Aluminum hull, what type of rivets?

[Grandad]

Re: Aluminum hull, what type of rivets?

Blind rivets in aircraft manufacturing:
http://www.helicoil.in/pop.htm.

Thanks jig. - Grandad

 

[starcraftkid]

Re: Aluminum hull, what type of rivets?

The solid rivets in our Starcrafts are Brazier Head and they are a soft alloy. The ones I used were 1100F from www.rivetsinstock.com

I do suspect they use something pretty soft but on the Lowe hull they look most like the universal head style rivet.
The heads are small in comparison to rivet shank size compared to the OEM Starcraft rivets.
I'm a bit concerned because lately I've run across a rash of these boats with popped rivets, all from the early to mid 90's era.
Both jon boats and v hulls.
They used some sort of thick filler rubber between all the seams and unlike Starcraft they use only one row of rivets.
There's a lot of places where the metal is gathered or buckled where they came to the end or at a curve.
What I've been doing it working the metal back into shape and re-riveting, but I'm concerned as to whether the original rivets lost their heads due to stress or some sort of corrosion due to a mismatched alloy combination.
In the past 2 months I've seen over two dozen popped rivets in two brands of boats. Both Grumman and Lowe branded hulls, which I believe at that time were either the same or related through a corporate link. Those year Grumman hulls sure to look like Lowe hulls, and the same position rivets are those I find broken all the time. So far its only on saltwater used boats. I've not run into one with this issue on a boat that I can say has never seen saltwater. I've been using rivets intended for truck bodies, their a soft 5056 chromated alloy buck type solid rivet. Since the inside shows on these boats I prefer not to use a pop type rivet, especially where one odd rivet will stand out in the open. The problem is I've yet to find them locally in the exact proper head style. I can get brazier head style rivets in the soft alloy but I don't seem to find soft alloy universal head rivets around here.
Not all the rivets on these hulls are universal type heads, only those used on the seams at the transom and spray rails, the rest are brazier head style. The larger brazier head rivets won't fit due to the larger diameter head due to how close the rivet holes are.

When a rivet is found missing its head, the remaining rivet stub is smooth, not corroded, and not torn looking. It looks as clean as the small end of a new rivet. The remaining stub is almost always still well anchored in the hole, and rarely does the missing rivet produce a leak. I've also yet to have two adjacent rivets missing on the same hull. The rivets tend to be broken off flush with the inner panel, just barely holding onto the outer hull skin preventing a leak, so basically just the head itself is popping off. I have drilled and removed a few adjacent rivets to be able to use a bolt to pull the panels tighter. I also find that the inner sealer is still very pliable, remove three adjacent rivets and it will push the panels apart without creating a noticeable gap in the seam. What ever they used its very compressible and remains somewhat sticky with time. It closely resembles the butyl rubber used in automotive windshield setting.

 

[efdog]

Re: Aluminum hull, what type of rivets?

I'll have to agree with Jig and Bond-O that closed end blind Rivets are very strong and will work excellent for this application. Jig helped me patch more that 12 cracks and gauges in my aluminum boat...All with closed end blind rivets (I went with a steel Mandrel for the added strength). I've fish the boat hard several times per week since May, and in some big waters at times. Check out my patch thread if you want to see how I did it.

These pics actually don't even do justice...and EVERY rivet is tight, and no leaks at all.

 

[djpeters]

Re: Aluminum hull, what type of rivets?

Interesting that you just have random tails missing like that. Sounds like you have a good plan going to fix it right. I can't think of a reason why they would look like you describe. I had a few on my SC where the tails were corroded a little (less than a dozen). They were still holding strong, but they got replaced.
I only used the soft alloy ones on mine. No worries with these as far as work hardening them and making them brittle. The harder ones though, I would imagine you'd need to know what you doing when bucking them.

 

[jigngrub]

Re: Aluminum hull, what type of rivets?

I'll have to agree with Jig and Bond-O that closed end blind Rivets are very strong and will work excellent for this application. Jig helped me patch more that 12 cracks and gauges in my aluminum boat...All with closed end blind rivets (I went with a steel Mandrel for the added strength). I've fish the boat hard several times per week since May, and in some big waters at times. Check out my patch thread if you want to see how I did it.

