I percieve that classic "rules" seem to have some different interpretations by regions.  Question is how many "mods" are legal?  I understand that (non visible) changes to improve structural integrity are OK, but I desparately want to shorten the flaps on an Oriental.  Will that get me keelhauled?  Or worse, will it get me DQ'd?

Note: if I had built an Oriental in 1964 or later I would have built it with shortened flaps - just like every other airplane I ever had.  The Oriental ARF I have flies well but will fly much better with the flaps shortened.

Hi Dennis,

Being an ARF, you would lose AP anyway, if the contest is even using them.  And, if no AP is in effect, then no originality points are used, so no penalty at all is a possible outcome.

Bill <><

What about reducing chord of flaps? Wouldn't that give the desired effect but less noticeable visually? Maybe it would make a difference on tip stall characteristics ?

It's pretty well been accepted that, unless the changes are extreme, you will be allowed to fly at VSC. I can 't imagine a contest where they've forgotten that Classic is supposed to be fun.

Most of the questions so far generally fall into trim issues. Don't get too worried about the type of changes that would come from what has been discussed so far.

John Miller

What? you guys are having FUN??? I thought we were all at each others throats!!! 

Of course I'm kidding, John & Ron THANK YOU for keeping our eyes on the REAL prize! 

When we took the Oriental out we had a great fun day.  The bird needed a few tweaks; props, line rake, tip weight - the usual litany, and EVERY thing we did made it just a little bit better.  WHAT A HOOT when it all works!  Last thing we wanted to try was to cut back the flaps and improve the 88 degree square corners!

Gordon: Reducing the flap area will reduce control loads, however, the REAL problem I am going after is the shed vortex at the wing tip - and flap tip.  Full span flaps, in effect, have to turn that column of air, but if the flaps end 4" or 5" inboard, the flaps stay free of the worst of the vortex - controls lightened, & corners tightened.

Gordon's question about mods for a larger engine is also interesting.  However, I would suggest that an LA 40 or LA46 as well as numerous other similar modern engines are available that are roughly the same size & weight of a K&B 45 but which would be vastly more powerful - have you considered any of those possibilities?

BTW I have a K&B 45 if you are interested, but don't know if the darned thing will actually run...! 

Ty: Steve Wooley had some business dealings in Detroit area and as a result he built/finished a LOT of the Cobra in Big Art's basement while he was semi-living in town.  I loved Steve, but I'm with you.  You might have lost "fidelity" points for not painting it green, but I think you should have earned some "good taste" points!

Still magical when we can capture the flair of the original, even if we do not completely duplicate it.

Ty:
Ringmasters are just "aesthetically challenged".

Bill:
I'm just a damnyankee but I never had a mint julep that was GREEN.(?)   

If you mean mint green like Mint Chocolate Chip Ice Cream then we ARE on the same page! 

At the risk of getting back on topic, I done the deed.  Hope to fly it tommorrow, uh I mean later today...!

We really have to be practical about mods. Fidelity points, etc are to prevent the extremes, not the necessary. For example, a Nobler with a foam wing would lose some fidlity points since Noblers did not have have a foam wings, but it would be allowed to fly. Extremes would be add a couple inches to a tail moment, or using a tuned pipe, or asymetrical wing panels being changed to less asymetry or equal panels.
There have been arguments about tail wheel heights, but again that would only be a small loss of fidelity points, but tail wheel heights always varied some. Some people think the Gieseke height tail wheel shouldn't be applied to other airplanes, but personally I would rather close that book.

Remember this is not a scale contest, we should enjoy it.

Designers have always played with flap width and length on their airplanes. I have seen many original airplanes over the years that have flaps trimmed, or pieces add to, and painted later when the mod worked out.  Even shortend flaps, with the outboard section changed to trim taps, are not uncommon.

Widening the fuselage to accomodate an engine certainly is no problem. This has no advantage aerodynamically.

Engine improvements, to me, are also no problem. I am currently working on Jack Sheeks "Sea Vixen". Jack had engines ranging from a .35 to a .40 to a .45. in the original airplane. Some details and dimensions are simply not on the "Sea Vixen" drawing. For example, the fuselage formers are not showm. The article says they are 2 1/16" wide. The top view show the formers "close to 2 1/8" but aft of the ply doublers and about 2 1/16" between the doublers. If I made them to that dimension inside the doublers, the mounts would be to far apart for the ROJett .40. which has mounting holes that are close to edge of the mounts. I will also use 1/32" ply doublers instead of the 1/16" that were typically used. My solution will be to have the mounts the proper width for the engine and add to the width of the fuselage sides to get the proper width. I would not be concerned about adding fuselage width, but I won't decrease the width.

Likewise I wouldn't complain about changing the thrust line 1/16" to add a plate under the engine, but in most cases the mounts can be moved the thickness of the desired plate, keeping the thrust line the same, with the added avantage of giving room for tank adjustment.

Again, we like to replicate the originals as close as we can, but keep in mind the the designers made changes, and this is not a scale event. Have fun with it.

Bill,

3/8" sq. will probably work, but I tend to want the 3/8 + pad under the engine. I always use the Windy/Big Jim crutch too. With the lighter (1/32") doublers, I still like the vibration absorption and strength.

