Trifecta

[Kim Doherty]

Ken,

Your model looks great! I like the fuselage and the nose work.

Kim

[Ken Culbertson]

Ken,

Your model looks great! I like the fuselage and especially the nose.
I assume that the pushrod we see on the stab is part of your KT rudder actuator. Even for this use I would not use a piece of all-thread. Get a piece of 4/40 threaded wire, eliminate the connector and use one run of wire. All-thread should never be bent or used over a distance.

Kim

Thanks!  It *is* music wire. It has to have the ball link if the drive mechanism is not in line with the cam.  Normally the pushrod drives the cam directly but it is a profile.  The pressure on that pushrod is next to nothing.  Mounting the logarithmic horn was easier that I thought.  I used ball bearings mounted on the inside of the fuselage sides.  Solid as it gets and smooooth.  The hard/fun part is going to be making the hatch to change cams.   I am trying a lot of new things (to me) on this plane.

Ken

[Brent Williams]

Glad to hear you are making progress!

[Kim Doherty]

Thanks!  It *is* music wire. It has to have the ball link if the drive mechanism is not in line with the cam.  Normally the pushrod drives the cam directly but it is a profile.  The pressure on that pushrod is next to nothing.  Mounting the logarithmic horn was easier that I thought.  I used ball bearings mounted on the inside of the fuselage sides.  Solid as it gets and smooooth.  The hard/fun part is going to be making the hatch to change cams.   I am trying a lot of new things (to me) on this plane.

Ken

Ken

Sorry, when I enlarged the pic on my phone a very distinct “thread” pattern showed up on the wire. I blew it up to see what was going on right at the horn.

Kim

[Scott Richlen]

Ken:

What's that small horn for?  What does it do?  (the one in the center of the horn that the pushrod doesn't attach to)

Thanks!

[Ken Culbertson]

Ken:

What's that small horn for?  What does it do?  (the one in the center of the horn that the pushrod doesn't attach to)

Thanks!

It drives the CAM rudder.  Since it is a profile I can't use the pushrod like you can on a full body.  As it turns out I had to reverse it and drive the cam from the top of the elevator.

[Scott Richlen]

It drives the CAM rudder.  Since it is a profile I can't use the pushrod like you can on a full body.  As it turns out I had to reverse it and drive the cam from the top of the elevator. 

Thanks Ken.  Can you post some pictures of the details of how that operates?  I just rebuilt on of my planes and want to install a Rabe Rudder, but am having a real challenge due to the geometries.

[Ken Culbertson]

Thanks Ken.  Can you post some pictures of the details of how that operates?  I just rebuilt on of my planes and want to install a Rabe Rudder, but am having a real challenge due to the geometries.

This is an adaptation of Keith Trostle's CAM rudder which was inspired by the Rabe.  The CAM allows you to trim the rudder for both upright and inverted.  The one in that picture gives me 1/16" extra on upright maneuvers immediately and 1/16" on outside increasing to 3/16" at 30 degrees.  I think if you search "CAM Rudder" you will find some details and I know I posted a short video of the one I had in my Endgame design.  This one is not representative since I had to mount it on the top of my stab to drive a twin rudder on a profile.   Normally it would be under the stab and driven by the pushrod directly.  You can get a similar effect from a Rabe if you mount the horn in line with the stab and drive it from the centerline of the elevator.  It just won't be proportionally adjustable.

You might be shocked at how little rudder it takes to give noticeable results.  Those tiny amounts I use are enough to tighten the lines in the rounds and overheads yet produce no visible yaw.  The extra on outsides is for procession.

Keith did a full article for this which is also here somewhere.

Ken

[Trostle]

Thanks Ken.  Can you post some pictures of the details of how that operates?  I just rebuilt on of my planes and want to install a Rabe Rudder, but am having a real challenge due to the geometries.

