Rx pack mAh size for a Thermik XL?

[Cycross]

Hello,

I am in the midst of acquiring a Thermik XL from Jurgen of Schmierer-Modellbau (Jurgen tells me it's been ordered! :) ). I know I need to run an independent battery pack for a plane this size.

I am planning on 125MGs for ailerons, 85MGs for flaps, and 5245MGs for the tailgroup. Gonna use 81MGs for the airbrakes but its only gonna be used in the landing finals so I reckon they won't be of consideration.

I don't really intend to do too much stress acrobatics from this bird, just float around and fly for say 3 hours max.

Can anyone familiar with this setup or glider advise an appropriate size battery? Am looking at 1100mAh 2S1P A123s but afraid that it is insufficient mAh to last that long.

Thanks in advance.
Jeremy

[target]

No experience with Thermic XL, but if you look on the Soaring USA website, they recommend a 5 cell pack of Sub-C 3300MaH for the battery for Thermic XL.
Sounds like there is room and need for weight in the nose for balancing....

Try a pack configuration like this:

llll-

or this:

lll-

You can make up a "mock-up" of the cells first with some 7/8" diameter dowels, cut to the same length as the cells, about 42mm long... Then tape the dowels together in different ways to get the best fit in the nose of the fuse.

Good luck,
Target

PS. If you are set on using the A123's, then maybe a 2S2P would be much safer??

[Cycross]

Thanks Target for sharing.

I am actually planning to electrify this bird, hence any weight savings at the nose end might be better for me. I did consider lipos with a regulator, but the fire hazard issue has me thinking about alternatives. No doubt, NiMh has been the safest route, albeit the weight penalty.

[MTT]

I am actually planning to electrify this bird, hence any weight savings at the nose end might be better for me.

With big e-sailplanes like the XL, weight in the nose usually is not an issue...
Whatever weight you have there, is easily compensated by shifting the main battery pack around as required.

I fly an XL, equipped with a Kontronik FUN 500-27, driving a 18x11 folder through a 5.2:1 gearbox.
Immediately aft of the motor I have a 4-cell 2400 mAh pack, aft of that are the speed control and the rx.
The main battery pack is a 4s2p 4200 mAH pack, located halfway under the wing (not visible in the attached pics ).

.

[dhauch]

MTT, how does this launch, do you have to run and throw it to get it flying,
or can you launch it standing still ?

thx,

dave www.rc-builds.com

[ACooper]

MTT, how does this launch, do you have to run and throw it to get it flying,
or can you launch it standing still ?

thx,

dave www.rc-builds.com

I was thinking the same thing Dave...MTT how does that combo work? I have the same motor and all of the motor calc programs that I have top it out around 500 watts. That would only be around 50 watts a pound for such a large sailplane:confused:

Enquiring minds want to know :D

[MTT]

It launches very well, without running, just needs a good toss.
A little headwind helps, but I have also launched it in still air without problems.

Don't know why your Motocalc comes up with those numbers,my Motocalc gives me :
800 W in , 669 W out
With an AUW of 4.5 kg = 9.92 lbs, that is 148W/kg = 67w/lb

As I said, the launch is OK, and the climb performance is moderate, I would say, probably a 30 deg climb angle.
It will get to 700-800 ft (measured by picolario) in a minute, and the pack is good for 3 climbs.

Not spectacular performance, agreed, but for me the XL is foremost a sailplane, the electric drive is just the means to get to thermal hunting altitude and I can do without spectacular climb performance.

[Cycross]

Hi MTT,

I am thinking of the same setup as what you have, as I tend to agree, the powerplant is to get to height, period. The thermal hunt is the mainstay requirement.

Costwise it does make sense as well, the neu, hacker options are pretty much pricer vis-a-vis.

Can you share what size spinner are you using on your plane?

[MTT]

I'm not sure now, and I can't check, since i'm not at home, but I believe the spinner on the XL is 45mm diameter. the yoke I use is a clamp-on style yoke, which used to be sold by Shredair ( www.shredair.com).
"Used to", because Dieter, the owner of Shredair, and his wife Marcela, who is from Colombia, have shut down the business and are relocating to Colombia.
He is posting a travel blog on the website, it's quite interesting.

Michael

[target]

Thanks Target for sharing.

I am actually planning to electrify this bird, hence any weight savings at the nose end might be better for me. I did consider lipos with a regulator, but the fire hazard issue has me thinking about alternatives. No doubt, NiMh has been the safest route, albeit the weight penalty.


Sorry I missed the E-power opening statement. :o

Still, I would think that 1100 MaH of any battery chemistry to be pushing past the safe limit for 3 hours of flight with a six-servo plane, wouldn't it??

Is an add-on BEC out of the question?

[ACooper]

Thanks MTT! 669 out! Good info to have!

