TopModel Samsara 3.2 meter glider, build thread on Aloft's Forum.

[Konrad]

Reading the manual (now there's a novel concept ) I see that Top Models recommends that the aileron have 10mm to 14mm of downward travel. On my ship I'm measuring 10mm of downward travel. This is on the light side, but as I plan to mix the flaps with aileron I think my roll authority will be adequate.

I see that the manual recommends that the upward motion of the aileron be 18mm for landing (crow). But The upward motion of the aileron in roll is a bit larger at 20mm to 25mm.

In the past (distant past) I use to set up my ailerons for crow (landing) for about 70° upward movement. And I often liked aileron differential for normal flight* to be about 1.25:1 up to 2:1.

What is the current philosophy for setting up gliders?

*In crow I would set up reverse differential allowing the aileron to come down into profile for roll control in crow.

 

[Doc James Hammond]

Looking good Konrad - must be getting closer to heave it off time!

I'm still advocating a "How to" section By the way.

Great stuff!

James.

 

[Konrad]

Thanks James!

I think I've past the half way mark! I did a preliminary CofG check and with the 225 gram battery it's looking like I'll meet the 90mm to 100mm balance point. But to reach the manual CofG mark of 67mm to 75 mmm will take some nose weight.

I calculate that 90mm plus is the sweet spot, so I'm not too concerned with current build and component weight.

When I'm finished, I'll try to pull out the good parts (clean up) of this build and make a "How To Thread", maybe called "Konrad's pearls of wisdom", that Wayne can later move into a specific area of the forum.

P.S.
Flight testing has shown that I needed a 335 gram battery to to reach my flying CofG. My CofG is now at 92mm (6/17/2018)

 

[Doc James Hammond]

Only problem there is that you just might not be the only one with Pearls of Wisdom...

I'd call it "Aloft Knowledge Directory" or some such, then any can feel free to post the good stuff.

Also likes to "how to" videos would work.

Just an idea.

Doc.

 

[Konrad]

I'm sure, I'm not the only one with good ideas or has taken the time to write up the process and annotate the photos. But you are correct, for the forum directory the name needs to be more inclusive.

I'm old school, I find I can usually soak up knowledge faster reading text, along with some good isometric drawings, than watching videos.

 

[Doc James Hammond]

I agree there Konrad.

Old skool? - when I started making planes there were no calculators let alone computers/videos. People thought you were cheating if you attacked a problem with a side rule. Pretty sure I've still got mine somewhere.

But every picture does indeed tell a story and the ones we have here are invaluable.

Cheers,

Doc.

 

[Konrad]

Wow you must be as old as dirt! I still recall my Dad buying his first electronic calculator in 1968. He did teach me how to use a slide rule, more as a party trick than as a useful tool.

One of the few flaws with my Samsara is that the rudder horn hard point does not align with the cover horn. I had to add some balsa to allow the mounting of the control horn (See patch).

I have to admit that I've mounted the rudder servo about a 1mm too high up on the fin to allow the push rod to exit in the middle of the cover's horn.

On my next 1.8 meter fuselage (Element) I will flip the elevator servo to allow better nesting of the servo motors. This will allow me to drop the rudder servo 1.0mm.

All the best,
Konrad

 

[Konrad]

Added control horns to the wing surfaces. Note that I've offset the horn to take into account the push rod being to the outside if using "Z" bends.



Mid build gripe session.

Already covered that the wing hold downs are too wide apart and that the canopy should not be carbon! I also found that the hard point for the rudder horn does not go high enough up the rudder .

Staying with the wings I'd like to see more of the mass kept near the center of rotation (twist) to minimize flutter.

For example I don't like the dual wiring loom tubes in the wing. Only need one and it should be near the spar.

I see no inflight benefit to the rear spruce drag spar in the center section, it should be removed to move the wing's mass closer to the main spar.

There is no need for rib cap strips. The covering will supply more than enough lateral support for the ribs as does the trailing edge sheeting.

Removal of the cap strips will save a lot on assembly time and glue weight (Notice all the glue blobs!). Removal of the cap strips will allow the servo mounting plates to be placed 2mm deeper into the wing.

With the labor credit gained by removal of the cap strips, Top Model should use built up wing control surface, or at least router out lightening holes in the ailerons! This should add little or no cost to the construction of the base model. I see TopModel does much of this in their other larger gliders.

The fuselage part line is not the center line of the fuselage It is off to port (left) about 1.5mm.

The holes in the control horns while close to 1.5mm do not fit the clevis pins which are 1.6mm (0.063") Drill the holes before gluing them on the control surfaces!

The elevator rocker bed dimension stated in the manual is in gross error.

Still love the Samsara and can't wait to get her into the air!

All the best,
Konrad

 

[Doc James Hammond]

I guess we have to understand that this is a mass produced airframe, Konrad and where it would have taken you or I a couple of days to put the wing together, it was probably done with jigs in an hour flat. There are mistakes etc and probably these could be tidied up a bit, but as a producer of airframes myself I know how easy it is to make a bunch of things THEN find out there is a small fault you did not notice (Blobs on the rib caps etc) Generally as these are not show stoppers, I let them pass, but as soon as someone DOES let me know than I try to fix them pronto. It would probably never happen but if you could sit down with the manufacturer for a half hour you could tidy up all these small niggles, and thats why I actively envisage people to let me know when I have a fault.

 

[Konrad]

James,

I agree!

As a former manufacturing engineer, even more so as a machinist (also in aerospace), I'm painfully aware of how fast the assembly line runs. As an engineer we ran work studies and measured takt and process times in seconds.

