Conchfish AL 17.6T build

[m32825]

Kevin,

As you mentioned in a previous post, it all becomes clearer once you're on the hull. I understand most of what you're talking about, but the paragraph with "cross pc that is 5-8" above the keel bar's surface" has me scratching my head?

I tried a strap and that works great even without a piece of angle. I had gone just about as far as I could with clamps, it also occurred to me that I won't be able to use that approach at all with the remaining pair of panels. A new method was necessary.

This is like a video game. The back part that's almost flat is the easy level. Just when you get comfortable with that the angle starts to matter, and you have to adjust, but the adjustment is different each time. Then the outside longitudinals start twisting followed closely by the keel curving. Then you're close to the bow where everything is changing at the same time!

Approaching the bow I've got a little shy of 1/8" of VKB exposed in the center, with the edges angled back.
​​​
    -- Carl

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[kmorin]

Carl,
my remarks about adding flat bars to the VKB were intended to explain that a couple of vertical (radial) flat bars could added to the keel w tacks fore and aft, where the flat bar touched the keel bar's edge.  A set of  1/4" x 1-1/2" (section) by 8" long, pc of metal 1-3 times along the curve of the forefoot. This would result in one, two, or three flat bars that could be used to tack a 'cross bar' too. The cross bar would end up attached to the vertical/curve radial flat bars' edges at various distances from the outer/now upper edge of the VKB. 

These flat bars would the keel thickness and hold the inner sheet edges from sliding over the VKB, and also provide places to put different cross bars that can be used to help make the fit of inner edge sheet bottom panel to the VKB's outer edges.  The cross bar's could be used to 'hold downward' (in present orientation) the inner edges of the bottom panels so they could be cold aligned, with good control, to the VKB edge using wedges fit under the cross bar tacked to the FB's tacked to the VKB.  Once the bottom seam is tacked in place, these would be removed and the tacks gouged in prep for the final seam weld.

These cross bars, notched angle or more flat bar, would provide various leverage points at adjustable distances away for the eventual weld seam.... by tacking a cross bar (transverse to the keel) @ 90 to the bars' orientation parallel to the keel plane- you'd establish a series of points that would allow you to put wedges (wood or metal) to pull each inner edge of the bottom panels down to the VKB edge for tacking - W/Out having to clamp at the outer edge which appear to me  to  be  in  conflict  with  the inner  edge  fit? showing that fit to be closing up- not aligning to the edges of the VKB.

Once a set of wedges was forced under the cross bars, pushing down on the inner bottom panels' edges, the vertical bars' thickness would help guide those edges to the edges of the VKB... and .... the wedges would push those edges down in good control w/o adding stress to the whole frame- just locally to that set of tacks.  IF you have more than one set of FB's then the wedges/levers could be added in increments- spreading the loads to all the FB's and gradually pulling the curved fit into place.

Reacting to current images;
I'd release the outer clamps (shown), and let the center seam lead the outer long seam tacks by more distance: the reason to do this is to allow you to keep the inner edges of the bottom panels farther outward even with the edges of the VKB.  This is for better fit which will slightly deform the bow panels' shape if allowed to slide inward toward one another.  Keeping the bow panels' inner edges on the VKB's outer edges will create a slightly more 'spooned' bow shape and the outer edges will not be as far inside the long's inner edges.

In my view of the shape - by allowing the inner edges to slide inboard; the bottom forward shape will subtly change and become a slightly sharper V, with less 'spoon' or fullness to the forefoot, and that will likely allow the outer seams to falls short (be inside) of their intended intersection with the longitudinal that is supposed to support their weld seam on the longs' inner edges.

My advice at this (pictorial) junction is to concentrate all effort on the inner seam fit and tack-up; let the outer seam follow and not be clamped/trapped/tacked anywhere nearly as close to the keel seam tacks as shown.  I'd leave the chine seam to follow a longer distance than what I think is shown.

Hope this helps make my remarks more useful, or at least clarify what I was discussing?

Cheers,
Kevin Morin
Kenai, AK

 
 

[m32825]

Kevin,

I appreciate the additional detail on the tee bar and cross bar. That gives me another tool to deploy if I get stuck. I remember reading about dogs and wedges in Pollard's book, but hadn't made the mental leap to actually using the concept.

In my previous post, I had the outboard clamps in place temporarily to get a preview of coming attractions. I took them back off before advancing the keel seam. The keel has been leading by a few inches the whole way. I've been using 1.5" spacing between tacks recently and plan to use that the rest of the way to the bow.

