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Author Topic: Turbo Cessna 195 Indoor Nocal Short kit from Volare Products  (Read 2821 times)
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tross
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« Reply #25 on: December 25, 2016, 09:59:50 AM »

I really like this Don (and George!) Grin
Thanks for explaining it in detail.
Always thought there was more to it and now I know for sure. Shocked
I need to stock on some stuff and will probably add this to the order.
Hope it's in stock! Grin Cheesy Smiley Grin

TR
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« Reply #26 on: December 26, 2016, 12:21:17 PM »

Thank you, Don for the great build write-up on this model!

This all started when I was designing and building my prototype and I emailed Don asking a series of specific questions about building an Indoor middle-sized NoCal.  Some of you may remember Don's Indoor NoCal web page.  He identified 3 different sizes of NoCals, basically huge ones (like the Holser Fury), ultra-light ones (2 or 3 grams in weight), and a size in between - under 6 grams and about 50 square inches of area.  As I laid out this model in the plan, I saw it would be a 16" fuselage and a 56 square in wing.  I thought maybe I could build my own to approach 6 grams.

I was afraid that my plane would come out heavy at 8 grams, but it came in right at 6 grams.  Given his advice, I tested my model and easily broke 2 minutes with only minor adjustments.  I believe my model is a) a little too heavy and b) has a prop that is too big.   I use blades that were wider than what Don recommended (I built it before he suggested a size).  I am building a new prop with narrower blades and which will be lighter.  This will accomplish two things.  The narrower prop will fly the model better and allow me to use a narrower motor.  And the assembly will be lighter, making my tail heavier and fixing the nose-heavy state without adding weight (at least, I hope so).  Also, a narrower motor is a lighter motor, therefore I am lessening the weight in two ways.  I am thinking I can extend my 2 minute test flight, maybe getting to well over 3 minutes.  Here is a video of my test - https://www.youtube.com/watch?v=FvuOIsQ6SzM

You can see the model never really climbed and ended with too many turns remaining.  This shows nose heavy (not climbing) and prop blades that are too wide (not using the motor effectively).

Don gave me great tips and I asked if he would like a laser-cut short kit to build and test and he said "sure".  I integrated some of his tips into the wood that I sent and what is shown above it the results of his experience with the prototype short kit.   I sent him prop blades that were narrower and that is what he shows above.  The thing that really surprised me out of all of my communication with Don (and reading this thread) is this:  I am not that far away from building competitive models in this "class".  The wood sizes are something I am comfortable with - it is all 1/16" wood, except the 1/32" prop blades - I didn't have to use super-light structures or technique.  The biggest "secret" to this was the propeller - I am used to outdoor props and they don't work to obtain high flight times on indoor models (I have obtained 2:25 on a Blatter 40 with a Sleek Streek prop, but I think that is approaching a maximum expectation from an outdoor prop).

As for the short kit, I will make each one from SELECT balsa.  I am weighing all of my 1/16" sheet stock and will only use sheets that weigh 12 grams or less for this model.  That works out to be about 6.7 pound wood (or less).  This will match Don's requirements and provide everyone with "good wood".  As for availability, I make all my kits in small batches and/or on demand.  This kit is ready to go (includes plan with notes, and laser cut wood for body and prop).

I am really looking forward to pushing my limits and the limits of this plane this winter.  I've never been able to approach 3 minutes indoors and I am hoping this plane takes me past that mark and beyond, maybe even to 4 minutes!


--george
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dslusarc
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« Reply #27 on: December 26, 2016, 12:48:28 PM »

Before your first test flight here are a few things to check for.

1) Looking towards the front of the model, make sure the inside wing (model's right wing or the left wing looking at the photo) has no washin or washout.

2) The outside wing (model's left wing or the right wing in the photo) must have 1/16" washout

3) From the top view, make sure you have sufficient right thrust

4) From the top view, make sure the rudder is offset 1/16" to the right.


Make a loop of 3/32" rubber ~18" inches long. I used a 19" loop of .095" rubber as a I have a rubber stripper. 3/32" rubber is around .093" wide so start with 18" since it is a slightly thinner.


For my first test flight I wound 1000 turns in the loop to see what it would do. The model circled right just fine but was stalling about every 10-15 feet of forward flight. With this trim setup a stall looks a little different then what you may be use to. The inside wing raises up then the nose goes up some and the model skids then the right wing stalls and drops, it is not your normal classic stall, it does this because the left wing has washout and the right wing does not. So I added a little clay to the nose and tried again. This time it was much better the stall was almost gone so added a little more clay and the stall went away completely. You want just enough clay to keep the stall away. Now wind it up a little more say 1300 turns and see how it goes, the model should climb out nicely like shown in my videos. If as the model is coming down the last 10 feet or so you see the stall starting to come back or the right wing rocking up and down then either add a small dab of clay (about a 3/32" diameter ball) to the nose but also check to make sure there is no washin on the inside wing. Sometimes a little washin will creep in and that will make the right tip stall late in the flight. If there is washin remove it first instead of adding the nose weight.

