Fuselage shape.

[Matt Neumann]

Taking a cue from Brett Buck on another thread I will start one here on fuselage shape.  Hopefully Brett can explain a bit better his "3 billboards in formation" comment.  I sort of understand the thought of larger side area.  Especially in overheads.  My Stuka's had a bubble canopy but the side was somewhat tall but I also had a large rudder.  I think Randy Smith said this was good in that in wind the wind could push the tail out slightly easing line tension on the downwind side of things while in the upwind side of things would push the tail inward helping tension.  Hope I explained that OK. 

Yet others such as Brett's plane has a large side area more consistent along its length without the really large rudder if I remember right.

My Enterprise planes are a turtle deck with a larger rudder giving a larger amount of side area than the Stuka's on the fuselage while keeping the larger rudder.

While other peoples planes do not have near the side area all around.

So, strengths and weaknesses of each of these basic ideas?

[Dan McEntee]

     Well you have several seasons on the Enterprise ships now, how do you compare that model to your various Stukas?  I think you also have some small fins on the stabilizer tips? It's been a while since I have see one. I have been aware f Randy's assessment of rear fuselage side area for a long time, and maybe the first such fuselage/rudder combo was the Nobler?? And many other designs followed suit through the years. Piped ships tend to have deeper fuselages to accommodate the pipe also. I think that if the fuselage is designed and constructed carefully, it's probably much stronger and more stiff with that box type configuration. And as long as you can keep weight under control, it's another benefit of the concept. It's an interesting subject!
   Type at you later,
     Dan McEntee

[Dave_Trible]

Matt I think Randy's assessment is generally correct.   All well and good BELOW 45 degrees.   I don't think we have too many problems there anyway.  However ABOVE 45 degrees that very thing can work against you maintaining line tension.   There things like speed,  engine and rudder offset have to take over to keep the airplane out and somewhat overcome the weathervaining  affect.    More overall side area adds more force(s) to the equation good or bad.  Does the prop wash overcome the side stream wind pressure?   Maybe to some degree but might depend on wind velocity.   We also have the prop wash spiraling down the fuselage.   There is room to know more about that and how to distribute the area aft to take best advantage of it.   I think that is why Igor's airplanes have some sub-rudder on them.

Dave

[Matt Neumann]

A lot of this will ALWAYS be how well the plane is trimmed.  Most likely the biggest factor overall.  I know some have a scientific approach to designing.  Me.  I put my thumb up and say that looks about right. 

As for the difference between the Stuka's and the Enterprise models.  Not much except power plant.  Took awhile but I think I finally got the electrics to feel like the IC engined planes.  One of the biggest things that helped is I am now flying with the larger props that I did with the Stuka's.  I have a 13 3B on it now.  Contrary to some beliefs, electrics are not plug and play.  Still have to fiddle with props and settings.  With that said the current set up with the plane I have been flying the past few seasons now finally feels a lot like the Stuka's did. 

On strength and twistability, that is different from side area.  A wider body is less likely to twist than a narrow body viewed from the top.  My blue Enterprise is the widest fuselage I have ever built and it certainly is the stiffest.  But not sure on side area.  It is much more rounded that the Stuka's which helps in rigidity.  But is a flat side better aerodynamically for our purposes?

I am not sure what they are called but I have some extensions on the tips of the flaps and elevators.  Did that for looks more than anything.  I am thinking Randy Smith said they are supposed to help but I am not sure in what way and if they actually do or not.  I just thought they look cool.   Bob McDonald called them "Batman tips".  I was hoping it would help with turbulence in calm air.  As in produce less of it.  Not sure if it did not not. 

[Matt Neumann]

Matt I think Randy's assessment is generally correct.   All well and good BELOW 45 degrees.   I don't think we have too many problems there anyway.  However ABOVE 45 degrees that very thing can work against you maintaining line tension.   There things like speed,  engine and rudder offset have to take over to keep the airplane out and somewhat overcome the weathervaining  affect.    More overall side area adds more force(s) to the equation good or bad.  Does the prop wash overcome the side stream wind pressure?   Maybe to some degree but might depend on wind velocity.   We also have the prop wash spiraling down the fuselage.   There is room to know more about that and how to distribute the area aft to take best advantage of it.   I think that is why Igor's airplanes have some sub-rudder on them.

Dave

Actually I would think overhead it would not matter as much on a larger rudder.  At that point it will be a lot closer to be pointing into or out of the wind no matter what and you won't get much weather vaining.  You will be either going directly into or out of the wind and the wind just won't be hitting the side straight on.  Hope I explainded that right as well.

[Ken Culbertson]

I am not sure what they are called but I have some extensions on the tips of the flaps and elevators.  Did that for looks more than anything.  I am thinking Randy Smith said they are supposed to help but I am not sure in what way and if they actually do or not.  I just thought they look cool.   Bob McDonald called them "Batman tips".  I was hoping it would help with turbulence in calm air.  As in produce less of it.  Not sure if it did not not. 

I can only add antidotal comments since I have never actually studied this.  My personal belief is that the large aft side area we seem to be talking about is a leftover from the 60-70's.  It was the only way you were going to do a RWO or enter the OH8 in any kind of wind.  If you can remember back that far you will remember that turning into a heavy wind in the OH8 was a religious experience. Now we have Star Lifters up front to get us to the top.  I don't think side area has anywhere near the effect that it once did and may actually be hurting.  We see the plane's profile the same no matter where it is in the hemisphere.  The image that the wind sees constantly shifts from a side view to a top view.  The higher it is the less fuselage, and more wing is exposed to the wind.  It is not side area that causes problems over 45 in wind, it is wing area.....or not.

Ken

A word on the tip plates.  They work by keeping the tip vortex from rolling back onto the wing and killing lift.  I have tip plates or twin rudders on everything I build.  I am going to try some on the flaps.