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

[Konrad]

WOW, are MKS servos expensive. Some background, while waiting for my radio's firmware to be updated, I had brought along an old FVK Brisk III which I had problems finding servos to fit in the rear servo pocket. I was allowed to roam the warehouse looking for servos that would fit. Out of desperation I tried the MKS HV6100 and found they were the perfect fit. Now much to my surprise I found that close to a thousand dollars of other incidental stuff had piled into my shopping cart. All I wanted were two $40 servos!
http://forum.alofthobbies.com/index...-from-the-all-the-folks-at-aloft-hobbies.124/

One of those incidental items was the nice Top Model Samsara 3.2 meter glider. This will be the topic for this build thread. I have to admit this was an impulse purchase!
https://alofthobbies.com/topmodel-samsara.html

I've been looking for an entry level 3 plus meter ship that had more performance than the great 2.6 meter Multiplex Heron.
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=21046.0

While I often like throwing around $2000 gliders there is something to be said for flying a simple honest low cost glider. And upon opening up the box this model it just that. Now as I said I hadn't planned this purchase I'm sure I'll be asking for help and ideas from the "Aloft Forum" hive mind on how to configure and set up this model.

To give folks an ideas as to the market sector this model is aimed at the only other model, that I'm aware of, that looks close to this, is the smaller Horizon Hobby Mystique 2.9 meter. Yesterday I was looking at the now obsolete (discontinued) Mystique 2.9 meter and almost bought one. But for the fact that dealers are forced to stay with the MAP even when the product is no longer supported by Horizon Hobbies. I'm loath to buy an obsolete product for full retail when there is no parts support (one of the definitions of obsolete). As the Top Model Samsara 3.2 meter and the Horizon Hobby Mystique 2.9 meter glider look to be in the same class of model, I'm likely to make comparisons between the two.
https://www.horizonhobby.com/produc.../almost-ready-to-fly/mystique-29m-arf-efl4905
Both are glass fuselage ships with minimal carbon stiffening (2.4gHz friendly) Both use traditional "D" tube built up balsa wings. And both use a full flying stab. What I liked about the Top Model Samsara 3.2 meter is that she has about 10% larger wing span and has what is claimed to be an AG airfoil. The tail feathers are arranged in a more modern configuration and the rudder is further aft of the wings to aid in spiral stability. Oh, and the street price is $60 less than the smaller Horizon Hobby Mystique 2.9 meter. Actually the street price is about the same.

Let the fun begin!

Konrad

Caution:
The Center of Gravity location called out in the manual is in gross error. The CofG should be set at 85mm for the maiden flights. Mine is now set at 93mm to 95mm. For the first flights with the CofG in the 90mm range set the elevator rocker to 20mm not the 22.5 in the manual. With KST XO8 tail servos the mass of my Samsara is 2.06 KG. (Use as light a set of servos and wiring harness as practical)
https://alofthobbies.com/kst-x08h-servo-2-8kg-38-oz-in-09-sec-8-grams-wide-voltage.html
No need for XO8 plus on the elevator. The Samsara can't fly fast enough (flutter) to need the added servo power.
See this post for my current set up values.

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

Flight report. With the aileron to flap mix set at 20% using Mike Shellmin's Open TX templet "E-Soar Plus V3" I now get good aileron (roll) control. http://rc-soar.com/opentx/setups/esoarplus/index.htm The Samsara with the CofG set at 91mm (95mm April 2019) stalls straight ahead. I also don't...

forum.alofthobbies.com

5/30/2019
The all up weight is now 1.94 KG with a 50 gram repair.
1.940Kg. Most of this weight loss is a change to the ubiquitous 2200 4 cell at 260g battery that the aft CofG allows.

11/6/2020
TopModels has changed the configuration of the Samsara. The elevator servo has been moved to under the wing. I think this is counter productive. They have changed the CG from 67mm -75mm to 75mm-85mm. 85mm is a good starting point for a maiden flight. Don't be afraid to move the CG aft as your trim flights indicate. (I like a CG at close to 95mm, still like the elevator rigged at 20mm).