My model with the added nose weight shown in the photo came out to 4.9 grams.

The incidence angles built into the plane are correct so there should be no need to adjust any wing or tail incidence. Just the CG location with ballast. If you model happens to be nose heavy, do not reduce incidence, instead add a little bit of clay to the tail. Nocals need a certain fixed amount of incidence to fly so stalling or diving has to be corrected with CG location (provided the plane is relatively warp free and built to the plan).

One thing to note is that more rubber is in front of the CG than behind it. The loop I use is 2.4 grams. So as the rubber loop gets longer, I can start to remove some of the nose ballast I have. I am expecting a loop about 22" long (about 2.8 grams) when flying in West Baden in a few months (98 feet high) so that extra rubber weight will require some of the nose weight to be removed. This is something to be aware of if your flying in varying ceiling heights and have variation in motor weight.

The last two flight videos I was winding to 1750 turns and backing off 250 turns to remove the high torque so was launching with 1500 winds in the motor. So I was flying on the middle of the rubber torque curve. Average RPM is around 340 so that means 4 minutes needs 1360 used turns and 5 minutes needs 1700 used turns. In March I will be at the EAA contest which has about a 45 foot ceiling. I will fly on the same rubber as I did in the gym but will be able to climb higher so I think 4 minutes will be attainable at that site. When I go to West Baden I am expecting 5 minutes. I will keep taking videos as I go from contest to contest.    

Once you build this plane and are comfortable with trying to go a step or two further. I plan on doing a light build of this model. Before I do that, there are some easy ways to drop more weight off this model with not much additional effort. I will do a more detailed break down of the weights and where weight savings can be taken.

Don
    
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dslusarc
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« Reply #28 on: December 26, 2016, 01:41:06 PM »

Thank you, Don for the great build write-up on this model!


George,

Glad to do it. Hopefully this will help more people get into indoor Nocal!

Don
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« Reply #29 on: December 26, 2016, 05:05:53 PM »

Something I added to the parts, specifically the prop blades - I added 15 degree index marks, but they are not directly on the blade.  If you notice on Don's prop forming photo, he has marked the cylinder with a 15degree line and has indexed the prop centerline.  Of course, this requires laying out an angle on the cylinder.

http://www.hippocketaeronautics.com/hpa_forum/index.php?action=dlattach;topic=21522.0;attach=159811;image

It might be easier for someone to mark a vertical line on the cylinder, rather than this 15 degree angle.  if so, then they can use these laser-cut index marks.  Because marking balsa in the laser is actually burning away wood, I kept these marks off the prop blank.  If you mark the VERTICAL line, then you can align my laser marks with that vertical line and get the blades set properly.  Here are steps to accomplish that:

1.  Note the witness marks on the sheet for the blades (green lines point to them):
http://www.volareproducts.com/files/images/Props1.jpg

2.  remove ONE blade and lay it drectly over the other and use a fine point pen to mark the second blade:
http://www.volareproducts.com/files/images/Props2.jpg

3. remove the second blade and stack them again, carefully aligning them.  Transfer the first marks to the second blade.
http://www.volareproducts.com/files/images/Props3.jpg

Now you can use these marks to line up on the vertical line on your cylinder.  Be sure the blade blank angles to the left, not to the right - make their positions just the same as Don's photo.

I hope this will help someone.

--george

Turbo Cessna 195 Indoor Nocal Short kit from Volare Products
Turbo Cessna 195 Indoor Nocal Short kit from Volare Products
Turbo Cessna 195 Indoor Nocal Short kit from Volare Products
Turbo Cessna 195 Indoor Nocal Short kit from Volare Products
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« Reply #30 on: December 26, 2016, 05:40:46 PM »

Excellent idea!
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« Reply #31 on: December 29, 2016, 10:02:31 PM »

Wow, great stuff!  Many thanks Don for the detailed instructions.  Well done George!
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« Reply #32 on: January 11, 2017, 10:13:25 AM »

I built a second one.  I used light wood, duco, followed Don's guidelines, and used the specified prop.  My first one was 6 grams.  Testing will take place tomorrow.

