Brian I'll agree on the purchase price of a VW being 'cheap'.
The critical aspect is that to keep costs down you need to virtually exactly duplicate an existing installation.
As soon as LAA engineering note a change then you will be asked to produce an analysis to support it. At the moment I know of 2 aircraft grounded because of this requirement. The analysis is not that difficult if you are sufficiently technical or know the right people - if you do not then you'll use the price difference....
If the manufacturer has prodcuced an analysis fine - but the vast majority have not and so the individual will have to satisfy LAA engineering.
Airframe Welding - Sonerai II LS
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Brian Hope
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Pete, on an aircraft like the Sonerai, the plans do not show detailed firewall forward installation, so the builder and his inspector have a degree of freedom. 'Good aeronautical practise' is the benchmark. Provided the engine is going to fit as per standard Sonerais - with the X casting and therefore probably a Great Plains engine rather than an Aero Vee, the rest is down to the builder and inspector and does not require mod approval. If he was going to fit a non VW engine and the mount required changing, that would be a different matter.
Brian I know a chap with a Sonerai IIL - he had to produce a stress analysis for his mount. Where I am based there is a Spitfire replica which LAA engineering will not approve without a full analysis - although it was produced by the kit manufacturer (using normal aeronautical practice).
In the days when the Sonerai was a 'current' design you could use engineering practice and get these things approved - that is no longer allowed (a friend had to produce a stress analysis for a battery mount on the firewall of his Condor!).
So my point is that you MUST EXACTLY duplicate an already approved aircraft's details to avoid these pitfalls. If you do that then a cheap engine and installation is possible. Diverge from that already approved desing (possibly because the parts are no longer available) and the pitfalls await.
We know why we have got here, but the change from an enabling organisation to one that approves as a delegated regulator has had a big impact on projects like these.
In the days when the Sonerai was a 'current' design you could use engineering practice and get these things approved - that is no longer allowed (a friend had to produce a stress analysis for a battery mount on the firewall of his Condor!).
So my point is that you MUST EXACTLY duplicate an already approved aircraft's details to avoid these pitfalls. If you do that then a cheap engine and installation is possible. Diverge from that already approved desing (possibly because the parts are no longer available) and the pitfalls await.
We know why we have got here, but the change from an enabling organisation to one that approves as a delegated regulator has had a big impact on projects like these.
Pete Morris
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Brian Hope
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Pete, the Condor was a CoA design so there is a standard approved firewall forward to which they must comply. Therefore any changes, such as altering the battery box, are mods.
If Craig decides to go ahead with his Sonerai, and he is building it in accordance with the approved plans, engine mount etc, then the minor issues such as where he fits his gascolator, how he runs his exhaust system etc are down to him and his inspector. As far as the engine goes, it must conform to an already approved set up, so if for instance he decided to use a home grown electronic ignition, that would need approval. However, if he uses a Leburg or mags, he won't have a problem.
If the Spitfire you are talking about is a new design, or has a new mount etc, or is an approved kit that has a standard firewall forward, then it will need approvals.
That is my understanding of the rules but you would be wise to check with Engineering before proceeding.
If Craig decides to go ahead with his Sonerai, and he is building it in accordance with the approved plans, engine mount etc, then the minor issues such as where he fits his gascolator, how he runs his exhaust system etc are down to him and his inspector. As far as the engine goes, it must conform to an already approved set up, so if for instance he decided to use a home grown electronic ignition, that would need approval. However, if he uses a Leburg or mags, he won't have a problem.
If the Spitfire you are talking about is a new design, or has a new mount etc, or is an approved kit that has a standard firewall forward, then it will need approvals.
That is my understanding of the rules but you would be wise to check with Engineering before proceeding.
Last edited by Brian Hope on Fri May 28, 2010 7:29 pm, edited 1 time in total.
welshman wrote:Strange things happen with welding rules, it appears that fuel tanks do not have to be welded by an approved welder never mind what material its made of, but exhaust systems do require an approved welder.
Personally I'd prefere to see a reasonable weld by a competant welder (not CAA welder ) on something I was flying than take a chance on a Glass reinforced plastic (GRP) aircraft that has been manufactured in someones garage/workshop that does not have heat and humidity control.
as a composites guy myself, id much rather trust epoxy than a high temp welding process
Only just seen the thread so my comments are a bit late.
Having built an RV9A, I wanted a more challenging project so decided to build a Wittman Tailwind. I had never welded before. I took a two week welding course with TWI and submitted my three test pieces at the end of the two weeks. The test pieces and tube thicknesses are completely defined in the CAA regs. My test pieces passed so within three weeks I was a CAA approved welder for 4130. If you are an experienced welder then you won't need much training but I would recommend one day with a CAA approved training organisation to learn the techniques and standards required to pass the tests. The test pieces are examined visually, microscopically, and destructively so they need to be right. The costs to have the test pieces examined is around £750. To keep your CAA ticket you need to do one piece each year so about £250/annum.
