Making an expanding foam seat (BAG SEAT) in your seven.
Well, I don’t know if this is a common problem or is just me. But I’m a big lad… big… wide whatever, and despite I fit well in most sevens (including narrow and Caterham s3 chasis) I never find a confortable position where I’m completely happy to drive.
Aside of that, my torso is proportionally longer than my legs compared with the average population and my preferences for the driving position have been allways more “gt and rallye style” quite erect rather than single seater style… all laid back. This creates me all sorts of problems with the standard off the shelf available seats… head too near to the roll cage, head over the aeroscreen diffusing line, ergonomy problems reaching gear levers and operating pedas confortably for hel-toe driving… so finally opted for a bag seat after many years of fighting with off the shelf seats (I have to say that the JK that I had in my previous car were the best by far, but still not perfect for me).
It took me ages to actually bite the bullet and start doing it, but finally it’s been really easy. Total working time, under 3 hours with ZERO experience before.
I’ve followed the attached tutorial, I think is quite complete, but I could give you my two cents of experience here after having tied that myself:
I've done it without the insert as I wanted to seat as low as possible.
Main two advises here:
1- Use an EXTREMELY BIG bag. Real big. The main danger of a bag seat is the possibility of overflow making a huge mess… so the bigger the better to minimise this risk
2- Use good quality foam. It makes a difference of how easy is to mix and how temperature sensitive is to start the reaction.
Try to be extremely carefull with the foam, whatever it touches is disposable. Be carefull where you dispose the containers you will use to mix, as the remainders will start to expand and they may make a mess over your workbench. AVOID contact with skin...b
Then… you mask the interior of the car, with a big cloth, cardboard to limit the expansion to the sides, and hard porexpan to approximate you driving position.
Mix 300cc of each component, and start the fun. Place it in the bag, wait till start to expand, distribute it by hand where you want to have it and sit. Wait 15 minutes. Get out, check the results and start filling the gaps with smaller amount of mixes. Finally I used 700cc of each component. It’s been a lot of excess that then it’s been cut away.
The result is far from being aesthetic at all, but is really confi and the feel is perfect. A hack saw blade works perfect for cutting and trimming. If the bag is left any major kink or crest just sand it down with 80 grain sand paper. All toguether resulted in a 0,9kg seat with a very nice driving position... another plus
Finally cover it with gaffer tape. It is a very long and tedious job to have to cover it… but is a must.
Now… things I would have done differently:
I would have limited the forward expansion… maybe placing the bag further backwards It just expanded way too much to the peal area and I lost quite a lot of foam there.
I would have done it with a mate or with the misses… to help to pour and fill the gaps just lifting my butt and back rather than having to go out and estimate where the foam should go.
Eventually, being that easy, I’ll do another one during the season correcting all this small mistakes.
Find a link to the biggest bags I’ve found on-line. They have been perfect for the purpose.