Making a Race (foam bag) seat. experience after the first trial

[maurici]

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:

http://www.sjmmarsh.f2s.com/Caterham/Foam Seat.html

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

-t

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

 

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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.

 

https://www.msar.co.uk/moulding-kits/msar-hd-x-large-seat-moulding-bag.html

[iowlee]

Hi Maurici

I also do not have a typical 7 driver physique. I am 6ft 8 ish 

I have made this 2 part liquid foam seat and although it was Ok I changed to the Schroth Indi (bean bag and liquid) seat.

Oh my god such a world of difference. 

Yes it is quite a bit more expensive but the finish quality just felt better. I had 2 goes at the 2 part liquid one to get one that I was happy with.

I also had the Indi covered by a local trimmer rather than my first foam seat covering with Tape.

You definitely need someone to help make the seat. I also found the indi one much easier to sand/shape after setting.

Lee

 

[John Loudon - Sponsorship Liaison]

This has to be mentioned. Always makes me smile when foam seats get a mention

https://www.lotus7.club/comment/13499#comment-13499  

[maurici]

6 minutes ago, John said:

This has to be mentioned. Always makes me smile when foam seats get a mention

https://www.lotus7.club/comment/13499#comment-13499  

Absolutely superb. Brilliant. I've had to walk out of the office finishing a few minutes earlier and still droping tears of laughter while walking to the car.

It is very well written, yes, but the fact itself is absolutely SUPERB.

[maurici]

12 minutes ago, iowlee said:

Hi Maurici

I also do not have a typical 7 driver physique. I am 6ft 8 ish 

I have made this 2 part liquid foam seat and although it was Ok I changed to the Schroth Indi (bean bag and liquid) seat.

Oh my god such a world of difference. 

Yes it is quite a bit more expensive but the finish quality just felt better. I had 2 goes at the 2 part liquid one to get one that I was happy with.

I also had the Indi covered by a local trimmer rather than my first foam seat covering with Tape.

You definitely need someone to help make the seat. I also found the indi one much easier to sand/shape after setting.

Lee

 

You are not the first actually sujjesting the bean seat kit. But it is much more expensive and it scares the hell out of me to fack it up and lose about 160 quid...

Would you be kind enough to explain the process or link me somewhere to see it?

 

[stephenh]

Brilliant story in John's link. 

Maurici, can you really fit in a narrow? When I sat in Simon's car (passenger seat) at a trackday last year, I got stuck, and he had to haul me out!

[Paul T]

Nice job, if you really wanted to go to town you you could the foam to make a fibreglass mould and lay your own fibreglass/carbon fibre seat 

For future ref it might be worth investing in a can of this...

https://www.toolstation.com/pu-foam-cleaner/p30658?utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=Cj0KCQiAtvPjBRDPARIsAJfZz0pJMxh2b9NcWAL4fuP0oZaWdFtbiXICaPxLUq83ScdXHDggyMsEz7AaAu6iEALw_wcB

[Andrzej]

Following above advice from @maurici and other found on locostbuilders , YT etc.,  decided to make a foam seat myself -  a proper racing item

 

First not in Westfield , but I am going to make one for the Westfield too, as it feels soooo comfortable, so fited to the body ! and allows for proper attachement of 5 + 6 straps 

As it is in MNR which has higher body - nose and engine cover, and a diagonal pipe across sitting area, so the seat position can not be as low. So the seat tooks a lot of foam - approx 10 l of the 35kg/m3 foam, and some 200 at the bottom.  One important observation - the liquids need to be warmed up to 25 deg C or more so it expands properly. I made few liters in lower temperatures, to it was not expanding as it could. 

Also I decided to add some reinforecments with epoxy resin and fiberglas , ans "painted" all of the seat with epoxy before taping with duck tape. 

Sadly due to huge delays of parts delivery ordered almost half year ago in MNR, cant try the seat on the track , but hope to drive it eventualy.

 

here some pictures , maybe will help someone with similar work:

 

https://aswestfield.wordpress.com/majsterkowanie/

 

Slideshow abowe with pictures from following stages , below only two start and finish 

 

Start - determining sitting height and back position so could reach the dashboard and steering whell 

 

 

 

[mark.anson]

Having made several expandable foam seats for the Jedi in the past few years with varying degrees of success, I finally bit the bullet and had a professionally made bead seat. I found the expandable foam ones tend to shrink over time (something to with the way the foam is made these days) which caused it to move about in the cockpit. The bead seats are expensive and its really not a DIY job unless you know what your doing but its worth it in the end.

 

[Andrzej]

What time it takes for the foam seat to "shrink" ? maybe could do with adding on sides , back and bottom some medium stiff foam (like used for paddig on the seats) for 1-2 seassons? 

 

As for the bead seat - I am affraid that here in my country I will not find a specialist, and the cost not small and might be  multiplicated if I do something wrong ... 

 

[John Loudon - Sponsorship Liaison]

29 minutes ago, Andrzej said:

What time it takes for the foam seat to "shrink" ? maybe could do with adding on sides , back and bottom some medium stiff foam (like used for paddig on the seats) for 1-2 seassons? 

 

As for the bead seat - I am affraid that here in my country I will not find a specialist, and the cost not small and might be  multiplicated if I do something wrong ... 

 

3-6 months I am afraid. I have been there and found out

[Andrzej]

ouch... not  sure If I manage to complete building the car for 3 months if ther MNR parts supply will be like was so far...

[John Loudon - Sponsorship Liaison]

To be fair, it gets worse with use so if you dont use it it should last OK until you start using it

[Andrzej]

If with use so maybe it is (the foam) compressed by the body weight on bumps and other - lateral etc g-forces. If so it might be reduced by using more dense foam - just wonder. I have tried two densities - 200kg/m3 - used it on the bottom andjust to see the difference, and main part of the seat - 35kg/m3 . This 200 foam is much much stiffer when pressig if . Havier, harder to cut , shape etc , but maybe some intermediate lets say 100kg/m3 foam would be good compromise. I had no knowledge what density people are using for those seats. 
Well hope I will have a chance to drive so much that I need second seat  . In fact I did made two seats , the second not wrapped in tape , not shaped , just the main "body" , just in case and little lower and little more back seating position .