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Aircraft question

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Re: Aircraft question
Post by Bluesqueak   » Mon Aug 22, 2016 6:54 pm

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Dilandu wrote:
They were forbidden to TARGET civilians, but they weren't held prosecuted for the collateral damage against targets, that they presumed as military (even if the identification was wrong).

I.e. they couldn't just "oh, we have pretty little town here... let's drop our load on it!" They always tried to hit some object: railway station, factory, dock - i.e. legitimate military targets. They often missed (but, must point out, that they often NOT missed - the accuracy of zeppelins raids under good conditions could be really imprsseive), but they always at least tried to attack something important, not just damage the general population.


That may have been the intention, but it wasn't what happened. The Zeppelin Raids 'military' targets were located in the middle of civilian housing and that civilian housing was badly hit; that's partly why - as John Prigent says - the WW1 bombings backfired terribly on Germany in World War II. If you target the London docks and instead hit a school near the docks (sixteen of the kids killed were between four and six years old), people aren't really going to look favourably on 'oops, we missed. But our accuracy under good conditions is much better.'

To put it in a Safehold context, when the Charisian vessels were seized in Ferayd, the intention was that no civilians would be harmed - certainly that no children would be harmed. That wasn't what happened - and while Charis had the SNARCS to point them to the truly guilty and didn't court martial those they knew had tried to minimise the loss of life, they still burnt the dock part of Ferayd to the ground.
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Re: Aircraft question
Post by Weird Harold   » Mon Aug 22, 2016 8:45 pm

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Silverwall wrote:By the way Zeppelin type airships are a non starter without aluminum frame construction.

Using the data here http://www.airships.net/helium-hydrogen-airships for the LZ127 Los Angeles with a deadweight of 77,000 lbs and a useful lift of 101400lbs we can do some calculations

Assuming that 1/2 the mass is aluminumn the mass penalty for replacing that with steel is 77600 lbs cutting our lift force for fuel crew and ordinance to a mere 23000 lbs....


That presumes the replacement material would be steel or some other ferrous alloy. Your objection falls apart if the aluminum is replaced with wood, bamboo, or some other material. Some net lift would be lost but not nearly as much as with steel or iron.

IIRC, the Grantville Gazette anthologies (Eric Flint's 1632/Ring of Fire series) have some good non-fiction articles on building airships with mid-1600s tech.
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Re: Aircraft question
Post by AirTech   » Mon Aug 22, 2016 10:05 pm

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Weird Harold wrote:
Silverwall wrote:By the way Zeppelin type airships are a non starter without aluminum frame construction.

Using the data here http://www.airships.net/helium-hydrogen-airships for the LZ127 Los Angeles with a deadweight of 77,000 lbs and a useful lift of 101400lbs we can do some calculations

Assuming that 1/2 the mass is aluminumn the mass penalty for replacing that with steel is 77600 lbs cutting our lift force for fuel crew and ordinance to a mere 23000 lbs....


That presumes the replacement material would be steel or some other ferrous alloy. Your objection falls apart if the aluminum is replaced with wood, bamboo, or some other material. Some net lift would be lost but not nearly as much as with steel or iron.

IIRC, the Grantville Gazette anthologies (Eric Flint's 1632/Ring of Fire series) have some good non-fiction articles on building airships with mid-1600s tech.


Timber construction is possible too - a moulded timber space frame (typical of most WWI and interwar aircraft) could be even lighter than aluminum at the expense of being less fire retardant. You could also just build a blimp (non rigid airship) ala Santos Dumont (or Goodyear)with a gondola for your engine and crew.
BTW Some stainless steel structured and skinned aircraft were built during the second world war as weight for weight the strength of Stainless is much the same as Aluminium Alloy (its just much thinner and less stiff in sheet form). (Look up the Budd RB Conestoga, Budd BB-1 Pioneer & Fleetwings Sea Bird)
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Re: Aircraft question
Post by Silverwall   » Mon Aug 22, 2016 10:32 pm

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Weird Harold wrote:
Silverwall wrote:By the way Zeppelin type airships are a non starter without aluminum frame construction.

Using the data here http://www.airships.net/helium-hydrogen-airships for the LZ127 Los Angeles with a deadweight of 77,000 lbs and a useful lift of 101400lbs we can do some calculations

Assuming that 1/2 the mass is aluminumn the mass penalty for replacing that with steel is 77600 lbs cutting our lift force for fuel crew and ordinance to a mere 23000 lbs....


That presumes the replacement material would be steel or some other ferrous alloy. Your objection falls apart if the aluminum is replaced with wood, bamboo, or some other material. Some net lift would be lost but not nearly as much as with steel or iron.

