Info on the Bird of the Future????

[Terror Dactyl]

Does anyone know where I can get info on the Bird of the Future? I know that Laser Arts is doing a short kit but I would like to find out more about the bird

I understand that it is a high tech airfoiled BoT and that is all I know.

Any info will be greatly appreciated.

[ejett]

Terror Dactyl:

I can speak to this a little since I have the wing rib kit and the inclination to try to build it as well. :)

Tony Estep is the designer of the rib setup and he did the layout and CAD work for the wing ribs. They are a Mark Drela airfoil and the spar is made external to the wing structure and "inserted" into the wing at the appropriate point during the construction.

Tony's layout is for a flat center section with dihedral tips, but I plan to make my version with the standard BoT polyhedral arrangement.

You will want to review Tony's Dark Star construction pages and download the wing plan from Yahoo groups Balsasailplanes group files section.

If you can't find this stuff, I can email you the BotF pdf's. Drop me a private message with your email address and I'll send them right out to you.

Here are the web links to Tony's Dark Star Article:

http://www.mvsaclub.com/articles/dark_star.htm
http://www.mvsaclub.com/articles/dark_star2.htm

EJ

[SoCalGliderFlyr]

I get such a big kick out of a high tech air foil on a built up open bay wing. It doesn't happen fellas! This is why the better performing RC sailplanes have hollow molded wings. A deviation of ten thou can throw the whole lot of super calculations off enough to be totally useless. Think of this the next time you are hand sanding a punky balsa leading edge.

[lp3]

There are plenty of high tech sailplanes with built up open bay wings.

http://www.airplane-model.com/Graphite-Contest.htm

http://www.kennedycomposites.com/

http://www.airplane-model.com/organic.htm

Try telling the Manufacturer of those sailplanes that accuracy does not matter.

In fact the trend seams to be in that direction even in F3J.

Mark Drela has several designs that use built up open bay wings.

In fact as far as I know the only sailplanes he has designed with molded wings are DLGs.

The winner of the RES world championship was flying a design that use built up open bay wings.

Here is a web sight that discusses the viability of built up wings:

http://www.mh-aerotools.de/airfoils/ribs.htm

[SoCalGliderFlyr]

Perhaps the phrase "high tech" is not as accurate as it should be. That is any wing that has a stretched covering over open bays negates any benefit that a super computer derived airfoil of less than 12 inch cord can accomplish. Now having the front half of the wing made in a mould does improve things a lot. But having the back half (from the spar) as open bays and stretched covering throws a lot of that "high tech" right down the drain.

As to structure: There is only new stronger materials. There is nothing new about a build up wing. We are referring to home built wings and not the ones done in CNC'd molds.

So get a grip on reality because I don't agree with your premise and neither does the science side of the equation.

[Terror Dactyl]

I also need to clarify my High tech usage as well. I will start with the term "scratch built", which used to mean that you had drawn the plans as well as cut the pieces out yourself before you started the assembly. This is not the case anymore as it is also being used to cover those that bought the plans and bought the ribs laser or cnc cut, I have no problem with that.

The high tech I was intending to mean was an airfoil that built within reasonable sanding tolerances and able to be bought (the BotF as a lot of different sized ribs) would give me a good flying wing with good wood and hopefully a winch proof eerrr stronger wing for my lead foot.

My budget will not let me go the high tech composite and I am one of those that likes the look of the open bays in the air as well as the older shapes in the air. I would much rather have a Minimoa than a D-600 type but that is another story.

Well have to get started on my Houston Hawk and I will PM ya ejett

Thanks to all for the help and hope to be in the air with y'all

[lp3]

I disagree with the initial implication that classically constructed wood sailplanes can not benefit from the use of "high tech" airfoils.

Grip that.

Check out the CARA at:

http://www.hilaunch.com/

[markdrela]

Perhaps the phrase "high tech" is not as accurate as it should be. That is any wing that has a stretched covering over open bays negates any benefit that a super computer derived airfoil of less than 12 inch cord can accomplish.

This is simply wrong. I designed the AG3x airfoil series specifically for built-up construction. The parts of the airfoil spanned by the covering (everywhere but the D-tube), the surface consists of flat facets, with little performance penalty over an equivalent unconstrained airfoil. This has been verified in the last set of UIUC tests, not yet published.

