I like the south end of the fuselage.  You can just shove it in the ground to have the airplane stand up for engine work.

There.  Nothing makes a project magazine-ready like suspension parts that are hand milled from solid billet aluminum.

If anyone needs me, I'll be sitting right here by the phone, waiting for the editor of Street Rodder to call.

It was dark outside, Mark.

And all my planes have at least one hand-machined part hiding someplace.  It's a requirement.

And besides: I couldn't figure out how to make it from wood.

Mark, it's going to be a long Winter for us. This thing should have been finished 3 weeks ago, as of last Saturday. With a trike gear, it almost requires twin fins or a V-tail...watch for it.  Steve

Interesting fuselage shape. Will it get a rudder?

Looking good Tim.  Looks like you've done a good job recreating the Genesis profile shape.  Below is a view of the original.

Fuse done.  Time to hinge surfaces, then start painting.

I've been busy-busy with real work, haven't had much time for modeling.

I have gotten the surfaces hinged (not shown), and the flap & elevator horns made.

I'm going with ball links all around, with fixed geometry at the flap horn and a slot in the elevator horn -- either to make sure I have fine enough adjustment, or an opportunity for my airplane's trim to go all to hell at contests, I'm not sure which.

Hmmm... Expected at least some sort of response, even if not directly from Tim. Especially as there has been no Sekrit Trap laid for the unsuspecting.

Clearly it is time to invoke WWBWD (What Would Bob Whitely Do).

"Tim, you cretin, you low-life, you pathetic poser, you pitiful acocolyte of Ted's, why can't you simply build models to my standards, some of the highest standards on this planet?! Those control horns absolutely suck!! Were I in your shop at this very moment my boots would be stomping these horrible bits into oblivion! And yet you are so stinkin' proud of them not only were pictures taken, said pictures were introduced to the Internet! And don't even think about powering your next OT or Classic model with an electric git-up as that will result in my next missive to you using harsh language!"

(For those lacking in the appreciation of humor, please stand by while we adjust your set.)

Dan

Tim, I see no similarity between the "KISS!"  horns and these pictured, except for the 3/32" wire size! It has two levers on the flap horn (cleaner install on a profile), and one on the elevator. Steel is heavy; avoid it if possible. Longer levers (1.5") would be my choice, and I think I'd opt for close hole spacing at the elev. horn instead of the slot. 

The "KISS!" is somewhat handicapped by a 3" BC, but mostly by excess pork in the hindquarters.  Steve 

   

Tim, not to criticize, but... if you had looked a little more closely at said "KISS" you would have noticed bushings to support the horns, of course they are probably buried in the fuselage.  Without the bushings you put all of the load on the hinges.  Not too late, but you will need to use split bushings to get past the bends.  Just don't skip it.

Oops.  I knew that.  Really I did.

Just reviewed thread from beginning to end although my attention was focused on built-up structure(s).

For Tim and many others I used to have some faith in built-up horizontal stabilizers, elevators, and fuselages, mainly as I enjoy building with a nod to FF models.

No more! These parts simply are not, cannot be, stiff enough for our application. And built-up pieces aren't even enough lighter to be worth the trade-off. Brett gave it a good shot when discussing the stabilizer pictured upstream a bit and possibly his response needs review.

For the fuselage it's a similar deal, although in my case it was Derek who demonstrated the folly of my ways in years ago fabricating built-up fuselages with strips and bits of balsa for an outline and zig-zags of more balsa strips arranged in a manner which would indicate light-and-stiff.

But it doesn't. In between all those neato pieces the unsupported sheeting used to bring the fuselage together flexes whenever given the chance and does so to a remarkable degree.

If unsupported sheeting is the primary problem one merely needs to give it some support. Plain ol' white foam as used in cutting wing cores helps some. Same white foam in a higher density would no doubt work better. But they both are a little shifty in actual use, primarily due to narrow width of fuselage.

Best profile fuselage I have ever built used SpyderFoam as the core. This stuff has a grain to it like wood and so it can be cut to orient the grain from one fuselage side to the other. It's easy to work with, as light as most white foams.

There aren't many tricks to a foam-core fuselage although Derek suggested that gaps between balsa structure and foam be limited to thickness of the sheeting to be used. Turns out this is a factor in stiffness, making those huge gaps in a built-up-and-skinned fuselage all the more daunting.

Finally, I used balsa inserts positioned so that when wing and stab cutouts were made there was left a strip of balsa about 3/8" wide around both wing and stabilizer. This on a 500-inch version of the Wimpact series which also uses a conventional foam wing. And a foam-cored stab, sheeted with 1/32" 10- to 12-pound balsa.

Dan


 

   

How did we ever get a plane to fly with the old Veco horns, that is a profile type plane?   With the speed the profile stunters fly at, I think the standard horn with the arm moved over to clear the fuselage is adequate.   Just have to drill the horn arm holes in a different place.   And with the cloth hinges it didn't matter where the arm was.  This is just for all round stunt/sport flying.   Not the high zoot stunter some people have.

I have tried that after the flaps/elevators were hinged.   Could not get it to work.  I just put a peice of plywood or use Kevlar thread to hold the horns in place. 

Dan:

I really would like your views on just how much I'm giving up by not having the horns centered in the (insert noun here -- cross-bar?  tie rod?  thingy?).  I get the fact that you feel that there'll be a difference in stiffness from the bellcrank to each flap -- but, how much difference do you see in practice?  And if I do go to fix that, are you suggesting a monstrously wide tie bar that goes into the flaps (and elevator) off center?

