Conchfish AL 17.6T build

[m32825]

Trimming the little inside lip to form an inside corner. I'm doing pretty good with the router on the accessible part (and I'm still on the first side) but am trying to figure out how to trim near obstructions?
 
 

[gandrfab]

Hand grinder, die grinder then manual file.

[m32825]

Hand grinder, die grinder then manual file.

 

Haha, not looking forward to that last part!

My concern is more about forming the inside corner than removing the lip. The multi tool I used to cut tacks might be good, have to try that on nooks and crannies.
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[kmorin]

Carl,
Two seams.  The inside seam I'd use the meat axe/widow maker tool to cut the edge when you roll the hull.    You can trim the flat of the pocket chine back to the edge... leaving you an inside edge fit once you have better position.  For now won't hurt anything.... you can get to it when the hull is rolled?

The outside seam looks like it was accessible as the position of the hull seems like it is now... where the inside chine pocket seam will be when you roll the hull?  Might have to work in an odd position? but the rotisserie should give good access and the same treatment as you did outside. Nearest the frames or other obstructions you'll just have to use the smallest tools in your shop ... then grind/sand the last few inches flat/flush and TIG float those areas after the MIG weld is done outside.

I'd say you can go ahead with the bottom sheathing/plates anytime as these seams you're addressing inside will be more available once the skiff is mounted to a rotisserie?

Looks good.

Cheers,
Kevin Morin
Kenai, AK

[m32825]

Hi Kevin,

This is an example of the great advantage of having other people look at your work. I've been looking at this boat laying on a table for so long that I don't think of it as movable. It didn't occur to me to think about being able to access that seam from the inside once it is on the rotisserie. I also had target fixation on the top seam and completely missed the other one further down. The lower one will be more involved because it runs all the way from the front to the back.

Work has been busy lately, hard to find time in the shop!

-- Carl

[m32825]

Working on making templates to trim the free edge of the next panel. One side down, one to go.

Started out by making a template for the existing edge.

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Used that template to make a complimentary template.

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No gap between original and compliment.
 

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[m32825]

Making templates for the other side. Watch me exercise my dust making super powers.

Making templates

[gandrfab]

m32825 how was your weather?
I had the news on when a tornado went over the FOX35 building.
No damage here, but did have some heavy rain.

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[m32825]

Gandrfab, all good here. The weather guy did a nice job of keeping it together (link below) as it passed. He's going to be the envy of all his weather brethren. I don't think that station has its own Doppler radar, would've been a great opportunity to image one from the inside. Might have been too close for a good picture, though! In a different view they had a camera on I-4 while the tornado passed, traffic just slowed down a little, they were like, "Eh, I've had worse commutes".

    -- Carl

P.S. Done with templates on both sides now.

 Live tornado report
 
 

[gandrfab]

I had that on my shop TV with an over the air antenna while it was happening.
Seeing the aftermath reported, it's amazing there are no injuries reported.

[m32825]

I've got the two remaining panels up on the hull to check how things fit. The outside edge is going to be the reference, I'll trim the inside edge as needed. The inside edge will be landing on a longitudinal. The rear 2/3 of the outside edge will be an open corner joint, the front third is two butted edges coming together at angles varying from about 135 to 165 degrees.

I put the rear part of the panel edge next to the vertical where it's going to form the open corner and I can see that I've got some variation. if I don't pick the right line for my open corner at the back of the panel, the front part of the panel won't align properly with the adjacent reference edge. Seems like starting at the front might make more sense because that reference edge has less variation than the back?

When I did the center panels the rule of thumb was to keep the tacks at the center a bit ahead of the outside tacks. Should I use the same plan for the next two panels?

-- Carl

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[kmorin]

Carl,
not completely clear on the note that you have "some variation" bit sure if you're referring to the vertical (pocket chine vertical) is not straight  (one axis) or the lower edge is not a line? (the other axis).  

Which ever section of the outer edge (chine) of the bottom panel is most straight or has the least curvature is the best place to start the tack up. If that is your reference line and you'll trim the inner seam to fit... then that's where the tacks should lead as you move forward toward the bow. Rule of tacking order it so favor/lead/advance by the control edge or reference edge/seam and in this case its the outer chine seam aft.

