Newbie - Advice needed on Spoiler/Wing mount project please


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robjohnson
robjohnson
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Hi there, this is my first post - I am 33 years old Car enthusiast from South London, the car is a Mazda RX7 and my challenge is to fit the rear Spoiler. 

The mount needs to be exceptionally stiff and strong, the wing is 1710mm and I estimate it will create extreme forces at higher speeds, therefore its essential that the mounts are extremely sturdy.

I have been thinking and researching about how to fit this wing for over a year looking at examples on pro time attack cars and competition vehicles, most of the solutions I saw were either beyond my engineering skill or ability (CNC/cad etc) or just looked inferior, unprofessional or just plain ineffective. 

I decided on composite layup because of the uneven working surface and awkward angles involves, my plan is to lay up carbon by hand - in the photos the Carbon is represented by the Cardboard template I have made up. 

I will then release the structure from the car and trim to shape before attaching to the car in final form with bolts, as you can see in the pictures I have the wing uprights (these will be scrapped as the dragon design is a bit lame imo) positioned pretty much where I want them to be - I will use the alloy uprights in the pic as a mold effectively to get the shape of the mount - I plan to make new uprights in Carbon sheet as you can see on the picture of the white car. 

I need you guys to help me out with any tips please, I am anticipating a lot of overlap/mechanical locking problems which might stop me releasing the mount, I have no power at the Garage.

I also need some help with the shopping list please, this mount will be subject to downforce of maybe 200kilos but also twisting and tearing forces, my concern is that the resin will crack because of the constant flexing forces. 

I am not so bothered about finish as it will be hidden by the boot hatch and the wing upright which will be a carbon sheet made by Carbon mods so will look perfect from the outside - my main concern is strength so what is the shopping list please - do I need Kevlar? what type of CF sheet do I need please. 

I also need to move the carbon riveted mounts from the underside of the wing outwards as it was originally designed to mount to a steel boot hatch - my hatch is GRP skin so not at option, my concern is that these mounts are resin infused and therefore much stronger than the hand lay up techniques I have available (no power at the garage) - I dont want to make new mounts with hand lay up and have them shear off at high speed which could cause a hideous accident - tempted to bolt through from the very top of the wing which would be unsightly but possibly the strongest and safest option.  

Please review the pics and video and give me some tips, I fixed a bumper with fibreglass from Easy Composites once but that is the only experience I have and I might a right mess of it. 

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Warren (Staff)
Warren (Staff)
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The way you are looking to place the mount, you will be relying on a wide panel gap so there is enough room for the mount to go through.  If not, you will need to recess as above, or trim the boot edge so it clears as the boot opens.

In an ideal world, id made a copy of the section or use panels from a scrappy car as the moulds so you can at least vacuum bag or resin infuse as the parts will be a bit stronger that way, but wet lay will still work if you are careful.

You will need as a minimum:

Yellow Filleting Wax

Easy-Lease Chemical Release Agent

EL2 Epoxy Laminating Resin

200g 2/2 Twill 3k Carbon Fibre

300g 2/2 twill Kevlar

 In essence the process is to lay on the wax in areas where you have sharp edges, holes, undercuts etc to smooth them out to get a good release.  Then wetlay the carbon onto the car in the shape you want.  I recommend you include some kevlar layers.  Not for specific strength, the carbon if done right will be strong enough, but for crash reasons.  The mount may well break and crack in an accident but its more likely to stay in one piece with some kevlar in there.

The biggest problem you are going to have is working on a car outside with epoxy resins. Much below 20C and the cure times go up rapidly. Much below 15C and you will get several days cure time if it cures at all as moisture absorption over the extended cure time can become significant and ruin the part.



Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
Edited 12 Years Ago by Warren (Staff)
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