combatpigg

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Over in the SPEED FREAK FORUM, there is a product review comparison between the DIAMOND DUST and the WHIPLASH. I instigated this thread to get some ideas from the 1/2A SPEED FREAKS here about how far down to scale the original, airfoil thickness, and anything else that might be of use or interest. The DIAMOND DUST has a mysterious looking ring in it's framework, and maybe someone can shed some light on what that is all about. I have a FORA 049 that needs a plane, so I thought this would be a quick, down and dirty plane for it.

BMatthews

I think you'll find that a simple all sheet wing of 1/8 will do just as well. For area I'd like to see something in the order of 180 to 200 sq inches. A simple box fuselage to fair in the engine and hold the "guts" would complete the picture.

With the seriously long chord of a delta wing root the airfoil acts pretty much like a flat plate unless you make it crazy thick.

Also while I like the idea of a simple delta the fact is that if you want to go fast and STAY fast in the turns a model similar to a Speed 400 electric pylon racer makes much more sense. Do a search, if you have not seen it already, for matchlessaero's Caliente for what truly works at our subsonic real world speeds. Conventional, high aspect (relatively) and THIN is where it's at baby! ! ! !

combatpigg

My Feedback: (3)

HI BRUCE! I can see why a conventional plane would do better in the turns, but don't you think a delta is inherently faster in a drag race? I was impressed to see what the innards of a DIAMOND DUST looked like. One thing is for sure, the AMA doesn't allow deltas to run in rulebook events, and I've never had it explained to me why? I don't know how accurate they are, but one of those onboard speed recorders would be a fun to have for this sort of thing.

BMatthews

I dunno, it would be interesting to do some drag measurements.

In any case after posting the first reply I did a bit of doodling with my CAD and didn't like any of the options I came up with. I'm now starting to think that an airfoiled delta with just enough thickness to house the gear is a better way to go. And then that brings us to the carbon delta that AJC made for the design contest last year.

So if I was doing something like this I think I'd use a very thin symetrical airfoil. Something like a NACA 0005 or whatever just lets you put the gear into the wing at the center section and no more. For simplicity in building it I think I'd split the ribs and make two flat bottom wings and glue the two together. No jig required that way. A single fin produces less drag but I know the fast prop guys really like the twin tail look. If that last little bit of speed is truly your goal then also consider a little streamline pod behind the engine cylinder It would be best if it was a full cowl like the control line speed models but even something to help fill the turbulent area would be better than nothing. Or best of all mount the engine horizontal and fair the cylinder into the wing leading edge.

Another option for a high speed model that would still turn without loosing much speed would be a flying wing with tip mounted fins that act like winglets. The engine could still be faired into the wing leading edge for an even cleaner look. I did this quicky sketch to show what I mean....

dioncuda

Hey,it is for the wire on the rx.This is my brothers plane.

combatpigg

My Feedback: (3)

Well you've talked me in to fairing the backside of the engine in. I think 24" sounds like a good round number for the span. I designed a fairly thick winged delta years ago that had the same span, and I don't think I could handle much less! This time I would like to make the airfoil thickness proportionate to the full size DD, which looks to be 1/2", or so. I suppose a 3/16" kite rod spar would be enough to keep the wing from folding? The guys who chime in from time to time with 1/2A pylon advice say they use HS 55s! They aren't hot doggin' around too much, and putting alot of pressure on them servos most likely...I would think you would need at least HS 81MGs. I saw a SPAD DELTA with an inverted "V" vertical fin that looked good, it could be made out of 3/32" sheet and be rock solid. Is there any truth to the claim that angling the ends of the tips of your ailerons/elevons in helps to prevent flutter? So far I have never experienced flutter on any 1/2As, and I have only used squared off tips. It looks like the FORA will only be able to pull a 4 pitch prop at a 4" diameter. I did the #s with the 5.5-2 APC at 36000, and came up with only about 80MPH ! At least it would SOUND like 160!

ajcoholic

My Feedback: (10)

a small ppane flying by at 80 mph will definitely look a lot faster.... that would be cool, whizzing by the general population of 40 and 60 size planes with the 1/2A delta...

I think though, that for speed you are going to have to listen to Bruce and go with a more modern pylon design. I think the delta's are too draggy for ultimate speed. Lots of talk in the last two years about it in the speed forum, thats for sure...

Delta's are a lot easier to build though and strong.

AJC

dennis

My Feedback: (90)

The loop is for the antenna

BMatthews

Matchlessaero may chime in here but the 4x4 option will certainly give you more top end.