You were not kidding about things slowing down near the bow! I'm within 18" of it now. Time to deal with the floating longs before moving ahead. I've been studying the geometry and think I understand the degrees of freedom. 

    -- Carl

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[kmorin]

Carl,
Glad you'd already seen the concept of a wedge-n-dog system for locally adjusting sheets/plates' edges to one another.  I was mentioning it in detail to show how you might use them to aid the keel bar to bottom plate edge fit up.  I think S. Pollard's book is a great overall summary of the topic of welded aluminum but as you've seen in your build; there's a bit left unsaid that could be added if you actually get into the details of a build.  We've had a more than a few discussions where we needed to get into the more minute details that would make Mr. Pollard's work a veritable tome!

One thing I didn't mention but is very useful in the fit at the keel is small floating pc of keel bar thick mtl.  BY putting small 1"x1" x 1/4" pc of bar or cut plate between the inner edges of the bottom panels - as the come to the keel -you'd keep the spacing needed and can tack fore and aft those pc to keep your tack pattern uniform but still have a spacer to keep the edges uniform along the outer edge of the VKB.  No need to tack them to keel, sometimes you might tack one to one side or the other of the bottom plates so you don't have to hold it while clamping tighter.

On the other hand, if you keep a 12"-20" 'nail bar' with a wide flat end handy; you can pry the plates apart as you get closer to the keel. (then) By inserting the spacer blocks, when closer to the keel bar's edge, you'd avoid extra tacks but still keep the two inner edges the correct seam gap from one another prior to a tight fit up with the VKB.  Difficulty is when one side is not evenly above the VKB's edge. Then the sheets will try to 'flip' or twist the spacer bar- making it difficult to hold the edges' correct gap before tacking.

Quick note about something I noticed in photo #'s 9613 & 1313;  The keel bar is not exposed as the two sheets touch edge to edge (great joint design for chines but not as weld-friendly for the VKB to hull plates at the bow stem) so the weld would simply be incorporating the VKB as a back-up w/o any weld fusion.  It would be good practice to cut this open, once the hull is fully tacked up- prior to the full weld-out.  Getting full VKB seam fusion, as you're showing in the rest of the VKB seam, is much preferred to leaving this seam with a cold back up bar as it is now. ( I know you know that but I noticed that short seam & thought I'd remark about it.)

Have we discussed the 'meat axe' or 'Widow Maker' cutting tool for back gouging or trimming weld penetration? Don't recall?  Anyway a little more controllable method of cutting this particular seam type than most other tooling configurations and worth exploring.

Looking good to me, the bottom panels may have some shaping to be done once tacked up- I can't tell from the photos posted but will keep an eye as you move to the bow stem with the first VKB at the forefoot.

Cheers,
Kevin Morin
Kenai, AK
 
 
 

[m32825]

Finally made it to the bow, whew! 

As you noticed, my hull plates were overlapping the VKB a bit near the bow. I think the VKB ended up 1/8 to 3/16 inside the ideal path for a portion of its curve. I trimmed the plate edges back for a consistent joint setup. 

The floating longitudinals needed to be pulled inwards at their ends. I used a fixture with turnbuckles to pull them down and still be able to position them along the edge of the plate. I kept an eye on their in-out position all the way to the bow. Once everything was completely tacked I added a piece of flat bar and removed the fixture. The curve into the bow came out nice and consistent.

I think I want to work on tacking up the tunnel next, while I can access it from all sides.

-- Carl

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[kmorin]

Carl, nicely done.

Great job getting the fit to the frame and the turnbuckles worked to make the 'hard spot' or 'hogg' that could have formed at the ends of the FB longs into a fully controlled point along a fair curve.  

The tacks on the VKB seam/keel seam can be left intact until you weld out.  By dressing the weld seam's groove formed by the sheet edges and the VKB in between the existing tacks you will be able to prep the seam for full VKB fusion welding regardless if the bottom's edges now overhang the edges of the VKB. 

The welds would only be as long from one tack to another but that's no problem. You'd start the weld on one tack, weld to the next and when finally welded out- go back and gouge out each tack for a 'puddle or two' length on either side, fore and aft.  Then you can fill these small short remaining weld grooves with either TIG or MIG.  

I tend to weld this entire area with TIG and carry a 'double keyhole' at the sides of the VKB and the inner edge of the bottom panel however, I'm using a cold wire feed TIG-gun and can 'pour' the filler into a weld that is keyholing on both sides.  Not quite as easy to do with two hand dip.

