Cutting foam for seats?, any suggestions. |
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Cutting foam for seats?, any suggestions. |
DougC |
Nov 4 2004, 02:18 PM
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#1
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Senior Member Group: Members Posts: 949 Joined: 6-July 04 From: Dallas, TX Member No.: 2,307 |
I'm doing custom bolsters on stock 914 seats and need some help. I'm using wire bolster frames from stock BMW seats from my M3 (they were really raggidy). I've mounted the frames using screw head machine bolts and nuts attached to the stock fiberglass. I will be slathering on the Bondo at all the attachment points tonight and letting it set up for a couple of days. Then I plan on doing final adjustments with a propane torch before adding the cushion bolster pads, to get the angles right. I will be using the stock BMW cushions which are(seem) huge. I've started to "shave" them down using an electric knife (probably a cheap one) and it's chewing the cushions up a bit, like it's not sharp enough. I've also used a razor blade without great results. This elec. knife is brand new [got mother-in-law's permission] BTW. I fill confident in my ability to get the contours just right as long as I could find something to cut with. Any suggestions? Here's a preliminary pic of the framed seats.
Doug C Attached image(s) |
seanery |
Nov 4 2004, 02:21 PM
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#2
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waiting to rebuild whitey! Group: Retired Admin Posts: 15,854 Joined: 7-January 03 From: Indy Member No.: 100 Region Association: None |
I would look for a way to reinforce the mounting locations. Since the bimmer's pieces are metal into the fiberglass seat shell all the stress will be on the mounting spots.
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DougC |
Nov 4 2004, 02:29 PM
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#3
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Senior Member Group: Members Posts: 949 Joined: 6-July 04 From: Dallas, TX Member No.: 2,307 |
I got a feel for the bolsters before I removed them from the BMW frames and I've replicated that feel on the 914 seats, in otherwords they feel just as firm. But, I hear what you're saying ang that's why I'll be adding a ton of Bondo in those areas. BTW, you can't see from the pictures but the upper wings are a continuous loop of metal..so, the rest is stuck and mounted in the fiberglass channel running down each side of the seat. I had to cut notched for that to work. Hey, I'm all ears for any suggestions!
Doug C |
scotty914 |
Nov 4 2004, 02:30 PM
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#4
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suby torque rules Group: Members Posts: 1,525 Joined: 20-July 03 From: maryland, the land of 25 year Member No.: 924 |
heres the best way that reasonably priced if you make it :
a hot wire cutter. it is basicly nicrhome wire and an adjustable power supply, the wire you can pick up at a hobby shop, the power supply can be a 2 amp battery charger hooked to a dimmer on the 120 v side. simply a wooden frame making a large C shape with the wire across the open side. then hook up the charger to the ends of the wires. you can make it feet wide or as small as you want. but it does take some playing with to get the right amperage. it will do a real nice job once you get the wire taught and the amps right. could be made for less than 10 bucks if you have the wood, charger and dimmer. more flash backs from hobby days paying off |
seanery |
Nov 4 2004, 02:33 PM
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#5
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waiting to rebuild whitey! Group: Retired Admin Posts: 15,854 Joined: 7-January 03 From: Indy Member No.: 100 Region Association: None |
is the bondo structural?
I think it will just crack. I think you need URY's guidance to glass those things into the structure. just my 2 cents, and I'm no engineer, but I DO break stuff. (IMG:style_emoticons/default/wacko.gif) |
DougC |
Nov 4 2004, 02:45 PM
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#6
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Senior Member Group: Members Posts: 949 Joined: 6-July 04 From: Dallas, TX Member No.: 2,307 |
Sean - that's a good point about the strength of Bondo, I could just as well use fiberglass. That probably makes more sence.
Scott - thanks for the idea and explanation for a wire cutter. Does someone sell a small, cheap version commercially? That build would be a project unto itself (for me). That said, I may try anyway. Doug C |
scotty914 |
Nov 4 2004, 02:56 PM
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#7
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suby torque rules Group: Members Posts: 1,525 Joined: 20-July 03 From: maryland, the land of 25 year Member No.: 924 |
a project ??? you could just nail 3 2x4 together and wrap the wire, clip on the charger. now hooking up the dimmer could be as esay as spliting the cord of the charger taking the hot side wire ( the wide prong on the plug is the nuetral ) and hooking up the two wires to the dimmer. and then lots of tape. when finished take the dimmer out and wire nut the wire back together
if i had the wire i could make this in 20 mins granted it would last as long as the project but who wants this laying arould |
DougC |
Nov 4 2004, 02:56 PM
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#8
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Senior Member Group: Members Posts: 949 Joined: 6-July 04 From: Dallas, TX Member No.: 2,307 |
Look what I found with a small search.
Doug C Attached image(s) |
scotty914 |
Nov 4 2004, 03:01 PM
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#9
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suby torque rules Group: Members Posts: 1,525 Joined: 20-July 03 From: maryland, the land of 25 year Member No.: 924 |
makes it look easy.... oh it is
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GWN7 |
Nov 4 2004, 04:45 PM
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#10
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King of Road Trips Group: Members Posts: 6,280 Joined: 31-December 02 From: Winnipeg, MB, Canada Member No.: 56 Region Association: Northstar Region |
I've never done it, but I saw a episode of American Hot Rod where they were doing the interior. They used what looked like a electric carving knife to shape the foam and a disc sander to finnish it smooth.
