Changing the shape of the RV wing for speed

[captain_john]

Hey, did anyone check out the thread elsewhere on the web where jetblackaircraft was bandying about the idea of reshaping the main airfoil to increase the upper envelope of the standard -7 wing?

He has no "product" per se, but suggests possibly offering a substitute set of pre-punched ribs and skins to use in lieu of the standard Van's stuff.

I think the idea is an interesting one. Not one I would consider on my first RV or maybe not even on the second one either. But, if I were a multiple repeat offender with some technical knowledge in this area, it would be an exciting experiment!

The Hughes H1 Racer sported 2 sets of wings. Why not your RV?

Of course, there are other issues one would need to consider when doing this type of mod. Flutter is high on the list, as the mod is supposed to use standard control surfaces.

Hmmmm, ahhhhhh... I dunno. To what end, I presume.

Maybe a new set of control surfaces should be on the list as well then? The new ones could have ribs and counterbalances. Would that help?

...just an idea. What do you think about it?

CJ

[weezbad]

yah i read it...tried to sell my spare spar while i was at it. lot of chance for 10 kts. no way for a retro fit but maybe on a new bild i suppose.

[captain_john]

I don't see it as a "no way for a retrofit", Willie. You could start new set of wings again, should you REALLY want to do this.

It will be an interesting one to watch, should people start doing this. The RV wing is fairly split down the middle in my opinion, handling-wise anyways for a Hershey bar shape.

It certainly stops flying when it stops flying and it has a good solid feel when it is lifting good.

If there is a problem, I would say that the flaps could be more effective. Makes me wonder if a single flap connecting the left and right and under the belly like the Mustang II would be a good design mod.

Willie, maybe using that spar for those canards (like I mentioned before) could help in the incipient stall, should you do those new wings? Hmmmmm, whatdyathink?

Maybe a motorcycle ramp would be a good use for it too?

CJ

[weezbad]

IYou could start new set of wings again, should you REALLY want to do this.

and that is wat i was reffering to. i sure wouldnt build a new plane to get a new style wing. i could knock out a set of wings in no time.

Maybe a motorcycle ramp would be a good use for it too?
CJ

man you are ruining my dreams of getting over on the system. i want to have my new spar and sell the old one. all while feeling like i came out on top....just like a wal mart shopper. no really i wish i would have just used my original....the finish on replacement was not nearly as nice as the original.

[captain_john]

Do you have any question about the match drilling with the replacement unit?

I mean, how did they match drill it to the center section without the center section?

CJ

[dsb]

Keep in mind that it's not difficult to build a new wing that will bolt up to your existing fuselage, but when you change airfoils you possibly change the center of pressure and the pitching moment. These changes could be accounted for with 'adjustments' if building a new fuselage, but would possibly be a real problem with existing mounting points. I have a few wings for a potential -4 sitting in SolidWorks, one of which is just a 0.60 taper of the NACA 23013.5 that Van's uses, and just with the taper it alters the MAC/COP enough that you would have to relocate the spar fore/aft within the fuse or redesign the tail as well. Once the spar is relocated you have to contend with the altered W/B issues... et al... ad nauseum... You get the idea, not imposible, but certainly not a 'bolt on' modification...

Dave

[captain_john]

Dave,

Spar location can be compensated for by adding or reducing leading and trailing edge length for the most part, no?

I am sure that strength of the leading edge ribs and where the stresses are applied bear heavily on this and without having a solidworks app and some good user data this is largely speculative.

What goals are you striving towards with your design?

I think the RV series is an excellent platform for such experimentation because of the intense market proliferation and the application of the true intent of "Experimental Amateur-Built" category!

CJ

[weezbad]

Do you have any question about the match drilling with the replacement unit?

I mean, how did they match drill it to the center section without the center section?

CJ

not at all. ok maybe a tiny bit but i have already had them on so im 99,9% sure they'll be good. ive communicated with others that said the same thing. no reaming or anything crazy....once i have them on with all of the bolts i'll get rid of the spar. i did use four of the NAS bolts when i fitted them to be certain i wouldnt have any issues...but we'll see when i get all of the larger bolts in....not to far from now

[captain_john]

I would bet that Van has somehow covered this base.

I mean, with all the kits out there some of them MUST have needed a replacement wing and/or spar at one time or another.

CJ

[dsb]

Dave,

Spar location can be compensated for by adding or reducing leading and trailing edge length for the most part, no?

I am sure that strength of the leading edge ribs and where the stresses are applied bear heavily on this and without having a solidworks app and some good user data this is largely speculative.

What goals are you striving towards with your design?

I think the RV series is an excellent platform for such experimentation because of the intense market proliferation and the application of the true intent of "Experimental Amateur-Built" category!

CJ

Any amount of displacement wrt to the spar v. the COP results in a torque that has to be compensated for... It's usually advantageous to locate the spar at the thickest part of the wing (chordwise...), the deeper the spar is for a given spar thickness, the stronger it is...

