Carl,
First, the tunnel weld sequence; the 'bottom extension' over the vent through hull opening won't hurt hull integrity and since it facilitates welding sequence and getting a full inside outside weld done... its really the only way given the shapes' intersections and the vent. Waiting to weld the vent will allow you to minimize tunnel top distortion and still seal the hull well.
Next, the longs should be tacked into the top of their slots in each x-verse frame with a hot single tack (or if not hot; double dime) to make sure the lower edge can be bent/pushed/fitted to the inside of the hull seam as back-up. The points along these seams that are more critical are farthest from the x-verse frames & the first of the two hull plates will need to be tacked to the longs' edge in order to make sure they hold as fair lines along each seam.
I'd bevel the under sides (OUTER EDGES of the seam as the hull sits now) of each of the three seams that are backed by longs at least 30 degrees but 45 is fine as well
if you can bevel with good control. The issue is the type of weld and that weld's native characteristics regarding a U or V grooved seam type. MIG will arc to the nearest 'shoulder' of parent metal. SO, beveling wider is better there... however, with that said; it will be imperative to have a full seam back up- even if only 1/8" wide- otherwise a hot single pass 'drag type' weld as shown in your previous examples may burn through and leave a hole to patch- or not fuse the back/lower/bottom of the longs and therefore compromise the weld seams' integrity?
SO: while beveling the sheet edges that will adjoin the long seams bottom edges- it is critical NOT to have the bevel create a cut long the inside (bilge side) of each sheet which is your tack up and build reference. IF the inside edges are cut while beveling the outside edges: the seam will not be fair when tacked to the backing longitudinals OR will leave a natural gap and burn-through spot!!
The keys to the weld are prep, tack up and bead/power supply settings.
The sheet edge needs to be fair and your mtl is NC cut so we can assume fair edges. May need to drag a Vixen file or hand sand the edges depending on 'dross' from the machine cutting process?? The longs need to be tacked to the keel first one side then the opposite- if the tacks are done while the hull is inverted then each tack will need to be
meticulously dressed. (
https://www.glenlforum.com/phpBB2/viewt ... 7&start=30) That will allow the second/matching/opposite hull panel to be installed and tacked w/o bulge/interference/distortion from the original tack set AND lay fair to the future weld joint.
These two middle bottom panels will not need 1/2 as much bevel
in the forefoot curve forward. There, the two panels' angle of incidence/joining/meeting is much steeper (by hull shape) so as the sheet's edges' are at greater angle outward; the bevel there can be 1/3 the sheet thickness @ say 30 deg. All that is needed there, to get fully fused root on the longitudinal and to take up both inside edges of the interior bottom panels, is to 'knock off' the edge of the sheets as they adjoin the keel joint.
However, further aft, the joint will from a pretty square U shape- and the arc will run to the top two edges and not fuse down inside to the back of the long. Therefore the bevel will need to be more of a 45 so the MIG arc will be able to fuse the long into the joint.
The longs' tack up should be done to each frame at the top (upper when hull is keel down or upright) to allow a firm point of contact with the x-verse frame but not to weld the long to the x-verse- yet.
Each of the inner panels' sheet edge would be clamped to the long at the keel first one side, then tacked along that long. As mentioned those tacks need to be small hot and dressed before adding the opposite panel. Since you're not able to weld inside the bilge yet the tacks will be outside/underside/bottom of the hull which is upright. I make tacking and arc cone remarks in this post linked... might not be the correct page but will lead to the description of the weld prep I'm inferring. I think the sketches will help make a better explanation that writing? For your use of these images the vertical green bars shown would be equivalent to your longitudinals and the horizontal mtl your bottom plate/panels/sheets.
Don't tack or weld to the x-verse frames until the entire long keel seam is tacked... I'd suggest tacks at the forefoot @ 2-3" OC and 4-6" OC aft in the straighter run of the keel. Same would be true of the outer hull panel when you move out to that seam. There if more sheet stress forward where the 'orange peel' trimmed panels are pulled inward to the bow shape- so more tacks hold the mtl. more firmly without and kinks/hogs/angle points.
For the tack welds, unless your PS provides tack weld timing/programming? I'd suggest hotter than a weld setting and higher wire feed speed in order to get a good fusion from a tack weld that can remain when that tack is dressed off in prep for further tacking or final welding.
Welding this type of backed up, beveled open seam is not really widely practiced so testing/mocking up/simulation coupon welds are very important.
Hope this helps with the methods that will work to bring your hull's panels together successfully and in sequence? If not? Pls post your questions so I can clarify my writing.
Cheers,
Kevin Morin
Kenai, AK
