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Cost of Rubbing Strakes


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1 hour ago, jake_crew said:

Aircraft are indeed widely bonded together, where weight saving is a priority.

 

Many cars also have significant areas of adhesive bonding rather than welding, esp when dissimilar materials are used.  In may cases the steel "safety cage" is welded steel, but other parts, incl suspension mounts & outer panels are aluminum bonded onto the steel.  When newly applied, these adhesives are stronger than the metal they are stuck to.  Rivets, bolts or other fasteners add significant weight and are not used much.

 

The only but is the long term behaviour of these adhesives, esp during English wet and salty winters and also after what seem to be minor impacts.

 

 

My youngest son's Lotus Elise has a bonded aluminium chassis. It is 20 years old and shows no sign of coming unglued, despite having survived a couple of accidents, one of which was a heavy frontal impact.

 

When new the first production model was submitted for NCAP safety tests and was still driveable after a 30mph impact with a 30 tonne concrete block. Still I understand, the only car to achieve this.

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44 minutes ago, cuthound said:

When new the first production model was submitted for NCAP safety tests and was still driveable after a 30mph impact with a 30 tonne concrete block. Still I understand, the only car to achieve this.

Likely to remain the only car to achieve that. Multiple crumple zones on modern cars would preclude their drivability following such a shunt. But the passengers would be far more cosseted. 

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4 minutes ago, WotEver said:

Likely to remain the only car to achieve that. Multiple crumple zones on modern cars would preclude their drivability following such a shunt. But the passengers would be far more cosseted. 

 

Indeed,  although the Lotus uses bolt on fibreglass honeycomb crash structures front and rear, which do a surprisingly good job of absorbing a heavy impact.

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I have owned a couple of modern Jaguar XK's, both of which were alloy bodied and stuck together with rivets and glue. My concern for these cars long term was that the rivets were zinc plated steel, especially as the first one I owned (2006/56 - 4 years old) showed considerable rivet corrosion under the back end - but clearly it did not stop me from buying another in 2017 (sadly now sold to fund the renovation of a narrow boat) :captain:

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Yes but a rubbing strake has to contend with the not inconsiderable weight of a boat hitting an immovable object albeit at a slow speed. I had an A2 that performed well in a shunt type accident but I don't think the care taken in the construction of an A2, Lotus Elise or Jaguar XK would be replicated by your average artisan on the canals particularly when someone goes shopping with a limited budget. 

 

It would be interesting to know what Kedian's opinion is of the logistics of what is required. 

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9 hours ago, zenataomm said:

That's looking at two each side, did I miss where you said that Laurie?

I agree that it could become complicated regarding fire control on the inside, especially as you're looking at a continuous weld.

 

Are you prepared to be stripping out cabin lining and insulation as well?

Are you looking to upsweep the guards at the pointy end or are you stopping in line with it?

One strip on each side.

No stripping out of boat etc...

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  • 2 weeks later...
On 15/07/2018 at 23:43, Mike the Boilerman said:

 

The cost of the material is trivial compared to welding it on.

 

When I last worked in an engineering firm we charged welding out at £1 per inch. This was in 1978.

In to days prices that works out to be £8400.00.

Clarrie is going in to be done in 2 weeks time.

 

I will let you know the outcome and price then.

 

She is being blacked at the same time, so I won't put the dry docking into the price.

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4 minutes ago, Laurie.Booth said:

In to days prices that works out to be £8400.00.

Clarrie is going in to be done in 2 weeks time.

 

I will let you know the outcome and price then.

 

She is being blacked at the same time, so I won't put the dry docking into the price.

 

 

Our £1 an inch was for a coded welder working to a guaranteed standard in a well equipped engineering factory, with a heavy hierarchy of management perched on top needing paying for. Most of our work was for the MoD.

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23 minutes ago, Mike the Boilerman said:

 

 

Our £1 an inch was for a coded welder working to a guaranteed standard in a well equipped engineering factory, with a heavy hierarchy of management perched on top needing paying for. Most of our work was for the MoD.

No wonder we pay so much tax, its to pay for the welding the M.O.D. have done.

 

Neil

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5 minutes ago, Neil Smith said:

No wonder we pay so much tax, its to pay for the welding the M.O.D. have done.

 

Neil

 

The point I was getting at is welding on a tank NEEDS to be to a known good standard. Welding on Clarrie's rubbing strakes whilst still important for the defence of the realm, doesn't so some costly controls on standards can be dispensed with.

