...discussion of MALE PLUG for hull build......

[micah202]

...after jamming-up tim's thread with this,,I thought I'd transfer this to it's own topic so that Chad,myself and anyone who wants,,can -have-it-out-,,and work through this idea..........

first,some background posts........
micah202 wrote:..from everything I've seen,this 'time-consuming extra-step' would save MUCH time and frustration with the build overall

Postby Chad » Mon Sep 10, 2012 11:15 am
...and full length longitudinal stringers and shear clamps, IMO.
I've given out plans for this build jig: Jig_iso.pdf
(124.82 KiB) Downloaded 8 times
...and to it I would also add some longitudinal stringers forward between f53 and 89 if I were to build again.

Micah202....
....methinks that would help,,but -nothing- like building the hull upside-down on a full frame!
...as I say,it seems like it'd be a lot of work,,but I'm sure it'd build a better boat quicker.
...sorry,no PDF's

Postby Chad » Tue Sep 11, 2012 5:06 am
Sorry, I missed your "male" jig description, and assumed you were talking female.

I can see that assembling and glassing the hull panels on an upside down jig would help create a fair hull since a builder could more easily see the fair shapes, but then what?

I think the glassed hull shell would still be very wobbly, and then you'd need a female jig to hold fair while you installed the interior. Unless you propose installing the bulkheads up into the upside hull- you first!

I think this boat's hull skins are too thin and pliable to hold a fair shape without the interior parts. I think right side up in a female jig is the only reasonable way to hold the skins fair while adding the structure that keeps it fair.

The Portland folks are reporting reasonable success with their more elaborate female jig, and my hull came out very fair (except in places where I didn't have enough support as mentioned above), so I don't think there's a big problem that needs a radical new solution. Heck, even the no-jig builders achieved fair hulls, once they realized the need to introduce some lateral curvature to the frame sides.

[micah202]

Sorry, I missed your "male" jig description, and assumed you were talking female.

I can see that assembling and glassing the hull panels on an upside down jig would help create a fair hull since a builder could more easily see the fair shapes, but then what?

I think the glassed hull shell would still be very wobbly, and then you'd need a female jig to hold fair while you installed the interior. Unless you propose installing the bulkheads up into the upside hull- you first!.............

..certainly -some- builders have been able to have some relative success with the simple methods so far,,especially after building 4 boats,
,,,with a male jig,,,certainly I propose building the boat with bulkheads and stringers in,
,,,much as I built a wooden sabot when I was 14!

... start with a solid base-frame,,a trailer frame might not be a bad idea especially if there's a few boats to be built.
......mount some permanent panels to the baseframe,in locations of the boat's various bulkheads.
......mount the actual bulkheads to these permanent panels...there's fairly precise measurements for the bulkheads and rocker now,,so these can actually be set up precisely.
.....cut notches in the bulkheads for stringers,,,install stringers ,,shape stringers with a plane.
.....lay-down panels with epoxy and fasteners.,I'd recommend sealing/finishing the panels -before- installation,,,simply scuff areas to be glued with ~40grit,brush straight epoxy to the area before applying bonding paste,,it is not necessary to have a primary bond to wood-trust me!,,,and there's MUCH benefit and time saved in properly sealing the wood!
..........with a bit of extra effort,,the bottom panel could be insalled before the side-panels,saving some access issues. .
......shape edges,,glass/epoxy hull,,,fairing,,,even finish the hull before flipping,,
.....build a landing-frame to put the hull on,,
.....unscrew the bulkheads from the permanent panels on the baseframe,,,remove hull,,,flip and place on landing frame.
....carry on with the keeltrunk and interior as if you have a solid hull to work in,cuz you do!!!

...so in summary,with the ' added effort' of a baseframe and some solid mounts for the bulkheads,,,there is MUCH time and frustration -saved- with building a male mold.........have-at-it!!!!

[Tim Ford]

Foist of all, I think this is a great discussion to have and thanks for all suggestions. Male or female, I'm sure going to the trouble of building plug/jib/strongback/what-have-you will ensure a fairer, firmer, more well-built little boaty.

But: I'm kind of wondering how much time this will save? For me to build that stuff would be time-consuming as hell. I don't think the fairing job is going to be all that time-consuming. Or, maybe I'm just a better fairer than carpenter (I did take Sculpture I in college....uh...gosh, 40 years ago...410/105/205 is much easier to shape than marble, let me tell you!).

SO maybe it's to each his own (or her own), but for me building a jig that is accurate enough to ensure a plumb and true build is an issue. Plus, even the fairest of these build on frames (or what have you) is going to need some additional fairing. I mean: it's plywood fur cryin out louds.

[micah202]

...just how time consuming is it to build a strongback frame and solidly attach some crossbeams at pre-determined points?
.....everything else is part of the boat .....and yer only need to square things up once!

...I guess the proof would be in building one,,,,if 2 committed plan holders in my town step forwards,,I'll get right on it!

[Tim Ford]

I like the word "committed." That's a good word for this project...as in, "You're starting to build one? You should be committed!"

[Chad]

Ok, so you're:
including some stringers in the mix which I think is great
you're initially bonding the hull skins to those stringers and not the bulkheads (the 1/4" sides of the bulkheads offer almost no gluing surface)
then finishing the exterior, all fine

then flipping the boat and crawling inside, hmm. With care you should be able to avoid popping the joints as you add the tabbing to the bulkheads, but you're going to be doing a lot of start-and-stop taping in between all the stringers which adds lots of time.

I did most of "your method" (but right side up) for my hull side panels- added the side stringers and shear clamp first and then glued the sides to them, then taped all the short segments.

IMGP1703.JPG

I recall it taking a very long time to do all the detail taping, trying to keep things neat going around all those corners, although I took the opportunity to use a lighter tape above the stringer line to save some high weight...

IMGP1915.JPG

I dunno- there are some trade offs. If I built again I'd think about it. I really like the idea of getting a very fair hull from the beginning which I think is very difficult with the raw 6mm ply. In my dreams I'd really like to be able to build with panels that are stiff enough not to need stringers, and maybe even get rid of some of the frames as well-- but that takes a foam core to avoid getting too heavy, which trades a whole different set of pros and cons...

[micah202]

.......chad,,I'd approach it slightly differently ....

....in my renovation,I bonded beveled strips along the edge of all bulkheads,etc,, so that any edge presented at least 1'' bonding surface,,,scuffed the glassed plywood,,painted both surfaces with straight epoxy,,applied bonding paste to the frame edge surface,,,put panel in place,,,attached with screws until cured. .....this procedure makes a darn solid bond.
............... I don't see a necessity of glassing each stringer as well...you gain a HUGE strength by having proper stringers under chines and gunnel ,not to mention mid-panel ....but with a bit of pre-planning,,you could have some friendly shapes so glassing would be simplified.

...certainly the product from a male mold would be worthy of climbing in,supposing the hull-bottom panel is supported as with any hull you're sitting in

[Chad]

Adding the bevel cleat strips to the bulkheads throughout, to the "high side" that gets planed to the local hull angle, then taping the other side afterward? -Could be doable- I did similar under my cockpit.

Peter goaded me on to tape those stringers: "anything not taped will crack" he said, or some such.

[micah202]

...certainly taping adds a further element of indestructible!!
...just wonder what you'd plan t'do with it!? ...niagara falls???

...by the way,,if anyone's worried about 2ndary bonds with epoxy and plywood,use my method above on a test peice,
,,,destructive testing will show the same as primary bonding to plywood-yer rip the outside ply right off