I was measuring the length of passport and found that I need to raise the tail wheel a couple inches off the ground to get the shortest length. Otherwise, the total length is longer. This is because the trailing edge of the rudder has a curve and the stick-out point is at the top.

So the question. Is the length of a pattern plane the length when all wheels are on the ground, or the shortest possible length after the tail is raised?

The second one. hold the fuse vertical, put the nose on the ground and measure how high the tallest part of the rudder is.

funny, I would have expected the opposite to happen, for it to get longer when level. Does the rudder sweep back a lot??

Often wondered about this too.
Same goes for te prop position. The lowest tip of the front prop of Brenner CD comes in front of the spinner when placed in a vertical position (due to 2,5 degrees upthrust of the Gaudius)
So a horizontal prop gives a shorter model than a vertical prop position

I noticed the same thing on my Passport in 09 before the worlds, and just to be sure I made a rudder with the straigth trailing edge and same area so it will be shorter, model flew exactly the same and you can be relaxed in every model processing.

Surely it must be measured with the body/datum line set at zero... not at an angle.
Otherwise you could hold a much larger model at 45deg and fit it in the box.
Who specifies the angle? Must be zero.
My you, never under estimate the European Bureaucrat.

David,

You hit on something of a misnomer in the regulations....Wherever the regs state that the model shall fit inside a 2 meter X 2 meter box, biasing the model will allow it to easily fit even if it's more than 2 meters long or wide. Of course that lands you outside the spirit of the regulation.

I had not thought of it before but it makes sense. Any verbiage that references a 2m X 2m box should be stricken from the regs. I've never seen any verbiage that spells out orthogonal measurement

The way a model is processed is correct....a set of calipers with jaws 2 meters apart. The regs should only reflect that and be done with it

On model processing at Worlds or Nats, just wonder how the measurement is made.

If the caliper method is used, how does the official make sure that the long bar of the caliper is parallel to the datum line?

Elementary

Maybe somebody with Nats experiences can help.

No time to deal with noise.

In the recent edition of Model Aviation, an article on the Worlds written by Jim Quinn had a photo with Ron Lockhart manning a standardized 2-meter "bracket" for checking wingspan and length compliance. For the length, seems to me they would measure it with the model in flight attitude, i.e. the zero datum position.

Method used to measure aircraft length at the 2011 Worlds in Muncie, IN.

Hummm, certainly not zero there then.
Maybe they allow for a little jiggery-pockery... lifting the tail to squeeze in a couple of mm's? Then again.
Judging from that pic, our German friend seems to be way inside.
Optical illusion?

I'd wager a dollar that the planes in the second pic are the Aussie planes...

Is the length measured from the tip of the spinner to the rudder??

The whole length, from any most forward point to any most aft point needs to fit inside the caliper. Most fit easily and there is no need to get the fuse attitude parallel to the caliper. Same is true for wings (installed)...the widest points are measured. Usually fit without any trimming necessary but I've heard of some last minute trim jobs done to fit within the caliper

Legend has it that the "F3A" spinner profile (shorter than a "standard" spinner profile) came about as a result of the size rule: it allows more "airplane" to fit within the length constraint.

John Pavlick

...and a few grams of weight savings plus IMHO they look better on the current fuse shapes compared to a standard shape spinner.

Glen,

Thanks for the pictures posted. Very helpful.


Sounds like, lengthwise, it will be a pass if the model can fit within the 2m caliper, provided that the tip of the spinner (if any) and the TE of the rudder are within the box outlined by the bar, and two jaws of the caliper.


On the 82mm f3a carbon fiber spinner sold by Chris at f3a unlimited, can somebody measure the height? My Passport requires one with height less than 62mm in order to pass the 2m rule. Assume no surgery work at the TE of the rudder. I was not able to get the info this week from Chris. Thanks

Hi John,
Hi All,
the profile that our friends at Tru-Turn call "FAI" was intended to preserve the look of a 2-1/4" FOX "conical" spinner.
It seemed that nearly every fiberglass fuselage plug for those kits popular at the time (early 80's) was carved to match that same FOX spinner.
It was clearly lighter and better balanced than anything else on the market at the time.
So what was Bob Obenberger supposed to call it? Sorta-like-a-FOX? I think not.
The FAI Pattern guys asked for it, so that's what he called it.
At the time (back when engine displacement was the "real" limit) length was immaterial.

So endeth the history lesson.
take care,
Dean Pappas

Received the height info for Chris for the 82mm MarQuet spinner. It is 73.5mm. 8.5mm more than what is ideal. Too bad.

I think the FAI rules allow up to 1% deviation, to take away any inconsistencies in calibration. (Same with weight, 1% allowance.)
So if you like gambling....

Magne

Now this is gambling.
If one has to fit in a 2m box, couldn't you interpretate it like this?
Compare the size difference.

A 1% deviation in length would be more than adequate. The US AMA 2011-2012 competition rule cited below, though, does not say it.

"4.3: Weight and Size: No model may weigh more than 5000 grams gross, excluding fuel, ready for takeoff. Electric models are weighed with batteries. In Sportsman, Intermediate and Advanced an allowance of 115 grams is permitted. No model may have a wingspan or total length longer than two (2) meters (78.74 inches).
Wherever practical, all aircraft should be weighed prior to the start of the contest. If weight is being enforced then all planes competing in that class must be weighed before the same round (round 1 or otherwise) for a baseline. Only two attempts at making weight will be allowed on the day specified for weigh- in. If no calibration system is available for the scales, a tolerance of 50 grams will be allowed for possible inaccuracies in the measurement instrument."


I probably will cut the current spinner slightly to meet the 2m rule.

Hi.
For FAI that is not the rule.
There is no mention of a '2m box' - there never was.
The code in summary says ; Max,, Length =2000mm, max wingspan = 2000mm with +/_ 1% for instrument tolerance.
Effectively 2020mm on any given day with any given measuring device.

Brian