What to material to use between a wood and metal joint?

[Mike Macartney]

Hi, On this 1914 Humberette body I am trying to decide what material I should use on these joints between the steel sheet metal work and the wood? Any ideas would be appreciated.

The joint I am talking about is between the trunk at the back which is wood and the sheet steel of the main body. I don't particularly want a crack to appear at this join after the car has been painted. Do I put a fillet of body filler on the join or use some sort of flexible seam sealer?

Below are some more close ups of the trunk to body join. There is no visible movement at the gap if you try and push the trunk down or up.

.This is the left hand side at the rear.

This is the right hand side at the rear.

This is where the dashboard/windshield support joins the front scuttle panel. I have the same problem here as to what medium to use at the join.

Here are some close ups of the join.

This is the left hand side at the front.

This at the centre at the front.

Your thoughts would be appreciated.

Mike

 

 

 

 

 

[Gunsmoke]

I assume the original body makers "scribed" the wood to make for a reasonably neat fit to the sheet metal, so my recommendation is to add a small amount of wood, perhaps 1/16"-1/8" thick (glued and clamped) to the old pieces where they have worn somewhat and "shave/scribe" it to get a reasonably neat fit. There would have always been a visible joint of some sort, as the wood shrinks or swells as humidity changes its dimensions. You might also want to place some thin canvas sheeting between wood and metal to prevent squeaks. Finally, are you sure "welting" was not used this early? 

[Mike Macartney]

This Humberette was a fairly cheap cyclecar at the time £135. The wooden trunk is part of the main frame of the car so I cannot remove it to add a small amount of wood. But, you have just given me an idea. I wonder if the top part of the trunk will remove? The part between the lid and the body at the top, I will try and have a look inside the trunk to see if I can see any fixings holding it. I have looked through photos of other Humberette's and they all seem to be a bit different. This car was in storage for 86 years so I believe what is there is pretty original. Thanking you for your ideas. Mike

[Friartuck]

What would be wrong with an air gap between the two surfaces?

[keiser31]

3 minutes ago, Friartuck said:

What would be wrong with an air gap between the two surfaces?

Moisture getting inside the seam.

[kgreen]

The rates of expansion between the two materials is different, meaning that one will shrink or expand quicker or faster than the adjacent part.  Leaving the joint open with a fibrous welting as suggested above would be acceptable.  Yes, that will allow moisture to enter the car but it was not likely made to be waterproof to begin with.  Alternatively, you could use a filet bead of flexible sealer at that joint.  Even if you painted that, it would crack as it is flexible, allowing differential movement between the wood and metal. 

[Spinneyhill]

Without "rigid" attachment between the parts there will always be some flex as it absorbs changes in the road surface, so a flexible joint is needed. Put in something that controls the crack and paint it to prevent the crack looking ragged. A nicely structured tiny air gap would do the job or a thin layer of canvas that doesn't absorb water, maybe.

[901 Packard]

No doubt that the wood was painted prior to assembly, at least primer or what was back then called "red lead". Take a razor blade cutter like an exacto knife, and see if there are any chips that can be removed from the crack. That might tell you if red lead was used to paint the wood prior to its original assembly. It would likely be there to protect to the wood from moisture. Red Lead was also available in a putty form to close gaps for assembly just like this. However as you point out, the dissimilar materials will expand and contract at different rates, so the only solution it to dissemble, repair the gap, and paint both items separately, then reinstall, which I would bet is how it was built originally, and live with the crack that will inevitably occur. If you want to seal it with sealer, then I would use 3M 5200 which is paintable. Mask both sides with fine line tape, and use the least amount possible. Run your finger down the seam multiple times to remove all but the necessary filler. When you remove the tape, then run your finger down the seam one last time to smooth out the tape line.  It will dry in 24 hrs. and stay for years. However personally, I would live with the crack.

[JV Puleo]

I seem to remember a reference to a problem like this in one of my early automobile repair books. It recommended a layer of canvas soaked in white lead... Of course, you can't get white lead anymore but I'm wondering if there might be a similar material. Were I faced with the problem, I'd use some sort of welting or padding... like thin felt weatherproofing... or perhaps a layer of industrial felt. It is still made in a variety of thicknesses. There might be a problem with it absorbing water so some thought would have to be given to how it might be painted or varnished...

[JFranklin]

If you know anybody in the telephone industry ask them about B- sealing tape. it is similar to the black sticky window flashing but narrow like about 1". It is waterproof, flexible, and seals but never hardens. We used it on sealing telephone cases and such.

Edited October 17, 2018 by JFranklin (see edit history)

[PFitz]

Some body building companies, like Walker, used graphited asbestos paper between all the steel and wood to prevent squeaks. Even where the sheet metal was tacked to the wood body framing.  Problem over time was that it absorbed and held moisture causing corrosion of the metal . The Derham bodied cars I've worked on used wax impregnated linen. It didn't absorb moisture and there was no corrosion of metal in contact with it.

 

It's easy, inexpensive, and low tech to make using any cotton cloth such as old bedsheets, old candle stubs, a coffee can and a sterno stove. Cut the cotton sheets into the over-sized shape of the pieces needed to fill each joint. Submerge in melted wax. Lift out slowly and let the excess wax drip off back into the coffee can. In few minutes when the wax cools, finish cutting the cotton to the shape need.

 

For auto seams, caulking gun tubes or cans of autobody seam sealer are meant to be compatible  with auto paints.