 

[Konrad]

Some initial impressions. I really like the long fuselage. I had some concerns that with the long thin boom it would be too flexible. This isn't the case! It takes a lot of force to twist the boom. I also had concerns about the hole in the boom for the stab rocker causing rigidity problems. Again this isn't the case as Top Model has added quite a bit of stiffening carbon around the opening. Yes, the vertical fin does show a bit of flex aft of the rocker opening. But this shouldn't be of much concern in flight. In fact I think a lot of this flex will be addressed when the tail post is glued in place The only knock I see against this fuselage is that the canopy (battery cover) is made of carbon. While this looks good from a marketing point of view. It is horrible in todays 2.4GHZ radio environment. I wish all OEMs would do away with the carbon canopy. This is the wrong place for carbon! Get rid of it and lower the cost of the kit. Or better yet use this carbon in real high stress places. I know some folks have concerns that the long tail boom will make it difficult to balance. I don't see this as a problem. If tail heavy just add larger batteries to the power plant! A long tail helps a plane fly much better than the misguided idea that weight hurts performance. Add weight as needed to trim the plane. A heavy plane in trim flies a lot better than a light plane out of trim!

I did notice that the fin cover doesn't fit properly. The vertical doesn't have a relief for the fairing molded into the side.

Now looking at what makes a glider a good or bad ship, that is the wings! I couldn't find anything on how these are built. So if anybody knows or has a crashed set of wings please let us know how they are built. As I said earlier these look to be typical balsa built up "D" tube wings. While true I did notice some unusual features. First the center section is not flat. It looks to have about 1° of dihedral. But what is unusual is the all the balsa sheeting looks to have continuos fibers spanning the dihedral kink. That is there is no center line joint! To my thinking this center section is just as strong as a classic straight section panel.

I also don't see any spars in the wing! The wing looks to be of the stress skin type construction (ALA Hal DeBOLT). (THIS IS AN ERROR, the wings have spars and a bit of carbon) The shear webs look to be super wide made from 18 thick balsa. It is these thick shear webs that keep the top and bottom sheeting in place. I noticed a neat feature to the shear webs in that they are made with what looks like 50 gram fiberglass laminated to the vertical sides of the webbing. This glass is acting like a shear web keeping the grain of the shear webs from splitting under the load from those nice 3.2 meter long wings. I did see what looks like glass tubes imbedded in the shear webs used as sockets for the outer wing panels. I also saw what looks like kevlar wrapping to keep these tubes from splitting the shear webs. And as a cost saving the wing joiner tubes are glass (actually they are brass tubes). While I don't think this wing could hold up to a properly powered winch launch, as this is an electric launch glider, the wing structure at first glance looks like it is more than a match for anything an electric open bay thermal ship should experience.

Somethings I didn't like are that there are too many wire loom tubes. Using a common bus bar architecture one only needs 4 wires (not six) to power and drive 2 servos. Both servos share the same neg and pos lead. I did see that the panel end ribs are cut to accept Top Models Multiplex connector holders. But there is no need to use heavy six pin connector out at the wing tips. I was a bit miffed that these holders weren't included in the kit.

The covering looks to be full weight Oracover (UltraCoat in the USA). This class of model should be covered in Oracover-lite much like the FVK ships. Also the covering over lap is a gross 12mm wide. I see no reason that production models should have film over laps of more than 6mm.

I also don't like the flat sheet wing tips. If using modern airfoils the wing tips should be a bit more modern.

On a funny note I had to laugh at seeing all the covering scraps add to the box. This is a great idea for supplying material to make patches!

 

[Konrad]

Starting to think how I'll outfit this model. First I have to say this is NOT a hot liner! So I see no benefit to having a kilowatt or more of power on the front. And with its modest 8.25% thick airfoil it isn't any kind of high performance ship. But as she is a great sport ship she lends herself perfectly to helping one clean out what has been laying around in the bottom of your equipment drawer. In my case I found some Aveox geared inrunners and some geared A30 Hacker out runners Both of these fit the fuselage fine. And as these are geared motor it looks like I'll need to drive these with 4 cell lipos. Again the fuselage can accommodate 4 cell 2200 size packs. If I was running direct drive out runner I might settle on 3 cell lipos. Another thing I like about this kit is that the firewall is not installed. As I like to trim my sailplanes to have an aft center of gravity, far too often factory installed firewalls have too much down thrust built into the fuselage. This is not a problem with the Samsaras.

Just a note; I can't fathom why the out runner in a can seems so popular. Why add the weigh and insulating properties of an outer can. If you need the weight get a motor with the next large stator size. And if you want to cook stuff use the wife's stove. Really the "Glider Drive" from Hobby King has no place in the front of such a nice model. Now I have learned that Dualsky will be coming out with a "glider friendly" motor. This will be a low KV, tapered front end out runner. Much like the long lamented Hyperion GS series of out runners.

To be honest any high quality analog servos should work fine with this glider. I'm a bit puzzled to see that Top Models is advocating the MKS 6100 in the tail. That having been said I'm thinking of using KST X08 and X08-plus servos in the back. Mainly because I have them.

