Rivet Question

[lckstckn2smknbrls]

I have a 1968 14' Falcon. 2 of the ribs have cracked at the very ends into a small triangle with a rivet in each. I want to add a rivet to each rib near the crack. I went to Fastenal they have solid aluminum rivets but it's 1/2 inch long and the floor and rib are much thinner around 1/8". The guys a Fastenal didn't know if the 1/2" long rivet will mushroom enough to hold 1/8" of material. Nor did they know if I were to cut the rivet down with my angle grinder would the heat generated adversely effect the aluminum rivet.

 

[Bullrider]

Re: Rivet Question

If you did soften the rivet to O condition from heat it will go back to its T condition when you drive it. Your biggest concern should be the size of the hole in relation to the rivet size. Say your rivet is .190 (3/16) your hole should be .192 a loose but not sloppy fit. This will reduce your chance of a stress crack in the structure.
Some rivets are intentionally softened to O condition and frozen until they are driven and hardened condition.
Aluminum age hardens in time after it has been softened by heat,unless the heat is too extreme and breaks down the metal.
The lenght of the buck tail should be diameter and a half of the rivet before bucking it. Meaning,your .190 diameter rivet should stick through about .245 to.275 before driven
cracked buck tails are ok if they dont intersect each other. the scratches from grinding the rivet shouldnt make cracks though.
Cheers!

 

[jbcurt00]

Re: Rivet Question

pix would definitely help, but sounds like an often found rib end crack of the hull, the chine or the rib flange where the last rivet along the side is driven.

Why the extra rivet to the rib near the crack? If you don't address why it cracked, the new rivet hole may crack too making a problem even worse....

Solid rivets come in lots of sizes, order the right head & shank length/diameter & buck them.

If Fastenal can't get the right rivet, you can get them here

Quick delivery, decent service and plenty of solid rivets to choose from to get the 'right' ones. I'd recommend the softer 1100F alloy, they will buck much better. The 2117T4 alloy is more difficult to buck into a nice looking mushroom on the backside.

 

[lckstckn2smknbrls]

Re: Rivet Question

pix would definitely help, but sounds like an often found rib end crack of the hull, the chine or the rib flange where the last rivet along the side is driven.

Why the extra rivet to the rib near the crack? If you don't address why it cracked, the new rivet hole may crack too making a problem even worse....

Solid rivets come in lots of sizes, order the right head & shank length/diameter & buck them.

If Fastenal can't get the right rivet, you can get them here

Quick delivery, decent service and plenty of solid rivets to choose from to get the 'right' ones. I'd recommend the softer 1100F alloy, they will buck much better. The 2117T4 alloy is more difficult to buck into a nice looking mushroom on the backside.

It didn't crack thru the rivet hole, Why two ribs cracked I don't know. My thinking is whatever stress involved was relieved and riveting the ribs where there at will strengthen the hull.
I checked the site you linked, they sell 100 to a box and I only need 2 rivets.

 

[lckstckn2smknbrls]

Re: Rivet Question

Since I'm going to bed the rivet in some 5200 and Gluvit all the rivets and seams I could go with 2 3/16" all stainless steel closed end rivets $1.37 each or even 2 all aluminum rivets that I already have.

 

[lckstckn2smknbrls]

Re: Rivet Question

If you did soften the rivet to O condition from heat it will go back to its T condition when you drive it. Your biggest concern should be the size of the hole in relation to the rivet size. Say your rivet is .190 (3/16) your hole should be .192 a loose but not sloppy fit. This will reduce your chance of a stress crack in the structure.
Some rivets are intentionally softened to O condition and frozen until they are driven and hardened condition.
Aluminum age hardens in time after it has been softened by heat,unless the heat is too extreme and breaks down the metal.
The lenght of the buck tail should be diameter and a half of the rivet before bucking it. Meaning,your .190 diameter rivet should stick through about .245 to.275 before driven
cracked buck tails are ok if they dont intersect each other. the scratches from grinding the rivet shouldnt make cracks though.
Cheers!

What's O and T condition?
If shortening the rivet won't adversely affect it I may go this way. I plan on using 3/16" and the proper size drill bit.

 

[jbcurt00]

Re: Rivet Question

I understand what you're saying, but I wouldn't be so sure that the only damage was 2 rivets, and the 2 new ones are the only ones that need to be added.

