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Widung
Sweden
189 Posts |
 Posted - 16/10/2007 : 17:36:40
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I making a new aluminium body on an ash frame - any advice and experience about treatment of the ash wood to avoid rot in the future?
Paint? Cuprinol? None at all? |
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Mike
United Kingdom
229 Posts |
Posted - 16/10/2007 : 18:08:01
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Ash is a hard wood so you need to soak the treatment into the grain and the best treatment is yacht varnish. The first coat is diluted with white spirts so its like "Gnats Piss" but it will soak into the grain, particularly the end grain. When dry, coat again but full strength varnish and leave a few days to harden off. Flatten off and then paint the wood with International paints satin black.
Forget Cuprinol I have seen rotten "new" ash bodies that have had the so called cuprinol treatment and if it is so good why are wooden yachts not painted in it. My M type was done the yacht varnish way in the 1960`s and I believe it still to be as good as new now. So is my 18/80,J2,PA and NA although my 1972 Midget has no wood!
Another recommendation is to glue all the joints with "CASCAMITE" first as it sticks like sxxt to a blanket and will never fail. Again my M type was done this way and was trialed for some 20 years with no joint failure. This is important when panelling in ALI as any joint movement will soon manifest itself in cracks to the alli and paintwork.
So how where they built originally? they were dry jointed and given a quick blow over with black paint. After all they were not expected to last more then ten years at best and it was cheap and chearful.
I have also restored in my time to flying condition a DH Tiger Moth, DH Puss Moth, DH Dragon Rapide and the ill fated DH Mosquito, all using wood, albeit it in spruce but it was treated with an aviation approved varnish not CUPRINOL. |
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John Reid
United Kingdom
704 Posts |
Posted - 16/10/2007 : 20:42:56
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An alternative to Cascamite is to use Aerodux 500, a Ciba-Geigy two pack (adhesive + hardener in 1:1) resorcinol-formaldehyde adhesive. Used extensively in wooden aircraft building and restoration.
I would endorse Mike's varnish treatment.
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Mike
United Kingdom
229 Posts |
Posted - 16/10/2007 : 22:41:38
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John,
I have used this glue in the aircraft industry and once used it in wooden slalom canoe construction but it was not as widely available as Cascamite indeed I have not seen it for years. I do remember though it was a very good wood glue. By the way Cascamite was bought out by Humbrol and I think it is now marketed as EXTRAMITE.
A word of caution if using CASCAMITE / EXTRAMITE it should when mixed with water look like toffee or "Snott" as someone once said to me. If it goes into a white paste then the tin has been in store too long, although the manufacturers denied it had a shelf life when I sent a tin back to them for comment. Three replacement tins arrived a week later no less!
M ELLIS |
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John Reid
United Kingdom
704 Posts |
Posted - 17/10/2007 : 00:06:26
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Mike,
You are right that Cascamite is more readily available, but Aerodux is still around and I have bought it from LAS Aerospace Ltd. Their website is www.lasaero.com .
Aerodux 500 is the resin at ú17.95 a kilo and Aerodux 501 is the hardener at ú7.60 a kilo. It is one of the approved glues currently listed by the Popular Flying Association for homebuilt aircraft.
John R |
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talbot
United Kingdom
718 Posts |
Posted - 17/10/2007 : 09:01:19
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Weren't the joints originally dry fitted to allow for some flexibility? The M type chassis isn't at all rigid and I fear that if glued joints can not move something else will.
Jan T |
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Mike
United Kingdom
229 Posts |
Posted - 17/10/2007 : 12:34:46
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The ash will take the flexibility with the joint glued. My M type did all the VSCC trials, ever tried the VSCC Lakeland Trial for example?
When I sold the car some 20 years on the body was still like new unlike some other M type restorations which were falling apart and they have never been trialed since restoration. By the way I could still win an MGCC concours after a VSCC trial.
Don`t forget the M type scuttle is only joined to the boat tail by the floor boards and an ash rail so the scuttle will flex one way and the boat tail the other. On some flimsy restorations I have seen doors fly open on undulating ground although it never happened to my M.
I think the body firm "Weyman" put cloth between the joints to stop them creaking, needless to say the body did not last too long.
Going back to wooden aircraft I think you will find more stress on the wooden airframe then an M type and the joints were glued.
M ELLIS |
Edited by - Mike on 17/10/2007 13:09:11 |
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Widung
Sweden
189 Posts |
Posted - 17/10/2007 : 20:27:37
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Thank you very much all of you - I am very happy that I asked, otherwise I would have used the wrong method!
A grateful Jan W |
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tholden
United Kingdom
1626 Posts |
Posted - 17/10/2007 : 23:54:27
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I agree with what Mike says about treating ash frames with varnish although Cuprinol may give better protection on the plywood which is far more prone to attack by the dreaded worm. As with most things MMM I also respect his view on the desirability of glueing joints based on his experiences.
However I think it is worth pointing out that there is a diversity of views on this particular subject. Coachbuilders I have spoken to over the years have been split in their opinions on whether joints should be glued or dry jointed. I think it is also worth pointing out that the design of the M type body leaves it less prone to damage from chassis flexing than the later square rigged cars and that different principles may apply.
