Gaps or no gaps between the seams?

[beekeeper]

O.K. I may have my answer. found this:
http://wiki.answers.com/Q/What_is_weight_per_square_foot_of_Plywood

1/4"=25lbs. 24sq.ft.1/4"of bottom = 18.75
3/8"=37.5lbs. 24sq. ft.of3/8' bottom=28lbs. = 28.125lbs.

1/4" bottom covered in epoxy and glass offers a 5% savings of 1.40lbs. total over a 3/8" epoxy saturated one.

Hope the math is correct. Jump in guys.

beekeeper

 

[seedtick]

bee,
that was the point i was trying to make over in the pirogue section - yours and Matt's hard data just confirmed it -to me anyway

why go thru all the aggravation and cost of glass, epoxy, application and sanding when building with thicker plywood (that doesn't require all that aggravation) doesn't result in a sunstantially heavier boat

now that we know the weight difference - does anyone know the strength difference - short beam shear, flex modulus, tensile strength or whatever - between 1/4" encapsulated vs. 3/8" epoxy saturated. If I remember correctly - here's goes my memory thing again - strength of wood goes up by the cube of the the thickness so 3/8 is something like 3.4 times stronger than 1/4. But i don't have any information on additional stregth due to epoxy

 

[JEM]

why go thru all the aggravation and cost of glass, epoxy, application and sanding when building with thicker plywood (that doesn't require all that aggravation) doesn't result in a sunstantially heavier boat

Not trying to split hairs but let's not loose site of a couple things:

-The bottom board still needs to be attached to the hull. The weight of the additional material needed to attach the bottom board to the hull must be added to the 4-5% increase estimate. I can't say how much that would be without knowing how long the seams are.

-The time required for either is going to end up being close to the same when all is said in done.

-The wood would be better protected with fiberglass on both sides.

-The cost will likely be more for using fiberglass cloth on both sides but that's a guess. Wouldn't be hard to figure a quote.

-Since I've worked with fiberglass cloth before, to me, it would be more aggravating to use the fiberglass tape to attach to the hull. You have to feather out the edges and make a smooth transition to the hull without it looking like a bulged out lump. Just covering the hull exterior in one shot with fiberglass cloth yields a much cleaner result that is easier to finish off. BUT THAT'S JUST MY PERSONAL PREFERENCE.

now that we know the weight difference - does anyone know the strength difference - short beam shear, flex modulus, tensile strength or whatever - between 1/4" encapsulated vs. 3/8" epoxy saturated. If I remember correctly - here's goes my memory thing again - strength of wood goes up by the cube of the the thickness so 3/8 is something like 3.4 times stronger than 1/4. But i don't have any information on additional stregth due to epoxy

Hard to say without having the specific bottom panel dimensions. Easiest way is to stick with what the original designer recommends. The strength debate would lead us right back into "how strong is strong enough?"

But again, either which way will work. It will only be wrong if

1) the hull fails

-or-

2) you don't enjoy the build process and using the boat when you are done.

 

[oldsparkey]

2. Or you don't enjoy the build process and using the boat when you are done.

I am not sure about anyone else but Me , Myself and I enjoy the building process as much as using the boat when it is done. In fact I have been accused of enjoying the build more then the paddling. :roll:
It is fun watching some pieces/sticks of wood and floppy cloth come together and make something that is useful , fun and offers a lot of enjoyment.

Chuck.

 

[JEM]

why go thru all the aggravation and cost of glass, epoxy, application and sanding when building with thicker plywood (that doesn't require all that aggravation) doesn't result in a sunstantially heavier boat

meant to ask earlier: what would an equivalent strength cyprus sinker board for his bottom run? I'm not familiar with cyprus properties so I'd just be guessing at the needed thickness. 1/2"? 5/8"?





/

 

[gbinga]

2. Or you don't enjoy the build process and using the boat when you are done.

I am not sure about anyone else but Me , Myself and I enjoy the building process as much as using the boat when it is done. In fact I have been accused of enjoying the build more then the paddling. :roll:
It is fun watching some pieces/sticks of wood and floppy cloth come together and make something that is useful , fun and offers a lot of enjoyment.

Chuck.

