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parseval pask

Airship Crew Chief

Posts: 46 Member Since: 07/02/13

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May 2 14 10:45 AM

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Hi All,

I origionally intended to build Parseval PL.19 but I cannot see myself finishing this in 2014 and I want to build something that reflects the 100 year aniversary of the outbreak of the Great War. I therefore chose instead an observation balloon as this should take alot less time to complete. The Sigfeld-Parseval Drachenballon was in my opinion one of the most iconic objects in the Great war so it seems fitting to add one to my collection of WWI flying machines. I will be building this out of dense foam, the type used in cavity wall insulation. I have been experimenting for a while with this stuff to see how it can be plausible to make large models of balloons and dirigibles.



I started like I usually do by getting GA’s. I got these from the internet and blew them up on the photocopier. The next step was to cut from the sheet of foam the body of the envelope. I decided to do this in sections and to get an exact 90 degree hole thru the middle I put three right angled triangles on the top as drill guides. Once I had cut out enough of these I put a rod thru each one and sandwiched them between two cardboard discs that I had made to match the cross section size (+ 2mm for sanding) of the envelope.  Although I have a hacksaw in the picture I found a really sharp bread knife did a better job. The outer layers of the foam were really rough and unsuitable so I drilled a hole thru a cutting block and fitted a rod at exactly 90 degrees to the base. The segments were then slid onto the rod and I cut across the block to make a flat surface. I then took off the slither I had removed, put it on the bottom of the cutting block, placed on top of the slither the segment again and cut across the other side.  I now had a segment with both sides smooth (I have though since discovered foam board that has almost perfectly smooth sides and will use this in future).  



To make the round ends I made a grinding tool out of plastic card. This I made to the same size and shape as my GA’s and glued sandpaper to the inside curve. A rod was placed thru the middle at exactly the same axis as the envelope. I then simply pushed one of the cylinder shaped segments onto the grinding tool while it was spinning in the drill. This quite literally took seconds to do. Once I had two I had all the segments I needed to make the envelope.



I found gluing a problem when experimenting because the foam becomes very hard when it has absorbed glue. This makes it impossible to sand down because the hardened parts sand down less than their surroundings, in other words the glued joins stick out like flanges and are extremely difficult to remove. The glue I ended up using was UHU clear glue which I smeared on the segments but made sure no glue went within about 10mm of the edges. It went on all surfaces and was left for about  15 minutes. I then slid each segment on the rod, pushing them together one by one. The whole lot was then sanded down and this took only a few minutes because this stuff sands really easy.



When experimenting I found that dense foam can be bent so the plan was to bend the metal rod and slid it thru the envelope to give a slight upward bend just like in the real thing. Well it worked in the practice run but not on the real thing. When I tried bending it, it broke in two places. I was able to glue it back together again and used this to my advantage, gluing it back so it acquired the upward bend I want. If I make another I will sand the segments at a slight angle so they sit naturally at a bend on the rod.



This is as far as I have got so far. I must say that building stuff this way is alot easier than the paper mashe and fibreglass method I used on the SS-Blimp and if this all goes tickedy-boo I can see myself knocking out alot more LTA stuff in the future. Next I need to cut/sand detail into the envelope but more importantly soak some varnish or paint into it to harden it as it is extremely soft at the moment. The giant air bag / scoop on the back will be made from plastic card heat moulded around a pattern. I somehow cannot get pictures on this post but I will have another go later.

Cheers, Alan.
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parseval pask

Airship Crew Chief

Posts: 46 Member Since:07/02/13

#2 [url]

Jul 9 14 9:53 AM

Amazing, I got the dam things on! All be it on the wrong post. I am a slow builder but I will keep you updated with my progress.

Cheers, Alan

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lta

Assistant Pilot In Command (APIC)

Posts: 132 Member Since:01/18/13

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Jul 14 14 12:28 PM

So far it's looking awesome. I can't wait far it to be completed

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parseval pask

Airship Crew Chief

Posts: 46 Member Since:07/02/13

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Sep 27 14 5:23 AM

I have been dragging my heels a bit on this one because it is now autumn in Europe and that means lots of fruit and berries everywhere. Fruit and berries make wine and cider and although making it is a bit of a chore drinking it when it is done is the opposite (although drinking it AND making aircraft at the same time is not recommended).

I took a little longer to get this far anyway because of the mandatory $$+* ups that are made when you do something for the first time. If I had decided to make the steering bag out of cardboard discs and glue paper around it I would have finished ages ago but I am determined to make as much of this as I can out of the dense foam because I am still experimenting/learning on how to use this and what I learn now will be of use in future projects.