IIRC, the Grantville Gazette anthologies (Eric Flint's 1632/Ring of Fire series) have some good non-fiction articles on building airships with mid-1600s tech.


I find it hard to believe that the skeleton of a large airship could be effectively built using wood/bamboo construction these things are huge and one of the reasons for using metals is the hogging problem and sideways bending. Can you provide a link to the Gazette issue discussing this? What you may gain in initial girder exchange mass is probably lost in extra bracing. I do not believe that the amount of open space we see here could be replicated in such a flexible product as bamboo. http://www.aviation-history.com/theory/ ... irship.htm

Bamboo is also very susceptible to environmental damage especially from water which would be a complication in an airship setting. Jointing Bamboo is also a real headache because of the materials tendency to split or crush at the exposed ends this is catastrophic in a geodesic construction like a zeppelin. Non of the approaches I see here look like they would scale well to a zeppelin style airship. https://books.google.co.nz/books?id=7hJ ... on&f=false

Structural rigidity is vital for large airships and at several hundred feet in length wood is way too flexible.

A goodyear style blimp is possible but we then get the wonderful issue of lifting gas. Helium is way beyond the tech available (fractional distillation of natural gas) and steam reformation of hydrogen requires an industrial chemistry set up that we have not seen any sign of.

Monoqoque construction like AirTech appears to be refers to is not really viable on this scale, That would require building the outer hull of the zeppelin in a manner similar to a modern jet liner. Looking at the Fleetwings entry on Wikipedia also raised another issue in Zeppelin construction - has anyone on safehold invented welding yet? As far as I know the current ironclads are rivet construction.
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Re: Aircraft question
Post by Weird Harold   » Mon Aug 22, 2016 10:47 pm

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Silverwall wrote:Can you provide a link to the Gazette issue discussing this?


Nah. It's somewhere in the middle of the 60+ online/ebook issues but it has been several years since I saw it.

I don't think "hogging" would be as problematic in an airship as it would be in a ocean-going ship. I don't know much about airship construction, but I do know that most people severely underestimate the strength of laminated wood.
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Re: Aircraft question
Post by Silverwall   » Mon Aug 22, 2016 11:06 pm

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Weird Harold wrote:
Silverwall wrote:Can you provide a link to the Gazette issue discussing this?


Nah. It's somewhere in the middle of the 60+ online/ebook issues but it has been several years since I saw it.

I don't think "hogging" would be as problematic in an airship as it would be in a ocean-going ship. I don't know much about airship construction, but I do know that most people severely underestimate the strength of laminated wood.


Laminated wood is awesome, the Mosquito was a true engineering wonder. However there is a big difference between a 4 foot diameter tube (rear hull of aforementioned mosquito) and the 20+ foot diameter of a airship. Tubes have much more structural rigidity at small diameter compared to large diameter.

One thing that really jumps out when looking at airship frames is how LITTLE metal they had in them :-) truly amazing spaces between framing elements of 15-30 feet and the canvas skin over those frames weighs a fraction of even laminated wood. The weight saving techniques of those designs is startling.
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Re: Aircraft question
Post by Weird Harold   » Mon Aug 22, 2016 11:46 pm

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Silverwall wrote:One thing that really jumps out when looking at airship frames is how LITTLE metal they had in them :-) truly amazing spaces between framing elements of 15-30 feet and the canvas skin over those frames weighs a fraction of even laminated wood. The weight saving techniques of those designs is startling.


The structural contribution of "doped canvas" is also largely underestimated.
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Re: Aircraft question
Post by Dilandu   » Tue Aug 23, 2016 1:53 am

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Silverwall wrote:By the way Zeppelin type airships are a non starter without aluminum frame construction.


Sigh.

https://en.wikipedia.org/wiki/List_of_S ... z_airships

Read. This. Immediatedly.

The Schutte-Lanz airships were rigid airships with wooden frames.
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Oh well, if shortening the front is what the Germans crave,
Let's shorten it to very end - the length of Fuhrer's grave.

(Red Army lyrics from 1945)
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Re: Aircraft question
Post by Dilandu   » Tue Aug 23, 2016 1:55 am

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Silverwall wrote:
I find it hard to believe that the skeleton of a large airship could be effectively built using wood/bamboo construction these things are huge and one of the reasons for using metals is the hogging problem and sideways bending.


You are just completely wrong.

Image

SL-1 during construction. All plywood and geodesic lines.
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Oh well, if shortening the front is what the Germans crave,
Let's shorten it to very end - the length of Fuhrer's grave.

(Red Army lyrics from 1945)
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Re: Aircraft question
Post by Randomiser   » Tue Aug 23, 2016 4:14 am

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Fascinating reference Dilandu. These airships were prone to structural deterioration from water penetration and none of them had a long service life, but the best carried out 37 missions in WW1.
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