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Riveted hulls

RJ,

Hadco has it in the 6061T6, I'm not sure I found it in 7075. I would call them and ask

Also call these guys:

http://www.intercontal.com/

Those are the only aluminum suppliers I had bookmarked, I'll look around some more and see what I can find.

edit: I did a search of my old posts and I did say I found it in 7075, either i did not bookmark it or Hadco changed their listing. I would call for sure.

Jim
 
All things equal, I think if I ever ordered a new boat or get around to trying to build one, I would use that 6061 for the skin just because of the corrosion problems due to being close to the salt water. I believe going up to 0.10 or even 0.12 would be about the same strength and would not add excess weight. Handling is what I am after and a few pounds just makes the driver pick his route alittle better.
 
Jim,

Well that would require thicker hulls and I would get into weight problems. Just trying to look at a means of getting a handle on the corrosion.

If I ever get a hull made again, it will have the structure painted with zinc chromate, and then the skin along every seem before it is riveted and then the entire hull. Especially that stainless cap in the front where the side and the bottom are coming together.

Everyone is having problems over here and getting a hull sandblasted every 4 to 5 years and repainted started hurting the wallet.
 
Pat,

I would consider using alclad sheets, and possibly not using stainless for that cap. You could have a unheatreated 6061 piece welded up that would be much thicker than the stainless, then have it heatreated. I would talk to a builder first though, they may already have tried it.

My outboards are built with stainless bolts and they use an anode to help with corrosion. It does not stop it though.

Jim
 
Cowboy, That is one fine boat Sean is selling. He said," it runs anywhere the big boats go, not as fast (who needs to go that fast anyway), and with alot less fuel." Wish I could buy it also, but I have 2 boats to get rid of first. I talked to both Sean and his dad and they said they have made some improvements on their boats over the other Palm Beach builders. Their gusseting is thicker plate and they have changed some of the design and structure of the hull. How does your Father's Kline perform, dry ground, power, responsiveness, etc.? It's probably 6061 .125 and it looks like a 220hp Continental?

Cracker, Thanks for the information. I will be investigating more about the aluminum sheet size and corrosion problems. There are quite a few aluminum builders here in LA. I saw that tensile strength info in the Kline catalog, and Hadco has it on their site. It would be nice if someone makes 7075 T-6 in 5' wide sheets, then you wouldn't have to add to the two 4' sheets to make a wider boat. When I got my boat, I installed a battery switch to help with the electrolosis. I'm also going to install a magnesium anode. Every little bit helps, I HOPE!!!!

Marshmaster Pat, Sean has a customer now that wants a 6061 boat. He is figuring up the cost and weight of the material now. He is going to use .125 6061 T-6. On a 12' boat with two 4' wide sheets, 7075 T-6 .090 weighs 62.88#'s a sheet =125.76#'s. A sheet of 6061 T-6 .125 weighs 84.7#'s, 2 sheets weigh 169.4#'s. You are only talking about 43.64#'s difference in weight using 6061, but not nearly the tensile strength of the 7075. 7075=83,000psi, 6061=45,000psi.
Sean favors an aircraft aluminum boat. He's into light weight, strength, 4 cylinders, and fresh water. He also says a 6061 T-6 hull wouldn't be nearly as strong as a 7075 hull and the sides could get dented up with the 6061 where the 7075 wouldn't. Upon hard impact, the 7075 would flex and could possibly split but not dent.
Hamant uses 6061 T-6 .125 bottom ,090 sides to build their 12'x7'6" deckover boats, and so do some of the other builders, Diamondback.
Sean likes to use the spray-can zinc chromate (Tempo makes it for outboards). He uses it at the riser cap before riveting the boat. He said if you use paint there before riveting, the rivets would crack the paint when installing them.
For maintainence, he uses Liquid Electrical Tape between the riser cap and the hull as well as on the rivets inside the boat to keep the loose rivets from leaking. He likes the way it flows and gets between the riser cap and the aluminum to create a protective seal. I'm sure there a better sealants out there then the L E Tape. I've used black 5200 with acetone to even it out.
Anyway Pat, I think a 6061 boat would be better choice for us since we use them in a salt enviroment. We just have to be careful about denting the sides. I don't want to have all the maintainence problems that come with the 7075, but I do want the responsiveness and strength. Decisions decisions decisions, I guess we can't have everything!!!!
I'll be talking to Sean about the new 6061 boat and my boat. I'll let you'll know what's happening with the new boat.
 
Cracker, Thanks for the info. That will be a great help in building a 7'6" wide boat. Now you don't have to rivet an additional 1' piece to two 4' sheets to make the width.

Thanks, again
 
maybe we have covered this before, but why do you like the single rudder?

That O360 is one of the toughest aircraft motors ever.

Jim
 
[/b][/i]Hey RJ if your gonna get someone in La to build your boat, you might wanna try a guy Named Chris Wall, hes in Springfield. My dad taught him how to weld and build the tuff swamp boats that we used to hunt Reserve. My Dad built alot of boats back then but doesnt build naymore. But I'm sure that Chris could build you a tuff boat that would last.
 
RJ - I am fairly certain that several of the older hulls around here are 6061 T6 sheet. They are all 0.125 on the outer skin. With the polymer wrapped up around the sides they were fairly strong. Since the bottom and are the same sheet, just split in the front, curved up and joined by the riser cap. That is the part I was thinking of spraying with zinc chromate and we use that Tempo stuff on everything aluminum as well.

