Spada 3M

[Doc J]

Hi Guys,
this new model, SPADA actually a Redshift MK II will begin to feature more in the near future and so I thought I'd start its own thread.

Here are some CAD pics of it. I hope that doesn't prompt anybody to copy what they see here. These drawings are not in proportion by the way, but give some idea. Its a bottom loading high-aspect ratio 3M model

Cheers,

Doc.

 

[Konrad]

That looks fantastic! I hope the wing hasn't changed too much. I really liked the Redshift's wing. Now I hope the tail boom is about 50mm longer than the Redshift and the nose is about 25mm shorter.* These are based on my experiance with directional control and stability issues I had with the Redshift. It would also bring the fuselage moments closer in line with current F3F practices.

It looks to have the real strong shoulder fillets another great feature from the Redshift.

* I know this will put some demands on the manufacture and layups to keep from needing too much nose weight.

 

[Doc J]

That looks fantastic! I hope wing hasn't changed too much. I really liked the Redshift's wing. Now I hope the tail boom is about 50mm longer than the Redshift and the nose is about 25mm shorter.* These are based on my experiance with directional control and stability issues I had with the Redshift. It would also bring the fuselage moments closer in line with current F3F practices.

It looks to have the real strong shoulder fillets another great feature from the Redshift.

* I know this will put some demands on the manufacture and layups to keep from needing too much nose weight.

Hi Konrad - the wing is exctly the same except some very minor refinements to the aerofoils to give just a teeny bit more attachment length, and the wing tips, which after a bit more results came out are now angled at 15 drgrees outward. That further concentrates and pressurizes the vortex caused by spanwise flow and unstable passage of air over the wing.

Fuse is longer but I'm pretty sure I didnt touch the nose. Never mind - I think you have a hacksaw.

I think the mods will cure most, if not all of the directional stability problems caused by my lack of study and attention on the MK1.

I'ts lurching along steadily, never as fast as we'd all like.

Cheers,

Doc.

 

[Doc J]

A few more views.

Doc.

 

[Doc J]

A few more views.

Doc.View attachment 12339View attachment 12340View attachment 12341View attachment 12342

Jonty look at your messages.

 

[2MUCH2DO]

I hope that there are wing and joiner ballast tube that use some readily available brass sizes, no fuse ballast, it survives your average ballasted landing in the rotor, and the price is right ;-) Oh and as a bonus it would be nice if it at least weren't harder than any others to install the modern wing controls, like IDS.

As for speed, thats always a plus, but it will likely be faster than me anyway.

 

[Konrad]

Hi Konrad - the wing is exactly the same except some very minor refinements to the aerofoils to give just a teeny bit more attachment length, and the wing tips, which after a bit more results came out are now angled at 15 degrees outward. That further concentrates and pressurizes the vortex caused by spanwise flow and unstable passage of air over the wing.

Fuse is longer but I'm pretty sure I didn't touch the nose. Never mind - I think you have a hacksaw.

I think the mods will cure most, if not all of the directional stability problems caused by my lack of study and attention on the MK1.

It's lurching along steadily, never as fast as we'd all like.

Cheers,

Doc.

Yikes, 15°! It is looking like air is lazier than I. It would rather run along the span than climb over the top of the wing to get out of the way.

There is more than one way to skin the cat. If the side area of the nose is kept low then the destabilizing nature of a long nose can be minimized. Conversely a longer tail will give the vertical rear area a longer moment arm to work with. Then there is the option of adding more vertical rear area. The last two have the cost of added parasitic drag. But such is the nature of stability.

I hope you touched the nose, with an FAI radius and bottom nose cavity.

As you know I loved the Redshift's wing (I hope it hasn't been optimized into irrelevance). The fuselage not so much.

BTW; I'm really liking the wing mounted ballasting systems. Can the ballast boxes be placed so that at full ballast the CG stays the same or moves aft ever so slightly. (I think I found that I liked the Redshift balance at 96mm). That is the one advantage of the fuselage ballast tube the fully ballasted GC can be shifted to optimize the CG at the new mass (CL).

 

[Konrad]

I hope that there are wing and joiner ballast tube that use some readily available brass sizes, no fuse ballast, it survives your average ballasted landing in the rotor, and the price is right ;-) Oh and as a bonus it would be nice if it at least weren't harder than any others to install the modern wing controls, like IDS.

As for speed, thats always a plus, but it will likely be faster than me anyway.

I second the IDS ready comment!

Having stress tested the Redshift structure I can say the rear rotor landings with the wing ballast resulted in much more damage to the wing internal structure than the crashes with the fuselage ballast. With the wing ballast there was a lot of wing joiner box damage along with the damage to the fuselage pass through window. With the fuselage ballast the wing joiners appeared to be fine and there was no added fuselage damage beyond what we had with the wing mounted ballast.

