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Author Topic: A6 rules?  (Read 4470 times)
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Wout Moerman
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« on: February 23, 2015, 08:04:14 AM »

Hi all,

Is it true that A6 now accepts film covering? I have the rules I've found quoted beneath, are these the most recent? I ask this because I want to introduce this class in the Netherlands as beginners class and want to have a proper start.
And is there a definition af "stabilizer" somewhere? I can see a canard in which I define the canard wing as wing and the rear wing as stabilizer, but I think this is not allowed.... But how is this excluded?

Quote
26. A-6. For event (222 )
26.1. General. Except for the specific rules which apply directly to A-6, the rules for Free Flight Indoor Rubber, Hand Launched Stick model shall apply.
26.2. The model shall be rubber powered and covered with paper or commercially available plastic; no microfilm allowed.
26.3. The total maximum projected wing area shall be 30 square inches. There is no restriction on the stabilizer area.
26.4. All wing, stabilizer and rudder wood including wing posts shall be 1/16” square wood minimum, except ribs shall be 1/32” X 1/16” minimum. Posts may be rounded in the area of the mounting tubes.
26.5. The motor stick shall be from solid wood of 6” maximum length measured from the front thrust bearing face to the front of the rear hook.
26.6. The propeller shall be 6” maximum diameter with flat blades from balsa no thinner than 1/32”.
26.7. The minimum weight of the model shall be 1.2 grams without rubber motor.
26.8. No special materials such as boron, carbon fiber or foam are to be used.
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adanjo
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« Reply #1 on: February 23, 2015, 08:52:20 AM »

Hi all,

Is it true that A6 now accepts film covering? I have the rules I've found quoted beneath, are these the most recent? I ask this because I want to introduce this class in the Netherlands as beginners class and want to have a proper start.
And is there a definition af "stabilizer" somewhere? I can see a canard in which I define the canard wing as wing and the rear wing as stabilizer, but I think this is not allowed.... But how is this excluded?

Visit AMA website.
http://www.modelaircraft.org/events/compreg.aspx

As a rule of thumb, larger wing is wing and smaller one is stabilizer.

Aki
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Wout Moerman
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« Reply #2 on: February 23, 2015, 09:02:02 AM »

Aki,

Thanks. I think I found the definition of wing here:
3. Area of Supporting Surface(s).
The projected area of a supporting or stabilizing surface is the area seen when looking directly down on the surface. Supporting surface area enclosed in a fuselage or stick shall not be considered as wing area. Projected area of horizontal stabilizing surface(s) in excess of 50 percent of the projected area of the supporting surface (wing area) shall be considered as wing area.
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Hepcat
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« Reply #3 on: February 23, 2015, 09:23:07 AM »

Wout,
I was just going to quote to you what you have shewn in reply #2.  Can I assume that you have noticed that the A6 rules (presumably) override this rule and allow unlimited stabilizer area.  So, as you say, in a Canard, where the foreplane is the stabilizer the foreplane can apparently be of any size and the rear (or tail) plane is limited to 30 square inches.

I suppose I had better give the rules another read!

John
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Olbill
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« Reply #4 on: February 23, 2015, 10:14:38 AM »

The specific rule for the stabilizer in the AMA A6 rules allows unlimited stabilizer area. This overrides the general rule about stab area in excess of 50% counting as wing area. The canard question is a little murky and would be up to the CD of an event. If I were CD I would count the larger surface as the wing.

And yes, plastic film is at long last legal for A6. For my recent builds I used 6# wood for my wing and tail spars.
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Wout Moerman
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« Reply #5 on: February 24, 2015, 03:15:11 AM »

I'm not really planning to build an A6 with a stabilizer bigger than the wing. But in my work I often have to interpret legislation and try to spot and repair loopholes. So therefore I noticed this vague area in the rules.
I will translate these rules into Dutch and probably will add something like "the biggest lifting area will be considered to be the wing"

The good thing about using film covering is that we can use plastic sandwich bags as covering, which is so much easier to buy than condenser paper or Esaki.
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Tapio Linkosalo
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« Reply #6 on: February 24, 2015, 05:36:29 AM »

Instead of sandwich bags, you might try the thin plastic sheet sold on hardware stores used to protect objects while painting. The funny thing is that the cheaper variety you pick the thinner is the material, so here actually (for our purposes) the cheaper is the better! The plastic is lighter than Esaki tissue, maybe 6 to 8 grams per sq meter.