[ACooper]

MTT...how do you like the Thermik XL?

[MTT]

I like it very much !

A 4m all molded sailplane for $ 900, of good quality, good flight characteristics, what's not to like ?

Mind you, there are differences when it comes to "all molded", the Valenta models are of reasonable quality, but they are no Jaro Muller sailplanes...

The XL flies and thermals very well, and with full-length camber changing flaps, you can set it up for slow thermal flying or aerobatics.
When I got mine and unpacked, I was surprised at the weight of the wing center section, it is heavy... and strong.
But in the end even with the electric drive, the AUW ended up at 4.5 kgs, which gives you a wing loading of 55 g/dm2, or 18 oz/sqft.

I have found that it thermals very well, with the 3 climbs I get out of my battery pack, I can fly about 20 minutes, even if there is only little or no thermal activity.
If there is moderate or strong thermal activity, the flight duration is determined by your or your rx battery's endurance...

[Cycross]

Thanks Michael, your review of the glider excites me much.

Did the kit come with instructions on throws, setup etc? I am aware its a blended wing profile of inboard SD7037 to MH32 tipside, but not sure what sort of camber is reasonable for cruise and thermal.

Also, does she flutter at speed? I am gonna be getting a CF D-Box version, hopefully able to get some mild acrobatics on the way down.

[MTT]

I have had flutter on it only once, during a dive, but that turned out to be caused by play in one of the flap pushrods.

[ACooper]

Would you have any video of your XL?

[Cycross]

Is an add-on BEC out of the question?

Definitely not, I am weighing the options. The con of a BEC is that it is just another extra link waiting to fail. Just my thoughts.

You are right there, I think now 1100mAh is indeed pushing thin. Thanks.

[MTT]

Sorry, no video....

[chronos333]

In my XL I had a HV UBEC but had some glitch issues so I went with 4 subc IB 3800 mah.
My servos are 3 MPX micro digi torque (flaps and elev), 2 Futaba 3150 (ailerons), 1Hs85 mg (rudder), 2HS81 (spoilers)
Motor is B50XL + GB 6.7:1 running 6S2P 4400mah
great plane
We are currently doing a big order with Jurgen, pm me if you want to combine shipping

[Cycross]

Thanks Chronos333 for chiming in.

I actually grew my interest on this model when I read your "XL Team" thread here in RCGroups.

What spinner are you using in your setup? is it a turbo spinner (the one with a central air hole)? I can't tell from your attached pics.

Thanks for the MO offer, it's not possible for me, I am on the other side of the world :( I am bleeding some from the personal shipping costs, but I believe it will be worth it.

[MTT]

I use a regular spinner, no turbo, without problems.

[Cycross]

It's way off-topic, but... Anyone can share the dimensions of the centre wing? Trying to see if it'll fit my existing glider bag. Thanks.

[Cycross]

I use a regular spinner, no turbo, without problems.

Thanks again.

[tiju000]

MTT, can you give me an idea of the rpm with your 18x11.

I'm one of the guy that toke part of the "original" post of the XL ( with Chronos)

I'm not sure what kind of motor to use. Actually I have 2 neu motors on hand ( 1512 and a 1509) The problem's the 1512 is a minimum a 5s but the 1509 could be a 3s or a 4s.

tks
Thierry

[MTT]

I have no means to actually measure the RPM, according to motocalc, it's 4930 RPM

[Cycross]

Finally, after a long wait since ordering mid Dec, Jurgen has finally delivered the plane to me. Kelvar fuse, D-Box. Beautiful, huge...and I like it! :)

Jurgen's service is top notch!

Mentally going through the build now, one major thing to do with E-conversion here is to chop the nose off. I am going to use a RFM 45mm spinner.

However, having not done this before, and no instructions, can anyone please share how they did it, and what down/side thrust angle this plane requires?

Powerplant is a Neu 1512/2D/6.7 with 18x10 whiskers.

Thanks!

[tiju000]

Look at our thread

http://www.rcgroups.com/forums/showthread.php?t=626392&highlight=thermik+xl

If I remembered we put no down and no right thrust.

The better way to cut the nose is by making a cardboard template a little smaller than the spinner.

The put a long piece of something fixed on the bottom of the center panel. Arrange to have this piece leveled and near the nose. So by making a 90 degree mark you will be square between the wing and the cute for the nose.

I have exactly the same setup of motor in my XL, I run 4s1p 5000 mah lipo and a 4 cells NICD 2400 for the RX. If I had to make it again I will try to put the rudder servo in the tail. Because I needed to put the rx battery far under the wing and the lipo sit almost under the wing also. I'll post some pics on our "old" thread to show the way I achieve it.

My plane is know at 4.7kg but the wing is all carbon stuff. Your d-box must be lighter.
Thierry

[chronos333]

its a nice colour scheme tiju isn't it???
;)