 

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Here, I've stopped the weld by 'piling up' the end to make sure there's no crater crack in the weld end puddle. This was a 1/4" VKB but the bottom plates are 1/4" as well. In the image you can see the sheet edge (bottom panel inner edge) has a 1/8" vertical edge and a 1/8" bevel to allow the weld arc to 'focus' on the VKB, and not be 'pulled away' by the outer shoulders of the 1/4" bottom plate.

If I recall (?) this was done at 300A, 5/32" pure tungsten, domed not spherically balled, 0.035", 5356 filler wire, 80Hz Freq. and little to no step movement between puddling the keel to bottom in order to keep the keyholes active while moving. Probably about 30 Ft^3/hr pure Argon.

If you use MIG then it's a great place to consider 'run-on & run-off' blocks.  Where a small plate, or sort length of inverted angle, is used at the leading edge of the weld and one at the trailing edge.  This gives a place to light up the arc- not on the hull; & to end the weld- not on the hull.  Once the weld is done just lift the run-on/run-off pc and the short section of weld attaching them to the keel seam will back break fairly cleanly offering a small spot to TIG float or to sand to a finish. 

In regards putting the next bottom panel on, not the tunnel lining plate; I'd consider a wooden 'gantry frame' attached to the table and spanning over the hull to the other side of the table. This could be a simple three pc. inverted U or something more closely approximating the hull's section - especially near the bow. 

The purpose is to form a clamping frame around the entire hull where you can use levers, screw clamps or dog-n-wedge rigging to push the outer bottom panel to the frame/edges of the fit. If you're familiar with a logging tool called a 'peavey' or 'can't hook (?) that class of lever will work to help push the remaining bottom panel onto the frame very easily and with good control. 

By drilling the gantry frame (2x6"??) for a 3/4" pipe (1" dia. hole) and welding short section of 1" pipe to the end of a 1-1/2" pipe you'd be able to easy make a tool (4' long) that will fix to the gantry and push down outboard with a leg pivoting 8-14" from the pipe cross pc end that will push down on the bottom panel. Could do this upper pivot with a bolt through the wooden U frame as well as a pipe stub for the hinge pin. (shown below)

Here's an old pic (below) using this basic method to add the spray rail to outside of a skiff. This material is 4"x3"x/14" angle with the short leg cut down to 2" so the long leg will be more vertical. The outside of the angle has been routed to a bull nose of 1/2" radius so the skiff won't 'chafe' other boats if they're rafted up and there's no real reason to have a sharp edge on this rail.

The 'tool' is a 'peavey' or "can't hook" depending on your area of the country where the far end is fixed to something and the near end is your lever handle.  In between is a pivot with a short leg, and in this case, another pivot ending in a short pc of angle to hold the spray rail. In your application you'd only need a flat there to push the edges of the outer bottom sheet to the frame/seam edges.

This tool hooks over the gunwale/sheer plate/guard deck flat and holds to the inside FB liner. Then the bottom is pulled toward the keel by the nylon truck strap and the middle leg pushes on the angle to hold it tight to the topsides. Tacks are located at the fore and after ends of bevels cut in the angle leg ends before the pc was hung to clamp and tack.

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What I'm suggesting is that instead of grabbing the sheer clamp/gunwale of your skiff you make a frame of wood shaped inverted as a U over the transverse section of your hull while it lays on the build fixture. Then using that frame as your upper pivot point- still fixed to the table- you could pull the lever arm down toward your floor and the middle 'leg' with pivots could be used to push the next hull panel to the frames for tacking at the seams.

The main difference in a peavey or can't-hook and what I'm suggesting is; to use the tool's leverage backwards. INstead of pulling on the long end expressed onto the middle hook- you'd push the middle leg/or foot in this case by forcing the long end/handle toward the frame of the hull.   Hope that I'm not making this text too confusing?

Hope this make sense as a suggestion? I'm pretty confident from your past fixture and jig solutions you'll see a clean solution to the next hull panels' tack up to your hull.  If not, I'll try to post a sketch that may help clarify my suggested tool use.

Cheers,
Kevin Morin
Kenai, AK
 

[m32825]

Kevin,

Nice keel weld picture! I like your angle idea for run on/off. Would I use that where I have tacks to start/stop or only when there are no tacks?