Scott,

If you have plans for any of Al Rabe's designs, you will see that these will show that all of his linkages to the rudder were external.  He had a small horn on the bottom of the elevator and another small horn on the side of the rudder with a small pushrod between the two.  Different rudder travel response to elevator control could be achieved by using different locations on the horn for the pushrod attachments.  Unfortuntely, the geometry of the positions of the horns makes it difficult to get the actual response you might want with the rudder.  Also, this system often results in rudder response being far in excess of what you really are looking for.  (This is one reason for some who have tried this approach have found it to be undesirable.)  I know of at least two people who found that having the pushrod connection to the elevator somewhere near the chord line of the elevator, still with an external horn on the rudder, gave the rudder response that worked for them.  This gave them the capability to have only slightly more right rudder on insides.  In other words, the elevator connection is not offset or not as much like results from using a horn.

The purpose of these things is to get slightly more right rudder on outside maneuvers.  Rabe's approach did this.  His system also decreased right rudder on inside maneuvers.  This also works in some cases, at least it worked well for him.  But there are other approaches that minimizes right rudder on insides or can be found to improve overall control by no rudder movement on insides or even slightly more right rudder on insides.

I repeat that I know that Al's system worked for him.  I do not understand all of the interactions going on between desirable rudder movement on inside and outside maneuvers when maneuvering on our hemisphere, but do know that Al trimmed his airplanes to be nose heavy and used a really  large line spacing at the handle.  His combination of balance, handle spacing and his rudder movement worked for his airplanes.  I have flown several of Al's Mustangs and one of his original Bearcats, one of those Mustangs he flew to placed second at the 78 World Championships.  Other than getting familiar to the larger handle, the airplanes were a pleasure to fly and were an eye opener on the effectiveness of the movable rudder.

Keith

[Ken Culbertson]

..something like this, totally off scale. I’ll make a better drawing when my fuselage gets ready.. L

I think you may be onto something if you are after more movement but I think the "tiller" approach is still easier.  One way to find out - make one!
Too bad we can't use "fly by wire".  We could just couple the elevator and rudder on the transmitter.

Ken

[Sean McEntee]

Don't discount a light, well built and well powered Ringmaster.  I can't think of any stunt event that one couldn't fly a ringmaster in.  I even think some dude in Tulsa flew the team trials a few years ago with an enlarged version...

[Ken Culbertson]

Don't discount a light, well built and well powered Ringmaster.  I can't think of any stunt event that one couldn't fly a ringmaster in.  I even think some dude in Tulsa flew the team trials a few years ago with an enlarged version...

Joe is one of those unusually gifted natural fliers.  If he showed up with a Cox PT-19 I would still like his chances to win.  I need something a bit more robust.

Ken

[Ken Culbertson]

Update.  Fuselage and tail assembly complete.  Starting to look like an airplane.  I have a BadAss 3515 coming.  Pretty sure the timer is going to be the Fiorotti with a Spin44 or 66 ESC.  I have hooked up the controls and they are fall down smooth.  I have never used ball bearings on horns before but I think I will from now on.  A lot of work but the results are measurable.  The wing is still a question mark.  I don't know if I can build a straight one in my tight quarters .  I am really looking forward to flying a plane with logarithmic flaps.  About the only thing on this plane that is not "state of the art" will be the pilot!

Ken

[Scott Richlen]

Ken:  nice workmanship!  You'll have to let us know how that control system works for you.

[Ken Culbertson]

Take a Umland Francherized Twister kit and scale down the tips and tail of the trophy trainer and you'd have a great looking airplane with a modern airfoil/numbers. That would be an awesome profile for an LA 46 or an Eflite Power 15.

Motorman

Definitely a good plane.  I need something a bit more robust for PA.  It is not that different from a Fancherized Twister which is a great practice plane but not quite up to the consistency required for PA.  This will be my third profile Sandpiper.  #2 was powered by an LA46, flew several PA events and performed as well as it's full bodied competitors.  All it needed was a better pilot!

Ken

[Ken Culbertson]

Things are progressing.  Frontend is loaded with wires and stuff.  It all works BadAss 3515-710, Spin44Pro, Fiorotti 6x timer.  It all works.  Got the wood for the wing which I am doing last because once it has a wing I am going to want to fly it and a lot of the "do dads" will just get skipped.  Happens every time with me.   So, I have looked(searched) the site trying to find what the initial settings should be for this combination.  I have had no luck.  Any help would be appreciated.  There has to be a Cheat Sheet on somebody's workbench somewhere.

