DE (Cabin Mod) tail Modifications

[rfeenstra]

It fly's again!!

[MrG]

cant wait to hear how it fly compared to last time was it worth  it ?  
Had to of lost some drag and are the tail mods helping

[John Reinking]

Would you be able to post any information/drawings of the ply formers?

[rfeenstra]

only flown it a couple of times, so don't have a lot if info.  Initial impressions are that it is much more stable, less "tail wagging".  Remember that my original build extended the wing span by about 32".  I don't know how a DE built to plans flies.  It seems to find a very stable trimmed speed compared to how it used to be.  CG is actually farther back (about 31% cord) but yet more stable.  Not a Lot faster, maybe 5-7 mph.  The trim is effective to a lower speed as the tab is bigger but it is more sensitive at cruise speeds.  I was hoping to actually loose some weight given that I could take the lead out of the tail, but that didn't happen.  Actually added 15lbs.  Can't quite figure out where as my calculations said that I should have been the same to a couple of pounds lighter.  so far, though, happy!

[rfeenstra]

Flew it for nearly 1.5 hours this evening. Very happy!  Flew for nearly 45 min. hands off the stick - just using rudder.  Slight turbulence upsets it slightly but then quickly settles back down to trimmed attitude/airspeed.  A hard push or pull on the stick then releasing  gives maybe 2 or 3 oscillations then settles back into level flight.  Typical cruise used to be about 50 to 55, now 60 feels good at the same engine setting.  Elevator authority is very good even at idle.  I have to be careful because I stalled it a foot off the ground with engine at idle.  I'll have to change my landing procedure slightly.  Still windy in the cabin, of course.  Need doors!  Next project.

John, there are no drawings!  Everything was "design/build", "That Looks Good" engineering. I had the advantage of having a Champ derivative sitting right next to the build table.  The tail/formers are a copy with the necessary changes fit the desired dimensions.  Former shape was determined by using pieces of wood screwed together so that things could be moved as i determined the shape of the wood stringers.  When all was reasonably set (certainly not perfect - not that patient), the screwed together pieces were put on a piece of plywood with the stringer locations marked. Then the shape was drawn freehand.  Then it was filled with as many holes as I could justify while maintaining necessary strength. The added 26" to the tail was a calculated guesstimate of what would be necessary to get the CG where I wanted it.  Turns out to have been correct as I am at 29% of MAC empty, 31% with 200 lb pilot, 32% with pilot and full fuel (18 gal.), 33% with pilot, passenger and partial fuel.  The unfortunate part is that I gained more weight than hoped. 15 lbs over the old version with all of the lead.  My calculations, weighing, and hoping pointed to a similar or even slightly lower weight.  Obviously, my calculations were erroneous!

Got a new prop coming on Monday that will, hopefully, take better advantage of the low RPM 65 hp.  The prop I have now over revs by over 200 RPM.  Probably gives me more horse power on takeoff, but too low a power setting at desired cruise RPM.

[John Reinking]

Thanks.   Blue skies

[Tom H]

rfeenstra, that is one slick DE.  Get those doors on and you'll probably pick up a few more mph.

Regarding the tail wag of a plans-built DE (more or less), our DE Stubby does not have any tail wag.  It, too, flies well, hands off, on a calm day.

CG when I fly is about 28%, and we think a bit more aft would be good, but don't want to add any more weight.  Good to hear of results all the way back to 33%, though.

Great job!

[MrG]

it sounds like it work as it was supposed to - good news and thanks for sharing and feedback MrR
A hard push or pull on the stick then releasing  gives maybe 2 or 3 oscillations then settles back into level flight -
Thats really good and most RV's are like this good sign of a nice plane, Looks good and flies good "Double Bonus"
I dont get a lot of wag either - though i really can't fly hands off unless its a perfect day at cruise and its a lot of rudder work,
pitch attitude with power change is way more than a cub/skyfox
Mine is flown around 25.5 with just me in it and i like that - passenger i get 27.6 man you notice the difference on landing.

