My E-Flite Blanik Build

[lenb]

Hi Mark.

I can tell you from the analytics there are plenty of people looking at this thread, however most never comment. Like me, they lurk in the corners enjoying what you are doing.

Thanks for sharing the journey.

Len

[Mark9]

Well, the Blanik maiden won't happen today, which is a good thing in disguise. I received a notification yesterday afternoon that the tug has engine problems. Also, the backup tug is not available as well.

Tried the Vanessa rig yesterday that I constructed. It was much easier than trying to put this big bird on a balancing jig. The only problem I had was trying to determine the proper fuselage angle when in the sling for a reading. I was using a “mark 9 calibrated eye ball” to determine that.

Anyhow, I could see each addition of lead shot to the bag on the nose as the plumb bob moved forward. I was somewhat surprised when I discovered I needed an additional 3.5 lbs. of lead to get to 20 mm. aft of the LE! That is just under 8.54 cubic inches of lead…a pretty large chunk. So far I have installed about 2 lbs., but have run out of ideas of where to put it.

I’ve potted in about ½ lb. in front of the battery of lead shot and wrapped the battery with 1 ½ lbs. of sheet lead I have. There are some small pockets in the nose that are not filled by the battery, but I have yet to come up with a solution of how to fix lead in those areas and not interfere with the battery installation. The key is to not let it start floating around in the airframe.

I might just need to bolt it to the radio tray behind the battery on either side of the tow release servo. Read of guys flying with the CG aft of 20 mm, but since this is my first ¼ scale aero tow ship don’t think I want to try that on the first flight. Not sure now when it will maiden. Anyhow, it gives me some time to develop a workable ballast solution and do a few cosmetic details to the airframe.

[Mark9]

Thanks Len, just added another step in the journey!

[ARUP]

Ask Len about 'moveable lead' on maidens of sailplanes!

[lenb]

LOL

That sucked.
Jeremy built a Blanik at the Cumberland event a couple years ago and asked me to maiden it, the nose weight was about 5lbs if I remember right. The weight was in a cone shape and velcro was holding it into the nose of the glider until it could be finalized as far as how much was needed.
On takeoff from the bumpy field the weight came loose and rolled back to the former in front of the wing. Instant tail heavy.
It was a miracle we got the plane around and back on the runway. ( or a foot from it )

Or you can watch this for another tail heavy story

[Swiss1]

Someone has to keep you on your toes!

[Sinkhappens86]

I was also concerned about the amount of lead in the nose of the Blanik. Ended up doing a lot of reading on forums and decided to go with it further back than the manual suggested. Really glad I didn't put anymore in. I will take a look at the wing when I bring it out at Salem and see where the mark is. I want to say 50mm back.

[stevekremer]

Well someone else that uses the Airtronics SD10g, welcome. I mixed lead shot and west systems epoxy and poured it into the nose of the blanik. about 4# worth. No problem with it moving around.

Steve K

[Csessa]

With advice from French1 (Stephane) who is flying at 40mm I put around 3.5 pounds but did it in 3 increments two of which could be removed. I ended up removing some because I like the CG back some. I think I am currently flying at 50mm.

the main portion is lead shot and west system epoxy poured into the nose. It is not going anywhere.

[Mark9]

Amusing story Len, that's what I want to avoid. Thanks for the input on CG and balancing ballast guys. I don't think I'll have the ballast moving around on it's own, I hope.

The 1/2 lb. of shot in the nose is quite well potted in with some BSI Finish Cure I had lying around. Never liked it for layups where I needed to sand it later, seemed to remain gummy. It is thin like my West Systems and flowed well though. No more room in front of the battery, in fact I needed to remove a few pieces of shot that blocked the slot for the battery retention strap.

The 1 1/2 lbs. around the 2 1/2 lb. battery are held in place by the battery retention strap. I can't pull the velcro strap apart in the direction that the forces are applied and sometimes during the build I have had trouble getting it loose when I want to! At the moment I'm planning to add lead plates just aft of the battery tray on either side of the tow release rod. These will be held in place with screws into the radio tray, possibly using blind nuts and machine screws. So, I will easily be able to adjust the CG to my liking as I get more familiar with the Blanik.