--george
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« Reply #33 on: January 13, 2017, 02:27:02 PM »

my report is that I used out-of-the-box 3/32" rubber and got a 3:49 flight.  This is my best indoor flight ever by over a minute.  post flight analysis:

1) I was overpowering the model - a 20" loop with 1500 turns was starting off with a severe right turn and even pulling the plane down until some of that torque burned off.  Don recommends 0.080" rubber or so next time.

2) the plane had a tendency to stall, especially in the last half of the cruise portion of flight - it would look like it was climbing fine, then after half a circuit or so, the left wing would drop and the model would recover - rinse and repeat.  Don says this is a symptom of a slightly tail heavy condition and to try adding the smallest of nose weight to trim it out.

3) also, the plane was very sensitive to any changes, weight, thrust, elevator - again, a indication that it need a slight bit of nose weight.

However, even as frustrating as the flight was, it was encouraging, since it is my goal to reach 4 minutes with this plane and I am right on the cusp of that.

That was my intent with this model and short kit - to create a package that any modeler that can build an embryo or peanut could build - and that would be capable of indoor-type performance.  I must give credit to Don - it was his advice on the propeller specs that make this happen.  He confirmed that the design was on the right path and gave great additional advice on the motor stick and use of lighter wood.

You, too, can do this!

(no photos or video of the flight since, apparently, I can't do two things at once, even though I tried!)

--george
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« Reply #34 on: January 17, 2017, 10:47:12 AM »

Don and George,

I built this model from your kit and got a 2:15 flight on the very first day out.  Looks and flies fantastic!!!! We fly in a gym with 22' ceiling and we live at 4740 ft elevation.  I have compiled my own flight and build notes which I will pass on FWIW.

First off, to both of you:
 
Congratulations on a fabulous concept: beginner NoCal.  The tips from Don S. were like a Rosetta stone.  With accurate parts and good wood, mine went together in about 3 days.  I have a friend who is much more of a newbie than me, and he also bought a kit.  He hasn't started his yet.  I found a few things that would have caused him a lot of frustration without help from an experienced NoCal person.  I am going to give you my thoughts for whatever it is worth.  I mean no disrespect by mentioning this stuff: I'd like to see a few more flyers at the gym, and give the beginners the best possible chance of success.  Beginners really gravitate to the laser cut stuff.  My buddy is strapped for time, and just having parts that fit without making templates etc etc is exactly his cup of tea.  But it is hard when the trimming process takes more than 2 or 3 flights, and they have followed the plan exactly...
 
Flying notes:   (Maybe this should read: “high altitude flying notes”…….)
 
The first 6 or 8 flights were not encouraging.  I live at 4740 ft elevation, and we have a 22 ft ceiling gym.  I elected to start with a 19" loop of 3/32 for a motor.  Beginners won't have a stripper, so this is a likely motor.  It was stalling and flying mostly straight ahead.  My beginner friend could not believe I was having so much trouble, me an "expert".  (to him maybe-he is a beginner).  It was balanced exactly per plan.  I've built 6 NoCals from plans before and never had problems like this.
 
1.    CG  Due to forward sweep of the wing, the CG shown on the plan is at 41% MAC.  That is really far aft for a conventional model with no lifting tail.  I could have figured it wrong, so check me, but that is what I got.  I had to put .65 gm of clay on the nose of mine, after I had balanced it per plan, in order to stop the stally wandering behavior.  This put the CG 1/4" ahead of the point shown on the plan.   I kept adding clay until it began to behave and ended up at 32% MAC and (see video) it flew fantastic once I got there.  25% MAC would be a full 1/2" ahead of the point indicated on the plan.  The farthest aft you can get it to fly is the place to put it to reduce the trim drag.  BTW with the CG at 32% MAC I don't get the late flight stalling phenomenon.
 
2.    Downthrust  The CG was easy to fix.  The downthrust not so easy.  For indoor, low ceiling flights with weenie motors, i.e. 3/32" loops, downthrust (IMHO) is not required.  Maybe it's the altitude??? Further, on long noses like this one, it is so effective, it will prevent climbing.  I bent out about half at the prop hanger, but if building again, I would use zero downthrust, and put the stick along the longitudinal axis.  Maybe a half degree, for the high wing.  For big motors, outside, 90 ft ceilings, maybe you need it.  My model, once I got the CG fwd to where it is stable, would not climb, just shallow speedy descent to the floor in about 1 to 2 circles.
 