5 better than last fuse so far is a great bonus and about on par with what i thought you may end up with - waiting to
see if you do a 2 piece door or full
Wife has signed of on a new fuse but have to wait till Jan to start. to many other projects running i need to finish

@john we have 2 x J3 cubs here and been looking how they did there fues here are some fuse images i scoured of the net
if you look at the 2.jpg image dam looks like a cabin eagle fuse with modified tail, there is enough images and drawings in the zip file
to get enough info - as i choose to add weight to rear instead of chopping the nose - the new fuse will work with same over hange out front
and wont need all the lead i have up the back and get some of the empty weight down

Link to zipped images zip file

the Kitfox , skyfox and Gazelle  are similar but more of a box section rear of  rear spar to tail -
i figure the smoothed out look - is worth that little more effort Just have to see how MrR's turned out "Hot"
MrR Any chance i can get a measurement from leading edge to rear post - ill compare the length to the cub and your new length

[MrG]

MrR
One last Q, what are the stick forces compared to the previous set up, if correct they should be a bit lighter ?  

[rfeenstra]

LE to tail post is 174".  My fuse is still shorter than a champ which is way shorter than a cub.  Cubs are a long airplane.  A friend of mine is in the process of covering his Cub and I was amazed that the fuse is almost 21 feet long.

Got the new prop on it.  I can finally get full power out of the engine, though I can't quite get to red line of 2300 rpm.  Probably will have an inch of pitch removed this coming winter. I'm now cruising at 70 mph indicated at 2100 rpm.  Way too windy in there at that speed.  Doors are next!  Probably a full frame door with a removable window.  I like looking down past the wheel so I may use Lexan for the whole thing.  A bit heavy, but...

Stick forces on the elevator are lighter.  I dont have to pull so hard in the flare.  Ailerons, of course, are unchanged and heavy.  I may look into spades to better coordinate all of the stick forces.  The horn on the rudder is shorter so there is less rudder pedal travel and definitely more pressure.  I like the added feedback, and the reduced pedal travel.  Seems to work good.

All of the changes I've made to the tail are a result of the extended wingspan due to the cabin.  When you change one thing, many things need to be redesigned.  In all fairness to Leonard and his initial design,  My DE is no longer a DE!  I like what I've done, but it was a lot of work.  Had I stayed with Leonard's design in the first place, without the cabin, none of this would have been necessary.  it's just that here in Northern country, no doors is just plain cold at 3000 feet, even on an 80 degree day.  Hense the desire to include a cabin with door hinges prepared for.  Now to just build the doors.

[Dave Stroud]

Good on ya, Dude for the nice work and even more for sharing real time info on how it comes out. You are venturing into areas where most won't head....Thanks...

[rfeenstra]

Thanks.  I thought this would be a good project to practice on before I start working on the 7GC I was using as a model for this project.  I have to do a major mod to the fuse on the 7GC in order to make it qualify as an experimental.  The mods will make it necessary to design all new formers and stringers.  I know I can do it now!

[MrG]

i Agree 100% if i started 6 months later i would of done a cabin, I looked at doing this but i wanted to go flying and pushed it to first flight in 18 months, also running a business 
My daughter made this happen to - I flew 3 weeks ago looking at logs 149 nm each way - i was at 5500ft about minis 5C  (23f) - that made me think and wife wont get in when cold
Mate said to me, only one way to stay in aviation is involve the wife, she been in a Aronica Chap why we were @ Taylor TX last year  and loved it - so she told me no cabin no ride.  

The info you supplied is awesome and sealed the deal - plus the wife thinks now yours looks like a plane   Its that mental thing too with her
i can get 64 knts @ 2100 i think thats 74 mph so you should do better with doors - i have spent so much time trying to reduce drag, even the 1/2 doors on mine made a difference
i do get 3300/3350 staring and level full throttle - plus mine is not a stumpy - running Franks Prop 

If i did my DE as a center stick and full bench seat - i would be happy your in behind the screen - but im happy to sit in it for 4 hrs and go somewhere, but have to make the boss happy too 
Thanks again for al the info MrR - I did not measure length of the cub yet so may not have to go as long as i thought - great work  
Talking with the regulators here now what we going to do when i do changes - New plane or just a fuse mod ? 

[MrG]

@rfeenstra one more Q
That looks like the tail of the champ, did you use same specs as your 7GC or scaled it ?

[rfeenstra]

It is somewhat copied. It is scaled down a bit and I added a little aerodynamic balancing on the elevator. The way the stab is mounted and the elevator control horn are copied from the Champ.