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Rough_Rider |
Nov 4 2004, 05:19 PM
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#11
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Smurf Zone Group: Members Posts: 525 Joined: 16-August 04 From: Beaverton, OR Member No.: 2,547 |
Hot wire is the best method out there. But if thats not possibel try these:
A thin wire saw can also work but won't be as clean cut as the hotwire. From my school days i remember using a hot knife & hot poker to burn shapes in foam. Take a sharp knife & heat the blade then quickly but gently cut / burn the foam. |
MarkV |
Nov 4 2004, 05:30 PM
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#12
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Fear the Jack Stands Group: Members Posts: 1,493 Joined: 15-January 03 From: Sunny Tucson, AZ Member No.: 154 Region Association: None |
I have a friend that has an upholstery shop. He has two tools he uses to cut foam. The first is an electric carving knife like you use on a Thanksgiving turkey. The second is a homemade tool hade from a 3' long piece of black metal pallet strap that he has stretched across a wooden "C" shaped frame. The edge of the strap has been sharpened with a grinder & it works like a big saw.
(IMG:style_emoticons/default/sawzall-smiley.gif) |
SpecialK |
Nov 4 2004, 05:35 PM
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#13
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aircraft surgeon Group: Benefactors Posts: 3,211 Joined: 15-March 04 From: Pacific, MO Member No.: 1,797 |
Hot wire is the best way to cut styrofoam, and maybe even polystyrene (rigid) foam, but I'm almost positive (I'll check) that you DON"T want to use the hot wire method on polyethylene or polyurethane foam rubber because of toxic fumes. A good electric knife is the way I've seen it done.
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seanery |
Nov 4 2004, 05:38 PM
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#14
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waiting to rebuild whitey! Group: Retired Admin Posts: 15,854 Joined: 7-January 03 From: Indy Member No.: 100 Region Association: None |
A little toxic fumes every once in a while can be fun (IMG:style_emoticons/default/wacko.gif)
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lapuwali |
Nov 4 2004, 05:40 PM
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#15
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Not another one! Group: Benefactors Posts: 4,526 Joined: 1-March 04 From: San Mateo, CA Member No.: 1,743 |
I'd back up those bolts with metal plates to spread the load. If you just run the bolts through the fiberglass, they're going to crack and break off pretty quickly. Gluing some big fender washers to the shell and running the bolts through that will also work. As it is, the wire bits are going to break loose on the outboard sides after you get in and out of the car a few times.
More fiberglass at the holes will help some, but metal plates as big as you can make them will help a lot more. I'm not sure what good Bondo would do at all, given that nothing will be visible. It certainly won't help structurally. |
tracks914 |
Nov 4 2004, 06:02 PM
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#16
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Canadian Member Group: Benefactors Posts: 2,083 Joined: 15-January 03 From: Timmins, Ontario, Canada Member No.: 153 Region Association: None |
QUOTE(Rough_Rider @ Nov 4 2004, 03:19 PM) From my school days i remember using a hot knife & I used to use hot knives at school too. (IMG:style_emoticons/default/smoke.gif) Oh wait, I wasn't cutting foam, I was cutting class. (IMG:style_emoticons/default/aktion035.gif) |
Kargeek |
Nov 4 2004, 06:09 PM
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#17
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Senior Member Group: Members Posts: 555 Joined: 14-March 03 From: Orange, CA Member No.: 430 |
I rebuilt the seats on my '74 BMW 2002 using built up foam glued onto polyester batting which was tied to the seat frame and springs. Depending on the density of the foam you can cut it a number of ways. I used a hack saw blade...grind the teeth to a knife edge and it will slice off what you need. The higher density foam you can actually grind to shape with a 40-60 grit disk sander.
I would go to your local upholstery supply store and check out the polyester batting. It’s about ½” thick. I would wrap it over the top of the wire frame bolsters- sandwich glue it together and trim it down to the seat pan. Take ¼” foam and wrap over the batting to build up the bolsters. Great idea! |
Hi_Fi_Guy |
Nov 4 2004, 06:22 PM
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#18
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Tuetonic terror Group: Members Posts: 375 Joined: 12-August 03 From: Sunny Phoenix, AZ Member No.: 1,019 |
I just finished recovering my stock seats and my advice would be so not owrry about the jaged edges you are getting and use a small layer of 1/4" High-Density foam between the foam yuo are cutting and whatever material you will be covering the area with. Use the 1/4" foam as a backing to your upholstery material and it will hide small issues with your cut foam and provide a uniform surface for the material.
As far as support I certainly would push fiberglass mat and resin over body filler and I also agree with the idea that some mounting bracket backing plates may be needed. Think of how many people"plop" into their seats dropping most of their weight onto the bolsers each time. Anyway, best of luck and please post pics when you get the seats finished so we can see what a great job you have done with the project. |
Dr Evil |
Nov 4 2004, 06:30 PM
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#19
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Send me your transmission! Group: Members Posts: 23,002 Joined: 21-November 03 From: Loveland, OH 45140 Member No.: 1,372 Region Association: MidAtlantic Region |
I have a great (expensive ) hot wire foam cutter and nichromewire. It does work great on polystyrene and EPP, but it will put of toxic fumes if you cut what you want to with it. If you can sharpen a hacksaw blade like a straight razor that may work well for you. Don't worry if it isnt perfectly smooth (just make it as close as possible) as the vinyl that you use should be thick enough to not only deal with the weight of an person, but also to cover any minor imperfections.
HTH |
Boboli914 |
Nov 4 2004, 06:53 PM
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#20
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Member Group: Members Posts: 101 Joined: 15-November 03 From: Pittsburgh,pa. Member No.: 1,345 |
2 cents here from a 20+ year upholsterer...Use your wifes/mothers or martha's(she does not need it right now) turkey knife to trim the foam.Also cut it about a half inch bigger than you want it to fill in voids later on.Any more ? feel free to email Boboli914@att.net (IMG:style_emoticons/default/flag.gif)
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