As someone else has commented the LAA allow a complete build on the basis of a single CAA approval without annual revalidation if that is what you want to do.
I bought a good quality DC only (won't weld aluminium) inverter based 150amp TIG welder for £500 second hand. This runs happily on a 13 amp socket and I've never used more than about 60amps welding current which was on the undercarriage mount. Bottles of gas are around £100/refill and I will have used 5 in my build by the time everything is completely finished.
4130 does not need stress relieving - this is an old wives tale that seems to be perpetuated by the gas welders union. As long as you use the correct filler the welds will be fine.
Full details of my build are on www.tailwindbuild.blogspot.com for anyone interested, the welding is in the earlier posts.
In summary, don't be frightened off the CAA qualification, the costs are as above and you end up with a professional qualification which you can use to then "sell" your services if you wish. This wasn't my objective but the satisfaction of seeing a complete airframe that I have created from lengths of tube and where every weld is my own work has been worth every penny of the time and cost of getting qualified.
Best regards
Peter
Having built an RV9A, I wanted a more challenging project so decided to build a Wittman Tailwind. I had never welded before. I took a two week welding course with TWI and submitted my three test pieces at the end of the two weeks. The test pieces and tube thicknesses are completely defined in the CAA regs. My test pieces passed so within three weeks I was a CAA approved welder for 4130. If you are an experienced welder then you won't need much training but I would recommend one day with a CAA approved training organisation to learn the techniques and standards required to pass the tests. The test pieces are examined visually, microscopically, and destructively so they need to be right. The costs to have the test pieces examined is around £750. To keep your CAA ticket you need to do one piece each year so about £250/annum.
As someone else has commented the LAA allow a complete build on the basis of a single CAA approval without annual revalidation if that is what you want to do.
I bought a good quality DC only (won't weld aluminium) inverter based 150amp TIG welder for £500 second hand. This runs happily on a 13 amp socket and I've never used more than about 60amps welding current which was on the undercarriage mount. Bottles of gas are around £100/refill and I will have used 5 in my build by the time everything is completely finished.
4130 does not need stress relieving - this is an old wives tale that seems to be perpetuated by the gas welders union. As long as you use the correct filler the welds will be fine.
Full details of my build are on www.tailwindbuild.blogspot.com for anyone interested, the welding is in the earlier posts.
In summary, don't be frightened off the CAA qualification, the costs are as above and you end up with a professional qualification which you can use to then "sell" your services if you wish. This wasn't my objective but the satisfaction of seeing a complete airframe that I have created from lengths of tube and where every weld is my own work has been worth every penny of the time and cost of getting qualified.
Best regards
Peter
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Bill McCarthy
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The nuc industry have the technology to do it properly (probably) - aircraft builders don't. The gas welders view is that you play a flame over the metal until it is dull red and then let it cool. This is inexact and capable of doing more harm than good. The important factors when TIG welding are to do it indoors with no significant air movement, not under any circumstances to force cool, but to let the metal cool naturally. If the metal is cold before welding (below say 15C) then it is worth gently heating it first, but a hairdryer is all that is needed.
I have also worked in the nuc industry and some of their practices are great in theory and less so in practice. We had to heat soak the production 20 computer 2000 ADC monitoring system at 40C for 48 hours as part of the system acceptance test. It passed the test but the net result is a predictable reduction in mean time to failure. Now testing throw-away samples to confirm heat tolerance might have been a good idea, but no - that isn't the nuc way
Best regards
Peter
I have also worked in the nuc industry and some of their practices are great in theory and less so in practice. We had to heat soak the production 20 computer 2000 ADC monitoring system at 40C for 48 hours as part of the system acceptance test. It passed the test but the net result is a predictable reduction in mean time to failure. Now testing throw-away samples to confirm heat tolerance might have been a good idea, but no - that isn't the nuc way
Best regards
Peter
Last edited by matherp on Fri May 28, 2010 6:05 pm, edited 2 times in total.
026807
I work in Oil and Gas and 4130 is almost never post weld heat treated (usually only when multiple major repairs are carried out on major assemblies (wellheads or BOPs) - even then it is regarded as an optional precaution). More directly airframes are almost never heat treated - even when MIG welded.
That includes all of the certified tubular airframe and any/all of the recent kits (Avid/Kitfox etc).
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Gas welders as stated earlier seem desparate to defend their methods
Please don't try to build a airframe like the nuclear industry - it'll never get off the ground!
That includes all of the certified tubular airframe and any/all of the recent kits (Avid/Kitfox etc).
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Gas welders as stated earlier seem desparate to defend their methods
Please don't try to build a airframe like the nuclear industry - it'll never get off the ground!