For the wing servos they need to be about 11mm thick. Again I don't understand why Top Models did this, but even though the wing is over 20mm thick the servo pocket and mount only allow 11mm thick servos. You might be able to use 12mm thick servos if you use bumped covers. Now here is where you need to be careful, many servo don't come with replaceable gear trains. Please make sure that the flap servo has a large metal gear train and that the gears can be replaced. While the X08 plus can drive the flaps KST doesn't support the X08 with replaceable gear sets.* I'm looking for 20 to 30 gram servos for the flaps like the DS225 and to keep the weight out of the tips I'm thinking of using a pair of X08-plus for the ailerons

https://alofthobbies.com/kst-ds225mg-wing-servo-6-50kg-90-3-oz-in-08-sec.html

https://alofthobbies.com/kst-x08h.html

Edit 3/21/19:
KST now offers replaceable gear set for the X0-8

KST X08 Gear Set

Sometimes crashes happen, and sometimes those crashes lead to stripped gears. No worries, we have you covered!Fits X08, X08H, X08N1 set replaces the gears in 1 servo

alofthobbies.com

 

[Wayne]

Sweet, Thank Konrad for all the info and feedback! Looking forward to the first flight.

 

[Konrad]

Already I need to make some corrections. Topmodel is not promoting the MKS servo. The MKS 6100 appears to be promoted by most of the web retailers. On the box top for the Samsara Topmodel lists the use of 4 Hitec HS85MG and 2 HS5055MG. On the Topmodel site they are listing the HS85MG and Savox HS 0257MG.
I'm a little confused by the Hitec recommendations. While I've really liked the HS 85 as an economy servo, it looks too thick, at 13mm, to fit in the servo pocket without bumped servo covers. I don't know how long the Samsara has been on the market but today I wouldn't mix analog and digital servos. Today if I was recommending Hitec I would stay with high voltage digital metal geared servos like four of HS5070MH and two 5087MH for the flaps. But as the HS5087 are 13mm thick I might spring for the D145SW thin wing servo. https://alofthobbies.com/radio/servos/hitec.html

These covers might help in opening up the range of suitable servos.
https://alofthobbies.com/servo-cover-small-humped.html

 

[Konrad]

So far the only real annoyance with the kit is that the flaps can only move in one direction. There is no relief at the hinge line to allow the flap to move both up and down from the profile setting.

I'll have to strip the flap and sand a relief bevel into the leading edge of the flap so that I can get both reflex and aileron action out of the flap. While the airfoil is a flat bottom style, in that it doesn't have the Eppler cusp, it might not respond to reflex like other modern airfoils. We still should be able to raise the flaps up to help with the roll rate.

 

[Konrad]

I have found that 80% of most problems with models, heck any product, can be traced to the manual!

The first discrepancies I found that the kit looks to have a bit more prefabrication done than how the manual is written. The manual has you install the wing hold down blocks and drill the holes for the axil for the stabilizer rocker. The kit comes with the hold down block glued in and the rocker pivot pin holes already drilled (I assume this done in a fixture). When I look at the manual online I wasn't thrilled about trying to drill these holes. I'm really happy Topmodel has done this for us!

Also this is not a 5 channel model! It is a 7 channel model!

I have noticed that the manual shows a rigging value for reflexing of the flaps about 3mm. I'm glad to see this. It at least indicates that Topmodel was expecting the end user to use reflex (speed mode with this model). I hope that the issues with my flaps are unique to my model. (Again easy to fix).

What has shocked me is that the center of gravity is shown way forward at 75mm. By my calculations (using CofG models) the center of gravity should be placed about 90mm or more aft of the leading edge. I'll place my components to meet the 90mm point and then ballast forward for the first flights. Hopefully someone here on the forum can confirm the true center of gravity point for a neutral pull out from the dive test.

While this model is an ARF it really is too nice to be using 5 min epoxy for assembly. I'll be using 30 minute to 3 hour epoxy.

As mentioned earlier I see no need to be using heavy 6 pin connectors out at the tips when 3 pins are all that is needed.

Looking at the stabilizer rocker bed I see it will introduce a lot of differential. With this style of rocker do you guys place the servo arm pointing aft in the center position in hopes of getting a better balance feel for the elevator?
I fail to see where I'm to place the stabilizer ball stud on the servo arm. I assume it is at the furthest point possible and still fit inside the vertical fin. Also does one really need to add the 10° kink to the elevator push rod?

Installation of the rudder post and the rudder hinges seem to be out of sequence.

