Tying the aircraft down

[Moneybox]

22 minutes ago, BrendAn said:

the cheapest hangar for mb might be to dig a hole with a ramp entrance and put a roof over it.  might need a pump and float switch when it rains.  

i have seen a similar concept where the roof was a swimming pool that moved aside for vertical takeoffs.

 

I think it might be advisable to test the rate of climb of an Evektor Sportstar while still on the ground 😏

[BrendAn]

3 minutes ago, onetrack said:

He's not a Brenda - he's Brendan, the huge snarly tattooed truckie, and that could create trouble for you, calling him a girl.

all depends if i want to play netball or womens afl.

[BrendAn]

6 hours ago, onetrack said:

Steel is horribly expensive today, and shed kit suppliers and builders don't care what they charge, they have more work than they can poke a stick at. If the Cue Council is agreeable to the construction of a used shed, then picking up a dismantled shed or used shed frame can be an attractive option. The sheds built from lipped channel are flimsy, they will buckle up in a willy-willy. Go for portal-frame structural steel.

 

I'm currently building an 8M x 12M x 4M shed using modified portal frames made from structural steel, that came from a powerhouse at Koolyanobbing. Stratco want $25,000 for a shed that size, made from pressed metal. I'll do it for less than half that figure and that includes buying all new Z-purlins and girts and new Colorbond sheeting.

I found a young bloke in Darlington who does draughting, structural design and council planning, and he's knocking up the plans for the shed, doing the structural calculations, and drawing up all the paperwork for the council, so I can get a building permit.

You have to do all this yourself in W.A. today, there was a big change in 2012 as regards building construction permits and procedures. Before 2012, you submitted plans, and the council had to do all the assessments, now YOU have to provide all the engineering certificates, calculations, etc, so the council just has to check it all out on the submitted paperwork and then approve or reject the submission. It reduces the amount of work the council has to do, and throws it all on your shoulders.

 

There's a FB page called "Best Sheds of W.A.", but it's set up by a shed builder who specialises in pressed-metal sheds, and all the followers want the cheapest pressed-metal shed they can get. But the group is full of useful information and contacts.

 

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The wreckage photos shows what happens to pressed-metal sheds, when a decent storm comes through. It can be pretty devastating.

 

 

 

 

that frame you made was a ripper. nice and strong.  the collapsed shed looks like my garden shed about a week after i assembled it.

[BrendAn]

2 hours ago, rgmwa said:

Unless the container setup has been designed to have one end enclosed, you might find it will not stand up to strong winds. The air gets trapped in one direction and the positive pressure significantly increases the total uplift on the roof. When the wind blows in the opposite or sideways directions, the internal pressure drops increasing the negative pressure wanting to pull it down, although that's usually less of a problem than the uplift.

 

Portal rafters can buckle under wind uplift whether they are made of trusses, I-beams or pressed metal lipped sections unless the bottom flanges or chords are braced back to the purlins at certain locations. Same with the columns. These sheds should also have wall and roof bracing and not rely on the sheeting to do the work.

 

While Increasing the truss span from 4.8m to 8m doesn't seem like a lot, it can increase the stresses in the trusses and columns by a factor of about 2.5 to 3 for the same loading, all things being equal. On the other hand most structures rarely if ever experience their full design loads.  I have a hangar made from second hand materials that has stood up quite happily for more than 20 years that I probably couldn't prove would stand up under the wind loads loads it should be designed for. So far, so good.

 

i have been thinking about this and if i remember correctly the arched roof that went on had a gap around the bottom. that would have relieved air pressure.

[skippydiesel]

6 hours ago, Moneybox said:

I don't know who owns it. It's surely on crown land as there's very little freehold land in Western Australia outside the town boundaries. When I told the owner of the current hanger that I was considering putting something up out there he said that it has to be a CASA approved structure because they don't want anything loose floating about the airstrip in bad weather. The shire operate it.

I have never heard of CASA becoming involved/setting standard for hangers - I very much doubt thewordy of the one and only Cue hanger people. Having a structure that will not blow away and do damage, is a reasonable position. Their structure/hanger doesn't sound so crash hot.

 

There are standards for public airfields / ALA's  - dimensions of runways, distances from obstructions,  slope, surface. et  etc etc

 

Is Cue an air  port ? (as in irregular or regular passenger service RPT)If so there may be more stringent requirements.

 

My research into a prefabricated shelter for my aircraft, would suggest that the suppliers must meet/exceed the wind standards for the area that the kit is being erected in - sounds like a reasonable requirement to me.

 

If local Council maintain the strip, likly they will set the standard for any structures - check it out!😈

 

[rgmwa]

Just now, BrendAn said:

i have been thinking about this and if i remember correctly the arched roof that went on had a gap around the bottom. that would have relieved air pressure.