The panel's wide after width is also more stable in terms of bending the length of the panel across its width.... narrower end forward is less effort to increase or decrease curvature due to change in with- should that be needed?
 
If the vertical chine pocket is supposed to be a line in the after few feet- and its not(?) then an 1" below its now upper edge, tack a straight edge to make it a line so it will accept the after line or long curve of the remaining bottom panel.

Pls let me know if I misunderstood your post and replied off point?

Cheers,
Kevin Morin
Kenai, AK

[m32825]

Kevin,

I'm not seeing a problem with the height of the vertical, it's the path that the top edge follows. The base of that vertical piece was placed relative to an etch line (potential error source #1) and is not exactly perpendicular along its length (potential error source #2). I'm still working on understanding the geometry.

Generally speaking, the top edge of the vertical leans toward the center of the boat somewhere between "not at all" and 1/16 of an inch (picture below). I'm not sure when/how this lean was introduced, perhaps it was when I tied in the transverse frames for the floor? I know they were perpendicular along their length earlier in the build.

The location of the inside corner of the vertical is dependent on the stack up of two potential error sources. That's why I was thinking about starting with the front third, where there are less variables.

-- Carl

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[kmorin]

Carl,
since you don't mention the origin of the scribed line? that was used to line up the vertical chine pocket 'liner' bar.... I'm going to assume (my favorite type of illogic- making an *ss out of u and me) that it was fair- either straight or a clean curve that came with the parts in the cutting process? So I'd say it wasn't much of a contribution to error?

To check, put a flat bar on the horizontal chine flat just above the outside tacks and see if the bar is actually wavy, hogged, or irregular along it's length?  Tap those tack in or out to fair the line of tacks.

Next is the lean.  I think the tiny amount of lean you're showing will very easily come out by using the bottom panel sheet edge as the control of the after chine line's cleanliness.  Tack at the after most point, outside at the chine. As you move forward, use the cut and faired edge of the bottom panel to clean up the vertical bar's (now) upper edge to form a clean joint.  By using the forward 2/3 of the bottom panel as a lever you can very easily move the seam inboard or outboard to get an inside edge joint that is cleanly aligned edge to edge on the inside of the hull.  Then tack that spot and move ahead another 3" and repeat.

I think this will remove any irregularities in the vertical bar's inner most edge and result in a clean seam.  The only potential problem I see is there may be some unfairness that is caused by welds/tacks/heat and contraction at the frame locations? if that is the case, where you can't pull that area smooth using the forward end of the bottom panel(?) then I'd turn the frames loose from that section of the vertical bar and re-tack & weld when the bottom is fully planked/plated/installed to the adjacent chines.

I think initiating the panel/plating aft and moving forward offer the most control of the after 1/3 of the hull due to the leverage provided by that long narrow bottom pc.

Cheers,
Kevin Morin
Kenai, AK
 

[m32825]

Hi Kevin,

Apologies for the delayed response. I picked up a cold at the end of last week. It always seems ironic to me to catch a cold when it's warm outside, adds insult to injury. On the mend now.

The tacks at the base are fair. I will take a closer look at the variation today, and see what it's like as a function of frame locations.

I see the logic of starting at the stern and working forwards, and that's what I'll be doing. While discussing that topic you mentioned that it would be easier to move the narrower end of the panel up or down. I had this mental image in my head of panels being easy to flex across the narrow axis of the sheet but being immovable in the plane.

After reading your comment I tried using a cantilever beam calculator to figure out how much force would be required to move a 4-in wide section of sheet 1/16 of an inch sideways by pushing in the plane of the sheet at the end of a 4-ft section. It was just a few pounds, which was not what my intuition was telling me. I happen to have a piece of flat bar with similar dimensions, so I went out to the shop and tried it. The results were similar to the calculation. Needless to say my intuition has been recalibrated!

While testing the fit of the new panels I noticed less force will be required for fitting them than the center pair. How important is it to work on both panels at the same time, keeping progress towards the bow symmetric? I would like to understand whether that is a general rule, or something specific to the center pair.