Pete Morris
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Bill McCarthy
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You will get away with post weld heat treatment in thin wall stuff, but it is still important to wrap the weld on completion to arrest the cooldown rate (post TIG weld). The most important thing is weld preparation, weld gap setting, and back purging to prevent oxidation on the inside of the tubing. Fusible inserts would not be necessary on thin wall tubing. If I embarked on a tubular framework for an aircraft (for myself) I would employ nuc standards to ensure the best possible outcome. I would then flush all framework as much as possible with hot linseed oil (as they did in the old days apparently) to prevent internal corrosion.
Bill
If you build an airframe you are free to do as you wish but the common wisdom of people who have built airframes is different. I quote from Jim Clement in the US who has built 10 Tailwinds re linseed:
"I totally agree that linseed inside tube treatment is not a good idea. If you ever have to weld after treatment, wear a firesuit and full face welding mask. Just when the weld starts to puddle it will blow out flaming linseed oil, like looking directly into a blow torch. Then as you try to continue welding it melts the coagulated oil and you will have a fireball around the area you are attempting to weld. Also as it drips to the floor that also will be burning."
Nobody building airframes, not even the gas welders, wrap welds after welding, as long as you are indoors and not in a draft, the metal stays plenty hot and I have the scars on my arms to prove it.
Cleanliness in weld preparation is very important but the fit of pieces does not actually need to be that accurate. With thin tubing the typical weld is thicker and stronger than the tubing and can make up for less than perfect gaps. As it happens, I used a notcher to get tight fitting joints but the EAA welding instructor whose video of joint preparation is on the EAA web site uses tin snips on thin tubing to get a rough fit and creates beautiful finished joints.
Nobody back purges in airframe building, it is totally impracticable to find a route for the gas flow and the costs of purging gas would probably exceed the rest of the build.
Building a safe, durable airframe does not need going beyond the practices that have been employed over many years by the certified industry, let alone home builders. The LAA requirement for CAA certification may seem onerous but it ensures a certain level of skill and familiarity with standard practice in aircraft building.
I'm sorry to have to contradict your points in this way but it is essential that prospective builders don't get put off by believing that airframe building to a safe quality is something beyond them given due care and appropriate training
best regards
Peter
If you build an airframe you are free to do as you wish but the common wisdom of people who have built airframes is different. I quote from Jim Clement in the US who has built 10 Tailwinds re linseed:
"I totally agree that linseed inside tube treatment is not a good idea. If you ever have to weld after treatment, wear a firesuit and full face welding mask. Just when the weld starts to puddle it will blow out flaming linseed oil, like looking directly into a blow torch. Then as you try to continue welding it melts the coagulated oil and you will have a fireball around the area you are attempting to weld. Also as it drips to the floor that also will be burning."
Nobody building airframes, not even the gas welders, wrap welds after welding, as long as you are indoors and not in a draft, the metal stays plenty hot and I have the scars on my arms to prove it.
Cleanliness in weld preparation is very important but the fit of pieces does not actually need to be that accurate. With thin tubing the typical weld is thicker and stronger than the tubing and can make up for less than perfect gaps. As it happens, I used a notcher to get tight fitting joints but the EAA welding instructor whose video of joint preparation is on the EAA web site uses tin snips on thin tubing to get a rough fit and creates beautiful finished joints.
Nobody back purges in airframe building, it is totally impracticable to find a route for the gas flow and the costs of purging gas would probably exceed the rest of the build.
Building a safe, durable airframe does not need going beyond the practices that have been employed over many years by the certified industry, let alone home builders. The LAA requirement for CAA certification may seem onerous but it ensures a certain level of skill and familiarity with standard practice in aircraft building.
I'm sorry to have to contradict your points in this way but it is essential that prospective builders don't get put off by believing that airframe building to a safe quality is something beyond them given due care and appropriate training
best regards
Peter
026807
No Bill - stop thinking nuclear! Your industry has adopted a large number of 'practices' on the basis that costs are irrelevant and the nuclear industry is always right.
My own experience of huge weld repairs of large 4130 fabrications is that the mechanical propoerties are amazingly relisient - much more so than the usual 'oilfield specs' materials. Where we have post weld heat treated these assemblies there has been NO improvement in mechanical properties - which were within specification to start with!
Do it the way the certified airframe builders do it - they actually know much better what works in their applications - how would you fancy my telling you how to weld in your industry?
My own experience of huge weld repairs of large 4130 fabrications is that the mechanical propoerties are amazingly relisient - much more so than the usual 'oilfield specs' materials. Where we have post weld heat treated these assemblies there has been NO improvement in mechanical properties - which were within specification to start with!
Do it the way the certified airframe builders do it - they actually know much better what works in their applications - how would you fancy my telling you how to weld in your industry?
Pete Morris
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ian herdis
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