Bandit 557

I like to draw up planes and see if they fly or not. So I drew up a 60" DLG. However, I've never seen one with more then a 48" span. (Gambler) Is there a reason for this? I have not built and tested this one yet, and will be busy on house remodeling untill the end of summer. If any one would like to look it over, or try it, here is my drawing.

Bandit

soholingo

There are built up 60" dlgs...

Catia:
http://www.soaringusa.com/products/p...&substring=dlg

Garnett:
http://www.soaringusa.com/products/p...&substring=dlg

Photon II
http://www.rc-model-data.com/photon-...2422-2422.html

Jay

BMatthews

Your design looks EXCELLENT! I don't doubt that it'll fly and be fine.

Two suggestions. First, extend the upper surface sheeting back about one inch so it's well past the high point of the airfoil. You'll likely want to add a support spar of 1/16 x 1/8 hard balsa under the rear edge to support the sheeting's lip. If you look at Mark Drela's built up airfoils this is something needed to avoid any ridges between ribs where the covering meets the sheeting.

The second is to run the carbon tow the rest of the way to the leading and trailing edges and even sand shallow grooves in them so the tow's fit down in the wood and you can add a skim of light filler over top. Tieing the launch forces into the leading and trailing edges more fully would aid in avoiding any glue joint failure at the launching tip. With that in mind you may also want to just loose the lightening holes in the tips. In the launch side because you want to support the carbon tow more effectively as it extends to the LE and TE and on the other side for symetry and because you'll need to add some tip weight to laterally balance the wings. So there's not much to be gained by removing the balsa.

charliey

Great effort, Bandit !
What do you figure for wingloading - as presently designed?

Cheers

Charliey

Bandit 557

Soholingo,

Thanks for the links, I have never seen them before. Nice looking planes.

BMatthews,

I believe that I chaged the wings as you stated, I can see where those changes would make for a smoother airflow and a better load transfer while launching. See the attached drawing and let me know if I got you right.

Charliey,

Thanks, As stated it has not yet been built, but I would like to come in at a total weight of about 11.5 to 12 oz. My radio gear is not the lightest stuff out there, so maybe some more weight can be saved. As for figuring out the wing loading, what's the easist formula for doing that math? Like I said above, I like to draw, build and fly. But I'm changing the windows in my house and replacing the siding also, so not much building for awhile. The forcast for the next few days is rain, so I'd better get back to it.

Bandit with 4 # hammer in hand, old steel framed windows gotta love em

BMatthews

EGGZACTLY! At least what you show in this latest version is precisely how I'd do it. Truth to tell the extra carbon at the tip may well be overkill. But it's better to add a couple of extra grams than to find oneself standing with a wingtip and grip post still in their hand while the rest of the model is cartwheeling down the field....

As for the sheeting I'm pretty sure you'll find that it aids the slower speed portion of the flight.

Bandit 557

Extended sheeting, Smooter airfoil, Less drag = better Slow speed flying? Please explain. Most of my flying has been either glow or slope.

I like overkill, sometimes I get a second flight that way!

Bandit

BMatthews

Yep, it's better all around. At slow speed the extended sheeting will avoid the lip at the covering transition that usually occures between ribs at the critical high point. Because there's no sudden transition the air will stick better and avoid a series of separation bubbles at each spot between the ribs. At high speeds the air will also tend to stay laminar for longer instead of tripping into turbulent flow at those same lips. So it's better all ways.

Bandit 557

Thank you for the reply. I can see what you mean and it makes sences.

The first window took me 14 hours to remove and install the new one. After 4, I'm down to about 4.5 hours per window, only 15 more to go. At ths rate I may be able to start building this plane in late July. Sooner if I work a little on it after dark, or on rainy days.

Bandit

Foreverflying

Hi Bandit,
Looks great! Basically a scaled up Gambler! I had the exact same idea! I want a light weight 60" glider for high start launching. Do you plan on having ribs laser cut? I might be interested in building one too. Would you mind? What airfoil are you using?
God bless!
Mike

Bandit 557

Foreverflying,

Sorry it took so long to reply, lost my computer and had to pick up a new one. Lighting strike?

Be my quest at building one. Thats why I posted the drawing.

The Airfoil is an AG-03.

I was not planning on having the ribs lazor cut. But if I can get the info from my old computer, I would be willing to work with you on any info that would be of help. I for one, would just cut them out by hand. I make a few copies of the ribs that I need to make, a little contact cement. A good sharp razor knife, an old emery board that I steel from the wife. And I can make all ribs I need in just a few short hours of light work while I watch a game or race on TV.

I did not get the ribs modified to show the changes that BMatthews suggested for the extended sheeting. However that would be a simple change for anyone paying a little attention as they cut the ribs out. When or if, I get the info recovered from the old computer I will make the chaghes and post them on here.

It can stop raining any time now. We have had 12.5" of rain in the last two weeks.

Bandit

Bandit 557

Hi everyone,

I was able to save the files of my drawings. Thank god for smart kids.

Taking the advise to extend the sheeting of the top wing, I have made some small changes to the plan that I had posted before. The changes show the extended upper sheeting, additional bracing, and the changes to the wing tip. Also to the ribs them selves. So here is the new completed plan for your pleasure.