I got the tunnel tacked up today. It was a nice change of pace to work with flat panels and straight lines. Trivial really, compared with the bow.

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You asked about tools for cutting. I have a nice carbide cutter that I use on the low speed setting of my angle grinder. It's good for tasks that are out in the open.

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I haven't used it yet, but I've also got an Arbortech tool that I learned about from older forum posts. When I realized how many linear feet of seams I had it seemed like a good addition to the glitter making arsenal.

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I think I understand the gantry concept. Seems like I would want to be able to move it along incrementally. I'm picturing a rectangular frame with a member that runs underneath the table to connect the uprights.

I'm assuming the remaining two hull panels are worked back to front in parallel? Are the bending forces needed similar to the other pair, looks like they might be less?

My boat is clamped to the table. I notice that the front legs of the table have just started to clear the floor. It seems the boat is trying to lift the front of the table. How much should I try to fight this?

    -- Carl

 P.S. I understand the cant hook idea, great picture to help get that concept across!
 
 
 
 
 

[kmorin]

Carl,
RE run-on blocks;
Usually they're a way to avoid having to heat up the tie-in weld start with using only the arc start level of amperage. So, if you have tacks, and will be cutting those out after the weld to facilitate tie-in on both ends of a set of seam welds; you'd skip the run-in block as you'll be gouging anyway. On the other hand, if you've welded between the existing tacks, or over them, and will be gouging in prep for a final pass- that is when run-in blocks are more an aide to a quality weld.

First the weld start, cold-lap potential is on the removable block- second, the arc is going at full weld amperage and balanced wire feed speed by the time you leave the block. (one or two puddles width or three times weld width in length) Therefore your weld down the face of the gouged area is at fully balanced weld heat/wattage and fully filling deposition. That is why they're more often used when you tie-in a finished or last pass of welds in a seam.

I have seen them used for every series/pass of weld sequence in hulls before as they reduce the work to gouge out starts and unless you use the 'whip-out' technique- they help avoid crater cracks at the ends of welds too. They take extra time that some builders consider complete waste of time... personal choice.

Re Tunnel
I think everyone who's worked on a welded boat will agree that working in straight line edges of any shape is somewhat easier than working in curves and keeping the later clean, sweet and w/o "hogg"s? (your) Tunnel looks nice, I'll assume the designer has experience and knows these dimensions are functional? Seems like a lot of planing area given up to that feature- what size wheel will this skiff have? (dia.)

It would be fun to rig a 3-4" fore and aft plate that pivoted at the top after edge of the tunnel to see if this 'vector plate' could adjust the wake's flow out of the tunnel to benefit the prop's engagement of water?

Re carbide cutters.
I think the reason the carbide burrs on your die grinder work so well, as is true of the router, is the speed/RPM/rotational velocity of the cutter; for several reasons. IF any carbide cutter is moved through the metal slowly- then it will be more difficult to take a wedge or chuck of metal out. If the cutter moves quicker- it has more momentum and also (key point) LESS TIME during impact/cutting of the metal.

Try running a cone burr on a drill- well don't try it for long as the slow RPM means low velocity impact to metal and that translates to both more time in contact- or deeper gouge- and less blade momentum to 'carry through' the cut- removing the chip. Slow speed with big, deep teeth means the cutter will load and stop the tool.

IMExp, high speed and low depth-of-cut is why a 15-20K RPM die grinder can use a burr with very deep cutting edges and the same seems true of a rotary blade. I'd want the grinder at the highest speed it can turn out- when the cutter engages it will slow enough!

I'd suggest you consider adding a 2nd blade (stagger the teeth) to your grinder with the carbide saw blade. The increased cutting area will A) 'float' the flat of the teeth on the area being cut; B) will shorten the time between carbide inserts being engaged into the metal to gouged/dressed/removed and finally, C) since the grinder's speed is a little low to begin with for cutting aluminum, spreading the cutting load to another set of teeth reduces the chances of 'hanging up' or jamming any given tooth into the metal or weld you're dressing.

Also if you draw a line from one side of the guard to another, the left side teeth are able to impact the metal being cut at nearly 90 deg. If you TIGged on a little extension to the steel blade guard the angle of incidence gets reduced very substantially, thereby, increasing the safety of the tool. At lower angle of incidence/impact/cutting the blade's teeth will engage a 'shallower' chip depth.