I mention not only the good features I see in a product but also the areas "I" feel could be improved upon. Some of these areas are critical like the carbon canopy and the too wide a hold down spacing. Others are just gripes (nit picking). I often ask myself why should an OEM improve their product if nobody notices. I'm trying to show with my builds and critiques that somebody is noticing.

As an example "I" feel that rib cap strips are of little value and if done incorrectly actually are a detriment. You might recall that when I stripped the bottom covering from the outer panels I was able to save 8 or so grams of weight from each panel. Much of this was by picking off the glue blobs.

I tried to offer Top Models a method to improve their product at no cost, maybe even as a cost saving exercise. That is remove the rib cap strips altogether (compensate for this in the rib cut file). This will save on 2/3 the weight of the cap strip eliminate the glue weight and save on the labor having to fit and align the cap strips. They actually do omit the cap strips on their higher end models. With this manufacturing credit (time savings) Top Model could make the Samsara even greater by cutting lightening holes in the aileron, or maybe redirect the saved time in building up the ailerons and flaps from parts rather than solid stock. It might be time for a Samsara 2018!

I need to make it clear that at this price point the Samsara is a fantastic deal. It is a great value and will give anyone a very good ship to experiment with F5J tactics. While I noticed some short comings The Samsara is high on my list of recommended glider* for all but the most rabid competitor!

All the best,


Konrad


* Haven't flown one yet so I'm actually reserving comment. But it is looking very good!

 

[Konrad]

Had a slight set back with this project. Thanks to Wayne of Aloft Hobbies I think I'm back on track.
https://forum.alofthobbies.com/inde...eceiver-is-not-ready-for-the-mass-market.227/

Rather that use the Multiplex 6 pin connector out at the wing tips I've chosen to stay with the 3 pin Jr style connector. Now I really liked the Top Models connector holder for the Multiplex connector it wouldn't work with the much smaller Jr style servo connectors. Luck would have it that the old Ernst Charge Receptacle P/N 101 fit the female (plastic housing) Jr connector almost perfectly.
https://www.towerhobbies.com/cgi-bin/wti0001p?&I=LXE962&P=7

While not as good a system as an auto align and plug system, having one side of the connector rigidly anchored to the wing helps a lot during set up.

All the best,
Konrad

 

[Wayne]

Yeah, I need to get some of the deans 3 pin connectors for the shop.. As well as a few other goodies.

 

[Konrad]

Love the old Dean three pin servo connector. Really I do! But I think the modern servo connector with its long pin and spring contact (JR style) make better high cycle servo lead connectors.

 

[Konrad]

Earlier we discussed a bit about the airflow changing from laminar to turbulent. It is thought that for most of the flight envelope the air is laminar over most of the bottom surface for most coefficients of lift. With that in mind many designer try to add gap seals/wipers to minimize drag and aid in control authority. I've chosen to add gap seal/wipers on the bottom of the ailerons but not on the top of the flap gap. I've made my seal out of 4mil mylar I used when vacuum bagging some of my composite wings. As this mylar come on rolls it has a natural curve that I use to try to keep the wiper against the control flap. It is against this curve that I add double sided tape. These seal/wipers are 25mm wide with half the width taken up with double sided tape (12mm).

I think my control wipers will stay against the control surface for most of the aileron's control surface movement. True when the aileron is lifted so high as to become spoilers they will separate. But I'm really not too concerned with trying to keep a low drag profile with the spoilers up!.

With the Samsara, Top Models has provisioned the wing panel part line with threaded holes to accept their mini Clip Fixing (P/N 03801). While not needed I think it is a nice piece of bling. They might keep the wing together during a ground loop minimizing damage.

All the best,
Konrad

 

[Doc James Hammond]

Thats what we used to do in the 70's and early 80's Konrad.

Works well and its replaceable easily.

Doc.

 

[Konrad]

Like I said I'm old school. I recall spending some huge amount of money for these from Airtronics way back then. Do you know with a built up open wing any better system?

I have some concerns that the seal and double sided tape add a 0.006" high trip strip just ahead of the control surface. On my built up ship I usually sand a low section into the wing to help keep the wiper from becoming a trip (turbulator) point. I forgot to do this when I stripped off the covering to add more RED.

 

[Doc James Hammond]

Hi Konrad, I wouldn't worry too much. On the top of the wing the boundary later will depart long, long, before its gets close to the hinge areas. If its on the bottom, then again the hinge lines are so far back that there will be little or no effect from a "turbulator" - intended, or otherwise. Added to that, at the speeds this type of plane, or indeed any other model sailplane with built up wings right up to DS speeds, the variations in the covering tensions, gaps, dips etc etc far, far, more damaging thank a very thin but more or less constant line. Most of the adverse effect is in our imagination - but its nice to look at the details!

 

[Konrad]

I know it is often difficult to see clear films in photos. Here are some cartoons I drew showing the "what and how" of these wipers. I was drawing these for foam hinges but the idea is the same for tape hinges

 

[Doc James Hammond]

On the top the wiper makes absolutely no difference except it looks good.

On the bottom its more useful but to be honest if the hinge line is on the bottom, flat and not in the middle of the control surface (as you have drawn it) then that's the best.

Whatever you do at the top of the wing only looks good or looks bad or makes you feel good etc. If there is an open gap it will be the same as adding a wiper - just lighter. No difference to the performance or the airflow.

 

[Konrad]

Doc. we covered this earlier, and it is well understood. This is why I did not add the wipers to the flaps (bottom hinged, taped). My cartoon was of the rudder and were drawn to show multiple conditions in one view (saves me for redrawing a lot of stuff more than once).

I go into wiper detail here in my Heron thread. By the second page things are a bit off topic
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=21046.0