Fasteners for aluminum sheet.

[Nessmuk]

I have stuff like rod holders, etc. I want to mount on a row boat seat.   The seat is aluminum and I can't get at the back side.    The only two solutions I can think of are sheet metal screws and/or epoxy.   I am concerned about the strength of sheet metal screws and would have to wait for warmer weather to use epoxy.    Thoughts/suggestions?

[ontherise]

Run a board across the gunwales

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[Nessmuk]

Not really interested in board across  the boat.    Trying to keep the boat as uncluttered as possible.

[Ice Pirates]

Pop-Rivits.....sorry about the line through the words i have no idea why its doing that

[Dick]

Watch for corrosion with sheet metal screws. Closed shank stainless or aluminum pop rivets are good. Don't do over size holes, or wrong grip range.

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[lrg355]

You need a blind fastener that resembles a rivet but is collapsed by tightening with a screw in the fastener then tightening further with a nut on the screw.  The military uses these on portable buildings.  Often referred to as "Spec Nuts" or "Riv Nuts".  Supply companies such as Mc Master Carr would have them.  You can use a credit card to buy from them.  Simply drill the proper size hole, push it in, and collapse the rear by tightening a screw and nut in it.  Be sure to order the correct size for the thickness of material you are in.  you can also put a another plate on top for extra support if the material is thin.  I use em frequently, but I have a special tool to collapse the back.  The proper size screw and a nut will suffice.

[Nessmuk]

You need a blind fastener that resembles a rivet but is collapsed by tightening with a screw in the fastener then tightening further with a nut on the screw.  The military uses these on portable buildings.  Often referred to as "Spec Nuts" or "Riv Nuts".  Supply companies such as Mc Master Carr would have them.  You can use a credit card to buy from them.  Simply drill the proper size hole, push it in, and collapse the rear by tightening a screw and nut in it.  Be sure to order the correct size for the thickness of material you are in.  you can also put a another plate on top for extra support if the material is thin.  I use em frequently, but I have a special tool to collapse the back.  The proper size screw and a nut will suffice.

 

IRG355

 

Thanks!  I was a machinist and like dealing with McMaster Carr.  I wasn't aware of Rivet Nuts.    Making a 7/16 round hole in 1/16 thick aluminum might be a bit tricky though.   Got to look this over more. Thanks!

[Big Dave]

Uni-bit , or stepbit drill will drill the thin sheet metal with out catching and tearing.  Put tape on the bit at the size you want to stop at to keep from drilling a size to big. 

[rolmops]

Herb's fasteners has everything you need advice on how to use it.

Aluminum is quite soft and if it is not thick enough rivets will pull right through them and that includes rivet nuts.

[CaptSpike]

I used well nuts to fasten downrigger stands to an aluminum seat I couldn't get to the back side off. They worked great.

What is nice about them is they are not permanent, should you decide to remove them later. Google them you'll see what they are. Basically a rubber insert that collapses as you tighten the screws. Also adds a little buffer between the plates and mounting surface.

 

Spike

[LongLine]

1. Put a plate larger tan the base of the holders on top of the seat then attach the holders to it.  You'll need to spread the load at the base if you want any kind of secure attachment.  The leverage generated by rods will be great & just about everything will rip out of thru 1/16" aluminum.  

2.If permanent - ever consider drywall toggles? replace the screw with stainless)

3. Cover the whole seat with a wide x long piece of wood, securely screw or bolt/washer nut thru it.  Board can probably be in just the four corners and can be made so it's removable.

4. Cover the whole seat with a thicker piece of aluminum - same as #3. Aluminum is easy to cut & shape.

 

I don't have a pic of the size of the seat, but I'd seriously consider screwing or riveting two 2" wide strips of 1/4" aluminum to the seat.  One at each end of the seat.  Then cut wood or aluminum to span the two and screw it to them.  This way you'd have an air space under it and you can make it removable if you want to sit in the seat sometime.

 

Tom B.

(LongLine)

[Nessmuk]

I ended up making a temporary mount on the transom for one side and will use the DR rod holder for the other.   Once the weather gets warm enough to use epoxy I plan on mounting some large 1/4" plates to the seat.   Every other option seems to have obvious issues and I have not been able to find info on tensile strength of fasteners in 1/16" aluminum sheet.   Fasteners worry me so I'll wait to use epoxy.   Done correctly, the epoxy should be a lot stronger than fasteners since it spreads out the load.

 

Though I have decided to not use fasteners, I think the best suggestion (from Spike) is the well nut.   The well nut would work but the big holes concern me.    Best thing about the well nut is documented strength.

[CaptSpike]

I ended up making a temporary mount on the transom for one side and will use the DR rod holder for the other.   Once the weather gets warm enough to use epoxy I plan on mounting some large 1/4" plates to the seat.   Every other option seems to have obvious issues and I have not been able to find info on tensile strength of fasteners in 1/16" aluminum sheet.   Fasteners worry me so I'll wait to use epoxy.   Done correctly, the epoxy should be a lot stronger than fasteners since it spreads out the load.

 

Though I have decided to not use fasteners, I think the best suggestion (from Spike) is the well nut.   The well nut would work but the big holes concern me.    Best thing about the well nut is documented strength.

I reason I used well nuts was because that is what was used to hold my trolling motor on the first boat I owned. It held the motor no problem so I used it for the seat. I can tell you I never had a problem with strength. Even hanging up the rigger balls on bottom.

Epoxy is only as good as the bond. I'd prefer a mechanical connection every day of the week.

 

Spike

Edited April 14, 2014 by CaptSpike