Bandit

Bandit 557

Still working on the house, but I did take some time, and tried to make some cut sheets. Hope you like them.

Bandit

BMatthews

You may want to look into one other change. The horizontal stab seems a hair small for the duty it's performing. Run the design through one of the online CG location calculators and see if the tail area and boom length is sufficient to support the CG at the location you've shown with roughly a 5 to 7% stability margin. I think you may find that you need to enlarge it by about 15 to 20% in area to achieve this. But that's just an eyeball guess without the location calculation to support this.

LInks to CG calculators is found in the sticky thread at the top of the Aerodynamics forum.

Bandit 557

As suggested, I changed the size of the stab. and beleive that it will help as stated. Let me know if any other changes sould be made.

Thanks for the help.

Bandit

CloudyIFR

Nice drawing.

I input as close as I could the dimensions from your plans into Sailplane Calc that gives you information on your tail sizes.

I just thought you might be interested.

Sailplane Calc is available for free download at www.TailwindGliders.com

Curtis
Montana

CloudyIFR

Oh, and if I were to make any changes I would increase the outer panels dihedral from the 4.25" as drawn to 5". This helps with Equivalent Dihedral Angle (EDA) which is a little low and I think I'd still increase the size of the vertical a little more. It's always easier to cut it down during flight testing, then again you could also just tape some stiff cardboard to it to increase it's size during flight testing also.

Just my .02 cents worth.

Curtis

BMatthews

Curtis' calculator seems to suggest that your previous tail area may be fine. Certainly the new one, which looks better to my eyes, is resulting in a rather high horizontal tail volume. I also see Mark Drela's suggests for sizing. Knowing Dr Drela's attention to details I'm going to assume that he suggests the lower volume values because they produce a good compromise between rearward balance points for better performance and lower drag by being smaller. So based on this you may want to download and run Curtis' Sailplane Calc while playing with the tail sizes to get the size down closer to the ranges suggested.

Having said this I've found that a bigger tail than required in connection with a rearward balance point doesn't have any bad habits when it comes to handling where a small tail can lead to some slight issues here and there.

Bandit 557

Thanks for the help! I changed the dihedral from the drawn 4.25", up to the 5" that was suggested. I down sized the horizontal stab a little and increased the size of the vertical stab. a little bit. When I desinged this it was all with the TLAR system. As I have never seen a DLG in person, and am a self taught rc pilot, that has never flown with anyone else. My personal knowledge of rc planes and flying is limited to personal experience and the help from all of you. Again thanks for the help

Bandit

Bandit 557

I have a lot of time on my hands now. Recovering from open hart surgery. So I've started to cut the ribs out for this dlg that I drew up about a year ago. My problem will be, that I will not be able to throw it once it is done. So I'd like to attach a tow hook to it. Where is the best piont compared to the CG to place the hook?

Thanks for any help

Bandit

CloudyIFR

Just slightly forward, perhaps start with about 3/8" of an inch forward.

Curtis
Montana

BMatthews

A small and light high start suitable for models of this sort up to around 11 to 12 oz can be made from a single loop of 1/4 inch wide rubber for rubber models that is about 15 to 20 feet long (so 30 to 40 feet of the strip rubber) attached to 100 to 150 feet of 10 lb test monofilament fishing line. A small and light 6x6 flag at the hook end is enough drag to lay the line back out nicely in all but the calmest of conditions. A small fishing swivel and locking loop at the end will do nicely for the towline eye to slip over the tow hook.

Walk this high start back about 25 to 30 paces. You'll be standing there holding the model back with only two fingers and considering that I'm a fool. But the first time you let go and hear it whistle to the top of the line it'll make a believer of you. I built the same "flea power start" and used it for my 9'ish oz Bridi HLG model and that thing whistles to the top. At 12 oz the climb may be lazy enough to perhaps stick to the shorter 100 foot line. But at down around 10 oz go with 150 feet. Don't be tempted to use heavier line as it'll just add drag and cut down the performance.

You can get the rubber needed from Sig, FAI Model supplies or Peck Polymer.

Best of luck with the healing and welcome to the "bonus" part of your life. Use it well and do something nice to someone every day and laugh at least once. You've beaten the big one so nothing else that can happen from here on out is important enough to stress about.

Bandit 557

Thank you for the replies.

I was very lucky to have caught the hart problem before the big one. I will not be able to go back to work until Aug. 1st. So lots of time to build stuff this summer.

I was thinking that about 3/8" would be about right, but it's always better to ask.

Also I was going to use an upstart from a Fling. Would your design be better?

Thanks again,

Bandit

BMatthews

I'm not familiar with the Upstart used by the Fling. But consider that the Fling is a smaller and very light glider. At 7 oz ready to fly you could pretty much chain together a bag of #64 rubber bands and launch it just fine with that. The Mini start I described worked well on my 10 oz 55 inch span model. How it would work with your model or what you would need instead will depend on how light your final model comes out.

cfircav8r

My Feedback: (1)

For the wing sheeting you might also try adding a 1/4" wide balsa cap onto the ribs from the leading edge sheeting back to the trailing edge sheeting. This will go a long way to reducing the sag between the ribs.