BTW, I do like a relative aft CG on my TD ships. My X3 will not pull out in a dive test nor does it tuck. It will just fly itself into the ground if you let it! In a flat glide it goes where you last pointed it. I need to get the Blanik back on the Vanessa rig and see where I am now. Wanted to do that yesterday, but other things got in the way.

[Mark9]

Well, the Blanik balancing saga continues. I had a chance to put it in the Vanessa rig again today with the lead I plan to bolt to each side of the tow release rod. As I said before the problem is determining the flight attitude while in the rig. The threads I've read on the use of the Vanessa were mostly discussing IMAC or large powered airplanes and said to level the thrust line for a proper reading, or use the horizontal stab mean camber line. Have any of you guys used one of these rigs on a glider?

I used my best estimate of the mean camber line for the Blanik stab airfoil and my torpedo level held next to it to achieve a proper reading. Is that the best way to approximate a good reading? I've never used a Vanessa rig before (always used the balancing on a pair of wedges technique). With what I have put in so far it says I'm at about 35 mm aft of the leading edge. To get to 20 mm the process I'm using says I need another 15 oz. of lead! Not sure if I can get another 15 oz. in the same spot. I think this airplane eats lead.

Mark

[lenb]

Mark.
At the field today in Salem, one of the guys who is flying a Blanik is currently at about 50mm and thinking he likes it there. Maybe start at 35 and see how you like it. The plane will fly fine, so don't be concerned it will fall out of the sky.

Len

[Mark9]

Len,
Thanks for the info, read some were going as far back as 70. But, also read a post from Peter G. that it may not recover from a spin at that CG. I'm not good at aerobatics, so not planning on doing much of that.

I was able to squeeze in a little more lead around the battery last night. Need to put it back on the rig again. By my estimates I might be around 30 mm now. Nice thing is that all but about 1/2 lb. of my nose ballast is removable. So, I will be able to adjust the CG easily by just removing lead sheets as I get more confident with the airplane.

Attached is a photo of the removable ballast installation. Sheets of lead wrapped around the battery. They stop at the front cell since it is almost on the internal skin of the nose. That is why I could only get 1/2 lb. of shot in the nose. The lead sheets on either side of the tow release rod are held in place by a 6-32 machine screw. They attach to blind T-nuts mounted in a 1/8" aircraft ply cross brace glued to the underside of the radio tray using the existing hole in the tray. They appear to be quite sturdy. Hope I get to fly this soon.

[jfrickie]

https://www.batteriesplus.com/batter...-acid/cyclon/6
Mark, I used 2 of these batteries and the pair weighs 3 lbs and that put the CG of the Blanik that I built right a 55 mm and it fly's great,the 6v 5000 mah ones

[Mark9]

Jim,
How are you doing? Thanks, I used the single cell 5000 mah ones and built my own pack, like these:

https://www.mbsbattery.com/EnerSys-C...medium=organic.

My postal scale says it weighs 2.5 lbs. I didn't get a chance to put the Blanik on the Vanessa rig yesterday, might try today. With all the feedback looks like most guys are flying it quite a bit behind the 15-20 mm recommended in the instructions. I know I'm at least at 30 mm now. Will probably try that first, when ever I get a chance for the maiden.

Sure wished the weather would calm down. It has been either blowing like crazy or raining this spring...not much flying. The aero tow guys have only met once, IIRC, since January and that day was way too windy for my little Fox. Ready to try the Blanik.
Mark

[jfrickie]

Hope to see you for the team selects and the TNT....check out the Mickey Sullivan Aerotow in October in Wichita....not too far from you so we can get together a fly 3 times this year!

[Mark9]

Sounds like a plan Jim. Would really enjoy flying with you guys. Just finished doing another CG check on the Blanik. I'm getting better with using the Vanessa rig. Sighted on the horizontal with a torpedo level using a prop stick and it shows that I should be at very close to 25 mm, may need to take some lead out! Never hurts to be a little conservative with a new airplane though! We have our class A monthly club event tomorrow and the WX looks good for a change...charging batteries now. Interesting, from a 4.2 m. to a 1.5 m.