The span of 3/32" wire joiner on W500 is about 2 1/4 inches as is span of joiner on elevator. Narrower parts would probably have been preferred but with them being fabricated by Derek in the Santa Barbara area, me in the NW, we both allowed for some leeway with these parts. If these pieces were viewed as "monstrous" they would not have been used.

Also of note is that flap and elevator horns bushed both left and right of upright. Right bushings centered in fuselage, left units hanging out in the breeze.

As to your central question: I do not know how much difference left and right is seen in practice. But that's the whole point: Not seeing any difference at all, no possibility of same in a rather critical part of control system.

Instead, let's look at what nearly all of us do know.

We know forces on CL Stunt control systems quite a lot higher than would seem to be the case (thanks again, Ted, for pointing this out so many years ago!) from merely looking at a fairly lightly-loaded, relatively small, certainly slow-flying model aircraft.

If this were not the case all of us would happily be fitting Du-Bro Kwik-links to our linkage when this is known to be the Kiss of Death for any CL Stunt model. Note that larger, heavier, faster RC ARFs get away with even cheesy D-B knock-offs with acceptable reliability.

We know that based upon what works in an RC Pattern model our use of 1/8-inch joiners for flap horns seems silly. I envision an accomplished Pattern flier (not you-know-who, maybe someone like Chip Hyde) being taken on a tour of an Impact, something I have actually done. Universal reaction to such hardware is one of disbelief.

We know that "tweaking" flap horns to get our wings level to the lines is a simple matter of using nothing more than finger pressure to net rather big changes, meaning mild pressure gets the job done. I think this is what one could call a clue...

We know that joiner material from coat hanger wire won't work. Not stiff enough.

We know that if we mock-up a flap horn installation that is fitted with two vertical pieces, one centered and one off to the left end, force applied to the centered vertical will certainly result in equal forces (or very nearly so remembering joiner has been heated during assembly) applied to each end of joiner. In our case that portion of the joiner which drives the flaps. Can't say the same thing when applying force to vertical on the left; there simply must be a difference from one end to the other of what is essentially a torsion bar.

Ah, but how much? We don't care to know, nor ought there to be much value in knowing, because...

We do know that with the vertical centered on flap and elevator joiners the best shot at equal flap/elevator movement has been incorporated into the linkage.

And so when out at the field, trying to bitch-slap the thing into trim, seeing a wee bit of roll in maneuvers, the last thing which potentially needs addressing--and is also one of the most difficult to fix--is differential drive to movable control surfaces.

So proceed as you see best, but with existing horns in need of proper bushings anyway the choice is fairly obvious from here.


Dan

Better yet, we can do some actual calculations.  All we need to know is differential line tension.  I shoulda showed you my test rig, but we were talking vegetables on your last visit.

Steve:  I'm finding that a tinfoil hat works pretty well, but I could just be making things worse: http://berkeley.intel-research.net/arahimi/helmet/.

Tim...Don't forget the zerk fittings!  Steve

This thread is making crazy. Murderous. Serial murderous. It's a TWISTER! Dammit.

It's an over-analyzed Twister, that's for sure.

Joe:

Hey, progress is being made.  And in spite of pressure from outside, I'm not going back to revise much unless I think it's really wrong.  I expect that I'll be flying it at the Regionals on May 25, 2013, or I'll have a report on the crash.

Here's the control rod from the flap horn to elevator, with rod ends that are Hand Machined from Solid Billet Aluminum.  Again, if this were 1985, and the plane a street rod, it would be insufferably cool.  (If it were 2000 and a street rod I'd have to paint it with black or gray primer, with red-oxide primer flames, to be cool.  And if I happened to be cursed with perfectly straight, solid sheet metal, I'd have to put in some dents and maybe some simulated rust-out.  I'm not sure what's cool today, but I'm sure it's not going to tempt me to build any street rods).

((Come to think of it, I wonder how many appearance points you'd get with a carefully "rat-rodded" CLPA ship -- the key, after all, to building a rat rod isn't to throw a car together for as little money as possible and go have fun with it.  The key is to make it look like you did that from ten feet away, while making it clear on close inspection by the "in" crowd that it was built in a pro shop after they received boatloads of money.))

This thread is making crazy. Murderous. Serial murderous. It's a TWISTER! Dammit.

Yes, and while I understand the sentiment, wouldn't discourage anyone from holding to this view, it is also this sort of thinking that makes "Pukey Profile" an apt description of so many profiles.

There are other ways to approach building a profile which flies quite well and none of these are difficult in any way although more time is of course involved.

With two Wimpacts and now the W500, Derek's Wimpact, he and I have proven this to our satisfaction and it might be time to remind some of you that none other than Brett Buck agrees. (Brett is the only person other than myself to fly my second Wimpact and it ought be self-evident why he was enlisted to do so.)

Dan

I'm not sure what's cool today...

Jive Combat Team Consulting Services makes a lot of money helping people with this issue.

With two Wimpacts and now the W500, Derek's Wimpact, he and I have proven this to our satisfaction and it might be time to remind some of you that none other than Brett Buck agrees. (Brett is the only person other than myself to fly my second Wimpact and it ought be self-evident why he was enlisted to do so.)

Is there an article on the Wimpact published somewhere?  Or posted on the web?  "How to build the ultimate profile" maybe?

...Seriously Uncool.

That's perfectly adequate for most engineering purposes.

And so when out at the field, trying to bitch-slap the thing into trim, seeing a wee bit of roll in maneuvers, the last thing which potentially needs addressing--and is also one of the most difficult to fix--is differential drive to movable control surfaces.   Dan

Why "the last thing"?
How about segmented inboard flap tips?  Segments can be made moveable or fixed.
Any videos of actual planes being bitch-slapped available?