3.    Decalage  With the CG at 32% MAC (plus downthrust) I needed (as you would guess) two huge paper (up elevator) tabs to get it to climb.  I use Avery sticky labels.  Then it flew great and I got the 2:15.  When I got home I pulled off the tabs and cut the "elevators" loose and bent each one up 1/16".  We'll see how that works.    I'd say it needs another degree at least to work with the CG at 32% MAC and more for 25% MAC Center of Gravity.  Maybe not, if no downthrust.
 
4.  Motor   After starting with a 3/32" motor loop 19" long, I steadily shortened the motor until it would almost hit the ceiling, and land with only 100 to 150 turns left.  Initially it was only getting about 12' high, flying very fast, and landing with 500 turns left.  Cut and re-tie motor....try.  repeat.  At the end of 2 hours, I was flying it at 1150 to 1200 turns on a 14" loop, and my best flight was 2:15.  Quite encouraged.  Now that it is a half gram lighter* (total wt of airframe with prop and nose clay=5.1 gm) , I will start over with a 17” motor (making the total model weight the same as before) then back off the torque to stay out of the rafters.  This plane/prop/motor has an incredible "cruise" phase.  It just won't come down and the prop slows the unwinding and limits RPM to really make for long flights.  I've never used longer than 6" props on NoCals, and this is a breakthrough for me.
 
 
Build Notes:
 
Don did a masterful log and it really helped.  A couple of things didn't work very well, and I (having some Cessna blood in me, actually no, not blood, I own a '53 180....) had to tweak some appearance items to suit my personal taste.
 
1.        Not much is said about the single center rib.  You have to tilt it.  You have to glue it to one wing or the other.  Then you have to gob a bunch of glue on the centerline to get a shaky butt joint so the right and left wing halves to hold together so you can go spray the frame with 3M77.   The 3M77 method is a HUGE time and frustration saver.   I made a couple of "bow tie" splints to tack glue left and right LEs and TEs together, giving me a single wing.  then after covering, I cut them off and this left the root ends of the LE/TE un hardened by glue, and easy to prep for the angle cuts.  To tilt the center rib accurately, I made a full size dihedral layout, then half-angle template then cut two angle braces from the foam insert in the kit.  I pinned these down over the plan. To these I pinned the lone center rib, gluing it to the left wing only.  I also put a temporary 1/16 square "rib" in the root end of the right wing to keep the LE and TE under control.  After covering I nipped it off and removed it.  Slitting the tissue to allow the dihedral is, is genius.  Thanks Don!!!
 
2.      Speaking of dihedral.  The 195 and all high wing Cessnas have very little, as you know.  The 2" just really didn't sit right.  It is more than some low wing NoCals I have flown successfully.   So I built mine with 1.5" and  still flies great.  Looks a little more authentic.  It is less sensitive to rudder and side thrust, as you would imagine.  takes more of each to get the desired turn.  See video.  It also flies great with 2" per your and don's videos.
 
3.     Landing gear.  I was afraid to put the supplied gear legs on it, and finally decided to make the gear more scale and have them exit the "fuselage" at the scale location and attach to the wheel in a more scale appearing way.  I think the tiny bit of extra work required to make this pass visual muster is worth it, and it results in a gear that wont snap off or wobble when you set the plane down on the table.  This adds weight, but the plane is still very light.  My landing gear forms a letter “A” and the short horizontal spreader piece is glued to the bottom of the lower longeron.  this is light and sturdy.  If doing it over, I would shorten both legs by 1/8”.  You must remove the tissue over the balsa gusset to get a good joint for the left leg.  It turned out more like a 180 gear than the more squat 195.
 
*4.    Weighty tail.  The .65 gm of clay on the nose really bothered me.  Over 10 % of the plane's weight in the form of clay.  So I put the tail on a diet.  I nipped off and removed all the ribs in the horizontal and vertical stabs.  I did the same to the aft most 3 diagonals in the fuselage.  I almost cut off the tailwheel, but nah, it really adds to the character.  I sanded the tail surface frames until they were barely over 1/32" thick.  I even whittled on the aft end of the motor stick as much as I dared.  It is oversized for 3/32 motors, but it does twist under full torque.  With these mods I could take off all but .12 gm of the clay and still balanced at .32% MAC.  Perfect.  The covered tail surfaces, even with all the material removed are still plenty stout.   I was sanding on them quite vigorously with a padded abrasive nail file.  But I had the plane propped up and a book under the surface to support it. Can't wait to try it.
 
5.   Prop jig didn't want to work because of all the undercamber in the blades.  Had to cut 1/8" off the face of the angled support to co-locate the blade with the hub.  I could have shifted my prop shaft UP to get the same effect, but my shaft already had the hook on it and that wouldn’t work.  I used a 4" can to form blades.  I "penciled" (tapered) the outer 1 inch of both ends of the bamboo hub, and enlarged the slots in the blades to matching tapers.  The performance of this prop is incredible.
 