Re Mini-Arbortech cutter.
Since there's only a pair of carbide teeth this cutter has to be held more carefully - introduced into a cut more slowly or they will load up and clog then stop the grinder motor- or more likely spin the drive belt. I've had to reserve use to narrow areas where the tool's size make it the only real solution. 

I also purchased a set of flat plastic diamond hones, like short files, that I regularly use on that Arbortech cutter to keep the edges nice and sharp. In general use, these dull too quickly, the belt can get 'glazed' if you use the tool too hard by entering a cut too fast too go too deep, too soon. I spray all these cutting tools with Pam frying pan spray to keep them from loading as quickly and reduce the heat at the cutting edge so the metal doesn't melt onto the blade's inserts and load the cutter.

Pam (tm?) is spray dispensed, cheap if you buy it as discounted in the bargain bin, cleans up with acetone, sticks pretty well to the tool but still provides a 'parting agent' and vaporizes faster@lower temp.s than other lubes which have higher % petroleum components, so if you don't get wiped up as well as you should it will make less of a mess in your welds.

Re; clamp frame.
I'm not sure how much force is going to be needed ? but I'll estimate a fraction of the inner bottom panels' fitting force. Yes, something that wraps the entire table would work but seems like its a bit more than needed- what about making a longer 'clamp lever' as I show and run it from the far side of the table top over to the 'working side' then standing on the opposite side you'd pull down as the pivot leg pushed downward- rotate my posted pic of the tool side ways to the left? (my) Gunwale is far side of your table/fixture, (my) spray rail is your bottom plank- you're standing up and the handle is pulled downward where I shown inward?

Re final bottom planks.
Yes, outer bottom panels would fit aft with their long straight lines then wrap the bow. I'm not sure you'll need much of any force to hold them down to their edges. May get by with one single lever from one side of the table to the other with the wt. of the lever adding some down force onto the opposite side?

I expect the narrow sliver of the orange peel shape combined with the much wider conic surface being wrapped will make these next planks go on w/ very little down force. This time I'd tack the outer most chine as the control edge and let the inner edge- toward the keel take up and changes in shape- then, if trimming is required, you'd have much better tool access to a seam you know will be backed-up vertically with the 2" long.

RE build fixture flat
I'd say it was very important to have the table flat and the 'front' legs firmly on the slab. I'd go so far as to say that was kind of critical due to the plans to build here inverted on this flat table? IF the keel is hogged downward (meaning its curling up now) then getting that out will likely require welding inside the hull first? 

On the other hand if you can get her tacked-up cleanly and transferred to a rotisserie then you'd have the ability to weld inside and outside as a balanced set of contractions. Also side-to-side balanced and fore-n-aft. A wire down her center line, once on the skiff is on the rotisserie, will allow you make sure you're not 'over welding' one side, or another. Instead of a wire- I guess it would be customary today to use a laser level as reference to a straight, level line in a plane.

Cheers,
Kevin Morin
Kenai, AK 
 

[m32825]

Kevin,

Re tunnel

The tunnel reduces planing area and impacts buoyancy. The trade is shallower running at the expense of static draft. Total volume is a little over half a cubic foot and these dimensions have been used in many boats.

The tunnel is five inches tall at the transom. I plan on a 30hp outboard with a ten inch prop. When everything is rigged right the bottom of the skeg will be even with the bottom of the boat, with the lower half of the prop running in the "hump" of water coming out of the tunnel.

I have seen tunnel extensions that claim to improve performance, they typically extend back horizontally but I've not seen anyone experiment with the angle.

Re carbide cutter

I doubled up my angle grinder blades and tried more rpms. That works well, good suggestions! I'll try a guard extension when I break out the TIG welder again.

Re clamp frame

Took a swing at it. I'm clamping to the deck because it's easy to access. I'll need to give it a try and see how it works. Do the pictures below resemble what you had in mind?

Re next steps

I'm thinking next step is to use the angle grinder to dress the tacks back to the center line. Then get the panels positioned with some initial tacks. Then determine how much to cut the edge back by using the edge of the center sheet as a reference. Seems like I need some sort of c-shaped offset measuring widget that can reach under the new panel, find the edge of the old panel, and allow me to make accurate marks.

    -- Carl
 

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Aftermath...

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[kmorin]

Carl,
My remarks are about the clamping frame.
Yes that is a great set of solutions to what is left of outside clamping forces to put on the final bottom plates.