I was looking into additional G loading, and a higher Va...

I agree wholeheartedly that it can be done, I just don't think it's a 'bolt on' mod...

Dave

[captain_john]

I see...

Dave, I mentioned this over in the other place but, howsabout the other design's flutter potential?

Wouldn't it be prudent to do something with the control surfaces in the order to prevent this?

CJ

[rv8or]

CJ--

They must have figured a way to match the spar/center without them being fab'd at the same time. Every set of -8 wings that was bought before the match drilled fuse came out came with a center section that is now a door stop/boat anchor...the fuse kit comes with it's own center section, and they fit (I hope ). FWIW.

Joe

[captain_john]

Joe, Wicked Stick doesn't have an extra center section and he has a SB, non match drilled -8.

What am I missing?

CJ

[rv8or]

I didn't explain that very well, sorry. They used to set up and ship the center section with the wing kit...I have one. When they switched to matched hole style kits for the -8 (2 summers ago?), the fuse kit now comes with a center section that will fit your wing...even if your wing came with it's own center section.

So, if you're one of the folks who bought your fuse kit since the change over--and already had the wing kit, the center section that came with the wing kit, matching serial number and all, is not used. Any ideas what I should do with mine, besides use it to collect dust?

Joe

[dsb]

I see...

Dave, I mentioned this over in the other place but, howsabout the other design's flutter potential?

Wouldn't it be prudent to do something with the control surfaces in the order to prevent this?

CJ

From what I've found, and I haven't studied it that much, it's more an aeroelasticity issue. It seems the issue would be greatly improved if not basically solved by using interior ribs and reducing the skin free span. Of course this complicates the construction and possibly adds a small amount of weight.

Dave

[captain_john]

Joe, now why do they do that?

My -7 is really no different. It has the same wing as an -8 (for all intents and purposes) yet I don't get a second center section. The -7 was pre-punched before the -8 was sooo, if they did it before why not do it again?

I suppose that the new center section has PP holes in it. That must be the reason.

Given the weird stuff they leave up to the builder, not having a PP center section is a simple thing for them to leave up to us.

I dunno about the rhyme and reason of Van.

It must make sense somehow?

CJ

[captain_john]

Dave, yes. I mentioned using ribs and counterbalances in the other place.

I understand that a full aileron rib would add to the build and be heavier. So would the counterbalance (more than the 1/2" iron pipe) but for the increased Vne...

I dunno. Are we dwelling in minutia?

CJ

[dsb]

It would seem that RV's flying beyond Vne isn't that unusual an occurence, so no I don't think it's a trivial issue, especially if you go into the project wanting to maximize the speed of the craft, or if you know you are going to be pointing the bird down hill with fair frequency... For me, the low Va limits the plane as much as the Vne concerns. Forget about aerobatics for a minute and think about the guy buzzing along merrily at 175mph only to encounter some chop... How long will he bounce before getting below 130mph(Va)? How many people would even bother to slow down that much? Van has a good article on the stresses put on a -9 in this situation (in response to the people wanting to put big motors in them...) and it's equally applicable to the rest of his planes, albeit with different numbers. I think it's a testament to Van's design that they hold up so well, but 'aerobatic' doesn't mean 'unbreakable'. Of course, it may be an hours thing, aluminum doesn't have a fatigue limit so it has X amount of stress cycles at birth, you stress it... and it has X - 1...

Dave

[Thermos]

Any amount of displacement wrt to the spar v. the COP results in a torque that has to be compensated for... It's usually advantageous to locate the spar at the thickest part of the wing (chordwise...), the deeper the spar is for a given spar thickness, the stronger it is...

I was looking into additional G loading, and a higher Va...

I agree wholeheartedly that it can be done, I just don't think it's a 'bolt on' mod...

Dave

To plagarize Monty Python..."who are you who are so wise in the ways of aerodynamics?"

It's nice to have an aero engineer around!

Dave

[tmbg]

Keep in mind that it's not difficult to build a new wing that will bolt up to your existing fuselage, but when you change airfoils you possibly change the center of pressure and the pitching moment. These changes could be accounted for with 'adjustments' if building a new fuselage, but would possibly be a real problem with existing mounting points. I have a few wings for a potential -4 sitting in SolidWorks, one of which is just a 0.60 taper of the NACA 23013.5 that Van's uses, and just with the taper it alters the MAC/COP enough that you would have to relocate the spar fore/aft within the fuse or redesign the tail as well. Once the spar is relocated you have to contend with the altered W/B issues... et al... ad nauseum... You get the idea, not imposible, but certainly not a 'bolt on' modification...

Dave

Hi Dave,

I sure would like to get together with you sometime on the topic of using SolidWorks to design wings... it's something I've been toying with for a couple weeks, and it'd be nice to see how it's done by someone that actually knows what they're doing!