Great, fantastic, masterful design, perfect wood selection and laser cutting.  totally awesome, putting the master Don S on the task and he can't be thanked enough for the detail and eloquence of his writeup.  Those photos!!! Thank you thank you thank you!!!!!
 
https://drive.google.com/file/d/0Bzjf1qWtwGc6aDhJUWp4bklFanM/view?ts=587bef8f
 
Steve
 

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« Reply #35 on: January 17, 2017, 12:17:18 PM »

A question for George: What is the ceiling in the space where you got your 3:45 flight?  That is an amazing time for a kit plane!!

To keep it real, I am going to keep trying with out of box rubber (3/32) to see what the best I can do will be.

This has been really enjoyable.  Thanks for finding the needle in a haystack (Turbo C-195, really?), one of my all time favorite airplanes, modified perfectly for a NoCal subject, and making it into such a cool kit.
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« Reply #36 on: January 17, 2017, 12:55:36 PM »

Here's my A-frame LG.  And that video link is permission limited.  I'll get a better one, just so you can see how it does at 4740 elevation, 22 ft ceiling, with 1.5" dihedral at 32% MAC for CG.
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« Reply #37 on: January 17, 2017, 01:06:50 PM »

One last photo and I will shut up.

My wing jointery described in previous post.  Not required, but helped me get it done.

"bowtie" splints tacked with two dots of glue, and temp rib (with red sharpie marks on it)
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« Reply #38 on: January 17, 2017, 01:21:03 PM »

What a great write-up!  Thank you and I hope this kit is everything you expected.

I am wondering if your CG issues are partially altitude related.  Don says the specs re really good - I think he was talking maybe 0.1 or 0.2g of nose weight to be added.  It seems to me that your up elevator and up thrust requirements are a result of the added nose weight.

Having said that, my last flights were frustrating with the tail heavy condition.  Maybe, it needs to be somewhere in between.

For my flights, here is a photo of our facility.

http://www.volareproducts.com/pics/PontiacIndoor.jpg

It is a full sized soccer field, with bleachers on one side.  I think the sides are 40 feet and the center is 70 feet.  My flight might have gotten above the 40' mark - it's really hard to estimate when standing in the middle.  Note that Don exceeded 3 minutes in a 24' gym.

--george

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« Reply #39 on: January 17, 2017, 05:56:42 PM »

Wow, what a great facility!!! Envious!

I had a terrible feeling that I had used the wrong graphical method to determine the Mean Aerodynamic Chord, which I did, but surprisingly the numbers did not change when I did it the right way.  The forward sweep of the wing makes the CG position at the root much more aft than it appears.

The plan shows the CG at 40% MAC.  That is quite a bit aft of all my other NoCals, which average 25 %.  I fly them for fun, and perhaps they are not competitive at 25% MAC, or you need to move it aft to win contests, but I could not get the stall and divergence to go away until I moved it up to where it is now, which is 34%.  Twenty five percent MAC is slam dunk easy and stable in pitch, but perhaps not as thrifty on energy usage as further back.  All I know about downthrust is that I don't have any in my other NoCals, but I only fly them in low ceiling sites, with smallish motors, and 6" props.  I admit I do not understand what if any effect altitude has on pitch stability vs CG, but I know my rubber models fly much better (longer with lower propeller RPM) in Boise  (2700 ft elev)than they do in Idaho Falls (4740 ft elev.)

It's all good and I really appreciate the kit and all the effort you and Don put in, to make it possible.  I doubt I'll break 3 minutes in our gym, but you never know!!!!!

Steve
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« Reply #40 on: January 17, 2017, 08:11:15 PM »

Steve,
Thank you for your report on how the No-Cal worked for you.  Actually I think you would have had success with less trouble if you had delayed making changes to the kit model because it had been designed  and developed by two of the best aero modellers in the country.  I have not seen a kit or the plan so I cannot respond in detail to your report but there are a few points I think require comment.
I should be interested to know how you estimated the mean chord because it was mentioned quite often and I know that the common method in many aeromodelling books does not give a correct answer.
Your first comment on flying was that the model flew straight ahead and was stalling.  You ‘corrected’ this by moving the cg forward.  I think this started most of your problems.  If a model is stalling and flying straight ahead I think the first thing to do is to make the model turn.  Don was clear about the initial settings; washout on the port wing, right sidethrust and right rudder. I suspect you did not have the correct amount of some or all of these to give a smooth level turn. 
The cg position given on the plan is not a long way back for a rubber duration model and the cg is not moved ‘even further back to reduce the trim drag’ but may very likely be moved further back to control variations in propeller thrust as the motor unwinds.
I wish you well in your ambition to do some high times and I am sure you will succeed.  It is obvious that you have learned the first rule of successful Indoor flying, which is to keep records of what you do and your willingness to modify things as necessary (as with your weight reduction in the tail) will stand you in good stead.
John
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« Reply #41 on: January 17, 2017, 11:24:20 PM »