I'll post any discrepancies as I run across them. Also please post any issues you might have found with the kit.

 

[Konrad]

I've just learned that Topmodel has just had a recent price increase in January, at least against the US dollar. Guys this might be a good time to get a Samsara if you can find a vendor that still has some new old stock! https://alofthobbies.com/topmodel-samsara.html

Let me say that this model compares nicely with my FVK 3.2 meter Graphite D tube wing. No. it isn't in the same league but for $400 verses $1100 it is close. I like that the Samsara has a much longer tail. Also that the tail has more surface area and that wings have a bit more dihedral.

Now if I was to buy another Samsara I'd buy the ARC version. But the covered ones really are a much better value. If you have a choice I'd recommend one of the solid white models. Because the bottom of the outer wing panels are colored. The transparent colored Samsaras are difficult to see at altitude, as the color panels really are too small for a 3 plus meter ship. But at low levels I love seeing the sun shining through the open structure. As I'll have to break out the covering iron to address my issues with the flaps, I think I'll also recover the whole bottom of the outer wing panels with some color.

 

[Konrad]

Ok, enough engineering, it's time to start cutting plastic and wood. The first thing that needs to be done is clean up the fuselage (Glass Reinforced Plastic - GRP). Paramount is to remove any obvious stress risers in the fuselage. There should be no sharp square corners in any of the fuselage cut out. Yes, removing material can often make the structure stronger!

I hope you can see that I have radiused all the corners in the fuselage cut out under the wing. I even had to under cut the sides a bit to allow enough area for the rear "T" nut. I had to clean up the canopy opening leaving a 5 mm ledge along the sides. You want a ledge all along the canopy opening, as this opening does weaken the nose a lot. I had to relieved the fin cover (push rod hood) to clear the rudder post. I also opened up the fin to allow easy access to the servo mounting flanges.

 

[Doc James Hammond]

Looking good!

I have one that I made up last year. Would anybody like to see my build?

Its completely different but much the same in the more important aspects.

Mine's not flown yet but tis ready to go.

Cheers,

J.

 

[Konrad]

Looking good!

I have one that I made up last year. Would anybody like to see my build?

Its completely different but much the same in the more important aspects.

Mine's not flown yet but tis ready to go.

Cheers,

J.

Yes, Please! I hate doing these alone.
"Its completely different but much the same in the more important aspects."
Is this a Top Model Samsara? I'd love to see how you set up your Samsara. I'd also like to learn of any issues you had in the build and how you solved them.

Please fly it! My main concern is that the 75mm CofG looks to about 20mm way too far forward.

Also how did you set up the elevator push rod?

 

[Wayne]

Yep, he brought it home after his visit last year. Like you he just couldn't help himself. Still not sure how James got it back to Taiwan without damage.

 

[Konrad]

That might be the most traveled SAMSARA!

I've noticed that many guys think installing a firewall is shrouded in magic and mystique. Really it is super simple.

I'm sorry I forgot to take detailed photos of the process. Got side track as I had to go to my local hobby shop (Aloft Hobbies) to pick up some spinner parts.

Next time I install a firewall I'll try to take more photos to make up a photo essay.

But the process is to fit the firewall so that it is about 1mm to 2mm smaller than the ID of the fuselage opening. You want the firewall to float (slip fit). Make sure you take into account the seam over laps. Now is the time to make sure that you can mount the motor to the firewall

You are going to use the motor's output shaft and the spinner itself to center the firewall.

Bolt the motor to the firewall. Slip the spinner onto the motor's shaft. Make sure you allow clearance for the motor mounting screws.

Now the fuselage front opening cut out needs to have the correct down and side thrust already sanded (defined) as this surface is what you are going to use to align the spinner.

I saturate the first 5mm inside the nose of the fuselage with 30 minute epoxy. I then put a large bead of 30 minute epoxy on the outside diameter of the firewall. I then drop the Motor, Firewall and Spinner assembly through the front of the fuselage. I then clean off any of the epoxy that will inevitable smear onto the very front of the fuselage. (To protect the spinner from bonding to the fuse some guy will wax the back plate of the spinner) Center the spinner on the fuselage using masking tape to keep it in place. Place the fuselage tail down so as to not put any side load in the motor and firewall as the epoxy cures.

Go to bed come back in the morning, remove the tape and admire you perfectly aligned fuselage and spinner. But you're not done yet, remove the spinner and motor. Mix up some 3 hour epoxy which you have added some milled fibers glass. With this 3 hour epoxy make two 360° filets to really bond the firewall to the fuselage. I like to wax the front of my motor and reinstall it, this is to make sure the aft filet doesn't interfere with the mounting of the motor. Set aside and when the 3 hour epoxy cures you are finished.