You just described the set up for PA 61, etc. When using a Sullivan plastic tank, a 1/8 pad under the engine, along with a 1/8" undercut of the mounts under the tank, is perfect. (I learned that from Bob Gieseke)  Of, course this has nothing to do with "Classic"

Bill,

Whoops, Yes, 1/2" + 1/8 pad under the engine, 1/8 undercut of mounts under the tank.

Good Morning Al...Great to see you posting here on ol stunthanger again.

Years ago...as you know I lived at VIRTUALLY the north end of Sea-Tac's main runway approach in that little apartment near Seattle. It was one of my daily thrills was to sit outside on the deck on a calm summer's eve with a can of Rainier light in my hand as I would look up to the sky and watch in amazement as those big Braniff Airplane lazer-like landing lights started annointing my eyeballs and filling my ears with the screeeeking sound of jet engines...as those huge airplanes would pass so closely over our heads.

What still seems so amazing was that  long moments after those planes had passed and disappeared over the crest of that hill... is that you then could hear this LOUD WHOOOOOSSSSSSHHHH STIRRING OF AIR that would follow and envelope the still night air.
Even the surrounding trees  leaves would begin to flutter and dust would be kicked up around our apt. complex parking lot from that tunneling air after the plane had touched down on the end of the runway.

Thinking back Al....it seemed that the intensity of those Vortex torrents of air off those landing planes seemed more noticable in those calm warm summer nights? Air pressure??? Or was the lack of wind kept the vortex from drifting off the flight path?
Even today Al...I can't drive by that old "10323 DesMoines Way S. without thinking about those days of living under the flight path of those great giants of the sky.

 Lots of folks in those apts. hated airplanes....but as you know, Al, I was a kid then...and soon learned to sleep like a deaf-dog as I had been bitten by my love for anything with wings, especially those with a handle...two 65 foot steel lines and a bellcrank with big flaps and elevators. Bottom line: I loved that old apt and the great memories that were created there.
So much has been cussed' and discussed about flap and elevator design...but I think still...one of the most overlooked problems...is votex patterns that are generated by our models in flight and just how we can dealing with this in those dead calm and hot tarmac days of summer. 

I guess the BEAT STILL GOES ON to understand our strange models of flight that go---ROUND ROUND ROUND!

Al
THANK YOU  for the comment.  You remain one of my favorite thinkers and DO-ers on CLPA design.   

Yes all those conversations we had - I listened and a lot of it got either applied or adapted (except I still haven't built a wiggly rudder! )  I knew you are of the alternative point of view on the subject of flap span AND flap throw, and I still struggle on how a case can be made for either side of the issue.

Trimming flap span DOES work, and in this case got me exactly what I wanted to achieve.  The explanation that the trailing vortex was at the root was first explained to me by a Detroit area gentleman named Ron Adams who was an early proponent of VERY large and heavy stunters.  Ron even carried the idea to using partial span elevators.  He had two designs published: an A6 Intruder (108 oz and 800 squares)  and the "Marute" (somewhat bigger but lighter).  HOWEVER, there are SO MANY  models flying with flaps out to the tips including most Orientals - seems like one idea or the other should gain precedence. 

Let me toss this out:  I think part of the issue rest in the basics physics of control feel and line tension.  Control feel is what we get pulling one way or the other to command a manuver,  while the bird is pulling back.  We cannot pull any harder than the airplanes ability to pull back - thus control feels "heavy".  In my case I was working too hard to get a full corner.  Conversely, a heavy/powerful airplane with higher line tension pulls back harder and the Pilot (within HIS physics!) senses a different feel.

I read about folks insisting that a Oriental needs a 46 to fly right - I struggle with that!  As you pointed out the bird is light with a friendly airfoil.  LOTS have been built/flown and winning with Fox 35's.  I am flying mine with a LA 40 that I think represents a 50% power upgrade!  However if folks are using the 46's and trimming for lots of line tension to overcome a slight heaviness in the control feel - maybe THAT is the case....?

The effect I get when cutting the flaps is different/superior to the effect (feel) I have gotten by narrowing the flaps.  I DID notice a loss of control load AND opening of the corner for narrow flaps.

I'm working on an ARF Cardinal for my Dad, the flaps have already been cut!  But I KNOW it will be a COLD day in .... Texas before we see a Bearcat with part span flaps with 3:2 elevator-flap ratio!!!

>>I DID notice a loss of control load AND opening of the corner for narrow flaps.<<

Oh Dennis, you really need to talk to Howard Rush. His Impact has the most trick flaps setup you've ever seen and is specifically design to reduce control loads while maintaining really pretty big flaps. Interesting approach.

Those tabs you see are hinged to the flaps and are actuated so that they work in the opposite direction of flap throw. Howard says that it reduces control loads substantially without doing much to the lift potential of the wing. Cool idea.

Doc
Thanks.  Now its TOO LATE to worry about cutting the flaps as the deed is DONE!.. I did get exactly what I was looking for too.   

Rear exhaust? Heck, I feel GUILTY about using an LA40 instead of a Fox 35! 

...and my FUN METER has been up against the pegs!