But that 7075 is strong stuff, we bent the side one night when I topped a marked levee that was about 9 to 10 feet up. It was supposed to be a good grade on the other side, but they pointed out the wrong crossing and it was a vertical drop. Flying isn't that bad really, but that landing hurt. When we repaired it, just sheared the rivet heads off along the gunnel and the sheet just popped back into shape. That was after running with the side bent for about 40 to 50 hours and then it sitting for about 5 months due to no time to handle the job. There was a slight split, but drilled the end of it and left it alone. We replaced the gunnel angle and other pieces with new angle just another 1/32 thicker for added strength. I am lucky that there is a really good aluminum shop about 45 miles away that we will deal with at work. They can order any of the aluminum except sheet.

RJ & Jim - They qoute the tensile strengths for 7075 and 6061 sheet, but those numbers are for the same thickness. Right???
If that is so, then going up from 0.90 to .125 would increase the strength of the 6061 some, but not up to the 7075.

I figure that if I don't try anymore flying lessons without wings, the hull should be plenty strong. I know of several welded hulls that have thin marine aluminum of 1/8, and 3/16. I am fairly certain that even .125 thick 6061 is stronger than that.
 
Pat,

The short answer is: that's right. Twice the thickness would mean twice the strength and more than twice the stiffness. I checked 2024T3 but its resistance to corrosion is worse than 7075.

Jim
 
Cracker, when I talked to Sean I asked him about the single rudder. He said that is what they have always used. He also said he could be going down a trail and make a 180 without the boat hardly moving from side to side. I believe it was Sniper who posted that there is very little air flow at the center of the prop and two rudders have more surface area. But if you think about it, that single rudder, with all that surface area, being in the center and when you turn that rudder and all the air flow hitting all of that large rudder it's going to make it really turn. With double rudders, the rudder turned towards the center of the motor is not catching as much air. Anyway that's his theory. I prefer the double rudders. I'm used to them and my boat turns great. I also don't like a rudder that long for backing into a shed. Also, I don't like the side wind resistance encountered in the winter during the hunting season. A friend of mine was in a bad accident because of a strong gust hitting his rudders and slamming them hard over. He was going down a fairly narrow canal with willow trees hanging over and it was blowing steady at 25 to 35 mph with gusts up to around 50. When he came to an opening in the trees, that crosswind slammed him.
I'm sure cowboy can tell you more about that one rudder.
 
Marshmaster Pat, 6061 T6-45,000psi, 5086-42,000psi, 5052-33,000psi, 7075 T6-83,000psi, A7075 T6-76,000psi, 2024 T3-70,000psi, A2024 T3-65,000psi. Most of the work boats you ran probably were made with .190(3/16) 5086 bottoms with .125 (1/8) 5052 sides.
My boat is .080 7075 T-6. In order to get a 6061 T-6 boat with almost the same strength, I would have to use .125( 1/8) or .160 (5/32) aluminum. Your hull at .090, you would have to use .160 or .190 (3/16"). 6061 is still softer and prone to denting.
To build a new boat like mine a 12' A model I would go with .125 6061 T-6. The weight increase would only be 60#'s + transom sheet ( 7075 .080 @ 55#'s 4x12 sheet, 6061 .125 @ 85#'s 4x12 sheet). It will be nice to get away from the corrosion problems, whatever the downside might be.
I am also going to raise my engine stand 2" to 3" so I can run a 76"or 78" two blade Power Plus or a 78" three blade narrow Sensenich. With that extra thrust over a 72" Signature two blade, I probably will run the same or better.
On the 6061 boats you have seen, do they also have riser caps on them?
What process did you use to shear the rivets and remove them? Never done it, just learning. Thanks, RJ
 
RJ - Yes they all had riser caps, all stainless steel. That appears to the main place the bad stuff starts.

I know a few of the fellows working for LA Wildlife and Fisheries, and they have the same problems in SW LA with their riveted hulls. There is a fellow over there that is repairing them along the riser with wider caps and autobody repair cement. But if that hull ever needed repairs, all that would have to be cut from the hull because they say you cannot ever get it apart.

We used an air hammer, (Craftsman - have a cheapoo that wouldn't work) with a chisel bit with the notch in the middle. Sharpened it on a file real good. Needs just about 3 seconds on the trigger and the head shears off. It took some practice to get the angle down where you don't mark the metal, so start in a place where you will not see it. But alittle sandpaper and those disappear as well.
 
Pat,

I was reviewing the strength tables for the various alloys. It looks like the higher the aluminum content the more corrosion resistant it is and the lower the strength. The higher the alloy content the stronger but less corrosion resistant.

That's why I like the alclad. The outer 5% of the sheet is pure aluminum, so it would be very corrosion resistant. The alloy metal would be exposed when you drill it though. Sandblasting it could remove the alclad if you are not careful also.

It looks like to me that the whole boat should be made from aluminum to minimize electrolysis in salt water. Steel weighs 3 times what aluminum weighs per cubic inch. So, an Al piece substituted for an SS piece could be 3 times thicker and weigh the same.

Maybe a good question for one of the builders would be to ask if they use alclad.

Here is some good stuff on the comparison of SS and AL strength:

http://www.americanmachinetools.com/tensile_strength.htm

Jim
 
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