low tech but good results.

I am builing a custom monocque chassis for my Speedster, after welding in 1mm sheet steel for the floor I found the heat distorted the metal, it made a twang noise every time I stepped in the chassis.
I blunted a 75mm bolster (thats 3 inches to you lot over the pond)on my grinder, put wood under the chassis and did some bashing, no more twang and it looks ok too. Please see photos and feel free to coment.

Very nice. But we like our "twang" on this side of the pond. I thought they gave you
a rough time over there if you don't use a donor chassis? (or is that "shassy"?)

I am not even using a Beetle engine but hey we all build our cars to what we want them to be! The twang? maybe it's not a twang but a ding or a twadong, it was just a noise that I didn't like when I stepped into my chassis, even though it will be sheeted in 12mm(half inch) ply wood after galvanising. Anyway it is amazing how much stiffer the floor is after a bashing with a hammer and chisel.

I didn't mean for authenticity(I don't worry about that). I thought (from reading "Which kit"
and others) that the registration process was based on the donor info and that building
yourself was a harder sell. Your car/work looks great.
Good luck.

The registration in the UK involves a totting up of points from the donor vehicle and a very serious safety check(SVA) if you don't use enough of the donor you get a Q registration plate which tells everyone on the road that you drive a 'KIT CAR' I am using an Alfa flat four engine, gearbox and steering, this will give me the 8 points I need to get a proper registration number plate which matches the age of the engine. I am making something for myself so selling it is many many years away.

even though it will be sheeted in 12mm(half inch) ply wood after galvanising" Why cover it with plywood? That will only trap water and rub the galvinise coating off causing rust. Why not cover with Dynamat or equivalent (like brush on PU bed liner)?

I was thinking of using a solid bed of liquid nails or silicone to stop rubbing. I need the ply to give more ridgidity to the floor, although the hammered pattern stops the floor from making a noise, there is still movement. keep coming with the suggestions, one guy on his own in his garage needs help!

Mick, as wet as it is over there, I can only assume you've decided to install some drain plugs. If you're hung up on the plywood idea, have you looked at marine-grade ply in the 6mm range? You're probably able to get Birch over there, too. Since that grows in northern climes, I'd think it would be better against the weather in its natural state.
My solution to the floor noise business was to go with the rigid framework under the floors, at 90-degree angles to the tunnel. I've attached some early skeleton photos of the jalopy for reference.
I'm also using some thick diamond plate aluminum, so there won't be any flex at all. Rattling maybe, but no flex. I'll be using the heaviest aluminum rivets I have to hold it down.
Since you're a darn good hammersmith and apparently not afraid of .025 or .030 welding wire, have you considered welding lats or longitudinals either under or over top of what you've already got? It's pretty easy to fill gaps from the box tubing to the high and low points you've created by quilting, and the whole works would be joined if you decide to powdercoat the chassis when you're finished.
Can you send me some shots of the underside of the car? One from the centerline of the beam and the other from underneath one of the sides?

I really like the monocoque thing you've got going there. Brilliant. Here is a little reading for you on several different types currently in use, including one by Porsche that lightens the whole works and may fit the bill for your twadong noise (under the next-to-bottom section, called "ULSAB Monocoque"). It's good info, IMHO, but the spelling and grammar are suspect. It HAD to have been written by a good engineer!

http://www.autozine.org/technical_school/chassis/tech_chassis.htm

Thanks for the ideas Cory, I am a fan of your car and always check out your updates. I think I am going to use exterior plywood, not too bothered about the looks as it will be covered with carpet or rubber mat. As it will be galvanised a little bit of water won't trouble me. Galvanising is so cheap over here, at around 75 pence per KG, the weight of my chassis when comlete will be 120 KG (about 265 pounds) I couldn't buy the paint for that! I have one picture of the underside, please see attached file. What do you call hot dip zink coating over there?

Nice work Mike,
The chassis loks like my Metalcrafters tube chassis. I noticed that the tunnel sheet metal cover appears to be welded permanantly. Mine is attached with about 12 sheet metal screws down by the floorpan on the sides for easy removal from the passenger compartment. The bottom is sealed up tight. I have had to change the throttle cable and clutch cables a couple times while I was sorting it out. Just my two cents on the subject. I'm not sure which mechanicals you are running.

Craig

Thanks Craig,
I am using an Alfa flat 4 engine and box, Porsche 924 front hubs with double A arm suspension, pushrod operated coil overs and modified porsche trailing arms with coil overs out back. So nothing Beetle only the door handles and headlamps!!

Also Craig, the underside of the tunnel is open but braced with triangulation so I can get at the gear linkage and cables.

Perfect. Sometimes we paint ourselves into a corner, if you know what I mean. Can't wait to see the finished product.
Craig

Good stuff, Mick. And pennies on the zinc now will save you bucks down the road.