In the last photo I'm trying to show how much clearance there is around a 30 mm outrunner motor. Again I shake my head in disbelief as to why so many think they need to use the HK Glider Driver. Any of the longer canned 30mm diameter outrunners should fit fine. Something like a Hacker A30XL-xx would be a perfect direct drive outrunner.

 

[Konrad]

I should have mentioned that the nose of the Samsara is pretty close to round. I measure it being round within 0.7mm. So while the top and bottom alignment is perfect I do allow the spinner to overhang the sides a bit at 0.3 mm. This is very good for a $400USD ship! Can you see the mismatch?

Having read that this was a 3 cell ship, I thought I was going to have issues fitting a 4 cell battery. I need 4 cells with the deep gear ratio and out runner motor. While my old 2250 mAh 4 cell pack fits and can handle the power, I found that the 3700 mAh Tattu battery fits just as easily. So regardless of the final CofG it looks like I won't need to be carrying dead weight. Now with the 3700 mAh battery I should be able to place this Samsara in orbit!
https://alofthobbies.com/tattu-3700-4s-45c.htm

l

 

[Wayne]

Snug as a bug in a rug.

That is the same basic method I use for setting a firewall. Since using this method I have never lost a firewall. I used to tack them in place with some medium CA, then add a bead of thickened epoxy. The CA required a tighter firewall fitment. I occasionally popped a firewall free with this method. Now I use only Epoxy and always sand down the inside of the fuselage a bit to remove any wax that me be present from a laminating resin.

Oh yeah, in the off chance you have an old model that is made from polyester resin (will smell like PLASTIC when cut with a dremel) you may not have very good adhesion with epoxy glues. You may want to add additional mechanical methods to secure that firewall.

 

[Konrad]

Polyester-what a stinking mess! You bring up a few good points.

When working with polyester, ether as a base material or as an adhesive make sure to check for chemical compatibility. Polyester often will not cure in the presence of many materials. One of those is oxogen, that is why there is a wax added to the formulation that is suppose to float to the surface to protect the polyester from the air as it cures. Yep you guessed it, not much will stick to this wax, if you should need to reapply any adhesive.

I think some (most) Fly Fly kits use some form of polyester in their "fiberglass" offering. Take this as a warning not all "Fiberglass Fuselages" are made equally.

Back to quality products made from epoxy resins. As we don't know which of the various release agents was used by the manufacture. It is a good idea to clean all bonding areas with alcohol, acetone and soap and water. One of these three should be the proper cleaner. Then add some teeth to both bonding surfaces with sandpaper. I like to use 180 to 220 grit to break the shine. Then clean the dust with a towel dampened with water.

Please note you will want to remove the release agent (wax) prior to sanding. There is no point in contaminating the sanded surface with the leftover release agent.

 

[Konrad]

Finding a proper spinners is a bit of a problem. As I'll be using 15 to 18 diameter props I find that the "Z" (offset, bent) hubs really help in allowing the blades to fold against the fuselage. The only 40mm "Z" hub spinner I've found is the E-flite (P/N EFLP12080S).
https://www.amainhobbies.com/eflite-40mm-spinner-eflp12080s/p276077

The issue with this spinner is that the collet is sized for 5mm motor shafts. And as a result of the minor diameter of the thread for the collet nut there isn't enough material to bore the collet to 6mm. (6mm is the shaft diameter of the gearbox used by Hacker on the A30-18M). Even the 5mm bore results in a collet that you need to be careful about tightening too much.

My initial set up is using these straight hub spinners, mainly for their low cost and that they can be fitted with a 6mm collet.
https://alofthobbies.com/aluminum-turbo-spinners-for-folding-props.html

 

[Wayne]

Didn't even know Eflite offered that style spinner, looks a bit nicer than the ones I have used in the past. We currently looking for some offset spinners that can hold up to some use. The ones I have used in the past did not last long, and they were very expensive.

 

[Konrad]

What failed, the hub arms, the pin holes, the spinner cone?

Now there is a bit of a side loading on the hub and the blades that isn't present in the straight hub. So if using "Z" hubs you will want to derate the rpm for the prop blades. Other than landing damage I've yet to fail a "Z" hub. But then again I don't drive my props like Steve Neu!

 

[Wayne]

No, it was the set screws that locked the hub down to the shafts. Nothing wrong with the basic design of the Z, just the soft alloy of the hubs I had bought. They were not a collet style. I actually prefer the collet style, they have given me almost no issues over the years.