Seat webbed area dimension

[Zandoz]

It's looking like the best seating alternative is going to be a foam covered plywood bench seat base, with the center rear cutout to fit around the driveshaft tunnel.

I've seen a number of recommendations for cutouts with webbing to make the seat a bit more butt friendly. What I've worked out in the old CAD system is a webbing cutout 11" wide, and 14" front to back. That is with 3" of two layers of 3/4" plywood surrounding the cutout.

Is that a big enough cutout to do any good? Is the 3" of wood surrounding sufficient? Too much? Not enough?

Now comes a biggie...I am going to have to put some kind of elements barrier (probably a sheet of aluminum) on the bottom side of the seat plywood, because there will be no floor under the seat at least on the driver side. The brake booster and master will be in that space. Approximately how much sag in the webbing can be expected when sat on? If more than about 1-1/4", I'm going to have to come up with another plan.

 

[tfeverfred]

11" wide? You must have an ass like Lady Gaga. I used webbing in my seat and made each side as wide and deep as possible. How much you sink in is relative to how tight you can stretch it. I think mine dipped a couple inches. One piece of 3/4" plywood is enough.

 

[Zandoz]

I know nothing of Lady Gaga, but this big ole butt needs it's own zip code. 11" is the approximate width I'd have available for webbing 3" or so wood on either side. unfortunately the arched top of the driveshaft tunnel will take an 8" wide bite out of the center rear of the seat. The result is a seat that the front half is a bench, but the rear half like a pair of buckets. The arch of the driveshaft tunnel at it's highest at the rear of the seat will be 3" high, and taper to nothing around mid-seat. It would be padded. I know it's a poor compromise for a butt the size of mine, but I do not know what else to do. I must keep the high point of the seat, the front, as low as possible. To get a good slope on the seat, this is the result. <shrug>

The reason for doubling up on the plywood is because of my weight.

 

[2old2fast]

8 inch wide tunnel ??
dave

 

[tfeverfred]

Drive shaft tunnel? How much is your car channeled, that it needs a drive shaft tunnel? And, it's probably good that you know nothing of Lady Gaga, but then, Google can be a friend or foe.

Pics would be VERY helpful.

 

[fletcherson]

Bill, how tall is the riser going to be for your seat? Mine is about six inches at the front, to nothing at the rear, as the back seat mount is at the kick up level. I was able to find a seat from a minivan that was the correct width and was very adaptable to my needs. It it strong, comfortable, has provisions for lap belts and was inexpensive. Could something like that work out in your build? I would have preferred to sit lower, but my T isn't long enough to allow me to sit on the floor and stretch my legs out.

 

[Zandoz]

8 inch wide tunnel ??
dave

Yes, unfortunatel...needs to fit over an 8" OD drive shaft loop

 

[Zandoz]

Drive shaft tunnel? How much is your car channeled, that it needs a drive shaft tunnel? And, it's probably good that you know nothing of Lady Gaga, but then, Google can be a friend or foe.

Pics would be VERY helpful.

No channeling at all...but the frame will be 6"-7" off the ground under the seat area.

On Lady Gaga, I have heard of her, but I'd not know her if she were close enough to me to bite me on the nose.

No pics to be had. At this point this project is several large piles of parts and a constantly evolving CAD file. I want to work everything out to the point of being at least plausible on electronic paper before commissioning the building of the frame and what custom bracketry will be needed. I can only afford one shot at this.

 

[Zandoz]

Bill, how tall is the riser going to be for your seat? Mine is about six inches at the front, to nothing at the rear, as the back seat mount is at the kick up level. I was able to find a seat from a minivan that was the correct width and was very adaptable to my needs. It it strong, comfortable, has provisions for lap belts and was inexpensive. Could something like that work out in your build? I would have preferred to sit lower, but my T isn't long enough to allow me to sit on the floor and stretch my legs out.

I had started out planning on a 5-1/2" riser on the front, and 2-1/4" on the rear, but since starting this thread I've started playing around trying to raise the rear to cut down on the intrusion of the tunnel. I know I'm probably not planning on enough slope to the seat as is, but I'm grasping at straws to come up with something that will be viable for me to park this big ole butt on, but still keep the high point of the seat low enough that I have a shot at getting in and out.

 

[Zandoz]

I was able to find a seat from a minivan that was the correct width and was very adaptable to my needs. It it strong, comfortable, has provisions for lap belts and was inexpensive. Could something like that work out in your build? I would have preferred to sit lower, but my T isn't long enough to allow me to sit on the floor and stretch my legs out.

I had hoped to use a mini van seat or one of the Corbeau Baja bench seats, but the frame of them sitting on that tunnel raises the seat too high, and would leave me riding more on the car than in it

 

[fletcherson]

I had hoped to use a mini van seat or one of the Corbeau Baja bench seats, but the frame of them sitting on that tunnel raises the seat too high, and would leave me riding more on the car than in it

That's what I was wondering. How tall the tunnel is verses the rise of the seat. I can't visualize the drive shaft having to come that high into the seating area, but I am not visualizing the air suspension and your particular suspension setup. My question is how is a plywood and web seat any different from a steel framed seat as far as the drive shaft tunnel? What am I missing? On mine, the kick up allows for the differential housing clearance, even though it's behind the seat area, and the riser at the front of the seat would more than clear the drive shaft. Are you planning on building a split seat to allow the drive shaft tunnel to come up through the center?