I'd suggest that the pic/ima #5999 my show a detail that might be easier to work? IF I understand that image (?) there are three bolts holding the pivot arm's location along the pulling arm?  I don't think I'd use that method. Until you're in the forward 1/3 of the hull and having to push both downward and some vector of inward toward the keel- I don't see the forces to try to move the pivot point frame/mount?

So I'd suggest that you might take the existing U shaped bracket and weld a shelf, of the same flat bar, inside just below the lowest bolt hold so there is a flat surface to push the lever arm's force to the pivot arm. Next, at the top I'd add another flat bar so the pivot arm hinge can slide inboard and outboard when there's no force on the pivot arm? You'd be making a box of the sliding pivot arm's hinge assembly- more agile to move inboard and outboard as that change is needed by the bottom sheets' changing shape- especially forward.

Then, for work forward where you'll have some tendency to slide this inboard or outboard due to the angle of the V of the bottom, I think a dry wall screw in one side or the other will be adequate to hold the entire pivot arm base assembly in the correct position along the lever arm?  So drilling a couple of smaller screw holes on the two vertical bars seems like they'd accommodate small screws that would adequate cross section to keep the pivot arm base at the correct location along the lever arm?

If you sketch this idea- making a welded rectangular 'box' of the pivot arm's hinge assembly- and side load it - the box itself will dig in to the 2x6 so there will be some resistance to sliding anyway.  I don't think the remaining sheet will provide enough side force to actually shear a dry wall screw (or two?) !!

The current lever arm clamp assembly looks like its great for the after 2/3 of the hull but the upper pivot pin on the vertical may need to be lowered when you get to the forward 1/4 of the length of the hull in order to accommodate the angle of the force being more horizontal and less vertical as you pull/wrap the last 2-3' of the bow?

What you have is agile fore and aft but much less so transversely.

Yes an offset marker would make life easier for the next sheet edge fit - if there's trimming required. I will work on a sketch.

Looks good,
Cheers,
Kevin Morin
Kenai, AK

[kmorin]

Carl,

the idea here is to tack some strips of various thickness together (yellow/brown colors) so the outboard edge of the 2" seam backing longitudinal is in the same plane as the top most edge that will be used to mark the cut line.

This could be done on the table saw with some aluminum or plastic or even hardwood and likely work fine?  It could be tacked up of scrap of different thicknesses.  The one caution is not to make the inside lower guide edge/block to tall or you'd have to lift the outboard bottom panel too high to get this marking jig in and out of the seam.

I show the bottom plate and 2" long (green) to the left and bottom of the assembly the remaining bottom pc to be marked for the cut along the outboard side of the 2" long in blue.  The parts that are one pc of the actual marking gauge are yellows & orange.

Might have to use blue paper tape on any surfaces that touch to get this to slide?  I'm assuming the 2" long to inner bottom sheet tacks are dressed in the plane of the 2" bar, the upper surface of the bottom panel and the tack edges are chamfered so the little marker can slide freely along the 2" long.

IN these images the bow is to the top of the sketch, the keel to the left, the remaining outer bottom and outer chine to the right and the skiff is inverted as shown in your images.

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Cheers,
Kevin Morin
Kenai, AK
 
 
 

[m32825]

Kevin,

Thanks for the pictures of the marking jig. I'll see what I can put together.

Good points on the fixture, how about this?

    -- Carl

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[kmorin]

Carl,
Lever arm's reworked pivot arm hinge mount looks much more moveable to me. IMO this will be more like the agility of your sheer clamping method for repositioning rapidly as you move forward.

Cheers,
Kevin Morin
Kenai, AK

[m32825]

Now I just need to clean up all my tacks so I can try it out, probably get there this weekend.

    -- Carl

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[m32825]

Made a little progress (this whole work thing is interfering with my boat build). Got the tacks smoothed along the top and front, vixen file worked best for that, so that the jig slides smoothly now. I started in on trimming the tacks back, router works well for that.

-- Carl

[starbright55]

Made a little progress (this whole work thing is interfering with my boat build).

-- Carl

 

Funny, the same thing is happening to me.
 

[m32825]

Trimming the tacks back to make room for the other panel to land. I utilized the Bosch tack-o-matic auxillary lighting attachment to see what I was doing (there's a router under the blue painter's tape). One side down, one to go.

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[kmorin]

Carl, progress is always slow - think about the guys who make boats from cellulose - they take tree trunks or rough lumber and start making their own material to make their parts from.  Even if working gets in the way it buys argonium and that's important.