The first thing I did was make a sanding tool out of cardboard the same diameter as my plans. I drew a two dimensional shape on the foam sheet and ground out the curved outline with the sheet in one hand and the tool in another. I then flipped it over and did the other side. This method seemed fool proof but it did not work for some reason and the steering bag looked like it had an unhealthy dose of Blackberry grog. To make this fool proof and 100% accurate I made a cardboard pattern of the steering bag. I placed the pattern on the dense foam and cut around it with a hacksaw file used for cutting tiles, and run a round file over the edges to make it plush with the flat sides. I made another ‘U’ shaped sanding tool for the steering bag with the non sanding arms the same length as the pattern side’s height and the sanding part (bottom of the ‘U’) a semi circle so as to cut a profile half of the steering bag. The idea is when the ‘U’ tool touches the glass table on which they both rest the exact amount would have been sanded off. THIS WAS EASY! I ended up with two perfect halves and a semi sphere I cut with the drill and another ‘U’ shaped tool for the top of the bag. It fitted perfectly but somehow looked wrong. After looking at the plans, looking at the model, looking at archive pictures, looking at the plans, looking at the model, looking at archive pictures, looking at the plans… you get it, I came to the conclusion the plans are wrong and the steering bag was too small. I guestimated the correct size of the steering bag and did what has been previously explained all over again. This time it looks right. The irony is I have used more foam making this steering bag than the envelope, that said if I ever make anything like this again I now know the best way to do it.

I just need to shape it now, similar to how the envelope has been done. Another small mistake I have made is the metal rod running thru the middle would have been better left sticking out the back so I can attach the steering bag firmly to it; instead I sawed it off flush with the envelope. Fortunately the rod is hollow, I will now most probable have to go hunting around for another smaller hollow rod that fits inside the original one to extend it.

Thanks for looking in, Alan.
Sorry I have taken so long to get back to you Guba. It is 1/72 scale and the model itself is about 378mm long.

I have been dragging my heels a bit on this one because it is now autumn in Europe and that means lots of fruit and berries everywhere. Fruit and berries make wine and cider and although making it is a bit of a chore drinking it when it is done is the opposite (although drinking it AND making aircraft at the same time is not recommended).

I took a little longer to get this far anyway because of the mandatory !%%% ups that are made when you do something for the first time. If I had decided to make the steering bag out of cardboard discs and glue paper around it I would have finished ages ago but I am determined to make as much of this as I can out of the dense foam because I am still experimenting/learning on how to use this and what I learn now will be of use in future projects.

The first thing I did was make a sanding tool out of cardboard the same diameter as my plans. I drew a two dimensional shape on the foam sheet and ground out the curved outline with the sheet in one hand and the tool in another. I then flipped it over and did the other side. This method seemed fool proof but it did not work for some reason and the steering bag looked like it had an unhealthy dose of Blackberry grog. To make this fool proof and 100% accurate I made a cardboard pattern of the steering bag. I placed the pattern on the dense foam and cut around it with a hacksaw file used for cutting tiles, and run a round file over the edges to make it plush with the flat sides. I made another ‘U’ shaped sanding tool for the steering bag with the non sanding arms the same length as the pattern side’s height and the sanding part (bottom of the ‘U’) a semi circle so as to cut a profile half of the steering bag. The idea is when the ‘U’ tool touches the glass table on which they both rest the exact amount would have been sanded off. THIS WAS EASY! I ended up with two perfect halves and a semi sphere I cut with the drill and another ‘U’ shaped tool for the top of the bag. It fitted perfectly but somehow looked wrong. After looking at the plans, looking at the model, looking at archive pictures, looking at the plans, looking at the model, looking at archive pictures, looking at the plans… you get it, I came to the conclusion the plans are wrong and the steering bag was too small. I guestimated the correct size of the steering bag and did what has been previously explained all over again. This time it looks right. The irony is I have used more foam making this steering bag than the envelope, that said if I ever make anything like this again I now know the best way to do it.

I just need to shape it now, similar to how the envelope has been done. Another small mistake I have made is the metal rod running thru the middle would have been better left sticking out the back so I can attach the steering bag firmly to it; instead I sawed it off flush with the envelope. Fortunately the rod is hollow, I will now most probable have to go hunting around for another smaller hollow rod that fits inside the original one to extend it.

Thanks for looking in, Alan.
 imageimageimageimage

Last Edited By: parseval pask Sep 27 14 5:49 AM. Edited 1 time.

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parseval pask

Airship Crew Chief

Posts: 46 Member Since:07/02/13

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Sep 22 15 10:38 AM

Hi All
This has been sadly neglected as I have wound down my hobbies due to work commitments. I have however some progress on this, the envelope is painted and the steering bag complete. the valves are on and I have started making the basket. I will upload a few pics when I can.
Cheers, Alan.

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