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Old 11-28-2020, 10:48 AM   #21
rotorwrench
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Default Re: Repair of Soft Wood

Up until the modern era, casein glues were common for wood. Polyvinyl acetate or PVA glues (Elmer's for one) took over the basic joining of wood and is still common but there is a caveat to use of PVA. It and casein adhesives don't take to moisture all that well over time. The FAA still lists resorcinol adhesive as the only product to be safely used in aircraft structure. The FAA and its predicessor, the CAA made these decisions due to the resorcinol-formandehyde adhesive being able to take moisture well beyond polyvinyl or milk protein based glues.

The caveat of epoxy is also found in FAA literature. They leave the use of epoxy based glues open in the advisory circular AC43.13-1B chapter 1 due to the fact that technology changes and some epoxy resins are capable of being used for aircraft structure but they have to be chosen for the capability to take both moisture and heat. If you look at all the stuff available from Jamestown Distributors and other boat supply companies, you will see all sorts of products for restoration of old wood spars, bulkheads, and transoms. Some may be worth looking into and some may be crap. It's best to ask boat repair shops that deal with this stuff to find out what may be good and what may not.

Cyanoacrylate adhesive is not yet listed in FAA publications. I do know that it has heat limitations but the long term strength capability isn't documented yet. Most ester based adhesives like Loktite need the access to oxygen to be limited for them to set up. Heat is used to get them to release their bond. Expansion and contraction rates may also be a problem with cyanoacrylates.

If a person will be keeping the car in a dry environment, the PVA glues would likely work OK for the most part. Just don't leave the car out in the rain a lot. Very hot and humid regions are hell on old wood structures.

Last edited by rotorwrench; 11-28-2020 at 11:09 AM.
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Old 11-28-2020, 12:50 PM   #22
BRENT in 10-uh-C
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Default Re: Repair of Soft Wood

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Originally Posted by Ljpjohnson View Post
Thanks for all the great info, there are a couple of pieces we are going to replace. I like the toothpick idea. Did that for screw holes on door hinges that had been stripped out. Most of the wood is fine. Just a back corner that must hav head a leak.
Hi Linda, I took the liberty to post some of your pix for everyone to visualize along with me. Based on the pictures from your social media post, I honestly feel your wood is too far deteriorated to be considered for any type of repair other than replacement.

I have added a few pictures of a couple cars like yours that we have fabricated new wood for to use an an example, -and I want to point out some things for you to take note of. I am going to assume you & your husband have just removed both exterior sheetmetal panels that are the foundation for the top material. If you did not remove those, please refer to my pictures below so you can see how those should be placed onto the roof rail, back rail, and strainers. These are a huge strengthening panel.

Next, notice how your Belt Rail has become detached from the quarter panel sheetmetal. This is likely due to flexing of the body (-a sign of weak wood). If you look at the pictures I have posted, you will see how the quarter panel and rear panel sheetmetal is tacked to the corner and back belt rail assemblies. Also notice how the finger joint on your rear corner rail is compromised. I am also going to guess that the Quarter Hinge Pillar wood is compromised also if you had to use toothpicks to repair screw holes. Generally in those areas if there is a problem with the threads in the wood, we drill a hole large enough to accept a 1.00" hardwood dowel and glue the dowel into the pillar wood. In your situation, I doubt that would be a viable repair. I wish you luck with your project however I feel like you are in a very unfortunate situation where most of the wood appears to need replacing.

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Old 11-28-2020, 01:33 PM   #23
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Default Re: Repair of Soft Wood

any sort of epoxy will only work as a temp band aid on that wood.


fix it right so it lasts another 75 years.
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Old 11-28-2020, 02:00 PM   #24
Mister Moose
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Default Re: Repair of Soft Wood

There is much that you can't tell from those photos, but even still I see numerous deteriorated areas, not just one. I see a finger joint separated with large gaps. And I again revert to the wood rot rule that what you can't see is more extensive than what you can see.

The boatbuilders test is to take a paring knife and poke around with vigor. Anyplace the blade sinks is trash. That exercise may reveal the extent of damaged wood to you.

Scarfing, epoxy (with or without polyester or carbon fiber), and sistering all have merit where the repair achieves the needed structural strength and is cheaper than ripping it all out and starting anew. Only you can make that judgement, but gather as much info on the extent of the needed repair vs the desired outcome before you decide.

Whew, this discussion makes me glad almost all of my body wood was healthy, about all we replaced were the mounting blocks and a few roof ribs.

Last edited by Mister Moose; 11-28-2020 at 06:35 PM.
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Old 11-29-2020, 10:25 AM   #25
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Default Re: Repair of Soft Wood

another thought on strengthening wood is using hanger bolts.


excellent for pulling two solid pieces of wood together, while using the epoxy elixirs............
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Old 01-30-2021, 05:40 PM   #26
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Thanks for ll the suggestions. I had also posted on a Model A Facebook group and an engineer that does restoration of buildings suggestion Abatron. They have a two step process and both are epoxy. The first is a liquid that hardens the soft wood and then an epoxy wood filler. We were able to do the repairs and the new top has been installed and looks good.
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Old 01-30-2021, 06:12 PM   #27
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Default Re: Repair of Soft Wood

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Originally Posted by Ljpjohnson View Post
Thanks for ll the suggestions. I had also posted on a Model A Facebook group and an engineer that does restoration of buildings suggestion Abatron. They have a two step process and both are epoxy. The first is a liquid that hardens the soft wood and then an epoxy wood filler. We were able to do the repairs and the new top has been installed and looks good.
Great news and thank you for the update!
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Old 02-01-2021, 12:18 PM   #28
BRENT in 10-uh-C
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Default Re: Repair of Soft Wood

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Originally Posted by Ljpjohnson View Post
Thanks for ll the suggestions. I had also posted on a Model A Facebook group and an engineer that does restoration of buildings suggestion Abatron. They have a two step process and both are epoxy. The first is a liquid that hardens the soft wood and then an epoxy wood filler. We were able to do the repairs and the new top has been installed and looks good.

I definitely wish you the best. Unfortunately, my first-hand experiences with a constantly twisting and flexxing Fordor body being driven 'counters' the recommendations of an engineer who is working with a structure that does not twist or flex like a vehicle does when they are driven. However, with that said, maybe if you make your Fordor a static fixture much like a house is, then your successes may be great using that product.
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