I'm remarking on a close up of the last tack regarding the surface of the surrounding aluminum not the tack- which looks great.  I notice the wire brush has left gouges in the surface of the material so I'll make some remarks about wire brushes used on 4" or larger grinder motors as wheels.

There are many SS alloy wire wheels for removing mill scale and oxide if you use one just before you weld? However, my opinion is that not all of these products are created equal for use on aluminum alloy weld prep.  The wires used to make up the bundles arranged around the wheel are of different diameters in different products' power brushes.

I only use wire wheels with an 0.014" dia SS wire and that photo shows why.  Any thicker wire will gouge the aluminum.
https://www.airgas.com/product/Tools-an ... AD64000386 this product has heavy wires (0.02" or so?) in the twisted bundles and will gouge the Dickens out of aluminum leaving tracks that require sanding to flatten. Some products have even heavier wire which will actually gouge more than this example.

https://www.airgas.com/product/Tools-an ... p/WBU13113 This Weiler wire wheel shows a generic photograph of the product.  However, the spec calls out 0.014" wire which is significantly smaller, more flexible and much less rigid when used on aluminum sheet.  Probably all wire wheel makes offer a small dia. wire in one model or another? but it's good to look at that spec. and try to use those brushes where the smaller dia. softer wire will do less gouging and just clean the millscale.

Using the tool along/parallel to the edges and even taping the edges or using a 'mask' to confine the wire wheel to 1/2" of the edge of the sheet will avoid having random wire gouges at random widths from the seams.  If you have a bunch of parts of similar edge outline- like your bottom panels- then as you did with the offset marking - just stack them and use each sheet to mask the other's edges when buffing.

Also, running the finer wire wheel along the edge and not at right angles keeps the edge of the sheet from 'cutting'/clipping/removing the finer wires and reducing your expensive wire wheel as quickly as running it on the sheet edge at a right angle.

Last, to make these finer wire, more expensive wheels last longer; using them with a very light touch is also helpful- you still get the mill scale off, you still get weld prep but conserve on the softer, finer wires' life span.  Using the tool on edge and not 'flat' or like a sander will also help to keep the wires from breaking off before you get your money's worth of use.

OK, an assumption on my part- you may be using finer wire brushes but the surface marks from buffing seemed to call for a note about the various products' spec.s and why the more flexible wire results in good welds with less clean up or sanding overall.

Cheers,
Kevin Morin
Kenai, AK
 
 
 

[m32825]

Kevin,

True, work does keep me supplied with consumables. 

Seems like there are three stages of scale removal. Before it's off the edge feels slippery under the wheel, once it's off the feel becomes more grippy and the metal has a matte finish. If I keep going after that I'm burnishing the metal and it starts getting shiny. So aim for the middle.

They don't they stamp a number on them, but I'm using Weiler 13085 wire wheels. I run them at 2800 rpms to avoid smearing the scale. I may be using too heavy a hand, perhaps more rpms and less pressure would be better? I'll try your suggestions on the remaining two panels. 

    -- Carl

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[m32825]

Got the tacks on the other side trimmed back.

Spent a little time getting my front table legs back on the ground. I ran straps between the bottoms of the front and back legs and used turnbuckles to pull them towards each other. My theory is that this tries to rotate the ends around the table's longitudinals, pulling the ends down and the center up. Seems to be working.

Next up: wire brushing and beveling.

-- Carl

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[m32825]

Kevin,

Wire brushing went well. I like using the other panel's edge as a reference, the finished product looks neater. It was hard to have any consistency when I was going across the edge.

Next up is beveling. The inner edges have to be trimmed before beveling. The back half of the outer edge is open corner and does not need beveling. The front half of the outer edge abuts the adjacent outer hull panel, and it needs to be opened up. What angle bevel and how deep should I go for those edges?

Taking inventory of "things I won't see again after the new panels are in place", there's an inside fillet at the base of the vertical (see red arrow below) that I'm going to tack the outside panels to. Even with a rotisserie, I don't think I'll be able to get a good angle to weld the seam from the inside. How should I handle that?

      -- Carl

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[kmorin]

Carl, the bottom panels look nicely uniform but the buffed/brushed/cleaned areas could be 1/2 what's shown and still work well since the welds won't be overhanging the weld groove/seam more than tiny fractions of an inch.  Won't hurt but not needed that wide especially with this thin sheet.

Regarding bevel the bottom panel's remaining edges to prep to tack up;
The inside (inner most, eventually upper) edge of the cut out sheet is the guide or control of the panels' placement onto adjoining seam edges or to the back up longitudinal where these remaining panels meet the inner bottom panel.