What I'm liking is the dampening in roll with the wing ballast. Yes, there is a cost in drag to initiate and stop the roll in the way of added control inputs. But at my level of flying I'm thinking the wing ballast system might come out on top, assuming the CG is held in check.

The Redshift mk1 had both ballast systems. But I think the benefits of a smaller fuselage cross section from the loss of a fuse ballast tube would out weigh any loss flexibility.

BTW: I think I own 3 of the 5 legally imported into the USA Redshifts. Yes, I think the Redshift has that much potential. Working with Doc I think the Spada will address the few fatal flaws we found. Ok, fatal flaws is exaggerating a bit. You can read all the gory details in my 3 Redshift build threads.

 

[2MUCH2DO]

Also,Doc, do you use Onshape? Or is this someone you are paying for cad, I'll admit, that I searched the public drawings for like 15 seconds to see if I could find the project, but someone making money should be paying. I use it for alot of little personal projects, but I have been thinking I hsould switch to fusion 360.

 

[Konrad]

What can you tell us about aileron length? Based on my experience with the Redshift, the stock Schwing Corsa 108, and the modified Schwing Corsa 108 wing tip, I'd like to see a tip length of around 65mm to 70mm

 

[Doc J]

I hope that there are wing and joiner ballast tube that use some readily available brass sizes, no fuse ballast, it survives your average ballasted landing in the rotor, and the price is right ;-) Oh and as a bonus it would be nice if it at least weren't harder than any others to install the modern wing controls, like IDS.

As for speed, thats always a plus, but it will likely be faster than me anyway.

Hi 2M,

Yes:
Joiner Ballast and wing ballast. Wing is 20mm x 10mm (.787" x 393") so 3/4" x 3/8" brass or other will fit. I have been told that its not too hard to find metric sizes in the USA now. I can't remember the joiner ballast size, but I'll check today.

Fuse ballast can be fitted but only by the user because it is not standard on the new model.

Price will make most people happy but as I don't control the final end-user prices of my partners, I can't tell you what it will be. Aloft are normally really good on that aspect, sometimes surprisingly so.

Modern wing controls should not be a problem - the wing thickenesses etc are the same as the orginal Redshift wing, BUT improved as the aileron servos are now further inboard. This is possble now with the advent of the stronger thin wing servos. This is also to lessen the MOI and hopefully improve the wing roll reaction speed.

If you have more questions tec or practical, fire away!

Cheers

Doc.

 

[Doc J]

Yikes, 15°! It is looking like air is lazier than I. It would rather run along the span than climb over the top of the wing to get out of the way.

Yes actually its about 50:50 at the wng tip at 150 to 200 Mph.

There is more than one way to skin the cat. If the side area of the nose is kept low then the destabilizing nature of a long nose can be minimized. Conversely a longer tail will give the vertical rear area a longer moment arm to work with. Then there is the option of adding more vertical rear area. The last two have the cost of added parasitic drag. But such is the nature of stability.

I think it will balance out very well, especially as the new fuselage section is "trianguloid" so that side forces are dissipated slightly in a better way - though in all honesty I bet the difference is tiny.

I hope you touched the nose, with an FAI radius and bottom nose cavity.

Yes to both. The radius is correct, and yes its a bottom loader.

As you know I loved the Redshift's wing (I hope it hasn't be optimized into irrelevance). The fuselage not so much.

Really its only the small change to the tips and the more inboard aileron servo positions. All else is the same, bar some very small refinements to the upper curves of aerofoil sections to give a bit more laminar flow attachment. The bottom curve with this section has always been very laminar.

BTW; I'm really liking the wing mounted ballasting systems. Can the ballast boxes be placed so that at full ballast the CG stays the same or moves aft ever so slightly. (I think I found that I liked the Redshift balance at 96mm). That is the one advantage of the fuselage ballast tube the fully ballasted GC can be shifted to optimize the CG at the new mass (CL).

I think the box positions will allow for a bit of juggling.

Cheeers,

Doc.

 

[Doc J]

I second the IDS ready comment!

Having stress tested the Redshift structure I can say the rear rotor landings with the wing ballast resulted in much more damage to the wing internal structure than the crashes with the fuselage ballast.

This is normal, but I do love your "Stess tested"

With the wing ballast there was a lot of wing joiner box damage along with the damage to the fuselage pass through window. With the fuselage ballast the wing joiners appeared to be fine and there was no added fuselage damage beyond what we had with the wing mounted ballast.

The new ballast tubes may be longer than before and nt we are using structural adhesive. I hope that the entire structure is beefed up.