 
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« Reply #7 on: February 24, 2015, 09:45:37 AM »

I'm not sure what's available in other areas but here in the states the lightest film (other than specialty film made for models) I found was veggie bags from Kroger stores. These were only slightly heavier than the very best condenser paper. I have them listed at 4mg per square inch which I believe converts to 6.2 g/sq meter.
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Tapio Linkosalo
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« Reply #8 on: February 26, 2015, 09:28:21 AM »


The protective plastic sheet that I bought from the "Bauhaus" hardware store (a major chain in Europe) has 10 square meters of plastic, weights 58 grams and costs one euro (!). I calculated that it makes 3.7 mg per square in?
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Wout Moerman
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« Reply #9 on: February 26, 2015, 04:03:12 PM »

I now have a sandwichbag that weighs 10 grams per square meter. That is 0.3 gram on the A6 I'm designing. Tapio, that means your sheet is only 5.8 grams per square meter! I'll look around in our building supply shops.
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« Reply #10 on: February 26, 2015, 07:03:29 PM »

The best CP I've ever had is 3.6mg/si. Either of the films mentioned should work well. They won't solve the problem of needing really light wood to make the minimum weight but they will solve the former problem of finding light condenser paper. The ultimate covering material for A6 is OS film. My new ones made the minimum weight even with 6# balsa for spars.
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Wout Moerman
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« Reply #11 on: March 01, 2015, 04:11:01 PM »

I am on my way building my A-6 design. i have the wing, stab, rudder and motorstick finished, together it weighs 0.48 gram. Still need the tailboom, prop and prophanger and covering. If the covering weighs 0.3 gram I still have 0.42 grams to spend on the prop&hanger and tailboom. No idea if I can make it that light. What are usual weights for an A-6 prop?
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« Reply #12 on: March 01, 2015, 07:12:45 PM »

Mine average about 200mg.
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« Reply #13 on: March 23, 2015, 09:58:17 PM »

Bill, that is an impressive weight for the prop.  This past weekend I built my first A6 and found the prop to be the biggest PIA of the whole build.  I am simply not used to making a prop out of thick sheet balsa.  When it was all said and done, my prop ended up around 240mg, including the two repairs to the prop spars required after a few test flight bumps.  While I much prefer formed props for F1L and LPP, I am looking forward to flying A6.  My first one came out to 1.250 g and I know where I can save for the next one.  My current tailboom is a bit on the heavy side.  Other than that, I am happy with how it turned out.  I cannot thank enough those who pushed for plastic in A6.  It makes building to weight so much more accessible to those with lesser materials.  Light wood is easy enough to find, but light C paper, not so much.  With the ability to use plastic covering, anyone who has built a few indoor models before ought to have light enough wood to make weight.

Anyone who has been thinking of getting into A6 but hasn't because of the C paper requirement, time to get building.  The 1/16 sq sticks make building about as easy as it gets.  For my model, I honestly didn't weigh any of the pieces until I got to the prop.  By that time, I realized my prop was too heavy, but I used the lightest 1/32 I had, so wouldn't really be able to get too much lighter.  I can live with an extra 50mg on this one.  Bottom line, if you are looking for another event to challenge yourself with, that isn't exhausting or too time consuming to build, give A6 a try.

Chris
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Wout Moerman
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« Reply #14 on: March 25, 2015, 04:33:15 PM »

Here is my A-6 design, which is based on the "Wortel". This is a famous Dutch design which is also translated into English under the name Flooper. Wortel is Dutch for root and can be either a carrot or a square root. I don't know which root the designers originally had in mind. Someday I'll ask them. It is based on the Dart but was sized up and made to perform more like a contest indoor model. Mine is scaled down to about 2/3 of the original size but the dimensions are somewhat altered to comply with the A-6 rules. Mine came out 0.1 gram underweight and was covered in sandwich bag plastic of 6.7 g/sq.m.

The first version didn't fly well. It cruised reasonably well but I wasn't able to get it to climb. I blamed this on the small amount of dihedral of the Original Wortel combined with the large flaring prop of the better A-6 designs. I increased the dihedral and made a new prop. This prop is not flaring, has a smaller blade area and a 35 degrees blade incidence. Now it climbs nicely in my too small living room. Coming Saturday I'll be flying in a big hall and will see what it does now.

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julio
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« Reply #15 on: March 27, 2015, 01:52:47 PM »

Wout

I googled “Wortel” looking for images of the original design. Found a lot of images of non-flying designs, all of them in a nice orange color.
I finally refined the search looking for the “Flopper” and found the model you based your A-6. It’s interesting to see you choose a different path from the usual designs in your particular A-6. It has the beauty of the simple. It’s also interesting the little change from the “standard(s)” A-6 props, as you mentioned, after the test flights of your first model version and how you improved the model behavior since then.
I hope you have good results this Saturday or the day you can test fly the model. Maybe you have a just for fun model or a competitive one. Please, post your results Smiley.

Julio
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« Reply #16 on: March 27, 2015, 09:06:51 PM »

What size (thickness) of rubber is usually used and size of prop hanger...I would like to try to build one of these.
I assume you can get supplies from indoor model supplies .

