And suddenly... I'm single :-D

[DamnedFrog]

Hello All

This is not a classified, this is a bad trick that happened to me this week end at my workshop.

The wooden floor of my Roadster, on passenger side only, litterally crumbled to dust and chips when I stood on it...

I never sat this place, nobody did it fortunately, this could have been a brutal and disgusting death on road for my passenger

The plywood of the floor is 30 years old, and it probabely experienced some periods of dampness. Perfectely dry, it has a perfect appearence but no strength at all

I'll recut both floors with high quality marine plywood, or a plain 4mm sheet of aluminium, I don't know which to choose.

Is there Marlin factory-ready spare parts of that kind ?

Regards,
Christophe.

[Alan c]

Re: And suddenly... I'm single :-D

Lucky escape - You wonder about the MOT tests when you hear this kind of thing.

[stevejgreen]

Re: And suddenly... I'm single :-D

Hello All

This is not a classified, this is a bad trick that happened to me this week end at my workshop.

The wooden floor of my Roadster, on passenger side only, litterally crumbled to dust and chips when I stood on it...

I never sat this place, nobody did it fortunately, this could have been a brutal and disgusting death on road for my passenger

The plywood of the floor is 30 years old, and it probabely experienced some periods of dampness. Perfectely dry, it has a perfect appearence but no strength at all

I'll recut both floors with high quality marine plywood, or a plain 4mm sheet of aluminium, I don't know which to choose.

Is there Marlin factory-ready spare parts of that kind ?

Regards,
Christophe.

Close escape but I guess it all depends on the original build materials.

Either Marine Ply or 4mm ally. But if you go aluminium it's an opportunity to recess the floor a little, lowering the seat, something the taller of us find makes the car more comfortable, no more looking at the top of the screen surround but through the screen!

[DamnedFrog]

Re: And suddenly... I'm single :-D

Hello Steve.

Yes indeed, the little recession of floor is a clever pro, I record it

But I'll have to compute some figures because the major difference between the plywood and the ally is that one is rigid and the second is flexible. A plywood floor would only apply a vertical force on the side corners untill its fails (imagine a floor made of a piece of glass), but an ally sheet (or, worse, a thin stainless steel sheet) would react as a "drum skin" and also apply a traction toward center on the side corners. The forces on the center shaft tunnel won't be the same at all. This has to be carefully designed.

Maybe an hybrid solution would make the job, 3mm high resistance ally sheet on all surface (2xxx, 6xxx) but an additional 5mm under the seat rails.

Regards,
Christophe.

Regards,
Christophe.

Close escape but I guess it all depends on the original build materials.

Either Marine Ply or 4mm ally. But if you go aluminium it's an opportunity to recess the floor a little, lowering the seat, something the taller of us find makes the car more comfortable, no more looking at the top of the screen surround but through the screen!

[stevejgreen]

Re: And suddenly... I'm single :-D

I knew it was somewhere
here or there

[scott h]

Re: And suddenly... I'm single :-D

During the restoration of my Berlinetta, which also has plywood floors, I was a bit concerned that the seats were only supported by the plywood and nothing else. Here is a pic and you can see the large area with no additional support.

253.jpg

So for piece of mind I added a cross member directly under the seats.

500.jpg

[DamnedFrog]

Re: And suddenly... I'm single :-D

Hello Scott.

For sure I was thinking about something like this

But my Roadster don't deserve a total restoration, so welding on the chassis is not an option since it needs a total emptying of the carbody.

I was thinking about parallel additional beams, welded or bolted between front and rear cross beams, but here again the amount of work would be important.

I'll use rather another technique: steel cables strongly bolted (but without tension) between the front and rear cross beams.

There will be a pair of 6mm stainless steel cable running under each floor between front and rear cross beams, cables themselve protected from dirt by an omega-shaped rail bolted on external side of floor.

The floors will be both changed, so the failure risk would be near zero, but with such a pair of "security belt" running under each board and beeing able to stand hundreds of Kg with a relative elasticity, I'm safe, not to say that even if the boards are floating again, nothing would happen

En Français: Chat échaudé craint l'eau froide

(the scalded cat is afraid of cold water, "echauder" is an old french verb outdated nowadays)

Regards,
Christophe.