Steve,

Glad to see the videos of the model flying successfully. Your comments on the CG got me thinking to where my actual CG location is located at. To keep things simple, I am going to reference the CG location from front of the leading edge spar as that is a position I think most can easily replicate as most are not familiar with CG location being expressed as a percentage of MAC :-)

So looking at the plans I measure the CG at 38mm from the front of the leading edge. My model less rubber balances at 36mm from the leading edge, and with the rubber it balances at 32mm from the front of the leading edge. I actually never checked the CG location because I setup Nocals a different way than I do other indoor duration models. On nocals I build in a fixed amount of wing and tail incidence. Typically the value is around 2-3 degrees total. Then I add nose weight until the model stops stalling. I do it this way due to the shorter tail moment and lower tail volumes of this type of model compared to other indoor duration models, going less incidence and closer to neutral point makes them next to impossible to trim. The 2-3 degree value is solely based on experience with Nocals, Low wings I have more (like 3-4 degrees, high wings lower around 2-3 degrees).

When George sent me his plan he already had a good value built in so I made no changes. So when I test flew my model the first day. I had a similar flight pattern, it was OK for about the first half then stalled as it was coming down so I added .1 gram to the nose and test flew again. Now instead of stalling every 15 seconds or so, it stalled about once a lap, so I added .1gr more and it went away. I like the nocals to fly just a little faster than stall speed on the way down. That is why I go in small nose weight changes. Too close to stall and it can mush reducing time, too nose down it also looses time. If the model dived on me instead of stalling I would slowly add tail weight until it stalled, then go back one iteration to prevent the stall. So my nocal trimming method is to keep the wing and stab incidence fixed and adjust the CG to get it to cruise and descend correctly. Then down thrust mainly for controlling the climb. Typically with the fixed incidence system I usually end up with a little down thrust to hold the nose down at higher torque levels. Watching your video it looked pretty good to me just at the very end it seemed a little nose heavy, I probably would have taken about a 1/8" ball of clay off the nose and flew again to see. However if running more incidence (which I think you said you had added up elevator trim) then a forward CG can make them look a little nose heavy at the end of the flight.  

In regards to the single center rib. This is something I have done so many times it is second nature to me so makes sense when I do it but it does need some further explaining. I do glue the rib so that the spar butt joint is right next to one side of the rib. Which side does not matter to me as long as the butt joint is on the same side of the rib. I do just butt joint the spars together with enough glue to hold the wing in one piece flat so it can be handled for covering. That joint can come loose when handling but I am just aware of it so I make sure not to grab it there. I guess I am just use to it. When I add the dihedral there is a gap on the lower side of the spar (see attached photo) and I either put a small wedge of wood into it, or a dab of Duco straight from the tube to fill the gap. Again another thing I do without thinking :-)

Lightening up the tail is a good way to reduce overall weight. The ratio of nose weight to tail weight is about 1.5 to 1 based on the moment arms. So reducing .2 grams from the tail surfaces means removing 1.5*.2 = .3 grams from the nose required to counter balance that .2 grams. That means reducing .2 grams off the tail actually makes the model .2+.3 = .5 grams lighter!

On that topic. There are multiple ways to reduce weight on this model I have been meaning to mention.
1. Bent or laminated strip on the tail and stab outlines. Two strips of 1/32 x 1/16 laminated would be plenty strong enough for the outlines. Another option would be to use the stock laser cut parts then after gluing the outline, carefully removing about half the material so the outline is around 1/16" sq instead of 1/16" x 1/8".
2. Replace all the diagonal strip wood in the fuselage with 1/32 x 1/16 strip, this will reduce the weight of those pieces by one half.  
3. The motor stick is overbuilt as I have shown in my build but too strong is better than too weak for a Nocal newcomer. A stick from 3/16" thick instead could be used as well as thinned a little more on the ends. As the model weight lowers the rubber size will be smaller so the stick does not have to be so strong. Also using lighter wood around 5.5 # density will help as well.
4. Wing ribs can be sliced from lighter density wood around 5# density and or from 1/20th sheet.
5. Sanding the prop blades thinner to .025" thick will reduce the weight of the blades by 20%
6. Replace the bamboo prop spar with hard 3/32" sq balsa that is rounded, it will be lighter than the bamboo. However if your model needs nose weight to fly then no point in reducing prop weight. Only reduce prop weight if the model needs tail weight.

