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I was wanting to build the hull out of full length pieces of aluminum and can get 5052-H32 aluminum in 1/8” coil cut to length, but not in 3/16. Has anyone built the Scrambler in aluminum already and what was your bottom thickness and how did it handle (what HP did you rig it with)? What issues will I run into if I change to 1/8" bottom?

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Charles Brammer

Charles

I can answer the question from experience. But, I'm a structural engingeer. But, 3/16 will be 3.4 times as stiff as 1/8. In tension it will be 50% stronger. Your call.

Bill

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Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

You make a compelling argument

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Charles Brammer

And also 100% easier to weld

Doug

Charles; Suggest you go back into this metal forum and look for any postings by mcmbuilder or kevin morin. They are very experienced and knowledgeable welders, especially in aluminum. A little reading now will save you some grief later.

Doug

Thanks for the advice. I will review their posts as you suggest. I’m by no means professional welder and welcome all advise on the subject. I’ve have been practicing on 1/8” aluminum for several months and I’m very comfortable working with that gage material with a spool gun. My ace in the hole is I also have two skilled aluminum Tig welders on staff at work to help work out issues that may arise. In fact, I’m actually building my scrambler at work in the mornings, at lunch and after work when the wife allows me the time away from the family. All the equipment is already there. I just need to have my project wrapped up by mid to late March (shop floor gets busy by April 1st).

As for the material thickness, I had talked to three different custom boat builders in my area about the 3/16 plate for the bottom. No one in Michigan uses that thick of stock to make jet sleds. They all use 1/8”. I think mostly because Alro Steel sells 1/8” aluminum off of coil stock so they can order it cut to length and eliminate any but welds. Personally, I’ve been uncomfortable with the idea of dropping down to such a thin gage. I compromised and Ordered .160 sheet stock today for my Scrambler bottom and 1/8” for the free board, flooring. I should have enough .160 left over to make two casting platforms.

The other issues I’m trying to think out are tricks in measuring out the longitudinal so they fit tight to the bow and transom. All I can think is to leave the bow loose on the forms and trim each one until it’s just touching. Then when they are all done tack weld the bow plate in place. Any thoughts?

I

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Charles Brammer

Hello.
Wish I had check the board more recently. Hasn't been a lot of topic talke lately so I have not been on here.
I know you have already purchased the thicker material, and nothing wrong with that. However the .125 for the bottom would have been very suitable. I really think the designers call for the thicker members to help with welding concerns. From reading the forum it seems most novice welders seem to opt for MIG welding the plates. Welding the outside corner joints are a lot easier to manage with the thicker plates. Another good advantage with the thicker plating would be better protection if you are using the boat in rocky areas. I have built about 60 boats in the 14'-19' range and used .125 plate for all the bottoms. Even used some .090 on the sides for some of the 14' models. The only repair I ever performed to any of the boats was one where the operator hit a rock in the river running about 30mph and ripped about a 16" gash in the bottom. Would not have happened with the .190.

Good luck with your build!!

Thanks for your feedback. I am one of those novice aluminum mig welder wannabes so I should be greatful I did go with .160 for my bottom. I spent a lot of time practicing on my welding so they would look nice…the entire time practicing on flat tables with over lapping parts. I haven’t had one horizontal weld yet! My vertical weld that join the frames and longitudinal look awful (but they won’t break). I’m looking forward to next week when I get to weld on my back looking up at the inside of the hull plating while reaching up over my head (oh goody).

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Charles Brammer

A weld that looks awful will generally not be a good weld and will break. On your vertical welds practice running the beads downhill with the MIG process. Angle your gun slightly up and don't let the deposited weld metal run below your wire tip. A slight weave back and forth will be helpful in doing this. Keep playing with the settings until you get a bead that does not have "V" groove running down the middle of the bead,,, this will be too hot. You want the bead to be flat or have a slight crown on the face. Look at the weld edges and make sure you see good fusion into your base metals. THen you will have the settings well adjusted. The vertical down is a lot easier weld to make, will hold just as well and look a lot better too. This may sound complicated but believe me it is not.

Thanks for the advise. I could use some pointers on overhead welding to if you dont mind.

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Charles Brammer

I had a friend that once told me he was excellent at overhead welding....as long as he could turn in "over"
Doug

It takes a while for me to convince my students that over head is actually the easiest position weld in, but once they get it going good they realize it really is an easy weld to make.

First resist the temptation to turn your machine down, if anything a little hotter than in the horizonital position. Like all welding it comes down to watching your bead tie in to the base metal, controlling your arc, or in the case of MIG, controlling your stickout, then controlling your angles. Keep a close stickout, keep your angle more to the top plate in your weldement, if it is a typical 90 degree fillet weld then use about a 60/30 angle with more emphasis towards the top but keeping your bead equal on both plates. In other words keep the center of the bead in the center of the joint. With the angle more to the top plate gravity will help the legs of the weld equal out. Then you need to use a slight push angle. Keep the wire in the leading edge of puddle and watch the toes of the weld bead tie into both plates.

Honestly overhead is not a difficult weld,,,,,,, the hardest thing is getting in a comfortable position. Learn to relax your arms and don't try to "manhandle" the process. If you do you will get very shaky and unable to control your stickout or angles. Also really concentrate on watching the puddle tie in. In doing so you will quickly learn what you need to adjust as far as your technique.

Thank you for your advise. You communicate very well and have given me the information I was looking for.

The aluminum boat builders book says to allow for 1/32 shrink on the plating for each longitudinal I'm welding to. I'm guessing I will have to do some additional trimming once I get the bottom plat welded into place.

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Charles Brammer

The shrinkage is all kinda relative. I will be surprised if you have to any trimming. I have never encountered a skrinkage problem to that extent. Another note on the welding. You will get a black smutty appearance on the weld(MIG only). Don't let anyone tell you the weld is too hot. That is a common misconception many people have. The way to tell if you are welding too hot is to look at the backside of the welding joint, if it is "sucked in" then you are too hot. More people make the mistake of welding too cold than too hot.