Alternative Fasteners for Aluminum boats?i

Nismoron

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I know this question gets asked every time a new batch of aluminum boat owners comes around. I've searched and found LOTS of answers, but most of them were uneducated answers or answers from people that have not used their boats in saltwater.

What is the best fastener material to use for aluminum boats? I know it depends on what and where it is being fastened. The reason that I ask this is that I work for a fastener supplier. I can get my hands on all kinds of neat stuff! haha We mostly specialize small stainless fasteners for the medical industry as well as your standard grade 5 and grade 8 steel bolts. But we also carry some galvanized stuff, nylon (yes nylon bolts and such) as well as bronze, brass, copper, aluminum, and even titanium.

While restoring my Mariner, I plan to reconstruct everything that I can with aluminum rivets. Do I need to use the ones with steel or stainless shafts? Also, what is best to use for stuff that NEEDS to be screwed into the hull. Stuff like transducers, trim tabs, deck hardware etc. I will use aluminum screws where I can, but strength can be an issue with deck hardware and trim tabs. I've seen where people use stainless and coat it with 5200 or gluvit. But I'm just trying to find what the BEST faster is. Because I can probably get it.
 

Watermann

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Good topic Nismo,

My Chief had some nasty surprises for me when I started removing the rivets. The factory used ferrous steel mandrels in their AL rivets and they weren't very careful about collecting the mandrels after popping in the rivets. I had to remove the bow deck support to get to the backside of it to clean out the powdered rust and repair the pitting left behind by the rusted out mandrels behind it. I found many more of the same rusted out mandrels along the way too.



All of the steel mandrels inside the AL rivets were completely rusted out and ceased being a fastener and would just pull out. That's why I removed every one of them I could find including removing the 100 or so in the gunnels.



The only way I would ever use steel mandrel blind rivets would be closed end ones with 5200 sealing each and every mandrel hole. I did use some 100% SS blind rivets for my motor mount fabrication where they attached to the ribs just because of their increased strength but the surfaces were all primed and painted to help eliminate the possibility of dissimilar metal corrosion.

So I would recommend using 100% AL blinds with a pneumatic rivet gun because the gun seems to get the rivets tighter than the hand popper... and it's fun to use. I'm not opposed to SS other than it's steep cost but just about every SS fastener I use gets coated with something as a barrier between it and the AL, either paint, 5200 or 4200 above the waterline.
 
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GA_Boater

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Go with what Starcraft used when they built the boat. Stainless for all bolts, screws, etc. The one thing they messed up on is using steel mandrel pop rivets. The mandrels often fall out over the years and end up in the bilge rusting and causing corroded aluminum. So avoid steel mandrel rivets.

As far as stainless and 5200, no matter what fasteners you use, 5200 or 4200 is the best sealant. Gluvit is used for sealing the inside of the hull because after umpty ump years, solid rivets may loosen and the Starcraft installed seals/sealant deteriorate. After repairing the loose/bad rivets, coat the inside of the hull with Gluvit or Coat-it for backup.

No, I haven't used my boat in salt water, but other than being more detrimental to aluminum, fresh water leaks just like salt water. And still contributes to corrosion, it just takes longer.
 

Watermann

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I didn't address the non rivet issue of what screws to use, GA said it though. SS is the only thing to use period, galvanized equals failure and rusting sooner or later, the same goes with zinc coating. For decking I used the same thing SC did, large flange 100% AL rivets. Seems the AL ones with steel mandrels were used around the craft but not in the decking.
 
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Nismoron

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No, I haven't used my boat in salt water, but other than being more detrimental to aluminum, fresh water leaks just like salt water. And still contributes to corrosion, it just takes longer.

I wasn't trying to ruffle any feathers with my "uneducated and non-saltwater users" comment. But there are alot of Joe-Bubba's out there with Jon Boats that have used whatever faster and it "worked fine" just like their pressure treated bunks and casting deck. haha

SO. Educate me a little on rivets. We carry several hundred sizes and types. But I do not deal with them much. Both of my customers use small stainless fasteners for the food and medical equipment. We know that steel mandrel rivets are bad. So what are the viable alternatives? Stainless mandrels? Aluminum mandrels? I think we even have some that are Inconel...
 