These changes should get this design in the 4 gram range. Reducing weight is kind of an all or nothing type of thing. A 4 gram model needs less rubber than a 5 gram model so the entire strength of the model can be "weaker" as the whole model is lighter. You do not want to use a motor stick sized for a 4 gram model on a 6 gram model. The idea is to make it strong enough for the weight it is being built to. Sometimes it is a leap of faith when doing it to all parts of the plane, especially the first time but it is fun to experiment with. I do plan on building a light version of this model using typical indoor techniques and plan on posting photos as I do that build.  


Don
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« Reply #42 on: January 18, 2017, 02:27:34 AM »

Don,

I could not get the video to play, so good if you were able to see it.  Those banners and obstacles hanging from the ceiling are maddening, but they put them up there without asking me!!!!

I was afraid my comments would ruffle some feathers, but in my excitement over the model, I just kind of shot from the hip while it was fresh.    Thanks for sharing your knowledge, and thanks for so patiently addressing all the concerns I put into my post.

I mentioned Mean Aerodynamic Chord MAC because the forward sweep of the 195 makes it almost impossible to correlate CG at the root rib with more typical planforms.  I used a simple graphical method to determine that the MAC for the 195 NoCal is the section very close to half way to the wingtip.  I don't have access to any more sophisticated methods so that is what I used.  I don't have the drawing in front of me (out in the shop) or I'd give you more precise measurements.  What I do know for sure is that I added clay until the flight (circling in about 30 to 40 ft circle) stopped doing the stall followed by left wallow, that you described earlier.  As soon as that happened I checked it and it was 1/4" fwd of plan, in the flying configuration, motor, prop, everything.  Hey wait a minute: you indicate that yours in same configuration balances at 32 mm vs 38 on plan.  That's 6 mm and that's 1/4 inch in my book.  Maybe I am not getting dementia after all.   It's all meaningless, please just tell me how to get 3 minutes in my gym. Cheesy  But I did require substantial up elevator trim at that CG, and I'm still holding stock in the elevation theory.  My air density is less than yours.   It takes more AOA to get the lift up here.  I think my prop RPM average based on used turns, is about 475 on 3/32 motor.  Seems like that is higher than what you mentioned you had for your model.  Thin air.  I had some similar thoughts about building a really light model of the T-195, but that would not be kosher, or applicable to beginners or the kit that you and George have created.  But with that long nose and clipped wing, it is so perfect a subject, what the heck, it needs to be done!

Regards,
Steve
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« Reply #43 on: February 09, 2017, 07:28:08 PM »

Ok, this is likely my final report on my Turbo Cessna 195 NoCal.  I flew it again today.  I will report in two sections:  a short story and a long story:

the Short:  THIS PLANE IS A WINNER!!!* (* - well, the combo of the plane and listening to Coach Don S)

the Long:

Coming out of last month, I explained my situation to Don and he suggested the following:

1) somewhere between 0.1 and 0.2 g of noseweight
2) replace the 0.092" rubber with 0.080" (up to 2700 turns)
3) add some braces to the wing LE & TE to stiffen them up (I glued on 6" slices of 1/32" sheet to the LE and TE on both sides)

I did that and went flying today.  I had a test flight and felt the 0.17g noseweight I added was too much, so I took off about 1/3rd of that - that's an estimate - I haven't weighed what remains on the model.  For my next flight, I wound to about 2100 turns and put in a 4:19 flight!  I achieved my goal for this plane, just like that! 

I wound again and called for a time.  I launched with about 2200 turns and recorded my first official over 4 minutes:  a 4:21 (only 2 seconds more than the previous flight).

I set it aside to give my motor a rest and to fly some other planes.  My flying buddy, Winn Moore, had built one of these and he tested his - he started with 3/32 rubber which is what he had known from last month.  I told him that I was using 0.080" and he found some in his box and loaded it up and I timed him for a 4:31 flight!   Whereas, I only needed two flights last month, it was clear I would need all three of my flights this month. 

My second official was like this:  I wound to 2400 (gradually approaching the number Don told me, but the motor was feeling tight).  The flight was a 5:17!  I broke what I did not think was possible for me - a 5 minute flight.