Another thing I noticed while fit checking is that, with the shape of the hull and using the outside edge as control, the inside edge is pulled tightly up against the opposite side. I will have to work farther down the seam from where I've tacked to trim the edge, but it will be easier to check for accurate fit.

I'm using the die grinder fixture to bevel the outer edges of the panels that are already in place. Back in the glitter business!

    -- Carl
 
 
 

[kmorin]

Carl,
bottom plates/panels/sheeting that adjoins the keel (VKB) are kind of critical not to have waves or hoggs- side to side.  SO working those inner sheets together works to resolve potential keel distortion.

However, the outer bottom panels have little impact on changing the shape of the keel's adjoining panels and won't move the frame and topsides tack up to speak of. Now, if the outer bottom panels' edges (chine outside, long seam inside) were off by 1/2" and you force one side w/o balancing that force on the other side you'd very likely twist the frame to the extent it is flexible. But a fraction or two of an inch of pushing and pulling the remaining bottom panels toward or away from the keel won't reshape the inner bottom panels already tacked around their perimeters to the framing elements.

Besides that level of misfit... putting on one side then following with the other side won't distort the hull.  I'd do the side with the most closely fitting after 6' of the outer chine and finish it at both inner and outer seam and then follow up opposite.

I'd say this was the very first skiff of the tiny size that I've ever seen with two bottom panels - so the Rule of Thumb to work symmetrically really comes from the 5 panel hull model. There the bottoms are in halves.  So working them together, like Starbrite55 is doing in his skiff on the adjacent thread, is to keep the VKB and the two panels cones intersecting evenly to avoid sheet 'unbending' torque on one side that isn't balanced on the other side. 

Also that RoT comes from unframed boats...like the RIB hull and many of my build threads, where the two sheets go together w/o and VKB and use one another to balance the bending to form uniform conical or cylindrical sections.

I don't see that need as often in frame boats or skiffs as the x-verse frames coupled with longs make a pretty stiff frame to pull the sides to... one at a time.

Another thing I noticed while fit checking is that, with the shape of the hull and using the outside edge as control, the inside edge is pulled tightly up against the opposite side. I will have to work farther down the seam from where I've tacked to trim the edge, but it will be easier to check for accurate fit.
 

I don't exactly understand this paragraph well enough to remark/reply.

Once you get the MIG bead to flow into the die grinder cut groove and leave a nice finish those welds will have the lowest 'wave' distortion from welds length-wise contraction.  Putting the weld as nearly as possible in between the two sheets' cross sections as opposed to outside them, or on top of the adjoining edges; goes a very long way to producing a clean hull.

Hope your cold leaves you soon and you can spend more time with your skiff build.

Cheers,
Kevin Morin
Kenai, AK


 

[m32825]

Hi Kevin,

I appreciate the explanation. I'm going to move ahead with one side at a time. I chuckled at "tiny boat", good reminder that it's all relative.

My "puzzle paragraph" ... For the center panels, I tacked in the center first, then had to push the outside down to tack. For the new panels I'll tack the outside first, and the inside edge will already be pressed against the longitudinal by the twist I'm trying to impose. I don't think it's a problem, but I'll need to work a little further down the line to trim the inside edge.

I spent time aligning the verticals. Wasn't hard once I figured out how hard I needed to whack it with the dead blow hammer. All that wavy stuff is gone now!

-- Carl
 

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[m32825]

Fitting next hull panel. Paid a visit to the Harbor Freight school of creatively modified clamps to minimize how much I have to lift the panel for trimming.

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[gandrfab]

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[m32825]

Need some problem solving help...

I started in on tacking the new panel on both sides. I lined up the outside corner on my reference edge and tacked it near the stern and then a few feet further along to hold my line while trimming the inside edge. I trimmed five or six feet of the inside edge without incident, leaving 1/8 inch gap, then beveled the trimmed edge and started tacking the panel along both edges. I made sure to lead with the reference edge and follow not far behind with the inside edge. Everything went well at the start but after I got a couple feet in I noticed that my 1/8 inch gap had narrowed.

I think what's going on is that the inside edge is a much "stiffer" edge (more resistant to being pulled) than the outside reference edge. When both edges are tacked and the tacks contract as they cool, the reference edge yields. This does two things, it begins to pull the reference edge inward and allows the gap along the inside edge to begin closing.

