Strip foam boat building

[michael pierzga]

Then go for it !!!

Keep up posted .

 

[svfrolic]

Buy a Kevlar canoe and maybe dress it up and you will have not only money in the bank but time on your hands to visit the water while quite possibly no additional back strain too in many cases.

Buying is not fun. What can I do, I like projects, the more naysayers the better;-)

 

[Oyster]

The pink board which is normally house insulation foam has little to no compression strength. Your glass bond to the pink board is marginal to questionable. Drop the canoe on a rock or attempt to go across uneven areas in the rivers and you will end up with a flawed hull without huge reinforcements in additional material by comparison to off the shelf canoes and internal components.

 

[Oyster]

Buying is not fun. What can I do, I like projects, the more naysayers the better;-)

Naysayers are one thing. A person can jump off of a cliff with a bed sheet hung on their backs. But the landing reduces the enjoyment and thrill of the planning. Go for it. Pink board as a stand alone material is not a functioning and seaworthy material unless you are holding onto a chunk of it offshore. Using structual fiberglass needed to skin the pink board is only as good as the substrate too, unless you use excessive amounts of the glass. Then you may as weill throw away the "mould", the pink board. Canoes need to be portable too, unless you want to struggle getting it to the water from loading it on a cartopper rack. Go for it, I have done crazier things. That material has its place in boat building. But stand alone hulls is not one.

One other thing is that take a look at all the Old Town Canoes that use thin wood as the hull form. They also have ribbands inside that are spaced narrow between them with canvas on the outside making it more resistant to abuse too. Your pink board canoe will need to have at least the same interior structure for a canoe unless you overglass the inside too, that will be usuable a year or so down the road, if you use it any at all in that year.

 

[svfrolic]

The pink board which is normally house insulation foam has little to no compression strength. Your glass bond to the pink board is marginal to questionable. Drop the canoe on a rock or attempt to go across uneven areas in the rivers and you will end up with a flawed hull without huge reinforcements in additional material by comparison to off the shelf canoes and internal components.

I know that so polystyrene foam wouldn't be my first choice. It works in surfboards though... and they are being dropped on rocks and go across uneven areas.
I think my first choice would be polyurethane foam 6 or 8 lb . Than can be bought fro Harbor Sales in block/sheet and cut to strips.
I was also thinking (optional) that I could glass both sides of the foam sheet and then cut the strips. I read about that method somewhere. Strips are glassed on both sides with glassed surface perpendicular to inner/outer skin. It supposed add rigidity to the construction.
Anyway, PU foam wold be the material of first choice not polystyrene.

 

[Oyster]

Whatever foam type you may use, when you cut strips or attempt to conform foam to a continuous changing shape and using strips to do so, you remove a lot of the structual intergrity of the foam as a mass sheet along each edge, even the most dense forms of it.

There is a material out there that is a form of a honeycomb configuation that transfers loads from one side of the structure to the other side, unlike strips of foam that gets glassed over even in a round shape.

While you can heat quality sheet foam with a heat gun and conform it to a round surface mould and is done all the time improve your main structure before you glass both sides, a canoe shape is a compound shape, which will require you to reduce the physical running distance of the foam around the entire structure on each end which removes some of the intergrity to get big sheets to conform properly.

 

[DCockey]

Reasons my friend, you must have a reason to do what ever you do. Why not is not a reason. There's no time saving, that's at vaste of time (except a good lesson )

For many people "Because I want to" is sufficient reason. Their lives are not governed by a need in every aspect for perceived logic and rationality.

 

[DCockey]

Whatever foam type you may use, when you cut strips or attempt to conform foam to a continuous changing shape and using strips to do so, you remove a lot of the structual intergrity of the foam as a mass sheet along each edge, even the most dense forms of it.

....

Unless the edges of the strips are glued together. That's standard proceedure in modern woodstrip building.

 

[Oyster]

Unless the edges of the strips are glued together. That's standard proceedure in modern woodstrip building.

Oh I know very well about strip plank construction methods. In free standing and larger hulls, fasteners are also part of the edge grain gluing too both for pulling the pieces into alignment and to hold them while the glue dries.

While they don't do a lot for face loading depending on the types of glue by comparison sometimes, in smaller structures and liteweight canoes, the scantlings are engineered as such to make a sound hull. We can see the bead and cove method on the edges too. Of course many strip plank canoes are built with edge butts because of the thin scantlings and depends on the glass on both sides to complete a matrix of sorts.

Thickened glue acts as a bonding agent for sure, but I would never consider right angle glue joints as stand alone component over any span. But you are getting back to additional work and for sure weight and costs for what, I ask in small craft? There are alternatives. This type of discussion comes up many times when people want portable dinghies. In these discussions plywood rules the day, or even solid stock wood.

If anyone can perfect canoes when it comes to weights and materials, I go no further than the Kevlar ones or if I wanted something more traditional, the industry has seen both the canvas covered ones or the incapsulated wood-glass structures when it comes to portability, or so I have witnessed anyway.