Most that have found 1 or 2 damaged rib ends, find more damage, often extremely well hidden. Some find lots. Read thru BlueFin's thread, he's found quite a bit of rib end cracking. And yep, it's usually caused by stress.

Repeated pounding thru wakes/waves, impact from above/below, lack of proper support while on the trailer, the hull filling w/ snow & water & left for extended periods, improperly loaded & trailered too fast down a washboard road.....

But again, w/out pix

And it's certainly your boat, proceed as you see fit....

BTW: If an new rivet will resolve a cracking problem at the rib end, I wonder why Starcraft modified their boat hull to include additional rib end bracing and offered a dealer installed retro fit brace to fix or prevent the cracking, along both gunwales & under each rib end.....

 

[Bullrider]

Re: Rivet Question

What's O and T condition?
If shortening the rivet won't adversely affect it I may go this way. I plan on using 3/16" and the proper size drill bit.

Another point to consider is to (carefully) bead blast the area to work harden the surface. This will increase service life of a lot of aluminums.
This is ONLY an example. For what you are doing I wouldnt be concerned.

6061-O: Annealed (or "soft", bendable condition) 6061-T4: Heat treated and naturally aged
6061-T6: Heat treated and artificially aged
6061-T65: Heat treated and artificially aged
6061-T6511: Heat treated and artificially aged

 

[barato2]

Re: Rivet Question

a lot depends on your planned duty for the boat. if you're just putting around farm ponds with a 6hp, sure, do the quickie patch fix. if you're fishing LK Michigan or other big water, it's worth doing some detective work to find the source of the problem rather than just putting a band-aid on it....or save this one for the farm ponds and get another hull for the big water.

 

[lckstckn2smknbrls]

Re: Rivet Question

Another point to consider is to (carefully) bead blast the area to work harden the surface. This will increase service life of a lot of aluminums.
This is ONLY an example. For what you are doing I wouldnt be concerned.

6061-O: Annealed (or "soft", bendable condition) 6061-T4: Heat treated and naturally aged
6061-T6: Heat treated and artificially aged
6061-T65: Heat treated and artificially aged
6061-T6511: Heat treated and artificially aged

Thank you for the explanation. I'll hack saw the rivets down, less heat.

 

[lckstckn2smknbrls]

Re: Rivet Question

I'll look for and read BlueFin's thread.
If the cracking was in the hull skin I'd be more worried but this boat is not going to be used on big waters just to cruise the Fox river and Chain O Lakes in NE Illinois.

 

[classiccat]

Re: Rivet Question

I'll look for and read BlueFin's thread.
If the cracking was in the hull skin I'd be more worried but this boat is not going to be used on big waters just to cruise the Fox river and Chain O Lakes in NE Illinois.

pics please :madgrin: :hungry:

 

[Bullrider]

Re: Rivet Question

Thank you for the explanation. I'll hack saw the rivets down, less heat.

I have used side cutters for small rivets and it works fine,maybe a file for the little nerd that sticks up

 

[lckstckn2smknbrls]

Re: Rivet Question

pics please :madgrin: :hungry:

Sorry no pictures for now it's in the garage full of supplies. I have been reading your resto thread the issue I have is nothing like what you had to go thru. I have 2 ribs that cracked at the ends without any damage to the skin. The crack doesn't involve the rivet or hole just the rib.

 

[lckstckn2smknbrls]

Re: Rivet Question

pics please :madgrin: :hungry:

If you go to page 22 post 531 of BlueFin's resto thread, 2 of my ribs are cracked the same at the ends but I don't have any of the other damage.

 

[lckstckn2smknbrls]

Re: Rivet Question

If you don't address why it cracked, the new rivet hole may crack too making a problem even worse....
Clues as to why the rib cracked.
The boat came from a charity in the Green Bay Wis area. It had the original floor but had a huge hole in the floor not wet rotted but dry rotted. I think the boat was outside for many years filled with snow every winter over loading the hull and draining out, good thing the plug was out. Further evidence is the roller bunk trailer has slightly deformed the bottom of the hull and best as I can recall the 2 cracked ribs are just in front of where the roller bunks end. The original foam was clean and dry and other than the mouse tunnels it could have been used again.