Ken

[Ken Culbertson]

Update - Started Wing today.  Going Old School.  Not much room for a proper Jig so I am using some old fashioned methods.  Halves built separately on arrow shaft jigs.  Aghhh.....  Having a shop with a real jig table is on my bucket list.  But so is returning to the NATs, visiting Switzerland and an evening with Alessandra Ambrosio.  I think I will run out of years first.

Ken

[Scott Richlen]

Ken:

Those are good looking ribs!  I like those blunt noses - really good aerodynamics.

They remind me of something familiar....let's see what is it? .... just on the tip of my tongue...

[Ken Culbertson]

Ken:

Those are good looking ribs!  I like those blunt noses - really good aerodynamics.

They remind me of something familiar....let's see what is it? .... just on the tip of my tongue...

[Steve Helmick]

PLEASE tell us about your date with Alessandra Ambrosio, and what she thinks of your stunt pattern!  Steve

[Ken Culbertson]

Making the wing "Old School".  No room for a proper Jig.  Good old Arrow shafts holding hand cut ribs.  What could go wrong?
BC Mount installed today.  Mount attaches to the spar bottom then the spaces above and below are filled with scrap balsa.  Mount glues to underside of wing LE sheeting.  This BC ain't coming out.

Ken

[Ken Culbertson]

PLEASE tell us about your date with Alessandra Ambrosio, and what she thinks of your stunt pattern!  Steve

She bailed, doesn't want a square getting her caught in a triangle.

[Ken Culbertson]

Update and Tip Weight question.  Finally got the wing built.  Doing using an old fashioned jig in a space way too small resulted in some washout.  Not much, just enough that I am really happy that I have adjustable everything in controls.  Starting to look like a plane.

My tip weight question is "Where does it go relative to the CG?"  I have always put the box just behind the spar.  On this one that would be a good 2" behind the CG.  My gut tells me that it should go just a bit in front of the CG but I can't explain why.  I suspect that the leadout position matters but that can change, the tip weight position in pretty fixed in most.  For what it is worth, my outboard flap on this one is about 3sq. in. larger than the inboard.  Both of the recent rebuilds needed a 1/2 x 6" wart so I built it in to this one.  Pix in post #41.  I went with the tips from the original full body. (post #43). I was reminded that the wing for the profile came from the fullbody with the damaged LG removed.  Classic being the first leg of the Trifecta, I caved.  I have used nothing but swept tips since the 60's.

One other thought.  We have been obsessed with all kinds of turbulation recently.  For reasons I preferr to keep between me and my sanding block I am going to add a 1/32" cap to the LE.  What would be the effect of leaving the ridge? (pix lower right)

Ken

Follow up - it went "or here" and I decided to skip the cap and just fill in the LE.

[Trostle]

My tip weight question is "Where does it go relative to the CG?"  I have always put the box just behind the spar.  On this one that would be a good 2" behind the CG.  My gut tells me that it should go just a bit in front of the CG but I can't explain why.

Ken

It would make sense to place the tip weight as close to the lateral CG position as possible so as to not change the lateral CG.  However, placing the weight 1" or 2" in front of that lateral CG position would not make much difference because of the moments involved.  Position a 1/4oz tip weight 1 " behind the lateral CG would hardly have the effect of that 1/4 oz weight in the tail 24" or so behind the CG.

Keith

[Scott Richlen]

Put the weight box in front of the spar.  Think of it this way: if you put it in the wrong position (adding weight behind or in front of the CG when you needed opposite balancing weight) the moment arm of the tail will allow you to add less weight to the plane than having to add it to the nose to rebalance.  Hopefully this explanation is easy to follow.

[Ken Culbertson]

It is going in the front 1/4" in front of the sheeting (the box will be made from 1/4" bass so I can screw on the hatch easily.  What is the point of making a light weight box anyway.  Keith is right but I was not as concerned with the weight affecting the CG as I was yaw.  Having the weight ahead of the leadouts will add to inward yaw.  I suspect the effects are minimal anyway but the little things do adds up. 