 

[svfrolic]

Whatever foam type you may use, when you cut strips or attempt to conform foam to a continuous changing shape and using strips to do so, you remove a lot of the structual intergrity of the foam as a mass sheet along each edge, even the most dense forms of it.

The strips would be glued together

[/QUOTE]There is a material out there that is a form of a honeycomb configuation that transfers loads from one side of the structure to the other side, unlike strips of foam that gets glassed over even in a round shape. [/QUOTE]
Yes, I was thinking about Nidacore but I didn't price their product yet

[/QUOTE]While you can heat quality sheet foam with a heat gun and conform it to a round surface mould and is done all the time improve your main structure before you glass both sides, a canoe shape is a compound shape, which will require you to reduce the physical running distance of the foam around the entire structure on each end which removes some of the intergrity to get big sheets to conform properly.[/QUOTE]
I have never tried that but I like the idea. It is like Farrier trimarans are build just on the smaller scale.
http://www.pwt.net.au/Feature Articles List/Build of the trimaran - KISS.pdf
It would require different mold but would be interesting to try...

 

[svfrolic]

For many people "Because I want to" is sufficient reason. Their lives are not governed by a need in every aspect for perceived logic and rationality.

I think having a hobby is perfectly logic and rational.

 

[kvsgkvng]

Pre-skinned foam strips construction

I know that so polystyrene foam wouldn't be my first choice. It works in surfboards though... <snip>
I was also thinking (optional) that I could glass both sides of the foam sheet and then cut the strips. I read about that method somewhere. Strips are glassed on both sides with glassed surface perpendicular to inner/outer skin. It supposed add rigidity to the construction.<snip>

Polystyrene foam is just fine. It is widely available, inexpensive and does provide necessary structural characteristics for a core. For, example, Dow Corning "Styrofoam Highload 40, 60 or 100" would be a well suited as a core material for the job. Grade 40 is a bit weak for larger builds; Grade 100 is a bit expensive and not readily stocked. Grade 60 however fits the bill very well and the cost is very moderate compared to three times more expensive specialty foams. It has density of 3 lb/ft³ compressive strength 60 psi, chemically inert except petrol, water impermeable and stocked in any construction supply warehouse.

Regarding cutting already glassed foam into strips -- it is an excellent structural idea! Perpendicular glass would provide good shear resistance, but only in one direction. There would be a need for second direction reinforcement or second core layer perpendicular to the first one. In this case I think diagonal planking would work well. If not, then substantial frame needed to support planks in weak direction.

I see one problem though -- pre-glassed strips would be very rigid to bend in plane of skins. This technique would work only in hulls with very gentle curves and long strips, because if stressed too much, they will buckle or crack.

My question is -- why use core at all? In my club we have canoe and kayaks made out of single or double layers of Kevlar. Nothing else! It is light, sufficiently rigid for a small craft and works fine. One does need a mold though to build such a boat...

If you are using the core as a formwork and leaving it there afterwards, then most likely it is overkill, though convenient. JMHO

 

[Oyster]

The strips would be glued together

There is a material out there that is a form of a honeycomb configuation that transfers loads from one side of the structure to the other side, unlike strips of foam that gets glassed over even in a round shape. Yes, I was thinking about Nidacore but I didn't price their product yet

While you can heat quality sheet foam with a heat gun and conform it to a round surface mould and is done all the time improve your main structure before you glass both sides, a canoe shape is a compound shape, which will require you to reduce the physical running distance of the foam around the entire structure on each end which removes some of the intergrity to get big sheets to conform properly.
I have never tried that but I like the idea. It is like Farrier trimarans are build just on the smaller scale.
http://www.pwt.net.au/Feature Articles List/Build of the trimaran - KISS.pdf
It would require different mold but would be interesting to try...

Yep, and the devil is in the details. Take a closer look at the fiberglass that they are using inside the structure, over and above the amount of work that is required for the mould to keep the shape long before the initial work begins. By all means go for it and then let us know how much you have in the final product and what the final canoe weighs.


But also he is not using longitual strips either and the shape does not change as drastic over a shorter distance either. He has fewer joints that you will end up with when using the strips to conform to the shape. I have never been a person that subscribes to standard building. But I also understand the amount of work that will be required. As folks say, hopefully a person learns from their own mistakes and will not repeat them. I won't anyway.

 

[TeddyDiver]

I just feel like I want to build something. I like projects. Is that a reason?

Sure yes.. but why even then spoil the outcome with stupid choices . Why not do a good job and start with some study and research of the subject and then do something to be proud of?
BR Teddy

 

[DCockey]

Oyster and TeddyDiver, have you looked at the links I posted above on John Lindahl's method of building A Cats using longitudinal foam strips covered with epoxy/carbon fiber? If so do you see any reasons that method could not be used for canoes, or why epoxy/glass could not be used in place of the epoxy/carbon fiber if an increase in weight was acceptable?