12 replies to this topic

[steble]

opinions please, i currently have fibreglass doors and they are horrid so getting rid of them.

what are alloy door skins like? anything bad about them or are they just the same as having a steel one?

cheers
steve

[tiger99]

Remember that you lose a lot of side impact protection if you use alloy or fibreglass, and your insurance company needs to know of all "material facts", if you are using the car on the road. You could also start with a late model door with side impact bar built in.

I used to have a Rover P4 with complete alloy doors. They were great, light for their size, and resisted corrosion quite well. They were said to dent easily, but I never found that to happen. But an alloy skin on a steel frame is another matter altogether. There is a real risk of electrolytic corrosion at the joint between the two metals.

I am assuming that you want the car to have a long life. You should paint the steelwork before fitting the new skin, with the usual etch primer, and as many coats of normal primer as you want, also do the same with the inside of the alloy skin. I would then use a generous amount of adhesive, the stuff used for bonding panels on cars designed to be assembled that way, on the edge of the frame, and then place the skin in position. Once the bonding has set, put more on the frame edge, before turning over the edge of the skin. That will be messy, you have to do it while the adhesive is wet!

That way the interface between metals is completely filled with adhesive, with some layers of paint too. But I would still spray lots of waxoyl around the inside of the seam.

One problem is that there are normally a few welds near the top of the skin, and you can't do that, because of the adhesive, and also rather exotic techniques are required to weld alloy to steel. I think you could live without these welds as an adhesive bonded skin will be more secure than one which is mostly relying on just being crimped.

Oh, and normally I would not like bonded panels, definitely not anywhere in the monocoque, but doorskins are not a part of the monocoque and don't normally carry dynamic loads.

[j-b_2009]

alloy doorskins also dent ridiculously easily.

[malynch27]

If I had the cash, I'd do it! As you have fibreglass doors anyway your insurance shouldn't change too much either. There was a how to article in Miniworld/Mini Magazine a few months back on how to fit the skins too and it sisnt look too hard and there was no welding Ally to steel either.

[Ibexx]

You could have a look at carbon fibre ones. Expensive, but very light and strong.

[j-b_2009]

or strip the unwanted metal on the steel doors, fit perspex and youll be surprised how little they weigh

[AndyR]

I went through this exact dilemma about a year ago. I had some F/G doors on the car which i bought and fitted myself, with loads of bracing etc, and they were poor - incredibly flexible/wobbly/rattly - but they were very light

I decided to get my old frames repaired and ally skinned by minidoor. I wish i had done this at the start! They are loads stiffer - mainly because of the metal hoop still being kept, obviously not as stiff as the full steel door but after the F/G doors its nothing im going to complain about.

They are not loads lighter but you can definitely feel the difference - with perspex and some of the frame cut out it does save a few kilos

Downside - you have to find the parking space miles away from the shops to avoid parking next to another car - they dent very easily!! Dont close the door still holding onto the handle as it can dent in the handle! But its nothing i cant live with - i treat my car like a newborn anyways!

In my opinion, its not a massive weight saving if you are keeping the winder mechanism etc by going ally skin, but if you are after weight saving i would highly recommend them over Fibreglass, as a compromise.

Hope this helps

Andy

[steble]

hmmm i might just gut the doors and keep the steel skin then, the fg doors have to go they are a nightmare. keep thinking tey will snap while driving along.

carbon ones won't be any diff unless they were made from pre preg carbon and i can't afford that even if i made them myself, couldn't afford the material.

how much lighter than a steel skin is an alloy one? or is the weight saving mostly in gutting them anyway.

[Ibexx]

I've heard a few people say that the carbon doors are much stiffer (bot pre preg). There are also carbon skins available:

http://home.freeuk.n...acing/doors.htm

[AndyR]

I couldnt give you an exact weight difference, but it is noticable, if i had to put a number to it i would say maybe at a push a couple kilos per door. But you could reduce that even more by chopping some of the frame out around the winder mech etc. The carbon doors in theory will be stiffer, but it does depend on the layup of the carbon, how much is used and in what way it is orientated. Ive not had a carbon door in my hands so couldnt say for sure. From my experience of composite materials the door itself is not going to be much stiffer in carbon as its essentially a flat sheet, which would take a large amount of carbon fabric to stiffen such a shape - but the hoop will be stiffer im sure. Im fairly positive that you wont find pre-preg carbon doors out there on the market. The cost would be extortionate, but they would be lovely!! Unless you have a door sized autoclave in your garage?! Even then the pre preg itself is pretty expensive.

Like ive said before, im happy with the ally skinned doors i have, but mine is not a daily driver - if it was i would get the steel.

Andy

[steble]

with andy on the carbon

trust me the hoop will be no diff than the fibreglass ones, even if they were pre preg it wouldn't be much different

i'm a composite laminator by trade, we make components for all the top f1 teams

i have access to a plenty big enough autoclave, but making a mould and then the doors will be way too expensive,

think gutted steel ones is the way forwards

[AndyR]

Ok, well i think we will have to agree to disagree. If properly laid up, pound for pound it will be stiffer. And i would put my house on the pre preg being stiffer, i use both methods daily and the difference between pre preg and infused carbon is huge - again if correctly orientated and with the right weave (actually even if incorrectly laid up it would be stiffer!!) Remember the hoop is a c shape in cross section, this shape can be made really stiff.

If i had autoclaves big enough to fit car parts in i would go hungry, as i would take my salary in carbon parts!!

Andy

[steble]

The stuff we use is too expensive, I agree it would be stiffer but not stiff enough. To make it stiff enough it will be too heavy and ecpensive for it to be worth it