Yes, it does have a gap and that helps to relieve some of the pressure. Basically, if the area of the opening/s allowing the wind in is greater than the sum of the areas of all the openings letting the wind out, the pressure will build up. If it's the other way around, you get a net suction effect. The effect of openings in the roof and walls in a building is taken into account in the design, for whichever direction the wind is blowing.

 

[Red]

4 hours ago, BrendAn said:

you got me😁.   my name is brendan at the moment anyway

Oops sorry BrendAn, slip of the tongue, but "at the moment"????!!!...😁

[Moneybox]

1 hour ago, Red said:

Oops sorry BrendAn, slip of the tongue, but "at the moment"????!!!...😁

Tying down? Slip of the tongue.... what is going on here?

[Blueadventures]

12 hours ago, onetrack said:

Steel is horribly expensive today, and shed kit suppliers and builders don't care what they charge, they have more work than they can poke a stick at. If the Cue Council is agreeable to the construction of a used shed, then picking up a dismantled shed or used shed frame can be an attractive option. The sheds built from lipped channel are flimsy, they will buckle up in a willy-willy. Go for portal-frame structural steel.

 

I'm currently building an 8M x 12M x 4M shed using modified portal frames made from structural steel, that came from a powerhouse at Koolyanobbing. Stratco want $25,000 for a shed that size, made from pressed metal. I'll do it for less than half that figure and that includes buying all new Z-purlins and girts and new Colorbond sheeting.

I found a young bloke in Darlington who does draughting, structural design and council planning, and he's knocking up the plans for the shed, doing the structural calculations, and drawing up all the paperwork for the council, so I can get a building permit.

You have to do all this yourself in W.A. today, there was a big change in 2012 as regards building construction permits and procedures. Before 2012, you submitted plans, and the council had to do all the assessments, now YOU have to provide all the engineering certificates, calculations, etc, so the council just has to check it all out on the submitted paperwork and then approve or reject the submission. It reduces the amount of work the council has to do, and throws it all on your shoulders.

 

There's a FB page called "Best Sheds of W.A.", but it's set up by a shed builder who specialises in pressed-metal sheds, and all the followers want the cheapest pressed-metal shed they can get. But the group is full of useful information and contacts.

 

Log into Facebook

WWW.FACEBOOK.COM

---

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The wreckage photos shows what happens to pressed-metal sheds, when a decent storm comes through. It can be pretty devastating.

 

 

 

 

No fly straps or cross bracing that we have in North Queensland for cyclone rating.  Cross bracing would have helped stop it falling back.

[Marty_d]

https://www.nowbuildings.com.au/sheds/farm-sheds/open-bay-farm-sheds/hangar/

[onetrack]

Marty, note the total lack of cross-bracing in the walls and roof of the shed you linked to. In addition, there's a serious lack of bracing at the apex of the rafters, and at the knee joints with the columns.

These are critical areas that come under heavy load with wind gusts.

Add in the fact that the lipped C-channel sections in the frame are notorious for twisting and thus losing inherent strength - and that this has to be addressed by using braces between the frame and purlins and girts - but the shed shows none of that style of frame bracing.

 

The minimum requirement for knee bracing -

 

 

Here is improved knee bracing - and also showing rafter bracing to the purlins to prevent twist - but this design still lacks adequate apex bracing, to my mind.

 

Edited 7 hours ago by onetrack

[Moneybox]

They are relying on the sheet steel to give it the diagonal bracing and that might work with enough tek screws fastening it.

[facthunter]

It all looks too lite for me.  Nev

[rgmwa]

1 hour ago, Moneybox said:

They are relying on the sheet steel to give it the diagonal bracing and that might work with enough tek screws fastening it.

They do have some tension rod diagonal bracing in the roof and may also have it in the end bay side walls. They have also braced the unsupported rafter and column flanges back to the purlins and girts to resist buckling. I don't like the look of the portal connections much, but they may be OK.

Other cold-formed structures I've seen used back to back C-sections bolted together with central gusset plates and spacers, and used bolts instead of Tek screws, but there are many ways to skin a cat. Cold formed structure design is pretty specialised and the design calculations can become very complex because the components are so thin and secondary effects such as small eccentricities in the structure become very important.

It's pretty tedious and long-winded to do it by hand and you really need computer software written by experts, but then of course, it can be a case of garbage in, garbage out.

