Kernwrech's blog View Details
Posted by Kernwrech | Mar 29, 2007 @ 03:02 PM | 8,064 Views
Dear readers

Yesterday I got the holes I found from my new envelope plugged. It now holds air rather well. It can stay pressurised (no wrinkles) up to several hours, and it holds it's shape (rigid enough to fly) for couple of days. This test was done with air, the gas leakage rate will be some 2-3 times higher. There are still some leak inspections to be done, but i quess this will turn out to be a workable envelope.

The next step is to glue the keel mountings to the envelope, so I can get the balsa keel attached. The main reason for the keel is to (hopefully) keep the airframe rigid even if the envelope pressure is lost. Thus, my airship will be a semi-rigid, not a blimp.

I measured the weights of the pieces I've built this far:
Envelope: 40,6 g
keel (two girder pieces, 1,6m long): 6,3 g
rudder and mountings: 5,2 g

as the envelope volume is perhaps 150 liters or more, there will be plenty of lift for other components (RC gear, motor). After the seccond leakage test (and perhaps some more plugging) I will do a gas inflation test (with hydrogen or helium) to measure the lift generated. after this I will purchase the RC gear, once I have designed the system. I intend to use rewinded brushless electric motor from CD-rom drive (the motor isn't ready yet).

'Till the next time
Posted by Kernwrech | Jan 01, 2007 @ 09:09 AM | 8,956 Views

As you may or may not have read, I use hydrogen as lifting gas for my blimps.
Many people have openly criticised the use of hydrogen because it is extremely flammable. The Hindenburg disaster was perhaps the most spectacular hydrogen-related airship disaster in history, and mainly so because there were so much journalists and TV crew on site to capture the event. The debate has been on for decades about what initially caused the Hindenburg fire. I'm not going to enclose the subject here, but if you are interested, check out this site.

Anyway, The HB5 dirigible came to the end of it's way due to poor storaging conditions (see the LTA stuff blog entry). The frame was totally wrecked, but the balloon was intact although low on gas. However, I discovered that the aluminium layer of the foil balloon had started to fall of and fracture. This is where foil balloons usually start to leak like crazy when pressurised.
I decided to have a little fun in the name of science: The new year came, and all kinds of fireworks were allowed, so it was a perfect night for testing. My plan was to test how fireproof these balloons actually were (to justify future indoor storaging) and what would happen if one catches fire

I started by removing the HB5 frame from it's balloon. Then I took a foot-long gunpowder fuse, and taped it to the balloon from about halfway of it's length. I tied some crackling bombs to the secured end of the fuse, to ensure the balloon was going to be lit....Continue Reading
Posted by Kernwrech | Dec 23, 2006 @ 12:43 PM | 8,777 Views
Continued from part 1

the HB5 was found to be quite successfull blimp. It was built for outdoor use (although it hadn't been varnished to save weight), but it finally made it's point inside a school gym hall. Last autumn, our aviation club started having occasional indoor flying events in the local gym hall. I thought that it would be a great oppoturnity for trimming flights. I found the HB5 from the garden shed undamaged by the rainy, moist autumn weather. It had, however, lost so much gas, that it couldn't fly even with all of the ballast removed. I was in a hurry to fill the balloon for the next morning, but it all turned out well, although I didn't have as much gas in the balloon by morning as I had anticipated. It was enough for the HB5 to fly, so it was taken to the hall.

The other members of our club were grinning, and one asked "what's that party balloon about, pall?" the sniggering was cut short as the HB5 made it's first flight, totalling 2 minutes of rubberband powered flight and a slow descend. It was longer than any of the conventional rubber band models that were seen in the air that day. there were many kids flying simple rubber powered aeroplanes, and the whole setup soon started to resemble a WW1 airfight with the blimp and a lot of aeroplanes in the air at once (and luckily without midair collisions). The HB5 had it's moment of glory, as it made the flight record of the day. I had installed thinner rubber to cut down airspeed (to avoid it...Continue Reading
Posted by Kernwrech | Dec 23, 2006 @ 07:26 AM | 8,352 Views
This posting will cover my blimp hobby so far.
I quess I should write about the beginning and history first. I started with simple message ballooning (ie. balloon craft carrying message capsules).
At the time a had no supply for helium, so I filled my balloons with hydrogen gas. I'm making the gas by sinking some aluminium scrap pieces into caustic soda. The process creates hydrogen, heat and sodiumthetrahydroxoaluminate, being actually quite simple and fast way to create vast amounts of hydrogen.

-The first successfull (the first I got aloft) balloon, the HB1, had just enough hydrogen to lift the latex balloon and a small balsa frame carrying a message. It's had only one flight (after all it was a mere message balloon). It was loosing it's gas rapidly, and by the time I let it go, it was ascending very slowly. It flew over the field, into my neighbor's yard, and collided with a tree and got stuck My neighbor friendly gave it a push with a stick, and off it went. It flew over the roof of my neighbor's house, made some collisions with nearby spruce trees and then continued it's journey over the neighbourhood. It was later spotted by a friend of mine, about half a kilometer away. He told me it was well aloft, having cleared the treeline. Although it was carrying a message with my email address, I never heard from it again.

-The seccond balloon, logically named the HB2, had the same issues with lift, and because some caustic soda from reaction vat had entered...Continue Reading
Posted by Kernwrech | Dec 23, 2006 @ 03:55 AM | 8,064 Views
Hello everyone!

This is, I suppose, one of those ideas that bump in your head in the middle of the night. So, I decided to start a blog here. I quess I will mainly cover aeroplanes and blimps, but that doesn't mean I have to perclude some extra stuff like jet engines and robotics, now does it?

As much as I'd like to introduce myself, I feel that it is a private matter. With all the technological snares and viruses on the internet today, I just don't want to end up on some hacker's target list by being too open. the world's small, however, and thus I'm pretty sure you know someone who might know someone who knows me

I can tell you something about my hobbies: I started with free flying and/or rubber band powered small aeroplanes when I was around 7 years old. Despite that I'm just beginning with the RC stuff (I have had one RC glider with 2m wings for many years, but I haven't flew motor powered RC planes up to date). I have made a few playfull experiments with lighter than air also (like tieing balsa frames into foil balloons), and now I'm building my first serious blimp...

I have also done lots of electronics in the past. I quess it started as 5 years old playing with lightbulbs The hobby swell and now I have a garage full of stuff (and it looks like the insides of an scifi computer ). In the past I made mostly amusing gadgets, but now I focus on the stuff that has practical use.
Electronics is really only one part of the hobby. I have built a fully working jet engine from scratch (It was kinda upper secondary school science project), and have plans to buils a new one that would be a really serious powerplant.

I quess that covers all handicraft-based hobbies of mine. I hope I can keep this blog interesting and update it often.
'till the next time...