I'd want to avoid beveling so deep that you cut that reference edge due to it's guiding role in installation.  The second point is to get the outer edge back from the U of the joint so the arc doesn't wander over then and weld - leaving the longitudinal/FB's edge un-fused.  So the forward section of the inner seam should take 1/2 or even 3/4 of the 1/8" thickness leaving a land on the edge of the sheet of 3/32" to 1/16" or so insuring the lower edge is intact but the U is opened up to a \_/ shape to weld.

The angle should be 15-25 degrees, not 45! Your previously shown seam prep seemed fine?  I posted a picture of a beveled keel (above) and I think I used a https://bitsbits.com/product/2325-bevel/ or something just a little steeper? https://bitsbits.com/product/2301-edge-bevel/  ??  If  you did use a 45 degree bit to bevel that edge I'd leave 3/4 or the edge thickness and just put a tiny bevel? This could be done with a vixen file easier than router due to the small amount of bevel taken.

The outer seam or chine seam is a different event since there is no back up bar/FB so any weld on that sheet edge will be fusing the vertical chine or the lower topsides pc.s.  The penetration is not to pick up a bottom backer but to fuse the two sheets. SO much less bevel will be fine- you can back chip directly behind the weld and get a full penetration w/o having to bevel the outside edges  of the remaining bottom sheet where it fit adjoining the forward 1/2 or that seam.

If the forward 1/3 of this seam is nearly closed up then dragging the Vixen file along the outer edge of sheet will usually give enough removed material to allow a good penetration.  If you use the Vixen file then put some of the bevel on the existing upward edges of the chine vertical and any remaining sheet that will be involved in this seam.

As to the inside edge of the vertical chine bar, (lower pic) I'd say it has to be welded before you cover this area.  I thought they were welded?  I'd have welded that when the vertical bar wasn't trimmed down to the final taper?? I thought you'd done that area already?  Clamp a heat sink/strong back to it and weld it then trim it to profile if you haven't already?  If it's welded outside and remains open seam inside then clamp the heat sink to the flat/horizontal chine pc. AND the vertical pc and leave the clamps/Vise-Grips (tm) on until it cools to reduce rapid chilling that can increase contraction distortion.

Also in this pic is an angle extrusion tacked to what I think is a transverse frame and that looks like the weld seam there will be covered as well. I'd stitch weld all those angles onto the plate/frames underneath prior to sheeting as well. Also the end of the transverse frame needs attention but is in kind of shadow and I can't make out clearly what joint is there- but it seems close to the hull so getting in there to weld needs to be considered as well.

Looks good,

Cheers,
Kevin Morin
Kenai, AK


 
 
 

[m32825]

Kevin,

I appreciate the feedback. I haven't beveled any of the edges on the remaining sheets yet. I'm tracking what you're saying.

You caught me being lazy using an old picture to illustrate the inner hidden fillet. That portion has been welded already, but there's another few feet going all the way to the back that I need to hit. Also, good eye spotting the angle that supports the floor, I'll stitch that while I can get to it.

-- Carl
 

[m32825]

Kevin,

Looking at things more closely, I see a couple issues I want to address before tacking on the remaining pair of panels. 

Both issues involve the rearward portion of the vertical control edge, the part where I'm going to tack to form an open corner. The first issue is that one of my cockpit floor support transverse frames is pulling the vertical inwards 1/16" or so. I suppose I could live with it, but it bugs me now that I see it. The vertical is tacked on either side of the pulled area, so if I cut the frame loose it will likely relax back in line. The hull is relatively flat at this point, so the risk of collateral damage seems low.

The second issue is more complicated. The vertical on one side is perfect, the other side is short by 1/16" to 1/8" inch over a portion of its length. Looking at the cut layout, this piece was on the outer edge of a sheet, heat may have caused it to shift a bit while being cut? I can think of three options: 1) file the transverse frames down to meet the edge, 2) use TIG to build the edge higher, and 3) sister in a strip of 1/8" sheet behind the vertical to establish an edge at the proper height. Thoughts?

    -- Carl

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[m32825]

Kevin,

Prepare to fall off your chair laughing. My shop has been too cold for my taste lately. I don't like the shop any lower than 60, and it's been hitting 50 this week. Today I wired up a 7500W heater to take the edge off. First world problems to be sure.

-- Carl