Templating hull bottom V

[Spot]

Hi Yoya,
If you like templates to check you work then make templates. You will have to interpolate the pieces that are already missing but it should not be too bad.
-one for the longitudinal center line at the bottom, fill in what it missing along the curve (blue)
-one above the repair (green)
-one below the repair (brown)
-one to estimate the middle of the repair, splitting difference of above and below template (purple)


Then bevel, repair, and fair as guided by good practice. At the end of the day you may find yourself trusting eye and hand more than template.

[Kd9truck]

So I know nothing but it looks like you could use a 12 inch joint compound knife as a guide to smooth out the fairing compound like you are finishing a Sheetrock wall.

Are those osmosis blisters that have been exposed and drained on the rest of the hull?
Good luck

[Yoya]

Well, creating complex concaving and convexing surface templates of the hull's bottom is not my favorite hobby, and I do hope the general advice given here - go by hand and eye - will suffice. However, of the whole affair, regenerating the shape seems the most daunting task

[Yoya]

Originally Posted by cal40john

https://www.amazon.com/General-Tools...862048799&th=1

Yes this tool in a XL size might do it

[Yoya]

Originally Posted by Kd9truck

Are those osmosis blisters that have been exposed and drained on the rest of the hull?
Good luck

Yes, gel coat blisters. Nothing to drain. They are all dry

[Yoya]

Originally Posted by Spot

Hi Yoya,
If you like templates to check you work then make templates. You will have to interpolate the pieces that are already missing but it should not be too bad.
-one for the longitudinal center line at the bottom, fill in what it missing along the curve (blue)
-one above the repair (green)
-one below the repair (brown)
-one to estimate the middle of the repair, splitting difference of above and below template (purple)


Then bevel, repair, and fair as guided by good practice. At the end of the day you may find yourself trusting eye and hand more than template.

That's how I'll go about templating the complex hull area, by sections every 30-40 cm and interpolate in between. Hopefully working by hand and eye will do. And I'll be able to use the template if I cannot restore the shape

[Ninedotsix]

Originally Posted by Yoya

Bevelling only the edges will not be enough to get 1:12 ratio I believe

No need for template.
Your innate sense of “eye sweet” will tell you when it’s fair, and since most people tire of this drudgery long before it’s adequately executed, you should ask objective persons in your boatyard to tell you what they think as you progress.
Implied in the above is a warning not to let up until the repair becomes invisible.
Also, focus on using woven fiber reinforcement, not matting or “hair”.
Go on in layers, using slow cure epoxy resin, and I would start laying 25mm wide strip at the bottom, followed by 50mm, 75mm, 100 mm, etc.
Correspondingly, the lengths of the strips should increase proportionately as you fill in from the bottom of the hole, as you go up.
Resist the temptation to start building too quickly, as the overhead position makes it so the patch work may try to fall out. So, establish a base layer, and as soon as the layer starts to gel, you can add another layer.
Do all of the filling until the patch stands “proud” above the surrounding area, and only then start sanding. After sanding, do subsequent filling with more resin and cloth. Longboard the long lines, and block sand the short (transverse) lines.
Don’t use filler putty until you have the area eye sweet, with only barely noticeable sanding marks, then you can skim with a hard epoxy filler for below water.
You’ll be most satisfied by your work if you accept that it will take as long as it takes; much longer than you might think, and don’t compromise on strength by hiding this behind hair patches and thick soft filler.
I’m most concerned about what you describe as the trouble inside the hull skin that you say started this thing, and can’t make sense of that assessment.
Seems like if it’s as you say, “shower water”, then any boat with water in the bilge is doomed.
Cheers ~ 9.6

[Yoya]

Originally Posted by Ninedotsix

I’m most concerned about what you describe as the trouble inside the hull skin that you say started this thing, and can’t make sense of that assessment.
Seems like if it’s as you say, “shower water”, then any boat with water in the bilge is doomed.

I'll probably go by eye/hand and go slow.
I'm concerned as well. However, for a 45 years old boat with exposed laminate layers in the bilge, soaked in water, compromised areas may be a likely outcome

[bil56]

I redid a boat like this, it took much more grinding than 1/10 or 1/12 of slope.
our method: grind half of the hull, relaminate on one side, ditto on the other side, also restore the hull bottom stiffeners, this amounts to rebuilding a new and coherent laminate.
the final shape on the outside will be easily done by sanding, puttying, gelcoat, ...
for this kind of work, I prefer to use the same material, i.e. polyester resin, fiberglass fabrics.

./.