Airtronics Cumic

[byteme]

Ok, I need help from anyone who has built, flown or even seen a Cumic. I just happened on a deal for one and I need some info. Where is the CG on this plane? What is the wing loading and a good overall total flying weight? What is with the spoilers on the bottom of the wing? Was this the original design, or is it a bad idea? I'm really looking forward to flying this, but can't until I get these things figured out.
Thanks,
Dennis

[rogerflies]

The CG on the Cumic's E205 airfoil is at the spar. As I recall, the typical Cumic weighed about 70-75 ounces. They were a little heavier than the Sagittas. I had a highly modified pod-and-boom Cumic Plus (120" wing) that was a terrific floater at 54 ounces.

I never tried (or even saw one) with the spoilers on the bottom of the wing.

They were good fliers, as were all the similar Airtronics gliders.

Roger

[thermalfish]

Hi, I have a set of Cumic Plans in Tube I can mail cheap, I have a Cumic Plus that I will start to build soon, I will check the weight, but stock RES is about 54 oz, and probably can be cut down a little with todays equipment. Easiest to email direct: grandrapidsmortgage@yahoo.com Is it quite possible it is not spoilers that open on bottom, but could it be flaps (they would be at trailing edge), Thanks, Dan

[byteme]

I am at work right now, but when I get home I will take a pic of the bottom of the wing. I haven't put a reciever and battery to it yet, but I would put money on them being spoilers. give me a few hours and I will have the pics up. If they are spoilers I am intrested in thoughts as to the pitch corrections I will need to be ready for when I do open them up. Am sure I will want to be several mistakes up before that happens though. :eek:
Thanks,
Dennis

[OVSS Boss]

If you put spoilers on the bottom, the ship does not qualify for RES class contests.

Marc

[byteme]

OK, so you have seen them mounted on the bottom of a wing before? Is there some sort of advantage to this? Does it disqualify the plane because of the advantage or what? I have never seen them placed there, that is why I am asking so many questions. :confused:

[sadema]

I have a Cumic Plus, is beautiful, and it flies very well, he is slow of ailerons but with a mixture with the rudder the problem was solved. The aerobrakes are the ailerons that raise both simultaneously, have a very good answer, allowing perfect landings.

[OVSS Boss]

Yes I have, they are more effective in slowing the ship with less pitch change than spoilers. There are two ships I have seen them on, an Oly II and Steroid Lady. Plus you can have very large ones versus spoilers that have kind of an optimum size and the bigger they get, the more dramatic their effect in pitch.

Marc

[byteme]

This whole spoiler thing got me thinking and I decided to take it to the people who know best. I wrote an Email to the AMA to get the answer right from the rule book. Here is my Question and Answer:

Q:I have a question. I was told recently that my Cumic would be disqualified from competition because my spoilers are located on the bottom side of the main wing. Is this true? Any help would be greatly appreciated.

A: Dennis that's a fine line, but I don't really see it as a big deal. However, I would ask each CD prior to attending a contest to be sure they will allow that modification at a particular contest.

Steve Kaluf
Technical Director
Academy of Model Aeronautics
United States of America
Ph: 765-287-1256 x 230
Fax: 765-286-3303

So, I hope that muddied the waters just alittle bit more. :rolleyes:

[OVSS Boss]

You need to ask the question for what class, RES; Rudder, Elevator, Spoiler class is the three channel class that requires the spoiler to be top surface mounted and 2" forward of the TE. If you go to the rule book sections for soaring at www.modelaircraft.org you will find it there. Now, if you flew it in a regular thermal duration event, then yes, anything you did to it would be legal. My thought is here, why deny yourself a class to fly in just by not doing the top mounted spoilers.

In either case, bottom or top mounted spoilers are not flaps, and will not do anywhere near the same job.

The reason I referenced this to you is I do CD and am the current Soaring Nats Event Director. I just figured you would want to get the most out of the airframe under the rules structure we have.

Marc

[eye_rc_soar]

...deleted

[OVSS Boss]

Byte,
The exact link for the rulebook of soaring is:

www.modelaircraft.org/comp/0506Rulebook/RCsoaring.pdf

The rules having to do with RES class are in the first page, left column, paragraph 3.1.?. That should lay out what was the background for my above comments.