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8 minutes ago, Mike the Boilerman said:

 

The point I was getting at is welding on a tank NEEDS to be to a known good standard. Welding on Clarrie's rubbing strakes whilst still important for the defence of the realm, doesn't so some costly controls on standards can be dispensed with.

I will run a poll on how much it costs, when and if the job is done.

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On 15 July 2018 at 17:09, X Alan W said:

At the beginning of the purpose made leisure boat hull some builders used long tack welds top/bottom of the guard irons  water got trapped between the plate & iron forming rust which over time forced the guard irons to buckle outwards later Div1 builders then fully welded top/bottom edges of the guards

 

On 15 July 2018 at 17:11, David Mack said:

And before that, working boat builders rivetted the guards on - a necessarily intermittent attachment. 

 

On 15 July 2018 at 21:09, Detling said:

Usually wrought iron so not quite as rusty as steel

I believe tack welding of strakes and guards was indeed standard practice on early steel hulls for leisure boats and that the majority of extant riveted boats are of steel construction.

 

JP

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On 16/07/2018 at 14:22, zenataomm said:

True, however an aircraft travelling through the air even at 500 mph is in contact with a powerful force.

Ask this poor sod.

 

 

hqdefault.jpg

This was because the fitter used the wrong size screws to refit the window. It wasn't glued.

BA Flight 5390

 

Police found the windscreen panel and many of the 90 bolts securing it near Cholsey, Oxfordshire.[7] Investigators found that when the windscreen was installed 27 hours before the flight, 84 of the bolts used were 0.026 inches (0.66 mm) too small in diameter (8-32 vs. 10-32; see Unified Thread Standard) and the remainder were 0.1 inches (2.5 mm) too short (0.7 inch vs. 0.8 inch). The previous windscreen had also been fitted using incorrect bolts, which were replaced by the shift maintenance manager on a like-for-like basis without reference to maintenance documentation, as the plane was due to depart shortly.[8] The undersized bolts were unable to withstand the air pressure difference between the cabin and the outside atmosphere during flight. (The windscreen was not of the "plug" type – fitted from the inside so that cabin pressure helps to hold it in place – but of the type fitted from the outside so that cabin pressure tends to dislodge it.)[9]

Investigators found the shift maintenance manager responsible for installing the incorrect bolts and for failing to follow British Airways policies. They recommended that the CAA recognise the need for aircraft engineering personnel to wear corrective glasses if prescribed. They also faulted the policies themselves, which should have required testing or verification by another individual for this critical task. Finally, they found the local Birmingham Airport management responsible for not directly monitoring the shift maintenance manager's working practices.[10]

 

https://en.wikipedia.org/wiki/British_Airways_Flight_5390

Edited by Ray T
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2 hours ago, Captain Pegg said:

 

 

I believe tack welding of strakes and guards was indeed standard practice on early steel hulls for leisure boats and that the majority of extant riveted boats are of steel construction.

 

JP

There is still a good number of " Josher's" left most of which are iron or iron /composite I don't know if it was original practice but remember seeing Joe Gilbert at Charity Dock "slurping' a good amount of "bitcho/pitch" & letting it "go off some" on hull / back of guard before offering up & riveting the guard  he then ran the heat gun along the guard & brushed in the "gloop" I guess this was to lesson the chance of rust build up "tween" steel hull & guard on woolwitch/northwitch GU boats

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23 minutes ago, X Alan W said:

There is still a good number of " Josher's" left most of which are iron or iron /composite I don't know if it was original practice but remember seeing Joe Gilbert at Charity Dock "slurping' a good amount of "bitcho/pitch" & letting it "go off some" on hull / back of guard before offering up & riveting the guard  he then ran the heat gun along the guard & brushed in the "gloop" I guess this was to lesson the chance of rust build up "tween" steel hull & guard on woolwitch/northwitch GU boats

I was mostly thinking of all those ex-GU boats. Anyway I had better not any make any sarcastic comments about that because last time I said that canal carrying history started back in the 1930s as a joke reference their ubiquity I was taken seriously. :D

 

I am sure filling the gap with a 'sealant' was deliberate. On a more modern boat blacking covers the open joint as well and probably infiltrates and builds up over time. Corrosion beneath is still a risk though.

 

JP

Edited by Captain Pegg
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22 hours ago, Ray T said:

This was because the fitter used the wrong size screws to refit the window. It wasn't glued.

