between 1.47 and 1.48 just in case the judge's scale is not correct.

Brian T

[JasperKota]

Jasper's,

I advise my teams to have three broken in motors ready that weigh between 1.49 and 1.495 grams and two more motors ready that weigh between 1.47 and 1.48 just in case the judge's scale is not correct.

Brian T

Thank you for the advice, just received some more rubber today so definitely not concerned about running out. Will cut and prepare extra motors for competition. Sorry - I'm new to the event and am unfamiliar with the term broken in motors - is this just rubber that's been through some trim flights but has not been hard winded?

[calgoddard]

JasperKota -

I have been to many WS competitions and the Event Supervisors have always allowed ballast to be added if the airplanes are underweight, but only using materials that the students have brought with them. The students have typically not been allowed to leave the competition area to retrieve materials.

Airplanes can weigh a different amount at check-in on the day of the competition than at home due to inaccuracies in the scales and/or changes in humidity. Before the competition, place a mark on the motor stick of your airplane to indicate the location of the CG after the plane has been optimally trimmed. This is where it balances longitudinally with a legal motor installed. Bring Scotch brand clear adhesive tape (red Tartan plaid design) 1/2 inch wide with you into the competition area. It weighs .01 grams per inch. If your airplane does not meet the minimum legal weight at check-in, wrap a sufficient amount of the Scotch tape tightly around the motor stick, straddling the CG, to bring the airplane up to the minimum legal weight.

I do not like adding clay to a WS model to ballast up the the minimum legal weight. The clay can fall off during an official flight, and under the WS rules, the flight is over when the clay hits the floor. See Rule 4.j.

The Event Supervisors should inspect an airplane after an official flight to confirm that any clay ballast has not fallen off. If it has, and I were the Event Supervisor, I would disallow the flight, i.e. not count the time as an official flight, and not give a re-flight. If no timer saw the clay fall off and stopped his/her stopwatch when the clay hit the floor, I would give a zero flight score for that flight. However, as Jeff Anderson says, nothing on this web site is official. A rules clarification request or FAC question would have to be ruled on by Nationals to clarify the official outcome under these circumstances.

[JasperKota]

calgoddard -
What do you suggest as a replacement for clay? I don't think my plane has been trimmed to its fullest potential, but I have a week and would rather not make last minute changes, so in the future I'd like to be able to shift the COG by moving the ballast. Clay does the trick, but admittedly it is not very sticky. Nevertheless, I'll be sure to bring scotch tape. I'd rather secure a spot at states than potentially ruin it because I was overlooking the present.

[jander14indoor]

You can use most anything that is heavy for ballast. If you are afraid of it falling off and want it to move for adjustment, figure out how much and then make a ring or rectangle shape to go around your motor stick that can be slid along its length and have a way to lock it down so it doesn't move unintentionally.

As to last minute changes, yes most ES allow them. BUT, it is not required and I've seen the local ES recruited from the Civil Air Patrol use a meter stick to flatten a wing and measure its length flat... Now that was a few years back and I still appreciate that they volunteered there time.

So, be careful about depending on it. As much as I harp on min weight, its better to be a couple of hundredths to a tenth over than under and tiered. As already suggested, have materials IN YOUR HANDS at check in to correct as needed. KNOW how to do it quickly and correctly. Frankly, PRACTICE it just like any other aspect of the competition.

Oh, and the ES scales are NEVER wrong, how could you suggest such a thing? Well, I guess it could be, but you won't win that fight, so BE PREPARED!

Jeff Anderson
Livonia, MI

[calgoddard]

JasperKota -

If your airplane is seriously under the legal minimum weight, an alternative way to ballast up to the minimum weight is to use Duck brand poster mounting putty.

See:

http://www.staples.com/Duck-Mounting-Pu ... fgod0iAOWA

It is sticky so there is less chance that it will fall off your motor stick.

Make the the required ballast weight of putty into a C-shaped configuration that surrounds the motor stick at the CG and clamps against the same. Be careful not to have any clay extend underneath the motor stick as the knots of your rubber motor may engage the same and waste energy.

If your airplane is one or more grams under the legal weight, consider gluing a hard balsa stick, e.g. 1/8 inch x 1/8 inch x 10 inches to the top of the motor stick. Even if your motor stick is not bending or twisting under high launch torque, this "cap" reinforcement will pretty much foreclose any possibility of that happening. It is much better to carry structure than excess ballast.

[JasperKota]

The plane without clay was around 7.3 grams, so I had added it to bring it up. Just got my hands on some sticky tack from Lowes, and will now replace the clay. Thanks everyone, for being very insightful, I'll be bringing a tool kit to competition for last minute repairs and in case of inaccurate scales. Is check in directly before the 8 minute flight period?

[hogger]

How do you make a rubber with a weight in the precision of .001 gram? Maybe I am missing something or some special technique, but we are talking about a sliver of rubber at that weight. When I do mine, I make the first one by trial and error and estimating where to tie the knot to get closest and just under 1.5 grams. Then all subsequent ones, I just cut it about an inch longer than the first one to have enough handles to tie the knot. Then I try to tie the knot so it yields precisely the same length as my first one. Sometime, I went a little over and sometime I went a little under 1.5 grams, and I can't tell this until I make the final trim of the excess rubber. I tend to be a little more conservative so I don't lose that piece of rubber being 1.51 grams, so many come out to about 1.46-1.48 grams. My scale does not even have +-.001 gram precision. I keep the 1.48-149 for the competition and the ones at 1.46-1.47 and the ones over 1.5 for practice.

[bernard]

How do you make a rubber with a weight in the precision of .001 gram? Maybe I am missing something or some special technique, but we are talking about a sliver of rubber at that weight. When I do mine, I make the first one by trial and error and estimating where to tie the knot to get closest and just under 1.5 grams. Then all subsequent ones, I just cut it about an inch longer than the first one to have enough handles to tie the knot. Then I try to tie the knot so it yields precisely the same length as my first one. Sometime, I went a little over and sometime I went a little under 1.5 grams, and I can't tell this until I make the final trim of the excess rubber. I tend to be a little more conservative so I don't lose that piece of rubber being 1.51 grams, so many come out to about 1.46-1.48 grams. My scale does not even have +-.001 gram precision. I keep the 1.48-149 for the competition and the ones at 1.46-1.47 and the ones over 1.5 for practice.

Bring both 1.46-1.47 g and 1.48-1.49 g motors to competition. You don't know what the Event Supervisor's scale may read, perhaps it will read a 1.48 g motor on your scale as 1.51 g on theirs.

For tying motors, I tie a knot, pull it tight, and snip off most of the excess. Then I weigh again and if needed, I roll the knot and keep snipping. Finally, I add a drop of glue between the two strands at the knot.