The flat surface segments have no covering sag, and thus eliminate the attendant airfoil disruption. A builder who is skilled at sanding can easily get the D-tube contour to within a few mils using the LE templates that come with the BD laser set. The resulting overall accuracy and performance easily rivals that of a good bagged wing. The additional accuracy from molded construction doesn't buy much, except in the F3B speed task and maybe in strong-wind F3F.

[ejett]

I might just as well stick my neck out and comment on this thread again.

It is true that covering sag can adversely affect airfoil performance. One specific example I am aware of is the E205 (Sagitta). This airfoil performs much better if the whole top surface is sheeted. If you do that, your Sagitta will fly better.

Also, unless I missed something in the original post, Terror Dactyl was wanting info on the Bird of the Future project which was "dreamed up" and discusssed in detail in the Balsasailplanes group. The purpose of this updated design was to improve the strength of the wing and to use Dr. Drela's airfoils, which as he points out above, were developed specifically for built up construction.

Thus, the BotF concept was born. Is it better than the "high tech" stuff? No. Is it better than the original BoT? Maybe, Probably, We hope to find out. It is part of what we do as hobbyists.

If we wanted a "high tech" built up plane, we could build a Bubble Dancer. Thanks, Dr. Drela for releasing the fruits of that labor of love to the public domain; it is truly a remarkable ship. But, some of us like the BoT so well, that we wanted to update and freshen the design to give it more or new exposure because the design deserves it.

EJ

[BMatthews]

I feel like I procrastinated to the point that my concept got taken out from under me. This BotF sounds just like the Millenium Edition I was suggesting in THIS THREAD (http://www.rcgroups.com/forums/showthread.php?t=79545&highlight=bot+millenium)

Of course I'm sure I'm not the only one smart enough to know this would be a good thing so I won't charge too high a royalty.... :D

I'll be looking forward to reading the flight reports on this mod.

[ejett]

BMatthews:

I am pretty doggone sure that your thread provided the catalyst to get this project moving. But, as I recall, when it started to move it rolled pretty quickly to the point of getting the ribset designed and produced at Laser Arts.

I don't know if it had much to do with George Voss offering up the FG fuse or not, but what the heck, it came available and we WILL see at least one interpretation of a BotF (mine). :D

EJ

[SoCalGliderFlyr]

It is to be noted that the AG3X foils take the top sheeting to 45% and the bottom to 30%. The "open" construction of the top wing surface behind the sheeting is supported by additional length wise structure (used to call them drag spars). The bottom is flat to the trailing edge. This is not the "typical" sheet to the top of the spar construction and convex/concave rib outlines seen on most prior open structure designs.

Selig explored this with the 3021. He found (as have many modelers years before) that sheeting past the spar on the top improved the performance of most air foils. As did the ballpark placement of drag spars.

Another point on the AG3X series is that they are significantly thinner than prior comparable foils such as the 3021 and 205. This combined with modern building materials makes for a lighter and quicker and thus more agile aircraft.

As to laser cut ribs verses stacked and sanded. I don't question the accuracy of laser cutting. Stacked and sanded ribs can be just as consistent across a tapered wing depending on who did the sanding. The trick lies with using a template on the leading edge.

Hollow moulded wings are thin, light and strong as well as providing a true representation of the airfoil. The first three factors are just as critical as the fourth.

[gps3]

I too enjoy the look of an open bay wing. I too have thought of "updating" a classic design. In my case it's Otto's Challenger. I built one last winter. I think it's beautiful in the air. This winter I'm consdering buildng just an updated wing for it (RES only, no flaps this time). Can anyone familiar with the Challenger recommend an updated airfoil for it as is benig discussed on this thread. In regards to the discussion on this thread about the performance benefits, building my own sailplane is like creating a piece of art. And with all art, beauty is in the eye of the beholder.

[ejett]

I just wanted to interject here that if one wants to build a BoT (as opposed to a BotF), George Voss offers a laser cut ribset to the original airfoil and a FG fuse. If you buy the plans from RC Modeler mag, and use George's "short kit", you will probably come out spending about the same money as buying a Dynaflite kit and replacing the bad wood.

George's website is http://www.soaringspecialties.com

EJ

Thanks Bert!

[Bert]

That should be:

http://www.soaringspecialties.com


Bert