What I'm liking is the dampening in roll with the wing ballast. Yes, there is a cost in drag to initiate and stop the roll in the way of added control inputs. But at my level of flying I'm thinking the wing ballast system might come out on top, assuming the CG is held in check.

The Redshift mk1 had both ballast systems. But I think the benefits of a smaller fuselage cross section from the loss of a fuse ballast tube would out weigh any loss flexibility.

I think fuse ballast could be fitted, but as I have mentioned its not standard from me.

BTW: I think I own 3 of the 5 legally imported into the USA Redshifts. Yes, I think the Redshift has that much potential. Working with Doc I think the Spada will address the few fatal flaws we found. Ok, fatal flaws is exaggerating a bit. You can read all the gory details in my 3 Redshift build threads.

Most of the things we had discussed - at some length - have been incorporated in the new plane.

Just a bit of trouble undestanding your drawings, Konrad - can you elaborate or clarify?
View attachment 12344

 

[Doc J]

Also,Doc, do you use Onshape?

Yes, the drawings are done in Onshape.

Or is this someone you are paying for cad, I'll admit, that I searched the public drawings for like 15 seconds to see if I could find the project, but someone making money should be paying.

I have a CAD partner and while no money is exchanged between us, a lot of other things are.

I use it for alot of little personal projects, but I have been thinking I hsould switch to fusion 360.

Couldn't advise you on. that 2M, I have CAD skills but damn I'm slow. My CAD partner is a turbocharged genius.

Cheers,

Doc.

 

[Konrad]

The drawing is trying to show the elimination of the skin shear material (top skin filler, AKA balsa or foam) adjacent to the location on the IDS spoons. As it is now most installations of the spoon requires grinding out of the inner fiber and the shear material. This leaves only a single layer of fiber to carry the loads along the top control surface. If the control surface is designed from the start to accept the IDS spoon. The shear material can be left out and the inner skin fibers come up and bind with the outer skin. This will result in a much easier installation, stronger installation. And for marketing concerns a much better looking installation as there is less chance of over heating the skin or worse break through while trying to make the IDS spoon pocket.

An added benefit is that those of us luddites can still use the classic control horn. In fact this configuration adds strength to the classic control horn installation.

 

[Doc J]

The drawing is trying to show the elimination of the skin shear material (top skin filler, AKA balsa or foam) adjacent to the location on the IDS spoons. As it is now most installations of the spoon requires grinding out of the inner fiber and the shear material. This leaves only a single layer of fiber to carry the loads along the top control surface. If the control surface is designed from the start to accept the IDS spoon. The shear material can be left out and the inner skin fibers come up and bind with the outer skin. This will result in a much easier installation, stronger installation. And for marketing concerns a much better looking installation as there is less chance of over heating the skin or worse break through while trying to make the IDS spoon pocket.

An added benefit is that those of us luddites can still use the classic control horn. In fact this configuration adds strength to the classic control horn installation.

OK Got it Konrad - I'll look into that. Could be a good mod for all the models.

Thanks.

 

[Konrad]

Edit: To clean up. Topic moved to here

 

[Doc J]

Doc, I think we covered this before. But I was re-reading Hoerner's Fluid-Dynamic Drag and his ideas on junction drag. Thanks @Red . It looks like the CAD drawing isn't abidding by Hoerner's proven ideas. I see the Redshift fuse narrowing way too soon, and by a lot 2mm. If it's not too late can you fill out the fuse. These are proven ideas and even used by others. Such as we see on the Freestyler.

View attachment 12365

I think this is what we used to call the 'Area Square rule" or the 'Whitcomb area rule' when I was in skool. Its normally used for low speed - subsonic design. For the really fast stuff, a different rule applies.

From Wiki:

The Whitcomb area rule, named after NACA engineer Richard Whitcomb and also called the transonic area rule, is a design procedure used to reduce an aircraft's drag at transonic speeds which occur between about Mach 0.75 and 1.2. For supersonic speeds a different procedure called the supersonic area rule, developed by NACA aerodynamicist Robert Jones, is used.

Basically a parallel section along the fuselage before, at, and after the wing junction is better for wave drag and other flow problems. .75Mach is shade too fast for us at F3f but its close for DS record breaking. But then again its not a bad thing to do stuff like this.

So I did.

 

[Konrad]

Edit: To clean up. Topic moved to here

 

[Doc J]

Area rule AKA Coke Bottle fuse, is the another subject. And as you mention is a transonic phenomenon.

What Hoerner is discussing is a very real condition that happen at low speed and goes up by the cube of the lift coefficient. So for our turning ships this is a real concern. Mike Arnold put this to good use with his record breaking AR-5 and later F1 AR-6. I use this in most of my EF-1 and Q-500 racers.

Done done done, Konrad.

Doc.