These pics actually don't even do justice...and EVERY rivet is tight, and no leaks at all.

Good to see you're getting the Tracker out and putting her through the paces efdog, you did a good job on those patches and they're barely noticeable even being on the outside like that.

 

[jasoutside]

Re: Aluminum hull, what type of rivets?

That looks like great "Sea Trial" conditions Kinda miserable for fishen though eh.

 

[starcraftkid]

Re: Aluminum hull, what type of rivets?

I have the correct tools to buck the rivets and do the job just like the factory, my only concern was about which alloy rivet to use. From what I see if I use closed end pop rivets I have no choice in what their made of, the only choice is 'aluminum' but not what grade or alloy of aluminum.
I have about ten pounds of 2017-T4 rivets, given to me by someone in the aerospace industry. They apparently have exceeded their shelf life are marked 'Past Date'. These rivets, if used as intended by the aircraft industry are supposed to be heated to 940 degrees and quenched prior to installing them, that don't mean they get installed hot, just that the molecular structure of the rivets is modified by heating them. Once heated they say you must use them within 24 hours if they are not frozen. Once they're installed they achieve their rated hardness and strength.
Keep in mind that these were most likely intended to be used on an airplane with a pressurized cabin, where repeated stress would be a major issue.
Stress on a boat isn't all that high at each rivet, corrosion is more the issue from what I've seen.
I have used these same rivets for various other projects, one being a truck tool box and a cap for my truck bed. Neither are exposed to salt or any pressure though and the rivets have held up fine for many years.
These rivets match the head style used on my Lowe.
I guess the only way to see if they will work is to try them, if they're still in place in another 10 or more years I know they worked.
The original rivets all seemed to last around 20 years before they start popping, it just made me curious as to why or if they could have used a rivet that had an electrolysis issue.

 

[Bondo]

Re: Aluminum hull, what type of rivets?

These rivets, if used as intended by the aircraft industry are supposed to be heated to 940 degrees and quenched prior to installing them, that don't mean they get installed hot, just that the molecular structure of the rivets is modified by heating them. Once heated they say you must use them within 24 hours if they are not frozen. Once they're installed they achieve their rated hardness and strength.

Ayuh,... They're Aluminum,... What yer explainin' is how to anneal 'em,....

When you buck 'em in, they re-work-harden...

 

[mnjp]

Re: Aluminum hull, what type of rivets?

For the best rivet selection go to Fastenal, www.fastenal.com You can order any quantity you need, starting at 1

 

[dajen]

Re: Aluminum hull, what type of rivets?

Please don't blast me if I am in the wrong place or wrong subject. Did a lot of reading about aluminum rivets, bucking, etc. and all are interesting.

" know that the boat company I used to work for before I retired will sell you rivets and they are pretty cheap, "
Would be interesting to know the company and get some rivets to try, if you will provide the info.

Found a company that has rivets (closed hidden, alum/alum) very reasonable price ($7-$10) for 100. They also have stainless 18-8 sealing washers ($7 per 100) #10 which are .190" id .500" od and I wonder how well they would seal and if there is any problem using aluminum with stainless.
Don't know if I am allowed to post the company here but I am sure it will be deleted or I will be banned, even though my intention is good. It is called BoltDepot and I am sure you can find it. I would rather use the alum/alum instead of alum/steel to avoid rusting or corrosion. I feel the the washers would add strength, could help in sealing, and would provide filling the gap between the smaller rivet that grips between .125 and the larger one of .188.

15394 0.020" - 0.125" (62)

15395 0.188" - 0.250" (64)

I would still add some sort of sealer because even though the washer might seal against the surface, I don't know how a seal will be achieved between the two pieces of aluminum, consisting of the hull and frame. I also wonder if the washer (probably neoprene) would cause the rivet to loosen sooner or would the rivet pull down to the metal, leaving the washer to seal and not interfere with the holding power.

Would appreciate if anyone has used their rivets and how well they worked. For my purpose it is only on a 14' 1983 sears aluminum boat to be used on a lake but would be nice if it can be kept dry.

 

[Grandad]

Re: Aluminum hull, what type of rivets?