Seems like I need to remove a few of those inside tacks and then shim inside the gap to hold it open a few thousandths more than an eighth of an inch so that when the tack contracts the inside edge ends up where it should be.

I noticed the same kind of thing going on when I was working on the center panels. I would clamp down and trim a segment of the outer edge to land on the longitudinal, leaving 3/16" exposed. As I tacked that section down each tack would pull the longitudinal sideways a little more so that my 3/16" exposure dwindled. I had to remove a few of those and pull the longitudinal to the outside to compensate, clamp it, then tack to re-establish my line.

-- Carl

[kmorin]

Carl,
If I restate your question, w/ my understanding of the events you're experiencing,  you can correct me if I am not talking about what's happening accurately.

When you tack the bottom plate to the outer chine, ahead of the inboard seam backed by a long; the inner seam closes, before you tack it, even though you router trimmed the inboard seam's edge to match the outboard side of the long tacked to the frames and the inner bottom panel?

What to do to correct this ? OR where is the inboard cut edge getting it's expansion to cover the long's outer edge?

I think the tacks on the outer edge of this panel- the outer edge is an outside fillet with inner edges touching as guide to the fit- so the tacks may be larger, longer, hotter to make and therefore expand this outer edge more than the tacks long the inboard seam on top of the long.

First thing is to stop leading one set of tacks over the other. That does appear to be what's 'curling' or bending across the shape/panel's outline to curve it a few thousands inboard, covering the seam's flat bar/long' backer.  Once you get a section 'trimmed'; put two tacks one outside and one inside at the forward most end of the trimmed section, then go back and add all the edge/seam tacks in 3-4-6" spaces (as needed) and add them in pairs.  One outer chine tack for one transversely equal along the keel, but inboard at the hull panels' seam.

Since you're trimming the inside edge based on the long's outboard edge- another method would be to just wait to trim until the entire outer seam (chine) is tacked? That way, any heat/tack induced distortion is already in place when you trim the inside- and all the tacks left for that section are on the inboard seam. I'd still tack at the very forward end of any trimmed length to keep the trimmed width open at the 'far' end. Then go back and fill in the tacks, dress them for the eventual hull weld-out.

Hope this reply helps with a couple ideas of how to respond to the description of a closing gap- likely due to the outside being -stretched from seam tacks? I think you're experiencing this 'sheet' or panel distortion almost solely due to the very narrow width of these plates/panels of the hull.  The same tacks on full width bottom panels that reached from chine to keel, probably would act very differently due to the increased width.

I'd seen vaguely similar shape changes while tacking up reverse chine plates.  They're most often less than a foot wide and 20-30' long. And all the tacks are usually on one side to hang onto the bottom's outer most edge- well before the topsides are hung.  Not exactly your problem, but similar in tacking up long narrow pc.s with heat distortion on one side/edge.

If I didn't 'see' what you'd intended to ask about, or if my explanation of possible solutions aren't matching your hull? Please let me know and we'll take another stab at it.

Cheers,
Kevin Morin
Kenai, AK

[m32825]

Hi Kevin,

I am seeing the downrange panel seam close up a bit when I tack the inside edge. I think that's to be expected, because the tack shrinks as it cools. My mindset has been that once I had the edge trimmed it would stay where it was while I tacked it. I can see that I need to take steps to keep it where I want it.

I did not clearly convey what was happening, but your suggestion of going downrange and tacking it, then placing the tacks in between works well. I don't think the shrinkage from a single tack is a problem, but the accumulation from multiple tacks needs to be managed for the panel edge to stay put.

There are three stages to this panel. The rear part is horizontal. The middle part makes a turn from horizontal to angled. The front part is angled. I've got the rear part done and I'm working through the fit up for the middle part.

-- Carl

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[m32825]

Working on the next to last panel. Back half is tacked, adjusting fit of the front half.

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[m32825]

Turned the corner in the middle of the panel.

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[m32825]

Physics tells us that as we approach the speed of light, time slows down. I feel like the same thing happens as you approach the bow. Creeping along slowly...

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