I have to say that all the bodies I have ever used have had glued joints and that like Mike I have never had a problem with timbers splitting. However I know people who have had problems particularly with J F and L types where the chassis frames may well flex more than later models.
On these models it was once suggested to me that the best solution is to glue the joints which are in the lower part of the body close to the chasis mounting rails at either side and to leave dry and slightly flexible some of the joints at top of the door posts, rear of the body and upper part of the scuttle where the effects of flexing are most likely to damage the timbers.
These bodies from Carbodies and Mulliner were dirt cheap and it is possible that they were not glued to save time and money in construction. Whether the manufacturere would have deemed it desirable is an interesting question which we will probably never know the answer to ! However if flexibility was seen as desirable why go to so much trouble to put in the steel strengthening bar at the inside top of the body ?
So what is the answer ? I guess on M types I would glue all the joints. On the P's amd N's I would also glue them because both these chassis's are more rigid and the bodies are stronger. However on the J, F and L there is the possibility of timber damage if all the joints are glued and it might be wise to consider leaving some of the joints in the areas I mention above dry jointed.
Jack up one rear corner of a J.L or F type and see how the body moves then make your own decision. It is your choice !
Terry Holden |
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sam christie
United Kingdom
3056 Posts |
Posted - 18/10/2007 : 00:00:43
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Was there a suitable glue available in the early 1930's if the coachbuilders had decided to glue the joints?
Sam |
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Mike
United Kingdom
229 Posts |
Posted - 18/10/2007 : 07:55:47
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Glues of the 30`s were often made from animal by products including rendering down cattle bones, that`s why plywood was often eaten away by wood worm, as it was the glue they were after. Glues were not that readily available or of the quality of todays modern adhesives so cost was an important factor. Anyone remember their days in school and woodwork classes, there was always a pot on the gas ring of evil smelling dark toffee like glue called beetle glue.
By the way we are all guilty of panelling our cars in alli ( I am not!) but the J2/P and others had steel scuttle tops and steel side panels up to the lower rear door hinge. On J`s the back was wrapped in alli but P types were steel. Even doors were steel panelled, I remember dismantling five P type bodies and there was beech rails where the steel was hand beaten over the frame not ash. I think I have mentioned this before, it was not until the T type that wooden bucks were used to pre make the panels on before fitting them to the body.
Plywood was birch 5 ply not the cheap B & Q 3 ply crap, you can still get birch plywood which comes from Russia and is of excellant quality, again used in wooden aircraft construction.
So if they used steel panels it must have been to beef up the flimsy wooden body.
M ELLIS |
Edited by - Mike on 18/10/2007 10:14:50 |
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Richard Hardy
United Kingdom
2138 Posts |
Posted - 19/10/2007 : 14:40:10
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quote:
Originally posted by Yorvik
quote:
Originally posted by Yorvik
quote:
Originally posted by Yorvik
Differing views here. I carrried out quite a bit of research 20 years ago when I built the first of several bodies. Mike is correct, in that certain coach builders of larger cars, mainly bodies to Bentley and Rolls Royce had cloth between the joints.
I was advised by several specialists not to glue the joints as the body must be able to flex and short timbers in small cars cannot always accommodate large degrees of flex without breaking. Terry Holden is quite right in his comments that the midget and magna chassis can flex considerably and I certainly would not like to jack my car up on one corner if it had glued joints. In addition, if you glue the joints and they break then you are going to have an even bigger job inserting new timbers. One option which I have acted on is to use crosshead screws and a small drop of oil which allows screws to be torqued up very tight, especially if using a torque set drill. The Joint should remain tight without the need for glue, even if trialing.
I am involved in rebuilding an overturned Brooklands MG at the moment which involves inserting new replacement timbers to the broken frame. I would not be too keen to sort if I had to separate glued joints. It is however advisable to line the joint lines with waterproof flexible glue but not to glue the faces.
Food for thought but there is enough info here for people to form their own opinions on this one. I was incidentally advised that 3 or 4 heavy coats of Cuprinol 5 Star Treatment was fine for the job. The exposed lower timbers on my all weather car are as good as new after 20 years. I note however that one of the posts on this subject considers Cuprinol to be innapropriate.
Oh Mike, in the 1930s I think that steel was cheaper than aluminium. The MG was a cheap car, so possibly down to cheapness rather than strength!!
Rich H
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Edited by - Richard Hardy on 19/10/2007 16:48:23 |
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Mike
United Kingdom
229 Posts |
Posted - 19/10/2007 : 15:41:55
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Rich,
I agree, alli was dearer and possibly scarcer then steel, but do you not think that unless a coach builder had a good solid body he would panel in steel, knowing that any joint movement would soon crack the alli and paintwork.
Going back to aircraft and the use of alluminium, alli has no strength so stressed areas were done in DURAL an alluminium alloy. Engine cowls etc that required air scoops and the like were made in pure alli because you can weld it, unlike DURAL which cannot be welded. The cowlings soon started to crack due to flexing and vibration and as time went on the alli work hardened and cracked even worse.
In conclusion then, paint the alli in CUPRINOL glue the joints with upholstry glue and paint the wood in DULUX emulsion but most of all enjoy your MMM motoring because the way the cars are restored now they will still out live the owners and the oil reserves!
M ELLIS |
Edited by - Mike on 19/10/2007 16:06:48 |
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