Thank you..
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« Reply #17 on: March 28, 2015, 02:44:55 PM »

Craig, I used an EZB/F1D Harlan bearing for my prop hanger.  Rubber sizes I have seen range from around .035" to .050".  I know Harlan's Indoor Model Specialties has the bearings, and you may check out www.donsrc.com for custom stripped rubber.  It is run by Don Slusarczyc, a Cleveland area free flighter and frequent poster to the forums.  He will get you what you need.

Hope that helps.
Chris
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Wout Moerman
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« Reply #18 on: March 29, 2015, 11:09:30 AM »

I have flown my Wortel yesterday and it flew very well. It has a nice stable climb, a good recovery after bumping into the rafters and a good glide down. That glide is an indication that the 1.36 g/m rubber is a bit too much and next time I will use a 1.2 g/m motor, 0.5 gram motor weight. Flight times were around 2 minutes.

The pictures show a flight shot and a picure of my A-6 model and an original wortel.
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« Reply #19 on: February 20, 2017, 10:34:37 PM »

Assume that an A-6 has truly vertical tip plates.

It is my opinion that under the A-6 rules, the area of these tip plates does not count toward the 30 square inch max wing area (projected).

Clearly the tip plates provide effective dihderal for stability purposes and are not used for generating "lift."

Am I correct?

Olbill - this should be one you can answer. 

Thanks in advance. 
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« Reply #20 on: February 21, 2017, 11:01:36 AM »

Only projected area counts in the 30 si maximum. Vertical tip plates wouldn't count. Tip plates tilted outwards would count but only for their effect on projected area.

The theory on use of tip plates is that they increase the effective wingspan by helping control tip vortices and other effects that I'm not qualified to comment on. So there should be an increase in L/D if everything is working as expected.
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« Reply #21 on: February 21, 2017, 01:16:52 PM »

Thanks Bill.  Here is a follow-up question.

Can the tip plates be made from 1/64 inch sheet balsa wood and the model still be legal under the current AMA rules for A-6?

Or must they be made of 1/16 inch square balsa wood sticks and covered in either tissue or commercial plastic film?

The A-6 rules do not seem to expressly cover this issue.

I have had very good success with tip plates on my LPP and WS models and on one of my A-6 models.  The latter provoked some consternation by my competitors at our most recent local A-6 contest. Ultimately it survived what in effect was a low level protest. I was allowed to win that contest based on my highest cumulative flight total.  That A6, which may have been a little over weight to begin with, has crept up in weight due to repairs. It is now time for me to build another A-6 as I just barely managed to win that contest. I was told by a mentor long ago something to the effect that "you wouldn't start the Boston Marathon with two bricks in your pockets." It may have been the late, grate Cezar Banks who gave me that sage advice. 

In my experience, I cannot say that tip plates provide any duration advantage over wing tip dihedral sections on indoor models, but they make the wing a lot easier to build. Similarly, in my experience I cannot say that tip plates result in any duration disadvantage. I do like the way they look.   

I will note, however, that I have only ever seen one F1D model with tip plates.  I have not had the fortitude and patience to take on the F1D event, but that is a whole other story.   
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« Reply #22 on: February 21, 2017, 01:23:47 PM »

Here is a picture of my A-6 mentioned in my previous post, namely, Reply #21.

This picture was taken a while ago, but I note I had a hard copy of the A-6 rules sitting next to my model at that time.
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« Reply #23 on: February 21, 2017, 01:56:21 PM »

Here is a link to a video of a trim flight of my A-6 referred to in my last post:

https://www.youtube.com/watch?v=g6sdcA-fYlM&feature=youtu.be

The small circle size is intentional as our contest venue (a different gym from the one in the video) has six foot high beams spaced about 10 feet apart. If you can fly between the beams, and around the lights, you can fly up to about 26 feet.

You can see two problems with my model in the video.  

First, my A-6 is flying too fast, which reflects its excessive weight.

Second, it has a tip stall.

Note that Kang Lee is on the other side of the gym. He was flying one of his F-1D models in the same gym with me that day.
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« Reply #24 on: February 21, 2017, 03:01:31 PM »

Thanks Bill.  Here is a follow-up question.

Can the tip plates be made from 1/64 inch sheet balsa wood and the model still be legal under the current AMA rules for A-6?

Or must they be made of 1/16 inch square balsa wood sticks and covered in either tissue or commercial plastic film?

The A-6 rules do not seem to expressly cover this issue.

I think the rules are pretty clear on this issue.

"All wing, stabilizer and rudder wood including wing posts shall be 1/16” square wood minimum"

Tip plates are part of the wing, so they need to be 1/16" square.
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