20 Aluminum Boat Build

Sorry got sidetracked forgot to answer this one...

It is up to the yard how they wish to weld. But each welder must pass a weld test to meet Class standards, beit, downhand or overhead etc. As part of the test, all parameters are set from previous testing, and is applicable only within a certain range of thicknesses. So, however the welder and/or QA system is set up for the bench test, if it passes (I stress if..), then the welder can weld as per his approved cert. So regardless whether the procedure is correct or not, if they pass they feel all is ok.

The downside to this is when performing welds in critical locations they will required to be NDT, usually x-rayed. Any poor procedures will be highlighted in the x-ray. usually LOP/LOF and/or porosity. Thus a poor procedure that passes a bench test, of UTS for Class, does not necessarily translate to a 'good weld', when fabricating structure. It often leads to failed welds.

Following correct procedures whether a home build or a high speed passenger ferry...correct QA wins the day hands down. Cutting corners...never does!

 

Hi Guys - thank you for all the support and advice. The boat I am building is the Glen-l Chinook 20 footer.

Here are a couple of some of the frames i had to modify.

I added curvature to the frames to allow the steep deadrise at the bow.

 

Guys I also want to mention, this is my first boat build. Prior to this I really have not had any experience welding. I learned everything as I went. The boat plans was purchased back in mid December and I would say I'm 40 percent done. It's only been 2 months.

I want to say this because anyone out there wanting to build a boat should not be afraid of not having enough skill ( I have zero experience) and second don't listen to haters that say it can't be done ect.... . I say this bc most people that judge and are critical of the build most likely never built anything.

Happy building everyone and thank you for the support.

 

Did you do this because the pattern would not fit or the aluminum sheet would not fit??

As you build in a curvature, there is a chance then that you will not be able to curve it around the bow keel area. If I were doing it, I would just leave this area as it was and see how the plate
forms to the chine at the bow and the keel at the bow. Trying to curve it around one axis and then bend it around another makes the sheet hard to bend.
Better to only worry about the edges and let whatever happens with the sheet. So if the sheet is away from your straight frames, you can then cut a curve, if there is one parallel to the frame and weld it to the frames for support.

The other problem with building this with frames is that I would be concerned how you are going to get the inside weld on the chine where the frames touch the side of the hull. (and your
spray rail as well) Continuity in the weld has to exist or you can run into problems. Normally, you can cut back the outside angle of the frame to allow the welding nozzle to get to the inside
corner of the chine, even from both sides. Most of the boat building with aluminum books show this void in the frame to allow this to take place.

You could when you are welding the outside of the chine relieve, ie cut out or make a chamfer in the joint where the frame contacts the inside and absolutely
ensure that the weld goes through the sheet, and captures the frame as well. Or at least ensure that this one sided weld has 100 percent mixing of the sheets at this point.
Not an easy process.

Re your pattern. It looks too flimsy and not fitting properly to the frame, chine, keel etc. You are trying to ALMOST get to light tight with joints between the sheets. Allowing for maybe a little bevel at the joint. Don't expect to fill in joints where the fit was wide with weld material. You can tack in some 1 inch by 1 inch with a 1/4 inch hole in it, to the frames and flush to the direction of the sheet and bolt the pattern down.

I think that you said that you purchased some 1/4 inch for the bottom. What thickness for the sides? Don't use 1/4. If you are new to the game, 3/16 will work just fine. We used 1/8 inch but then as described below, we did not weld transverse framing connected to the hull side.

We always (normally) ran any structural member that we would weld to the sheeting, longitudinal. This way we could produce a fair boat as all of our boats were painted with a gloss
poly paint. Gloss shows every weld imperfection or mistake. The bottom would get longitudinal stringers, then framing what would not touch the bottom unless we were isolating
the engine compartment from the living area. The sides would get say 4 or 5 inch with a 1 inch flange welded longitudinally, well stitched welded, one above and one below, then
any framing between the trays would not be welded to the sides.
The minute you run a vertical bead on 3/16 you run the risk of puckering the sheet due to localised shrinkage and giving the boat the look of a starved cow.