Nismoron

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Maybe we need to make a "sticky" for the Newb that just bought his first project boat and wants to know what "floor/plywood/rivets/screws" to use. Maybe a redecking your first project boat" sticky thread. I see these four questions more than anything else... haha
 

theoldwizard1

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. Educate me a little on rivets. .
  • Right material. Some rivet use material that "hardens" every time it is stressed (which can cause brittleness failure over long periods of time)
  • Right diameter for the hole
  • Right length for the thickness of materiel being joined
  • Right head size (A "brazier" rivet has a large head)
  • Right striking tool
  • Right bucking tool
 

elkhunter338

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I am a salt water boat user with a starcraft. Mine speds 2-4 weeks a year in the salt the rest of the time in a dry shop. Rebuilt the boat 9 yrs ago did something right and somethings not the way I would do it now.

1. use solid alum rivits, 2. don't use alum pop rivits (they don't last in the salt for years, the thin alum is eaten up by salt). Use stainless rivits and bolts.
Make sure and coat the bare alum if it is going to be in contact with wood or another piece of alum.
On all the railing that bolts to the alum, I now use small plastic washers between the two metals if you don't it will eat the alum up, need to be able to let that area dry and rinse it with fresh water.
The way starcrafts are built I don't think any of them will hold up for years and years of salt water use. Since I only use it for 2-4 weeks a year I anticipate many many years of service, but if you keep your boat in the salt water for most of the year I wonder how long it will last.
Even with that I am still looking for a good fresh water 25-26 starcraft to rebuild and use it in the salt.
 

Nismoron

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PM sent on looking for that 25-26 footer.

I will only use mine in salt for 1 week and maybe 2 other weekends a year. It wont be much, but I dont want any corrosion to start. Once started, it will keep going. Even without additional salt.

I'm not sure that I have the abilities or facilities to deal with solid rivets. I just dont know anything about them. Pop rivets, I can handle. I have looked over my hull and I see ZERO rivets that need attention. The entire inside of the hull will get GLuvit anyway. haha. Overkill and Attention to detail are my forte's. I will be removing my splashwell for a transom job. Thus, I will be removing my gunwales as well. The guwales are fastened with pop rivets. The splashwell rivets are solid.
 

Gibbles

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On my 63 chief they used aluminum transom bolts, nuts, and the rivets were aluminum, and appeared to have aluminum mandrels (note it's been a while, and I prefer to do many tasks like that with a beer bottle in my hand), I did notice their use of steel bolts and nuts holding the rub rails in though... :rolleyes:
 
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Grandad

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I'm not sure that I have the abilities or facilities to deal with solid rivets. I just dont know anything about them. Pop rivets, I can handle. I have looked over my hull and I see ZERO rivets that need attention. The entire inside of the hull will get GLuvit anyway. haha. Overkill and Attention to detail are my forte's. I will be removing my splashwell for a transom job. Thus, I will be removing my gunwales as well. The guwales are fastened with pop rivets. The splashwell rivets are solid.
I hear you Nismoron. Don't fear solid rivets. I did before trying them for the first time for a hull repair. I found they're a piece of cake with the right equipment, a buddy and access to the backside. - Grandad
 

Nismoron

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I hear you Nismoron. Don't fear solid rivets. I did before trying them for the first time for a hull repair. I found they're a piece of cake with the right equipment, a buddy and access to the backside. - Grandad

What equipment?
 

classiccat

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PM sent on looking for that 25-26 footer.

The entire inside of the hull will get GLuvit anyway.

I recommend coating as little of the inner hull with gluvit as possible...stick to the rivets & seams. If it even partially delaminates, your good intentions would end-up being your worst nightmare as it loves to trap water against the aluminum:




^^^ I Don't know what kind of epoxy that the PO used here.
 