 

Paul 

Edited October 17, 2018 by PFitz (see edit history)

[Spinneyhill]

5 hours ago, PFitz said:

held moisture causing corrosion of the metal

Yep, graphite was right there. Galvanic corrosion.

[8E45E]

I believe hot paraffin wax may have been originally smeared onto the bare wood on the side where it mates to the metal body.

 

Craig 

[hidden_hunter]

One of my books talks about 'anti-squeek' material which you should occasionally keep oiled to prevent noises.

[Restorer32]

We rewooded a 1949 Bentley James Young full custom Sedanca Coupe' with about a cord of wood in the body. Every place where wood touched metal there was white athletic tape applied as an anti squeak. Probably WWII surplus.

[playswithbrass]

Twenty years ago I had a similar problem.I used urethane windshield setting sealer and painted over it.Still has not cracked.

[Restorer32]

We would leave a slight gap since the two pieces were obviously not made as a single unit.

[Mike Macartney]

Wow! This forum is absolutely brilliant. It's like having a group of old car enthusiasts in the next room. I thank all of you for your comments and ideas.

Gunsmoke gave me the idea of seeing if the wooden parts would remove. When I went and had a closer inspection I found the following at the rear.

Screws going through the wood framing from the inside of the body and into the wood of the part that was against the sheet metal skin on the trunk side.

On top of the section of wood that attached to the sheet metal I found under the filler, that I chipped away, 4 screws holding it to the vertical sides. All the screws came undone quite easily and with a little wriggling the part came away from the main body.

At the front of the body I found screws under the dash that were holding the wood that is the mounting for the windshield.

These also unscrewed easily and I was then able to remove this section of wood as well. Excellent! This is going to make life a lot easier. Note for myself - Look more closely for clues as to how wooden bits are fixed to the body! Although I have restored a lot of cars in my life I have never restored one of this era before. They have mainly been late vintage and classic cars.

I now know that the first restorer who bought this Humberette in 1995, after it had been in storage since 1926, repanelled the framing with new steel sheet.

You can see here that he must have got fed up trimming the sheet metal and left if too long at this end as it would be hidden by the wooden section that is screwed to the main body.

Removing the wooden beading at the side of the trunk to main body join.

After removing the old bit of wooden moulding, this is what was behind it.

I now have to reread all your ideas and try and decide how to proceed. If anybody has any more ideas I would be pleased to hear from them. Thanks again for all your help so far. Mike

 

 

[Simnut]

 

May not be conducive to the era of the car but is one of the best sealant/adhesives out there in my opinion.

[chistech]

I use roofing felt to close gaps like this and as an anti-squeak. Will not absorb water either. It's very similar to what was used on some cars years ago.

[Mike Macartney]

I am quite willing to use modern materials but would like to retain the original look. The problem being that all the Humberette's I have seen photos of have all been restored differently. I think the Sikaflex 291 maybe ideal for attaching wooden mouldings to cover the join at the sides of the wooden trunk (see the last photo I posted). I am still debating with myself what to use at the top of the trunk box and the wooden windshield mounting to scuttle panel.

[Friartuck]

Perhaps I didn't make my previous response clear enough. Coat each of the surfaces with the appropriate sealer on the wood and paint on the metal & wood. Assemble with an air gap. I do not suggest a fibrous material that would attract or promote moisture to collect between the two surfaces. Even if this little Humbrette is stored indoors, humidity can be factor for moisture.

Edited October 19, 2018 by Friartuck (see edit history)

[PFitz]

One other material I've found used between wood and metal by early body builders was "white lead". It was also used extensively in the boat building industry - often called "bedding compound".

 

The lead prevented corrosion of the metal and the linseed oil in it prevented rot in the wood. Later versions of bedding compound got rid of the lead, but you can still buy the real stuff  though antique boat restoration suppliers

 

  http://www.traditionalboatsupplies.com/consumables/leadbasedproducts/white-lead-paste

 

Paul

[Spinneyhill]

White lead sounds a lot like the old window putty.

[JV Puleo]

I think it is actually a white powder created by oxidizing sheet lead and mixing with linseed oil. Needless to say, it is now banned almost everywhere. The result of this is that the people who need it (usually artists) now make their own which isn't difficult but probably a lot more dangerous than just buying a can.

[Mike Macartney]

With all these old products that are now deemed as dangerous. It amazes me that I am still alive after being born in 1946. Lead paint on toys, DDT used by my mother to kill ants, asbestos iron rest on the ironing board, and many other items that are now banned. How come that there are so many 'old' people still alive?!

[Spinneyhill]

In PNG in 1981, our house outside, outside stairs, handrails, windows etc. were sprayed with DDT to control mosquitoes to prevent malaria. The oil palm settlers' houses (a wooden shack, basically) were sprayed inside and out and all their cooking gear etc. was sprayed too. Everything was sprayed. Hmmmm.

[Mike Macartney]

And you are still alive to tell the story after all these years! How have we survived so long?

[JFranklin]

I remember killing ants with a can of powdered CYANIDE! It did have a skull & crossbones though.

Edited October 23, 2018 by JFranklin (see edit history)

[chistech]

I still have about half a gallon of chlordane the I only use sparingly. Nothing kills ant like that stuff. Bottle is about 40 yrs old.

[Spinneyhill]

On 10/22/2018 at 4:23 AM, Mike Macartney said:

And you are still alive to tell the story after all these years! How have we survived so long?

Yeah, but if any apex predator eats too many of us, they will die!