Marc

The link is not going through correctly, the dates section should be "0506Rulebook" and it is not going through. The section is under the Competition section of the website.

Sorry it does not come through correctly.

[byteme]

You are right I should not limit myself when it comes to different class competitions, I just wanted to make sure moving them is necessary. I hate to do surgery on a perfectly good ship, but I guess I will scrub up and dig in. Thanks for all the info.

[OVSS Boss]

And that means you are going to the bottom or stock? Also, I just read you wanted CG, 37% of root cord on the 205. Brian Agnew did an article on the 205 many years ago and it was dead on for Sagittas and Cumic type planforms, I have flown three Sag's and all started there and never moved.

Marc

[byteme]

They are on the bottom now, I am going to move them to the top. Man I do not want to remove all that Monocoat!!!!!!

[OVSS Boss]

You is right there, that is a job, Done two Sags and a Grand Esprit. I work on the road, great hotel room project.


Good luck...Marc

[ChuckA]

They are on the bottom now, I am going to move them to the top. Man I do not want to remove all that Monocoat!!!!!!

Don't bother unless you plan to fly in the RES class at contests. If not flying RES contests, then fly it as is and enjoy a classic sailplane.

[rdwoebke]

One reason why the spoiler rule is as it is for the RES class is to make this a more simple class. By allowing bottom mounted spoilers,one can effectivly have "split flaps". This means that the bottom mounted spoiler could have the effect of increasing lift (and slowing the plane down) like flaps as well as decreasing lift (and increasing drag) at more than slight deployments.

I agree with Chuck though, if you are not a contest guy, just enjoy the plane as it is. If you have an inkling of contesting, you could always just unplug the spoilers and tape them shut and fly it rudder/elevator in an RES class.

Good luck either way.

Ryan

[LVsoaring]

Last year at Visalia, I was talking to Merrill Brady of MM Glider Tech and he was flying his Marauder in RES with top and bottom spoilers. He told me that it was the CD's discretion whether to allow bottom spoilers for RES class. There are some good pics of Merrill's set-up at his website, www.mmglidertech.com.

I just bought a Cumic Plus kit from another fellow here on RC Groups, and am seeking any and all hot tips. Any Cumic Plus builders and flyers, I could use your input!

Cheers!

Rick

[rdwoebke]

Last year at Visalia, I was talking to Merrill Brady of MM Glider Tech and he was flying his Marauder in RES with top and bottom spoilers. He told me that it was the CD's discretion whether to allow bottom spoilers for RES class.


With all due respect to Mister Brady and the CDs he has flown with, if the CD is an AMA CD and has sanctioned event 460, they should not be deviating from the rules unless they list it in section 4 when they sanction the contest. Otherwise it would not be fair to contestants that built and prepared models for the rules. Of course, not everyone is perfect and it is tough to know all of the rules, but that one is pretty well known.

Unsanctioned contests, they can do whatever they like.

Ryan

[OVSS Boss]

I agree with Ryan, Merrill has a nice ship, but at any AMA RES class contest that follows the book, it is not legal.

Marc

[LVsoaring]

Interesting input, I'm just now getting into contest flying, got a lot to learn and sometimes I don't know what to believe. Good hearing from you guys on the rules. By the way, Merrill did say that if it is an issue, he just disconnects the lower spoilers and tapes them closed.

[OVSS Boss]

That is a beautiful way to work, Merrill is a smart guy and it allows him to be very competitive with the ship in UNL contest in a stock set up. If you do not believe us, go to www.modelaircraft.org and go to competition pages and the sialplane rules, all this info is right there in the RES rules section.

Marc

[rdwoebke]

By the way, Merrill did say that if it is an issue, he just disconnects the lower spoilers and tapes them closed.

That is the right answer! Being flexable or the ability to be flexable is important in contest flying. Like for example, you could have an REF (rudder/elevator flap) Ava and fly it in "unlimited class" and then if the odd RES class pops up you could just tape down the flaps and fly it RE (and be at a disadvantage, but at least you are flying and not watching).

Ryan