As for the wing thickness you'll still need a fuselage or other pod to put the gear in if you go with that 3/16 thick wing and that means drag. You get more drag from intersection corners between surfaces than you do by making the wing thicker and putting everything inside that smooth package. Similarly you want to avoid that snarky looking inverted V fin arrangement of the SPAD design. Yeah it looks trick but it's a drag bucket with lots of turbulence in all three apexes of the V and wing to V joints. That's why I suggested you stick to a single fin. A single fin has two corner intersections, one on either side. These corner intersections create a bit of turbulent drag. Putting on two fins doubles that drag. Also the tighter the angle the more turbulence and thus drag.

Angling the fins inward won't affect their tendency to flutter or not in any way unless the tips are close enough together to set up a bit if a high pressure zone between them. Like a biplane with not enough wing separation. However any tendency to set up an affected zone like that would generate drag so we are back to page one again, a simple wing thick enough to hold the gear but no thicker with the engine laying over on it's side and faired into the wing and a single fin is the simplest and cleanest and therefore fastest planform you can make.

The Diamond Dust and Whiplash both give up a bit of true efficiency for the sake of simplicity and sexy looks. But the engines those guys are putting on them more than make up for all that. In the end I suspect that if you look at the speeds those guys are doing with their DD's and Whiplashes and then compare the speeds to very clean conventional ships like Forumula 1 or FAI pylon racing models you'll find that there is very little difference. The only real appeal to the simple delta planform is that it's easy to make. And even easier given the fact that both those designs come in simple to build kits or ARF.

combatpigg

My Feedback: (3)

Thanks for clearing up the loop mystery! The DIAMOND DUST has such a thin wing to begin with, a scaled down version would only be 1/4" thick, I guess TLAR engineering is called for here. AJC, I never knew that there was that much of a speed potential difference , I think I'll still go ahead with a thin winged delta, then take on a conventional speed plane later. I don't know how close to a flat plate you can make something like this before it starts behaving like a PBF, at 80 mph I want it to be a little bit numb to my dumb thumb when it's flying level. The full size DD has such a simple frame, I couldn't resist trying one for 1/2A. Here's a shot of my old delta, it weighs 12ozs RTF. I can see where I replaced the nose at one time, must be a sign of old age when you can't remember a crash from the past.

XJet

My goodness, how did you get that TD to suck fuel all that way? When I stuffed a TD051 into a 1/2A patternship I ended up using crank-pressure in order to get a consistent run.

combatpigg

My Feedback: (3)

HI XJET! That is a bladder setup, with pretty high fuel pressure. Here is a progress report of the 1/2A DD. It is mostly 3/8 by 3/8 sticks and it weighs 1.8ozs so far.

ChuckAuger

My Feedback: (12)

There was a guy in Nashville at Peeler flying a 1/2A Diamond Dust with a .020 on it. It had about an 8" span, and was maybe that long. It moved out pretty good. I fly some fast planes, but that guy did an awesome job of keeping up with this little fellow.

I'm not sure if Jeremy stayed for Sunday (at the Nashville ProBro) or he might have seen it fly, the guy only flew it Sunday..

combatpigg

My Feedback: (3)

GEEEZ, How come I'm never around when all the neat stuff is going on[&o]! I would have gotten a kick out of seeing a micro DD. Bruce, all your points are well taken, and my next effort will have all the design features that you just mentioned. For the sake of simplicity, I am going with a flat wing, and an upright engine. A side mount set up with a thicker[airfoiled] wing will be coming up next, when this one is done. With the tiny radio gear available, the next one would only need to be 5/8" at the thickest point to fit everything in! I need to find out how big the data recorders are before I go shooting my mouth off like that. Here's a little more progress....

matchlessaero

No doubt about it Bruce. Truth be told, we are really trying to ask an engine to do something it was not really designed to do (its a combat engine, so its designed to spin low pitches at ridiculous speeds), but they will pull the greater pitched prop, and by the math, it will pull the plane much faster......

Augur, I missed the little .020 powered DD, but I think I may have designed it..... I built one for TD .020 a couple of years ago and it was a real hoot. Mine was fairly fast when I finally learned to prop the .020 right.

CP, you asked about a drag race between the two- Last summer I got to do just that. I flew my Caliente against a MVVS .28 powered 3/4 size DD. Happily, the Caliente won. We then flew through the speed trap, and in the end, I had the DD by about 4mph.

I look forward to hearing how your little DD goes. BTW, I am guessing your DD is going to come out pretty nose heavy unless you sink that engine a bit further back in the wing....