I found this tidbit of info:
(a) 1110 rivet Use 1100 rivet, made from pure aluminum, for riveting nonstructural parts fabricated from the softer alloys (1100, 3003, and 5052).
(b) 2117-T4 rivet. This rivet is most commonly used in aluminum alloy structures Its main advantage lies in the fact that it may be used in the condition received without any further treatment.
(c) 2017-T4 and 2024-T4 rivets. Use these rivets in aluminum alloy structures where strength higher than that of the 2117-T4 rivet is required. These rivets are generally used in sizes 3/16-inch diameter and larger.

I used the 2117 T4 (26,000 lb shear & 38,000 lb tensile) as available from Aircraft Spruce. I also purchased some 1100's since I didn't know if my air chisel come riveter could handle the tougher series. I was able to buck the 2117 T4's with no problem. I can't tell you what the corrosion or life expectancy of them is, though. I suspect they'll outlive me. - Grandad

 

[starcraftkid]

Re: Aluminum hull, what type of rivets?

What if you were to use 2017-T4 rivets and not heat treat them first?
Someone gave me a bucket of them with the right head type.

What concerns me the most is that so many rivets in this and various other hulls I've seen lately have rivets that lost their heads with no signs of stress or corrosion. Its like the head popped off and rivet retracted into the hole.

The rivet driver kit I have is made for aircraft repair, it has no problem bucking even the hardest dimpled rivets so long as you can apply proper pressure to the back side at the same time.

If they used very soft rivets from the factory, maybe that's why they're failing? The two layers of metal are compressed with a black rubber strip in between, removing a few rivets lets the metal really open up exposing a visible gap. A soft rivet may also begin to distort too early before applying pressure to the two panels?
What I am seeing is that the original rivets are partially expanded both on the ends and in between the layers of metal, which on the corners is over 1/4" overall, where as the flat areas are compressed better and only slightly more than the thickness of both layers of aluminum. It looks like they really relied on the rubber in between to do the sealing, not the rivets. If the rubber was not there, I could probably pass a tooth pick between the layers of metal on the sides, and double that at the lower corners. There's no way I'd ever compress that metal the same amount as the rest of the transom seam, not unless I removed every transom rivet and then every hole would be out of line. They clearly relied on the sealer to make it waterproof. The rivets were just a mechanical bond. I took a ride down to a new boat dealer and took a close look at some new hulls, their built the same way, some with even more of a gap, again relying on the rubber. Its as if they started riveting from the top sides and worked towards the corners, or they pre-punched all the holes and made up any variations with sealer.

I tried dealing with Fastenal, I have a store within walking distance here. They don't stock rivets and didn't seem to care about ordering what I wanted. They kept on about me not having an account there. I got tired of trying to explain to the kid I just needed a few rivets. I got the impression that every employee in the place was miserable and hated life. I got frustrated trying to deal with them and left. That was a few years ago, I never went back. Others around here have had the same experience. Its a place to go when you have no other choice.
Aircraft Spruce however looks like a good source, I'll probably order there.
I can't see where any rivet in a boat would need more than 16,000lb tensile strength rivets but I would like to figure out what causes so many on these to pop like this.

 

[jigngrub]

Re: Aluminum hull, what type of rivets?

I'd say the rivets are being chosen for ease of installation and price instead of doing a quality job... the easiest cheapest way is rarely the best way IMO.

I'm not impressed with Fastenal either, they're way overpriced even when you do have an account with them.

Jay Cee's has an excellent selection and great service with quick shipping, but the shipping charge is pretty expensive at $15 so I buy large quantities when I shop with them.


Another thought is rebucking, have you been rebucking these rivets that're failing?

I'm not a fan of rebucking rivets, I consider any rivet that has loosened and started to leak weakened and rebucking an already weakened rivet is futile.

 

[starcraftkid]

Re: Aluminum hull, what type of rivets?

On my boat, the rivets have never been touched. I won't rebuck a rivet either, if its loose, the only fix is a new rivet, often that means an oversize rivet as well. The problem here though isn't loose rivets, they never get loose, the heads just fall off.

I also wouldn't think that no single rivet on any boat like this is under any great stress, other than compressing the rubber gasket they're not really under any strain. Its not like a tank or pressure cylinder, its just a tub that floats. I'd venture to guess that there's more stress on the sheet metal itself in some areas than on the rivets.