 

[skippydiesel]

IF (??) the manufacturer is supplying a structure that has been "certified" for wind gusts in your area, they would be taking one hell of a risk if the structure was not up to par , of not only claims against the structures collapse but also for anything contained within and if iparts blow away and damage done elsewhere - whole thing could become very costly.😈

[facthunter]

THIN  sheet is suss. It easily crumples and can be ripped with set of vice Jaws and a bit of strength.  A pathetic gusset in a corner with bendy beams will never be rigid. You NEED trusses that are triangulated and the Proper computations The IG DOOR at one end complicates things  You have to engineer a triangle  ideally at both sides of the opening to make the corners stay square viewed from the front elevation  Nev

[Moneybox]

Anything you alter could upset your structural warranty and even a potential insurance payout. 

[facthunter]

There's a proper way to go about building/designing such structures. Ask to see the computations and see / check if they meet your expectations. I wouldn't go for JUST making it.  They'll easily worm out of Paying out by claiming the wind weas stronger than what the design met.  Nev

[Blueadventures]

4 hours ago, onetrack said:

Marty, note the total lack of cross-bracing in the walls and roof of the shed you linked to. In addition, there's a serious lack of bracing at the apex of the rafters, and at the knee joints with the columns.

These are critical areas that come under heavy load with wind gusts.

Add in the fact that the lipped C-channel sections in the frame are notorious for twisting and thus losing inherent strength - and that this has to be addressed by using braces between the frame and purlins and girts - but the shed shows none of that style of frame bracing.

 

The minimum requirement for knee bracing -

 

 

Here is improved knee bracing - and also showing rafter bracing to the purlins to prevent twist - but this design still lacks adequate apex bracing, to my mind.

 

The rafter bracing is what I referred to as Fly straps and the back side space on both sides would be cross braced and also the front ones,

[onetrack]

In W.A., the structural engineer certifies the design as safe and meeting structural standards, so I'd guess the buck stops with him.

As to wind speeds, that would have to be a curly one when it comes to a stoush over a collapsed shed.

Willy-willies/mini-tornadoes can develop high wind speeds over a small area and a short distance.

I can recall my father telling me about seeing a windmill tower screwed up so tightly by a willy-willy, the tower ended up looking like a length of steel wire rope.

You'd need an anemometer on the site to be able to get the exact wind speed of any willy-willy.

[rgmwa]

26 minutes ago, facthunter said:

 They'll easily worm out of Paying out by claiming the wind was stronger than what the design met.  Nev

No they can't, unless you bought a kit designed for Victoria or Tasmania and decided to put in on your block in Port Hedland.

[rgmwa]

19 minutes ago, onetrack said:

In W.A., the structural engineer certifies the design as safe and meeting structural standards, so I'd guess the buck stops with him.

Correct. That's why engineering firms carry Professional Indemnity Insurance.

 

21 minutes ago, onetrack said:

As to wind speeds, that would have to be a curly one when it comes to a stoush over a collapsed shed.

Willy-willies/mini-tornadoes can develop high wind speeds over a small area and a short distance.

I can recall my father telling me about seeing a windmill tower screwed up so tightly by a willy-willy, the tower ended up looking like a length of steel wire rope.

You'd need an anemometer on the site to be able to get the exact wind speed of any willy-willy.

A study of willy-willies in NSW (557 willy willies sampled over 20 days) found they had wind speeds between 1.5m/sec and 7.5m/sec or (5km/hr to 27 km/hr). Seems a bit low to me, but that's what they said.

[Moneybox]

6 minutes ago, rgmwa said:

Correct. That's why engineering firms carry Professional Indemnity Insurance.

 

A study of willy-willies in NSW (557 willy willies sampled over 20 days) found they had wind speeds between 1.5m/sec and 7.5m/sec or (5km/hr to 27 km/hr). Seems a bit low to me, but that's what they said.

That sounds like their speed of travel.

[Blueadventures]

This is the bracing (Fly and cross) for our Northern Queensland ratings.

[rgmwa]

3 minutes ago, Moneybox said:

That sounds like their speed of travel.

Maybe, but then they would more likely have said travel speed, not wind speed. Here's the reference:

Abstract

An extensive census and sampling program conducted in semiarid north-west New South Wales, Australia, has provided quantitative information on willy-willy (dust devils) characteristics and their environmental range. The observation of 557 willy-willies, made over a 20 day census period in summer, indicates that willy-willy frequency varies according to local meteorological conditions. An air temperature lapse rate, measured between 12 and 252 cm of the surface, of 0.9 °C m⁻¹ was required for the initiation of the willy-willies, with their frequency increasing with lapse rate away from the surface. Willy-willies were also found to be restricted to wind speeds between 1.5 and 7.5 m s⁻¹. Analysis of the spatial distribution of willy-willy initiation sites with respect to vegetation cover in the 35 km² study area showed that willy–willy frequency increases with decreasing surface cover. The increased frequency of willy-willies with decreasing vegetation, could, over time, make willy-willies a potent mechanism in the evolution of the Australian landscape.