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classiccat

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Equipment needed for solid rivets:
  • Center punch
  • drill bits up-to 1/4" (3/16" is the most common)
  • cutting oil (for prolonging the life of your bits)
  • wood chisel (for blasting-off the heads &/or bucktails after you've cored them out drilling)
  • acetone (to clean-off the cutting oil)
  • bucking bar (or a thick piece of steel)
  • a drinking buddy
  • 4x riveting hammer
  • Rivet sets for 5/32, 3/16, 1/4 brazier heads (This is what you load into your riveting hammer)
  • oiler (for your riveting hammer; alternatively, you can put a few drops of tool oil at the inlet of the riveting hammer)
  • air compressor...a little 2-gallon is enough for doing a handful of rivets.


I like to core-out the rivets then blast-off the bucktail with a wood chisel.

Once the bucktail tail is off, see if you can gently punch it out...if it's still stuck, go-up to a slightly larger drillbit size and it should spin out (do not exceed the final hole size).

Drill-out the rivet hole to your final size. In most cases, starcraft used 5/32" which we drill-up to 3/16".

Debur the holes....especially the outside holes.

Insert the rivet into the hull ...head on the outside and press the riveting hammer / rivet set against the head. Have your buddy put slight pressure on the rivet tail with the bucking bar...only enough pressure to keep it steady on the rivet.

Start the riveting hammer at slow speed to get the process started...and watch the rivet stem start to expand & fill the hole.

After ~ 5 seconds of slow speed, gradually increase the speed and give it a blast at full-speed to mushroom the bucktail.

I used 5200 on most of my rivets below the waterline before inserting them...to compensate for my learning curve.
 

Nismoron

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I already have an air chisel too. I'll check into getting that rivet tip. So if you insert the rivet from the outside, put the bucking bar on the inside and hammer from the outside, how does the rear of the rivet crush?

I know about drilling out rivets. Done it many times. Just not on a boat. Are the splashwell rivets 5/32 as well? I may just do pop rivets/ At this point the only rivets that I foresee doing are the ones holding the splashwell and the ones removed from the gunwales to get to the spalshwell.

Oh, and what about the tiny pin rivets that hold the transom cap in place? What is the deal with those. They look like little nails or tacks.

As for the gluvit, when I said that the whole hull, I didn't mean I was going to paint the entire hull. I only meant the rivets and seams. I should have been more clear. haha
 

Grandad

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I already have an air chisel too. I'll check into getting that rivet tip. So if you insert the rivet from the outside, put the bucking bar on the inside and hammer from the outside, how does the rear of the rivet crush?

What happens is that the bucking bar does a little dance in response to the air chisel/riveter's pulses. That's why Bluefin said place the bar lightly on the tail end of the rivet. You'll quickly find your own technique when you start with few practice rivets in a sample before you start on the boat itself. Pressing too hard prevents the bar from hammering the tail of the rivet. On mine, my son used the gun under the hull while I held the bucking bar and called the shots, so to speak. We didn't hammer as long as Bluefin, perhaps only a couple of seconds. (I told my son that I needed to observe how well the tails were riveted, so I got the inside job. He got to enjoy riveting overhead while covered in 5200) - Grandad
 
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GA_Boater

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One other thing about driving from the manufactured head side is it helps seat the head against the work. Driving from the shop side wants to push the shaft through the hole and the chance of the shaft expanding before the outside is seated is greatly increased, causing poor clamping. Does that make sense?
 

MNhunter1

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I already have an air chisel too. I'll check into getting that rivet tip. So if you insert the rivet from the outside, put the bucking bar on the inside and hammer from the outside, how does the rear of the rivet crush?
I know about drilling out rivets. Done it many times. Just not on a boat. Are the splashwell rivets 5/32 as well? I may just do pop rivets/ At this point the only rivets that I foresee doing are the ones holding the splashwell and the ones removed from the gunwales to get to the spalshwell.
Oh, and what about the tiny pin rivets that hold the transom cap in place? What is the deal with those. They look like little nails or tacks.
As for the gluvit, when I said that the whole hull, I didn't mean I was going to paint the entire hull. I only meant the rivets and seams. I should have been more clear. haha

If you're only doing the splashwell and gunwale rivets, the closed end pop-rivets are just fine and consistent with how they were done at the factory. The solid rivets are the best option for any thru hull rivets if you have repairs to make.
 
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