1966 MFG Rebuild

[kcassells]

I would replace the lower 2x4 or at least flip it over. The weak spot is on the bottom

Instead of router bit I would just use block of wood and some 80 grit
Use 3/8 ply (23/32) for bulkheads
Can core the bulkheads with foam but make sure to brace them good, the foam has enough power to split them apart

I think those 2's are only to keep stringers aligned.

 

[demarko210]

I would replace the lower 2x4 or at least flip it over. The weak spot is on the bottom

Its just being used to hold the stringers in place. Its denominational lumber.

Instead of router bit I would just use block of wood and some 80 grit

I would be all year rounding the edges with a wood block. I would look like Popeye when done

Can core the bulkheads with foam but make sure to brace them good, the foam has enough power to split them apart

I am going to use the wood. Just was wondering some opinion on it.

 

[demarko210]

I'd suggest experimenting with a chamfer bit, and pulling as little material off as you can. If the idea is to remove sharp edges, the roundover fits the bill, but it may leave you with too little surface area between wood and fiberglass. A light touch with a chamfor bit would leave more actual wood against the fiberglass. That spells more weight displacement, and longer lasting to my way of thinking. Not that I have any specific experience to draw from. I'm just a jack-of-all-trades and sorting it out as I go.

I simply want to remove the sharp edge of the plywood so the 1708 can lay over it better.

 

[demarko210]

Never used a router to edge off the square edge but wished I had. I ended up using a sander to round off the edges. Takes awhile like that and inconsistent edging. Go for it.

I did that before with grinder and yes edges are inconsistent.
I always learn how to use new tools working on boats

 

[Pmt133]

I routered the tops of my stringers on my project as well. It was still a chore to get the 1708 to lay over a rounded 3/4 sheet.

Mind you in most places, my original stringers weren't capped and the deck just stapled to them. Anything is better than that.

 

[kcassells]

So to be clear are you foaming all compartments.
Why 6lb foam vs. 4 lb foam
Yes you should take the time to seal with poly once tops are cut down to height.

 

[demarko210]

Mind you in most places, my original stringers weren't capped and the deck just stapled to them. Anything is better than that.

I know most are like that. Most stringer probably just have resin and the stringer is bonded half way up. I will make cleats to screw the deck to instead of hitting the stringer or bulks.

I routered the tops of my stringers on my project as well. It was still a chore to get the 1708 to lay over a rounded 3/4 sheet.

Did you start from the top down or did you try to cap from one side to the other from the bottom? I will start from the top and let gravity help.

 

[demarko210]

So to be clear are you foaming all compartments.
Why 6lb foam vs. 4 lb foam
Yes you should take the time to seal with poly once tops are cut down to height.

Yes all except where the center console will get foam. I figure the boat was suppose to weigh 700 lbs dry I need about 10 cubic ft of foam to float 700 lbs.
The foam I mention was to use these templates to make the bulkheads 6lb foam just to get opinions on it. Encase these templates and pour in 6lb foam. The image got removed from the post. I will be using 2lb foam for the flotation.

 

[Pmt133]

I know most are like that. Most stringer probably just have resin and the stringer is bonded half way up. I will make cleats to screw the deck to instead of hitting the stringer or bulks.

Did you start from the top down or did you try to cap from one side to the other from the bottom? I will start from the top and let gravity help.

I did it both ways, gravity helped but when you'd get the top out, the edges would pull and vice-versa. The best was going down 8 inches on each side, the weight kept it good enough like that.

 

[demarko210]

I did it both ways, gravity helped but when you'd get the top out, the edges would pull and vice-versa. The best was going down 8 inches on each side, the weight kept it good enough like that.

Were you using epoxy or poly? Poly should have folded nice.

 

[Pmt133]

Were you using epoxy or poly? Poly should have folded nice.

Poly. Once it started kicking a bit it'd stick. I kind of realized less was more with it. Wet out leave it for 5-10 minutes and work elsewhere then go back and final roll was ultimately the play.

 

[demarko210]

Poly. Once it started kicking a bit it'd stick. I kind of realized less was more with it. Wet out leave it for 5-10 minutes and work elsewhere then go back and final roll was ultimately the play.

As I think about it, 1708 may not be needed to cap off. CSM can cap off the stringers also. I don't think strength is needed in that area as much as just waterproofing with CSM. I will likely just coat the stringers in CSM before they go into the boat so they are sealed like I did the transom. My stringers are only 3" and 2" in height.

