I'm Stuck. Need help and advice.

CatBuilder,

Thinking further---. if the lower edge of existing foam has not landed on a batten, which appears to be the case, the foam may have sagged a bit between stations, adding short sections of battens as I described may correct that and make the new foam align with the existing.

Hope this helps.

Allan

 

Thanks, Allan.

Actually, the lower edge of the existing foam is right on a batten for most of the length. There is even some batten sticking out in a few parts. Then, as you move toward the bow or stern, the foam has nothing holding it up, then moves onto yet another batten at the extreme ends of the boat.

The batten the existing foam rests on is curved and matches the curve of the bilge. The batten batten near the blue line is straight. Herein lies half of my problems.

 

CatBuilder,

What I am trying to express is that for the foam to lay fair, the edges need to always land on a batten. Where two pieces join, they should share a batten.

Allan

 

I agree with PAR add battens at any joints. If you dont want to use bog to fill the gaps then maybe get some 6 lb pour foam from us composites. rick

 

Any abrupt changes in angle on the surface, chines, knuckles, etc. or particularly hard radius areas, all need tight batten spacing. Strips of 1/4" plywood, let into the current crop of stringers and station molds can cover these areas if set on an angle the the battens. Then pull your foam down with fishing string tied to the battens.

 

Thanks.

Definitely I'll be gluing my short foam into longer pieces to do this in a single step next time, from bilge to sheer.

The already finished bilge foam is down correctly. Most of it is laying on a batten, but as you can see, that batten has a curve to match the rocker curve of the bilge. The other battens are straight. This is some of my problem. Some foam is laid up in a cure like the rocker, some is straight (like the sheer).

I already have hundreds of screw holes in each batten on the mold to allow me to pull the foam down. It's not that the new foam needs to be pulled down where it meets the finished bilge foam... it's that it needs to be pulled *up*. The meeting edge of the new foam needs to be pulled up, which is why it's tricky.

I was thinking a short stick jammed under the mold against the ground would even work just fine to hold the edge in the right spot while the bog sets.

That's one issue, the other is the shape of that sheer vs the shape of the rocker and how to reconcile those two different curves with very expensive squares of foam.

 

I'll look at adding more battens...

Might do the hull half with the bridgedeck opening this time just for psychological purposes!

 

That both ends of the foam land on a batten is needed, but even then there will probably be a difference in the "plane" ness of the two pieces, unless where they meet is flat. That's the reason for the long battens to begin with, to even out irregularities. The ends of a stick don't bend the same as the part inside the ends, the continuity is not the same. It's like trying to loft something using short sticks. You're trying to loft a fair curve from the bilge to the deck using short "sticks" of foam. You're going to have to fill on the inside to get it fair and you'll have to longboard the outside to get it fair.

 

may be use some masonite strips perpendicular to the battens, stapled to the back of the battens, with a small piece of batten at the point of intersection with the curve. I,ve never formed anything up using foam in place of ply, but I have formed a few million sq ft of concrete using ply. What Par is saying is correct, you have to have a batten or something there to hold your foam ( up or down) at a given point of change or curve. There will be strips of masonite running both directions on my hull form , it is cheep and holds a curve well.

 

That's what I was thinking. It might be the best way to go.

I am already 1/4" over spec on my foam thickness. Long boarding away a little bit on the outside and filing a little bit on the inside seems like a reasonable way to do this.

I didn't even consider that using long pieces of foam was just like using a batten (like a lofting batten). That's a great point. Makes perfect sense to me now why this isn't going to come out fair (until sanded).

Excellent advice. Thanks.

 

I wonder if you could use some sort of plastic "biscuits" and a router or biscuit slot cutter to help align the ends, like they use to align boards with wooden biscuits when gluing together.

Also the inside doesn't have to be quite so critically fair as the outside. Some spatter paint will cover up a lot of discrepancies.

 

Can you sister another piece of batten on to the existing one to line the ends up?

 

I woke up thinking maybe longitudinal strip planking would be better.

I'm going to do this hull half as an inboard half, meaning, there will be a big part not built because that's where the bridgedeck attaches. I only have a couple feet to that point, then the ends and partial deck to build in.

SO... I figure I'll just strip plank those couple feet.

How long do my strip planks need to be?

 

My 5c..
Don't swap btw methods if you want some progress. There's a new learning curve with the change... As you might have noticed..

 

Yes, I did just notice that!

I am out there wondering how long my planks need to be, what I need to do in order to hold the planks in place and all that.

I guess maybe I'll just start throwing the foam up and worry about it later on. I can bog in any small 1/8" (3mm) gap on the inside and sand that same 1/8" (3mm) lump down on the outside.

Maybe I am overthinking this.

I mean, what would a professional boat building shop do?

They'd say "forget it - just get the foam up and fair it out!" "Get back to work!"