Attaching Seat Swivels to a foamed bench seat

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tucker99

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Boat is a 1981 14' Mirrocraft with original factory foamed bench seats. Have 2-Millenium seats mounted on 7" bar stool type swivels. I used SS sheet metal screws and need to tighten them every year. I've never liked that procedure and I'm looking for something more permanent. I remember a guy using high shear rivets. Not sure I could do that, looks like the back needs to be backed and I don't have access under the seats. Would 1/4" aluminum rivets be better than sheet metal screws?
 

gogittum

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I don't want to get in an argument and don't want to hurt anyone's feelings, but PLEASE don't use rivnuts.....and esp. DON'T loctite them. You'll never get them out.

I owned and operated a restaurant service business for years and came across many, many rivnuts on commercial cooking equipment cabinets, mostly in sheet stainless steel, but some in aluminum, too. I cursed those awful things every time I tangled with them.

Along with pop rivets, they don't do well in tension - boat seat will be in tension - and can often be pulled out of thin aluminum fairly easily. In shear, they're fine. A rivnut is just a pop rivet with threads.

Big thing is: They work by squeezing the metal between the shoulder/collar on the outside and the pulled plug on the inside and the grip isn't all that great. When you start to loosen a screw in a rivnut, if there's any corrosion or damage or whatever on the threads, the whole rivnut will often turn instead of the screw - and you'll sit there a very long time playing at that.

Occasionally, you can wrench the screw down tighter to try and lock it in again, but that rarely works. Most often, the only alternative is to drill the whole mess out of there and that can be difficult.

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Mine may not be perfect and there may be better alternatives out there, but this is what I came up with for my 16 ft Starcraft Seafarer with aluminum seats. The screws go thru the wood into the aluminum. The wood adds a lot of additional strength. I put the boards on the seats to replace original because I felt they'd be more comfortable in hot weather, not to mention looking nicer.

The swivel seat base is much smaller than the seat and is quite short - almost impossible to get a screw or bolt under them, so I used Tee nuts under the 2 strips and bolted the strips to the swivel base, then screwed that to the underside of the seats, also with Tee nuts inside the seats.

4 heavy #12 sheet metal screws on each side anchor it solidly. When you lean back in the seat, you're putting tremendous pressure on those screws. So far, there's been no loosening at all - they're rock solid.

Picture

Incidentally, I made a folding grab bar for the center seat and knew I'd be swinging my full weight from that at times in rough water or even when I just lose my balance, so wanted it to be un-breakable. That meant nuts & bolts and "no" compromise. The red arrows point to the hinges.

I took that seat completely out of the boat - drilled all those 5/32" rivets out, pulled the seat, slid the foam out and bolted my grab bar hinges solidly with stainless 1/4"-20 bolts with back up washers. Trimmed the foam a bit to get it back in, then used sealed end, waterproof 3/16" steel shank pop rivets dipped in 5200 to put the seat back in with. It's absolutely rigid and doesn't leak a drop.

There Have been times when I lost balance and really did swing from it and am very glad I over-built it.

Looks like I'm still having problems with getting pictures to go where I want them. Oh well - they're there for you.
 

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Weldorthemagnificent

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I use clamp on swivels. Works mint for me. The kind I got from bass pro have a little angle bracket that screws into the bench sides to hook the clamp on base over to prevent it from slipping off

Sent from my CLT-L04 using Tapatalk

 

tucker99

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I like the rivnuts; great idea thanks. Tool, SS rivnuts, & SS bolts $53 from Amazon.
 

LDUBS

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Weldorthemagnificent said:
I use clamp on swivels. Works mint for me. The kind I got from bass pro have a little angle bracket that screws into the bench sides to hook the clamp on base over to prevent it from slipping off

Sent from my CLT-L04 using Tapatalk


^^^^ X2. Great system right there.
 

Clint KY

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I mounted my swivels to a 18" square of 1/2" plywood and then glued the plywood to the aluminum seat top. I used a tube of construction adhesive and even my 220 lb butt will not move them. I picked 18" because that is how wide the seats are in my boat.
 

Glades

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I cut a 4" access hole on the front/back of the seat, removed enough foam to get my hand in there and put screw on/push on access plate
This way you can add some big fender washers and lock nuts.
I actually used 1/8" Al bar stock long enough for 2 of the bolts, so one on each side. I did this bc on mine, that Al seat isn't very thick and these help stiffen it.
 

airshot

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If you have wood or sheetmetal screws that keep comming loose, just add a small dab of " shoe goop" on the threads and it wont vibrate out, yet it can easily be removed when needed....a little goes a long way !!
 

airshot

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coat the threads with marine silicone and the won’t back out.
My only issue with silicone is that once you use it, nothing else will stick to that spot. With the goop, anything will restick to that area....but you are correct, silicone does work!!
 

InSaneFisherMan

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On my mirrorcraft I took the seats out, removed foam and put wood reinforcements under the seats. Attached SS hardware and then poured new foam.

The aluminum seats flexed way too much without reinforcement.

The shorter rear seat, added a shorter piece of wood reinforcement.

This allows me to use both seats while underway and not have to worry about any failures.
 

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crannman

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I posted my install in “Sears Jon Boats”.
Counterbored the swivel mount for the rivnuts so it is flush with the bench and tack welded a 2” washer to the spring on the post to provide a nice bearing surface on the black plastic insert.
 

DaleH

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SEAT BASES: Highly recommend the Attwood SP-67749 Swivl-Eze Lock'N-Pin Aluminum Boat Seat Pedestal Mount. They use a 3/4” diameter pin and the base is 7” x 7” square, available in an aluminum base or stainless steel base.

MOUNTING: I mounted the bases to the boat seats (tin, foam-filled) using high shear/high strength 1/4” rivets and they are holding well. I also used the stainless steel version of the base (and matching seat base), as I boat in saltwaters. Over 10-years use in saltwater and the bases are still secure to the seats.

Seatbase.jpg

LOCATIONS: I went w/ the middle seat offset to the left and the bow seat centered. My reasoning for the middle seat is for both balance and for my visibility viewing while up on plane and cruising.

When going around headway speed or drifting/anchored or even trolling, then they can switch to the bow seat, centered so they have ample room. Less balance issues where they are so far up in the bow 'V'. Unless calm out, I find most don't like cruising fast being up in the bow, especially when hitting/crossing boat wakes.

Works for me! I also only use 2 seats, but have 3 seat bases and can switch them around in seconds.

Skiff.jpg
 

moecarama

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I'm putting together a 1236 jon for a winter project.The previous owner had swivels and pedestals mounted to the bench,which eventually failed. I installed the tilt and slides Swivel Ez, so seats can move from side to side and balance weight.
 

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