Here is my own .049 powered version of the DD.... (really it has nothing in common other than its a delta planform). This one will outrun a .061 powered Shrike....
And... here is the SuperCaliente (clipped wing Caliente) that blows the doors off the delta...[8D]

combatpigg

My Feedback: (3)

HI MATCH! I really like those planes of yours The CALIENTE is very business like! The delta is unique with the clear covering, better not take your eyes off it. I hope you're wrong about my CG, I guess the optimum set up is NUETRAL, which for alot of flyers would seem tail heavy. The trick is to limit flap travel, and to have a dual rate control for high and low speed. I am amazed that a 1/2A beat a 3/4 DD by 4 mph! To some people looking in, 4 mph might not sound like much, but on a long straight away it is very noticeable. Even so, you were just lucky, and my DD,[with Lt. Commander BEAVIS on board] is gonna smoke ya someday! I'm in a hurry to get this one done because my SON just finished his tour of duty in IRAQ, and will be coming through shortly to inspect our model airplane collection. Hopefully it will be up to his standards, or I might get KP![] PS, How fast do those 2 planes of yours go?

combatpigg

My Feedback: (3)

Now don't tell me that this doesn't look like a DIAMOND DUST! Thanks to a certain moderator who chimes in here from time to time, and the infuence HIS suggestions had on the final product, it ended up looking a little like a CL TEAM RACE MODEL, and if it doesn't RC very well, maybe there is still hope for it with a bellcrank and a pair of lead outs. The plane ended up weighing 12.8 ozs RTF, [except the trim sceme that will go on the top side]. It will be interesting to see how well it handles with the ultra thin wing, hopefully better than a PBF!

Larry Driskill

Nice Pigg, How did the balance turn out?

combatpigg

My Feedback: (3)

Thanks, LARRY, It balances about 1/3 of the way from the LE to the TE, which is right about at the most forward edge of the yellow stripe. I figured that since this plane is going to become a family heirloom, that I should go ALL OUT with the trim, so this is what the GRAPHIC DESIGN DEPT. came up with...

matchlessaero

Looks great CP, I love the purple color. You will have to keep us posted on how the first flights go!

BMB

Here is my 1/2a diamond dust. It weights 11 oz. I built this little delta with scrap in the garage almost two years ago. It is very difficult to launch and get trimmed but then it is a pleasure to fly. It's very acrobatic and the Norvell 074 is a great engine. By the way, it is fast!

combatpigg

My Feedback: (3)

Hi BMB! That's a HOT looking DD! With an .074 on it TERRIFYING is probably a better term[X(]!I just got back from the field and have a great report to file, this DD flew from launch to landing like a dream. I flew it with a COX 5-3, and it was dialed in well enough handling wise to enter a "heat" the first flight. I tried full elevator and aileron in all possible combinations to get it to tumble or spin, and all it would do is wobble. The rolls are fast and drill bit like, and the vertical acceleration might be right up there with the helicopters. If anyone is interested in building one of these, let me know, because I'm going to draw it up. The only other thing I would like to try is a TD 049 with the backplate mount. The TD weighs over an oz less, and I want to make sure that this design will balance, and fly OK with a COX on the nose.

2fast4u

My Feedback: (5)

When we were running 1/2A Pylon with Quickee 200's and .049's, an older gent showed up with a delta running an .020. He smoked us all!!! That thing moved out!!! Low drag, great turns, great speed. A Baby Dust should rock.

combatpigg

My Feedback: (3)

HI 2FAST4U! I'd pay admission to see that[X(]! Todat I thought that I would be a nice guy and give a COX TD 049 a chance to BASK IN THE GLORY of going 80mph,[probably never been done], and on the first run with a 5-3 prop, it flew nicely, maybe 70mph or so. The next flight was with a 4.25-4 [from a 6-4] MAS prop, and I let it go a little rich to be safe. Half way through the run, [which had to be 80mph] the piston came apart. The lighter COX engine didn't make any difference to the planes' handling. This engine is the one that got tested on the dyno, and I'm surprised that it let go. I might have let the ball socket get loose, who knows, run em till they puke, right? This photo shows how big the plane looks in comparison to the engine. The wing has 320sq", and it weighs just under 13ozs.My thanks to BRUCE for his input for the design, he talked me into doing a couple of things, and talked me out of a couple things, this was a fun,[and easy] project!

ajcoholic

My Feedback: (10)

Well, sorry about the cox engine but hey, the plane looks great and you have another fun one for combat too

I have some spare 051 piston/rod sets, perhaps you want one to replace your busted one??? I guess I better go have a shot of slivovitza, I am getting to be too nice ....

AJC