[greyV8pete]

Re: And suddenly... I'm single :-D

Hello Scott.

For sure I was thinking about something like this

But my Roadster don't deserve a total restoration, so welding on the chassis is not an option since it needs a total emptying of the carbody.

I was thinking about parallel additional beams, welded or bolted between front and rear cross beams, but here again the amount of work would be important.

I'll use rather another technique: steel cables strongly bolted (but without tension) between the front and rear cross beams.

There will be a pair of 6mm stainless steel cable running under each floor between front and rear cross beams, cables themselve protected from dirt by an omega-shaped rail bolted on external side of floor.

The floors will be both changed, so the failure risk would be near zero, but with such a pair of "security belt" running under each board and beeing able to stand hundreds of Kg with a relative elasticity, I'm safe, not to say that even if the boards are floating again, nothing would happen

En Français: Chat échaudé craint l'eau froide

(the scalded cat is afraid of cold water, "echauder" is an old french verb outdated nowadays)

Regards,
Christophe.

Bonjour Christophe.

I dont think cables are the answer as they are only strong in tension and will have no strength in bending, which is what you want.

I would use a piece of box section steel which could be welded between the chassis from underneath if the floor is now in, or even bolted using brackets or cut and bend flanges at each end.

Regards.
Peter.

[andyf]

Re: And suddenly... I'm single :-D

I knew it was somewhere
here or there

Take a look at the link posted by Steve, it shows the standard alternative to the marine ply flooring.

BTW Morgans use marine ply for their flooring as well.

[stevejgreen]

Re: And suddenly... I'm single :-D

Perhaps worth including a note about bending aluminium sheet.
Aluminium has a grain structure normally indicated by the direction of manufacturers print on the raw sheet. Folds made perpendicular to the grain are normally strong but those along the grain are likely to stress crack, especially if a sharp radius. So if folding a tray, upturned on all edges, make the folds in the longer sides against the grain and if possible use a large radius bend with the grain. The larger the radius that can be comfortably designed in, the better. When fitting, use an industrial adhesive in preference to multiple fixings that can cause local stress points.
If lowering the floor pan, avoid any unnecessary extra protrusions downwards, these will become targets for every speedbump or obstacle, with potentially nasty results. If you do need cross bracing, try to keep it inside the cockpit.

I did wonder whether the grain structure was something that was overlooked in the original design of the Roadster bulkhead, where there are multiple folds, all in the same direction, running across the width of the car. Each of these folds would carry the stress of braking, especially in the early non sevo equipped cars.
Possibly something to take note of if ever replacing or repairing a bulkhead or even narrowing a transmission tunnel

[mark westbrookwhite]

Re: And suddenly... I'm single :-D

When I bought my roadster in boxes it came with a set of 16swg galvanized floor panels supplied by YCC I didn't know at the time it was normal to have a wood floor. so I fitted these and have had no problems with them at all.

[DamnedFrog]

Re: And suddenly... I'm single :-D

Hello all

I'll think twice about all that, and take some nice pictures of the chosen system

Christophe.

[dogoncrazy]

Re: And suddenly... I'm single :-D

My previous Cabrio had galvanised panels fitted, the only downside was a certain amount of 'drumming'. My present car has both galvanised panels and ply inner panels. Marcos cars were built around a marine ply chassis with few problems so I don't foresee replacing yours with MARINE grade ply should be considered less than satisfactory. If going down that route I would coat the ply both sides with 'West' system epoxy and you can then forget it for your lifetime at least.

[cameronfurnival]

Re: And suddenly... I'm single :-D

wood can be quite versatile...

mosquito-restoration.jpeg

[DamnedFrog]

Re: And suddenly... I'm single :-D

Hello Cameron.

For sure, industrial grade plywood was invented in 30s especially for aircraft manufacturing and was classified as war material during WW2.

I fully agree with the system of metal sheet under a ply floor .

Christophe.