 

[fletcherson]

I had started out planning on a 5-1/2" riser on the front, and 2-1/4" on the rear, but since starting this thread I've started playing around trying to raise the rear to cut down on the intrusion of the tunnel. I know I'm probably not planning on enough slope to the seat as is, but I'm grasping at straws to come up with something that will be viable for me to park this big ole butt on, but still keep the high point of the seat low enough that I have a shot at getting in and out.

The seat mounts from the minivan had about two inches difference, front to rear, from memory. I removed them, obviously, and had a flat bottom steel framed seat. I experimented a little with riser height and re worked the seat connectors (hinge, if you will) to change the angle of the back, more to fit the tub, than anything, but it worked out to be very comfortable. A considerable amount of work, but with a stretched body, would have been less important because I was fighting desperately for leg room.

 

[Zandoz]

That's what I was wondering. How tall the tunnel is verses the rise of the seat. I can't visualize the drive shaft having to come that high into the seating area, but I am not visualizing the air suspension and your particular suspension setup. My question is how is a plywood and web seat any different from a steel framed seat as far as the drive shaft tunnel? What am I missing? On mine, the kick up allows for the differential housing clearance, even though it's behind the seat area, and the riser at the front of the seat would more than clear the drive shaft. Are you planning on building a split seat to allow the drive shaft tunnel to come up through the center?

The seat mounts from the minivan had about two inches difference, front to rear, from memory. I removed them, obviously, and had a flat bottom steel framed seat. I experimented a little with riser height and re worked the seat connectors (hinge, if you will) to change the angle of the back, more to fit the tub, than anything, but it worked out to be very comfortable. A considerable amount of work, but with a stretched body, would have been less important because I was fighting desperately for leg room.

At the rear of the seat the tunnel would be about 6-1/2" above the floor, and about 2" above the seat plywood. The tunnel will angle down towards the front, and pass below the top of the plywood about mid seat. To clear the tunnel, there would be an 8" wide cutout from mid seat to the rear. That cutout would allow the rear of the seat to be lower than the top of the tunnel.

 

[fletcherson]

Ok, I see. That's a tuff one. You will be limited for seat width. I don't know if I have anything to add. I don't know what you can do other than up on the seat, or a redesign to reduce the required tunnel height... Perhaps a different pinion location, and that's a different differential. or less suspension travel, but that's dependent on your need to drop the car for egress, etc...on mine, the drivers location actually encroaches the drive shaft area, so if the tunnel pertruded through the seat, I doubt I could drive it comfortably. I can barely fit comfortably after relocating the shifter to the passenger side of the tail shaft. I think that you said your body is wider. That may help you there.

 

[Zandoz]

Ok, I see. That's a tuff one. You will be limited for seat width. I don't know if I have anything to add. I don't know what you can do other than up on the seat, or a redesign to reduce the required tunnel height... Perhaps a different pinion location, and that's a different differential. or less suspension travel, but that's dependent on your need to drop the car for egress, etc...on mine, the drivers location actually encroaches the drive shaft area, so if the tunnel pertruded through the seat, I doubt I could drive it comfortably. I can barely fit comfortably after relocating the shifter to the passenger side of the tail shaft. I think that you said your body is wider. That may help you there.

Yeah, I'm kinda stuck between a rock and a hard place. If I raise the frame, body and seat it would reduce the tunnel intrusion, but it would make it difficult to impossible for me to get in and out. If I leave the plans as in, it is likely to be pretty uncomfortable for this old wide load butt. The potential saving point for the current plan is that the part of the tunnel that would be 2"-3" above the seat would be dome shaped, and would be padded. With the upholstery on the domed intrusion would not even be visible.

Another off the wall idea came to me last night, but I've not yet tried it in the old CAD system. Instead of a conventional plywood and padding seat, build a framework of 1-1/2" or 2" square extruded aluminum T-Slot...then fasten webbing into the slot.

Basically building a glorified lawn chair style seat. The advantage is that without the 3"-4" padding on top, the whole webbed seat could be raised without taking away from my ability to get in. With it being higher than the plywood, and the domed top of the tunnel, the opening for the tunnel would be smaller. <shrug>

 

[tfeverfred]

Can you post pics of your drawings?

 

[Zandoz]

Can you post pics of your drawings?

I will as soon as I get the current revision in progress cleaned up.

 

[Zandoz]

Sorry it has taken so long to get the promised pics posted, but I ended up having to deal with setting up a new computer before I could get the CAD files updated.

I've got an overhead and side view that I've played with transparency to try to clarify the items that effect the positioning of the seat...and the brake pedal, booster, and master that have been discussed recently in another thread.





As of right now, the plan for the drive shaft tunnel is to truncate it to a short section between the drive shaft loop and for lack of a better term, the rear bulkhead. Almost the entire area under the seat forward of the drive shaft loop will be open to the ground...with the seat acting as a hatch. That area will be occupied by the brake system components under the driver side, and an air tank for the rear suspension under the passenger side. The transmission tail section and most of the drive shaft will be between the two.

 

[Gerry]

This may or may not help. By curving the seat up under the legs it gives more support and 'lengthens' the seat. My Bucket is a 15 with 2" added in the length and a friend who is a good 18 stone (18 x 14lbs) says he can sit in it comfortably.

 

[Swampdog]

I like that. My 265 pounds sound so much better as 26 stones.