You are going to spend a lot of bucks to get this to a finished state
Rwatson I think mentioned Boat Building with aluminum by Pollard. Others Boat Building with Steel by Klingel with an aluminum addendum by Colvin, not really comprehensive but better than nothing, The Complete Guide to Metal Boats, Roberts-Goodson, and Aluminum Boatbuilding by Sims


The frames appear to be pretty loose at the gunwhale, ie not attached to each other, free to move.
I am not sure how you are going to deal with this

When we made sheet patterns for a male mold, both sides were the same. The male mold just held the angles etc. Because the sheets were symmetrical, when we aligned corresponding
but adjacent points, sometimes the sheet (different molds) would not be tight to the male mold in the bow. It did not matter, as a tight fit was most important. I am talking about maybe being 1/4 inch up of the mold
Then we would weld all the sheeting from the outside, flip the boat, weld all inside sheet, back cutting, then fit in stringers etc.


When it is secure, make your patterns. Do not assume that the right and the left are 100 percent symmetrical as you just have too many things that can shift here. Especially as
you load up your frame/jig.

Ensure that you get full penetration where say a chine meets the spray rail AND THE FRAME

 

I went back to pull some information out of an old thread about grinding and attached it for your information as you move forward.



Just a few things to look out for moving ahead and particularly if you are going to use 1/8 in the boat.

If you are going to weld any vertical frame or any other item to the side of the boat, chine to sheer, with 1/8, there will be distortion from the weld bead. If you make full length vertical welds on the side of the boat, your boat will look like a starved cow.

We always welded in a few side stringers, trays is what we called them, and they would be 1/8 by 5 inches (with a small flange on the keel side of the tray for stiffness) . We would turn down the heat, to where we would get some penetration but not the same as say the weld settings for a fillet structural weld, make a 3 inch pass then skip 6- 8 inches and then another 3 inch pass. There will be an imprint on the outside, a raised area where the weld bead is. And of course after this had cooled we would do another 3 inch pass on top of the tray at exactly the same bead location as on the first pass, etc

You can sand out the bump of the imprint, if you don't, you will see these bumps when you paint the boat.

Because you might be using 1/8th, you have to be careful that you do not terminate a stiff structural member in the middle of a 1/8 panel as this termination point will be stiff and can cause cracking as the too thin 1/8th will be flexing around this stiff point We have seen this many times in home builts boats that we have repaired.

Re grinding,

One of the biggest first time builders mistakes occurs is when they have done all the welding and want to take a grinder to smooth welds or take hard corners and soften them before painting.

There are three types of discs in play here
The hard grinding disc, the flap disc which is ridged but the sand paper inserts have some flexibility, and the sanding disc.
Each has a specific function

You need a depressed wheel grinding and flap disc (Normally they have the nut already in the plastic disc) so the nut that holds the disc on is below the face of the disc.

Assume the plate that you are welding is horizontal in all directions and you are working on a butt weld

Very carefully you grind the weld to within a 1/16 of the plate face without the disc touching anything but the weld bead. Then you have to ensure that the flapper disc is perfectly parallel to the plate, continue to take the bead down ensuring the disc is flat to the plate
and when the weld bead is almost gone the entire disc face has to be engaged to the face of the material
If you try to grind by using only say the front of the disc by raising the back of the grinder you will most certainly undercut the weld and it is almost impossible to fair (certainly with epoxy but this expensive and time consuming)
I used the butt weld first to make the point of full disc engagement to the plate.

The flap disc is a little more forgiving but still can undercut easy. It normally takes material off slower so you have time to gauge the progress. If you use the flap disc after the grinding disc, the material should be good enough to paint without further sanding but as it does not take a lot of time to sand, it never hurts to take a sanding disc to the surface. Finer grit of course

The sanding disc is used to give a slight round edge to a sharp edge. Norton and others I expect, have a 7 inch rubber disc that has say 6 - one inch holes in the disc. The sand paper has the same holes and when the paper is attached to the disc and the disc is turning you can actually see the spot that you are sanding.