Let me repost my other question from post #8 since it is equally important at the moment:
What would be the effect of leaving the ridge? (pix lower right)

Ken

[Ken Culbertson]

It is going in the front 1/4" in front of the sheeting (the box will be made from 1/4" bass so I can screw on the hatch easily.  What is the point of making a light weight box anyway.  Keith is right but I was not as concerned with the weight affecting the CG as I was yaw.  Having the weight ahead of the leadouts will add to yaw.  I suspect the effects are minimal but the little things do adds up. 

Let me repost my other question from reply #76 since it is equally important at the moment:
What would be the effect of leaving the ridge? (pix lower right)

Ken

[Ken Culbertson]

Slip fitted the wing after all the changes.  Never had one align on the 1st try.  Maybe it is an omen.  Now I have to decide on the flap hinges.  Round TE, Triangle TE, imbedded.  So many choices, so little time.

Ken

[Scott Richlen]

Ken:

Maybe it's the lighting, but in your last photo the leading edge looks like it has a sharp corner, rather than a radius.  Are you rounding that?  (Or does it only appear to be a corner?)  The reason I bring  this up is that you were asking about a ridge further back on the leading edge.  I'd think that a sharp leading edge would have much more effect (negatively) than a ridge further back.

[Ken Culbertson]

Ken:

Maybe it's the lighting, but in your last photo the leading edge looks like it has a sharp corner, rather than a radius.  Are you rounding that?  (Or does it only appear to be a corner?)  The reason I bring  this up is that you were asking about a ridge further back on the leading edge.  I'd think that a sharp leading edge would have much more effect (negatively) than a ridge further back.

It is the lighting and the center strip of the LE that makes it look sharp.  It has a 3/8" radius which is quite blunt.

Ken

[Scott Richlen]

Sounds like you are good then.  The plane is shaping up nicely.  Can't wait to see it in color.

[Ken Culbertson]

Sounds like you are good then.  The plane is shaping up nicely.  Can't wait to see it in color.

MEE TOO!  I have stolen a color pattern from an RC 3D Edge.  It looks cool.   I will post a sketch tomorrow and some alternates.  It is nice to be able to get feedback.

Ken

[Ken Culbertson]

Hinged the Flaps Friday.  Used undersized full span hinge wire.  They flop like cloth hinges.

Ken

[Scott Richlen]

I like the looks of those flaps with their cross-thatched ribs!  Even though the answer might be obvious, I'll ask anyway: what were your steps in building them?

[Ken Culbertson]

I like the looks of those flaps with their cross-thatched ribs!  Even though the answer might be obvious, I'll ask anyway: what were your steps in building them?

1/4" core with 1/16" x 1/4" caps on the LE recessed 1/16" to allow rounding.  1/8" CF strip centered on TE.  1/16" shims on underside of TE.  Cut out center except where the hinges go.  Crosshatch using 3/8" strips on 1" centers.  Sand "taper" from top of cap to top of CF TE.  Flaps are same length but the outboard has a 1/8" wider chord.

Since I don't have a workbench everything was build without a jig.  (First flight will be in an undisclosed location  ). Pretty simple with CA and glass.  The CA will sort of stick to glass and you have a defacto jig as soon as you glue the first "rib"  Pops right off with a single edge razor blade when you are done.

Ken

[Ken Culbertson]

Finally assembled.  Debating whether to MonoKote fuselage or paint.  Paint is a problem in the office so I am most likely going MonoKote - tomorrow.  Trim will be Rustoleum.  I have drawn up about 20 paint schemes, these are the remaining two.

ken

[Scott Richlen]

Ken:

I vote for the paint scheme on the right for its visibility (I am looking specifically at its side-view, the pilot doesn't see the top-view during flight.)  I think that it catches the eye better and would be easier to follow through the pattern.

[Matt Colan]

I like the right one as well

[Ken Culbertson]

I like the right one as well

The Right one wins - However, I reserve the right to adjust it during the masking.

Ken

PS:  This is more of a question to others out there that judge.  One thing I have noticed is that if the top wing pattern is different from the bottom pattern and there is enough offset from where the pilot does a maneuver and where I am standing I get the impression of a flat when the planes pattern changes.  It is especially noticeable to me in the loops and V8  I have videoed some that I thought were flats and played it back in slow motion and there was no flat, it was an optical illusion.  However, optical illusions are real when you only have less than 10 seconds to judge a maneuver.  I have always either left the bottom in base color (which in itself is a different pattern) or repeated most of the top pattern on the bottom.  This is the first time I plan to do a "reverse" color on the bottom.