 

[demarko210]

Posting how the routing came out yesterday. Routed all 4 boards they came out good. Forgot I need a center line stringer but that will have and odd shape with the bulkhead cutting through it. I ran the router over it 2 time each board and only routed the side facing the sky. My gut its telling me to do top and bottom. Only took about 10 minutes.

 

[demarko210]

@kcassells this is what I was mentioned about the bulkhead. I sealed with silicone and pour in the foam for the bulkhead shape.

 

[Ptr.Torch]

Yes all except where the center console will get foam. I figure the boat was suppose to weigh 700 lbs dry I need about 10 cubic ft of foam to float 700 lbs.
The foam I mention was to use these templates to make the bulkheads 6lb foam just to get opinions on it. Encase these templates and pour in 6lb foam. The image got removed from the post. I will be using 2lb foam for the flotation.
View attachment 404565

?? If the foam is for flotation, and this is just me engineer brain at work, then it must be securely held inside the boat, such that, you could lift the boat by the deck. If not, then in an inundation event, the deck floats up and out, the boat still sinks. The foam can't lift the boat up if it is free to float up and out. Am I right about that?
So how would you attach the foam and decking so it can't float away?

 

[kcassells]

Cool, I like your idea with 4lb
Torch has a point. Dang engineers. You could brace it out somehow but at that point you may as well ply and glass then foam.

 

[demarko210]

?? If the foam is for flotation, and this is just me engineer brain at work, then it must be securely held inside the boat, such that, you could lift the boat by the deck. If not, then in an inundation event, the deck floats up and out, the boat still sinks. The foam can't lift the boat up if it is free to float up and out. Am I right about that?
So how would you attach the foam and decking so it can't float away?

The foam bonds to things as it expands/cures/hardens that makes foam adhere to surfaces. If you look at boat demolition you have to dig the foam out of the boat with a shovel to remove it and that is old foam. It does not just float out. And typically under the deck the foam is mostly at the lowest point so it would be fighting water pushing down and pushing water up. You can glass over the foam also, so I think I will close off the top of the stringer with wood and glass over. This is my idea for the stringer.

More so for me the foam will be between the stringer not inside the stringer like it originally had.
Hopefully I will not need to use the foam for that purpose

 

[Ptr.Torch]

Cool, I like your idea with 4lb
Torch has a point. Dang engineers. You could brace it out somehow but at that point you may as well ply and glass then foam.

Not necessarily. I'm figuring to foam the entire bottom (first thoughts, may change as I figure it all out) then sheet with ply and seal with (?) something.

But if the ply is full width, then boards or bracing of some kind that sits on top of the flooring, and inside the gunwales, to "push down", would form a sort of ribbing that "hold it all down and inside".

 

[demarko210]

But if the ply is full width, then boards or bracing of some kind that sits on top of the flooring, and inside the gunwales, to "push down", would form a sort of ribbing that "hold it all down and inside".

My approach is to use math to add the appropriate volume of foam. I will use L x W x H to know how much foam is in each cavity. So I will cap off section between the outer stringers with plywood (1/4 inch) that contains a certain volume and pour in the 10% more foam to ensure the cavity is sealed. I will not pour foam to fill one large section unless I know how much the volume is. Foam will be poured where I have calculated the volume and enclose the space. Even in the gunnels if i do enclose the gunnels. I will build enclosed rectangles boxes behind the gunnel to hold the foam calculated in 1 2 3 cubic foot increments.

I dont think I will have enough foam below deck to hold the boat up but hoping it will suffice. Manual for the boat says it weighs 700 lbs dry I am going to shoot for 900 lbs 1350 lbs of buoyancy as I am going to put a 4 stroke 40-70 hp.

900 boat weight * 1.5 = 1350 lbs buoyancy
1350 buoyancy / 60 lb per cubic foot = 22.5 cubic feet of foam estimated. (2lb foam)

Once I add some 1708 on the inside gunnel and I feel it is stiff enough I may not enclose the gunnels. So that will reduce the foam. if that is the case I will section off parts of the casting deck below to hold foam. Also build 2 foam boxes above the deck that will set on both sides of the bilge.

As long as I feel I have enough, I am good.

 

[todhunter]

Remember that foam expansion is a direct correlation to the air & surface temperature of the cavity you are filling. You can do all the math you want, but if it's not above the foam manufacturer's recommended temperature for maximum expansion, your yield can be much less (like 50-60% of what you are expecting to get). Ask me how I know.