By the time I tried my third flight, Winn already recorded 3 - they were all over 4 minutes, so I knew I would need a good flight.  I was going to try to get 2500 out of the motor - but it broke!  Time was running out for the flying session (these long flights take a lot of time!) so I decided to tie the broken motor.  It had broken close to the end, so there was a pretty long section left.  It came out to be 17", just 2" shorter than the 19" loop I stared with.  In order to conserve the motor, I stopped winding at 2000 turns - much less than before, but I didn't know what it could take.

My third flight - with this old and repaired motor - was 4:52.  My three flights totaled 870 and Winn's three flights totaled 780 - I beat him by 90 seconds.

Here are my exact flights:

~2200 turns, 4:21, ~600 turns left
~2400 turns, 5:17, ~ 650 turns left
~2000 turns (shorter motor), 4:52, ~400 turns left

My flights, backed up by Winn's flights PROVE this plane and the most-knowledgeable advice provided by Don Slusarczyk.  Within the past month, this plane has met and exceeded my expectations.  Before this plane, my best indoor flight was somewhere around 2:30-2:40.  This plane gave me 3 Minutes, then 4 Minutes, and then and unexpected 5 MINUTES!  By the way, these flights used all the available vertical space at Pontiac - about 70 feet high in the center.  Winn had a couple of touches on girders and wires, but I don't think I had a single touch today.

We have developed a kit that can EASILY be built to spec and will easily fly over 4 minutes - even more.  Don said that my plane should fly over 5 minutes at Pontiac - and he was right. 

oh happy day!

--george

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« Reply #44 on: February 09, 2017, 11:29:35 PM »

George,

Just got home and read your report.

Congratulations on 5 minutes! That is an indoor free flight milestone. Well done!

Don



 
 
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« Reply #45 on: February 10, 2017, 09:11:18 AM »

George I have to ask: Are you flying this outdoors? I would never risk loosing such a great indoor flyer by going outside. CONGRATULATIONS ON THE ACHIEVEMENT.

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« Reply #46 on: February 10, 2017, 09:13:29 AM »

Allen,

No, I will not fly #2 outdoors, but #1 -the 6 gram initial prototype, I might just fly that outdoors.  I'm sure it will thermal away!

--george
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« Reply #47 on: February 11, 2017, 07:15:36 AM »

Great work.

Scott
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« Reply #48 on: March 13, 2017, 07:13:49 PM »

Here is my dad and his new Cessna nocal. Test flew it yesterday. He used lighter ~4# wood for the parts except the wing spars, he used 6#. Hollow rolled balsa tube fuselage and tail boom. I weighed it after he flew it and it was 2.97 grams. The first test flight was a loose right circle, I noticed there was no right rudder so that was added in then he flew it again and model flew great, even hit the basketball net and pulled right out. He had a 20" loop of ~.074 rubber if I recall correctly. Flight time was 3:05. I convinced him to put it away since it was flying great and we have a few contests coming up and I did not want to see it get broken messing around in the gym.

Don
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« Reply #49 on: March 13, 2017, 11:35:15 PM »

Don,

That is fantastic.  What a lightweight!  Your dad must be a magician to get that weight.  (No wonder the CGS Hawk was so revolutionary....) for my lightweight effort version, I used rolled tube motor stick and minimal formed outlines for tail surface and still ended up at 4.2 grams.  I thinned my prop down to just .7 grams, and that brought about a bunch of clay on the nose, so I shortened the aft end of motor stick until the aft rubber hook  is just aft of the wing TE.  that allowed some of the nose weight to go.  I am pretty sure all my wood was about 6.5 lb.  Since it was still pretty light, I decided on a whim to try a 10x16 prop and it flies OK on .085 x 16" loop, but above 1250 turns, it will just nose up and do one nearly full stop stall after launch, then either resume flying normally or flip on its back.  Below 1250 it is OK, but does not climb to the ceiling, so far.  A  longer loop of .085 won't climb above about 10' because of the weight I suppose.  Still experimenting and highest time so far 2:34 in 24' ceiling at 4740 MSL.  Maybe 300 turns remaining after landing.  For comparison, my "heavy" 5.25 g version has done 2:15 on a 14" loop of .093, about 1200 turns, std 10x15 prop.  Won't be winning any contests like this, but having a lot of fun with it, and learning as we go.

My flying buddy Jeff is also doing 2+ minutes with his heavier version, built  to plan, around 6 grams, .093" rubber loop about 16", per plan 10x15 prop.  It really climbs out with just 1000 turns, and has a most excellent cruise, just hanging and hanging up there near the ceiling.  His plane made several tours through the spaceframe ceiling structure, emerging unscathed each time.

Regards to you, George and your dad, and thanks again for your input to this fab design,

Steve
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