Any thoughts?

Ken

[Scott Richlen]

I have not noticed that when I have judged.

[Ken Culbertson]

Finally Ready for test flights!  With 20oz of power related stuff and 1oz opening tip weight she weighs in at 59oz.  The logarithmic controls are really smooth. 3" of leadout travel gives me 45 degrees on the elevator.  From what I can measure it looks like I get 20 degrees flap at 20 degrees elevator and 30 degrees flap at 45 degrees elevator. The best of both worlds.  I am really looking forward to having tighter corners.  As far as I know, this will be the first logarithmic setup in the Dallas area.



It will be airborne by the end of September.  I almost had it finished for the Southwesterns which I had to miss anyway due to a Covid scare so I am skipping the pre finish test and getting the color on.  15' finish!

The little holes in the side of the fuselage are screwdriver holes to tighten the numerous parts of the controls.

Ken

[frank williams]

Ken
Nice looking plane,, you're gonna love it.
...... but, although Houston isn't really Dallas area, I too have been playing with a very similar setup to test the Igor Log.  Great minds think alike I guess.  See the attachment. 

I built this a couple of years ago, and due to some health problems, didn't get to test till this year.  I had some motor issues also, trying to be too cute by half.  Should have put an ST60 on to begin with, but that another story.

The bottom line is that, after flying it for just a little bit, I really began to feel that the Igor Log was real.  Smooth rounds and snappy corners that just jump out of nowhere.  I'd be interested to get your impressions.

I used a grooved roller bearing in a wire loop like it appears you did.  I kept the dimensions of the IgorLog mechanism.  I built mine from a Mobest kit (Griffin) and modded it with a longer tail and more tail area.  The MoBest wing is an excellent wing to start DIY designs from.

Good Looking Plane ... hope to see you all after the Covid.

Frank

[Crist Rigotti]

Frank,
You are scaring me using Quick Links!

[Ken Culbertson]

Frank,
You are scaring me using Quick Links!

It's OK, they are adjustable.

Ken

[Ken Culbertson]

Finally to the "Crying and Shouting" stage and getting plenty of both.  I am invoking the 10' rule.  Trying to finish, mask and paint this thing at my office has left it looking just slightly worse than my first monokote job 50 years ago.  However from 10' or soon to be, in the air I think it will shine.  The rest of the wing and the stab will get the same look.

Ken 

[Ken Culbertson]

More Crying, some shouting.  I think my love affair with checkerboard has hit a rough spot.  I may skip the elevator. One piece of advice to those who use Roberts Pockets - make sure the elevator is not upside down when you glue them in.

[Scott Richlen]

Ken:

Don't beat yourself up too much.  We all start with these great dreams and high hopes for our next great stuntship.  And then reality sets in: hanger rash, a slip of the knife, too enthusiastic sanding, etc.

I think it looks good!  Carry on!

[Ken Culbertson]

HI Ken. LOVE that scheme. I may even steal it for one of my profiles.  Slightly modified of coarse. Don't want to be too blatant..

You are welcome to it!  I can't remember where I stole it from.   It is intended to look good in the air.

Ken

[Ken Culbertson]

Nearing completion.  If the ESC(Spin 44) and Timer (Fiorotti) were programmed I could fly it today.  A few more trim do-dads AMA number and the name on the wing and it shifts from building to trimming.

Ken

[Ken Culbertson]

60 Oz, ready to fly!  Someday I will probably recover it if it flys as well as it should.  Building in my office was difficult.  Applying a finish was impossible.  But - here it is!  2 weeks after the contest it was built for

I have a question about flap area near the fuselage.  Because of the logarithmic setup, the inside flap had to be just over an inch from the fuselage.  Now that the design is finished I have rearranged some of the bolt patterns so that about 1/2" of that space can be recovered.  What I am curious about is will that have any noticeable effect?  I think not but, being MonoKoted, adding that 1/2" back would be easy.