BA Flight 5390

 

Police found the windscreen panel and many of the 90 bolts securing it near Cholsey, Oxfordshire.[7] Investigators found that when the windscreen was installed 27 hours before the flight, 84 of the bolts used were 0.026 inches (0.66 mm) too small in diameter (8-32 vs. 10-32; see Unified Thread Standard) and the remainder were 0.1 inches (2.5 mm) too short (0.7 inch vs. 0.8 inch). The previous windscreen had also been fitted using incorrect bolts, which were replaced by the shift maintenance manager on a like-for-like basis without reference to maintenance documentation, as the plane was due to depart shortly.[8] The undersized bolts were unable to withstand the air pressure difference between the cabin and the outside atmosphere during flight. (The windscreen was not of the "plug" type – fitted from the inside so that cabin pressure helps to hold it in place – but of the type fitted from the outside so that cabin pressure tends to dislodge it.)[9]

Investigators found the shift maintenance manager responsible for installing the incorrect bolts and for failing to follow British Airways policies. They recommended that the CAA recognise the need for aircraft engineering personnel to wear corrective glasses if prescribed. They also faulted the policies themselves, which should have required testing or verification by another individual for this critical task. Finally, they found the local Birmingham Airport management responsible for not directly monitoring the shift maintenance manager's working practices.[10]

 

https://en.wikipedia.org/wiki/British_Airways_Flight_5390

So in a nutshell, the manager should have had his work inspected and the inspector should have been inspected too...

 

It’s like the who polices the police police question. 

 

I despair sometimes. 

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About 25 years ago I fixed a boiler for an aircraft maintenance technician, the sort of chap who would have fitted this window. Chatting about work he advised me never to fly with the well known (middle eastern) airline he worked for. He said although he has the theoretical authority to keep an aircraft on the ground until a repair was complete to his satisfaction and signed off,  sometimes this would be overruled by management and the aircraft would fly anyway, without the repair being signed off by the technical staff. Not supposed to be possible but it used to happen.

 

Horrifying really. Hopefully controls have improved since then. 

 

 

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On 30/07/2018 at 09:45, Mike the Boilerman said:

About 25 years ago I fixed a boiler for an aircraft maintenance technician, the sort of chap who would have fitted this window. Chatting about work he advised me never to fly with the well known (middle eastern) airline he worked for. He said although he has the theoretical authority to keep an aircraft on the ground until a repair was complete to his satisfaction and signed off,  sometimes this would be overruled by management and the aircraft would fly anyway, without the repair being signed off by the technical staff. Not supposed to be possible but it used to happen.

 

Horrifying really. Hopefully controls have improved since then. 

 

 

Mate of mine was a captain on BA flying 747-400s. On one landing the reverse thrust failed on one of the engines. The plane can stop quite happily with three, so the standard procedure was to disconnect the controls for that engine’s reverse thrust and bolt it into the ‘ahead’ position until such time as the fault can be rectified. On the next landing that engine’s reverse thrust mechanism (which hadn’t been disconnected) decided to work, ripping out the bolts locking it into position and wrecking the engine in the process. It really does make you question their procedures. 

Edited by WotEver
Corrected me numbers!
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Sorry if i have missed it but at work having a minute. 

 

Why not try Rivet Nuts or known as Rivnuts to traders. 

 

No welding involved. Could be worth a try if using a M8 size .

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On 30/07/2018 at 10:08, WotEver said:

Mate of mine was a captain on BA flying 746-400s. On one landing the reverse thrust failed on one of the engines. The plane can stop quite happily with three, so the standard procedure was to disconnect the controls for that engine’s reverse thrust and bolt it into the ‘ahead’ position until such time as the fault can be rectified. On the next landing that engine’s reverse thrust mechanism (which hadn’t been disconnected) decided to work, ripping out the bolts locking it into position and wrecking the engine in the process. It really does make you question their procedures. 

Perhaps it was because it was a freak and not a 747 400.  :)

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I once had a disturbing experience aboard a Danair Comet. Whilst taxiing to take off at Gatwick and looking out of the window I spied another Danair Comet in a sort of layby having an engine changed by the look of it, using a filthy old mobile crane operated by equally scruffy, oily fitters, holes in their overalls the lot. Danair obviousely didn't have a maintenance hanger at jolly old Gatwick. On looking out at the wing of our plane through the window I noticed broken of matchsticks stuck into pop rivet holes!!!!. Oh!!!! Too late to get off it now. Anyway at 37,000 ft high above somewhere I popped to the toilet, another worrying experience. In there it wasn't insulated and had an emergency escape door to the outside. All around this door there seemed to be a gap with thick ice all around it, through which I could see daylight, the strataspheric sky.  I nearly s--t myself and sat on the toilet for the entire flight, just in case. 

  • Horror 1
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