So the a butt weld grind procedure would be to lay the 7 inch grinding disc with full contact on the plate to grind the weld area, follow with the flap disc held flat and then if you want, give it a final sand with the sanding disc

Now for a 90 degree joint. (or 45 or)
The trick here is not to use just say the top of the disc to grind off the weld as it is almost impossible to keep the disc parallel to the plate. So say you are at a desk and the bead is on the corner closest to you. You use the bottom of the disc to cut the weld bead material off so that the disc is parallel to the plate. The entire diameter of the disc is over the material, which ensures flatness of the grind.
( I used the example of the desk to make the point to keep the entire disc over the material, normally you can work keeping the grinder at 45 degrees to the work and use the 4 oclock position as the grinding spot assuming that you are grinding to the right side of your body)

Then follow with the soft sanding disc to smooth the sharp edge.

As an experiment, when you get some plate in, take a 12 inch by 12 piece of 1/4 inch plate, oops, you might not have any 1/4 inch, weld a 12 inch cold weld across the plate,( by cold I mean that you will have a 1/4 inch bead width and maybe 3/16 inch tall) .

Follow the above method, the most important point is to keep the first two discs flat so you can feel ALL the disc engaging the plate, (after you have remove most of the 3/16th inch height) for this test, do not touch it with the sanding disc.
Then take a can of black gloss spray paint and spray the plate. If you have done a perfect job, you will not be able to see where the weld bead was.

 

Are you sure that the plans did not call for any longitudinal stringers - i.e. flatbar or angle running perpendicular to the frames (small pieces welded in between frames to make a long line, or long pieces slotted into the frames?
It seems that the frames are quite far apart with no stringers... compared to my Glen -L plans, which had several stringers on each side, albeit for a bit larger boat.

 

Great advice everyone, this is so helpful.

Cost wise - I purchased all aluminum for the build already. Cost me 4.5k, would have been cheaper but our president decided to tack on tariffs on aluminum imports.

A notch will be cut out of the frames where inside welds will be made.

1/8 inch will he used for sides

Once hull is welded on and flipped longintunual stringers will be attached and welded. Doing so will avoid the staved cow/horse look.

I have a total of 7 frames each frame is 30 inches apart. I think it will hold up fine, any closer will be a bit excessive.

Additional cross frames will be attached to frame at gunwale after the boat is rightside up.

I will take pictures as I go, to show you the progress.

 

My concern is that the hull sheet may lay more "flat" across the large spaces ( i think 30" is a fairly large space to be plates while unsupported by stringers at first), than it would if the stringers are in there ahead of time.
re: starved cow - i certainly experienced this somewhat,. but i think if you use too much heat, it will do it regardless of whether you weld the stringers to the hull sheet before or after it is held to the frames.
On my boat, the hull sheet is not really welded at all to the frames for the most part. the sheet is welded to the stringers and the stringers are welded to the frames. The sheet doesn't touch the frames. I am NOT saying this is the correct way at all, but it is the way i did it.
I did deviate from my plans in that I felt they were somewhat "older" style plans, calling for the short stringer sections to be welded intercostally between frames - i chose to cut slots in the frames and use long stringers instead.
I defer to the experts as to the proper way... just letting you know your above plan may not totally avoid issues like starved cow..

 

Correct sequencing will minimise any starved cow effect significantly...

 

Hey guys a small update, I drilled out 1 inch holes on the frames to allow the water to drain towards transom. Wanted to make sure this was done before the hull was tacked in place.

Also picture of how I welded the keel together. The total length of the keel is 20.5 feet long. It was made from a 3/8 plate 4 by 8. Where to keel joined together I sandwiched with additional plates to ensure structural integerity.

 

Anyone in the NJ area that would like to come by and take a look ?

 

Are you saying in this 3rd image, you have sandwiched 2 plates together, welded them, to be one?

 

This is the keel, it was two separate plates and I sandwiched them between two other plates to make on continuous section.

 

Sorry, that's terrible. You should never do that.

But,.. it is a home build thus I understand your position, albeit misguided.

 

Goal today was to figure out how far off the keel the floor was going to be. I used some orange string to outline where the crossmember of the floor should be. I basically ran the floor subframes parallel to the keel.

by adding the structure now, it will support the frames.