CORRECT

That's why we each get to do it our own way. That's what is fun about it, and also part of what keeps the forum interesting.

One other thing I'd like to mention. Doing a pirogue or a punt or a dory with interior chines is one thing. Doing a kayak or canoe would be quite another. Trying to do a multi-chine boat (something with more than just a flat bottom and two sides) with interior chines instead of fillets - - well, I hate to say "impossible", but I certainly wouldn't try it.

GBinGA

 

[beekeeper]

JEM
Thought I indicated 3/4"x3/4" chines would be used to attach the sides. If the 4%-5% savings you calculated did not include this I misunderstood. Two 12' short leaf pine chines would add 7lbs. calculated useing;http://www.woodweb.com/cgi-bin/calculators/calc.pl?calculator=weight_bd_ft
I estimate total savings for my 10' boat would have been 1.4lbs.( 5% for bottom) plus 7lbs.( chins est.) = 8.4 lbs. total. Seems any other factors about the weight differences would be splitting hairs. Don't know about you, but I can't afford to loose any more hair> :wink:
When I make my decision it will be based on this and the other factors discussed ( method of build, intended use, cost, type of boat, etc.). That's when I will have to split hairs. Every builder has to decide what's best (for them).

beekeeper

 

[seedtick]

Matt, here's some information on the comparative mechanical properties of different wood........

http://www.fpl.fs.fed.us/documnts/fplgt ... 3/ch04.pdf

their values for cypress is likely new growth cypress instead of sinker - i personally find the new growth cypress to be a little more brittle and not as strong as the first growth cypress. I attribute that to the closer ring growth of the old stuff.

Don't know what the mechanical properties of the $10/ sheet luan stuff is, so it's tough to make an apples and apples comparison. Obviously a good void free plywood with multiple layers with different grain orientation is going to be stronger than a single layer board of the same thickness. I'm not trying to throw cypress planks in here as a replacement for plywood, Lord knows that if most folks posting here choke on the thought of having to buy marine plywood, they would die when confronted with the cost of cypress.

Friend Keith and I build with cypress the way the original designers did 5/8" to 3/4" thickness. The oldest plank pirogue that we've seen was something like 120 years old, it was 3/4". I reckon lasting 120 years makes 3/4" overkill by some standards The problem with getting thinner than 5/8" is that it gets increasingly harder to nail the bottom on the side as the sides get thinner, you start using lighter gauge nails so it doesn't split out and the thinner nails are more flexible, and the whole process snowballs into more trouble than using thicker side boards.

 

[Kayak Jack]

... You said you wold butcher the good stuff. So I suggested to go by the white pine type boards or shelving boards which normally comes in 1 1/2" widths and practice

OK, now I gotcha, thanks.

I'll probably never make a boat out of boards. Plywood does way too well for me, thanks.

 

[JEM]

Matt, here's some information on the comparative mechanical properties of different wood........

http://www.fpl.fs.fed.us/documnts/fplgt ... 3/ch04.pdf

their values for cypress is likely new growth cypress instead of sinker -

I've seen similar charts. I was curious if there was any hard data on the "sinker" variety.

 

[JEM]

they would die when confronted with the cost of cypress.

Well now I'm really curious. What does it run?

 

[seedtick]

never seen any hard data on sinker cypress, don't reckon there's enough of it around nor enough interest around to justify the testing

market prices for air dried sinker around here goes from $5 to $7+ per board ft, depending on quality and size

clear, wide (24+"), and long (20+ft) command the highest prices

growback or new growth cypress is less than $2 bd/ft

 

[bearridge]

So....a Beowulf table top, 36" wide, 9' long 'n 3" thick would run what? A trillion? Sorry. I hate that word. So.....half a trillion? If ya dont put a heap a "shine" on it? [grin]

 

[seedtick]

it's 13 feet long, but a silver tongued barrister like you can probably haggle the price down a bit

 

[JEM]

So....a Beowulf table top, 36" wide, 9' long 'n 3" thick would run what? A trillion? Sorry. I hate that word. So.....half a trillion? If ya dont put a heap a "shine" on it? [grin]

If it's price per board foot, that's about $405 - $567 for a piece of that size if I'm figuring right.

That is expensive but that's a pretty thick piece.

 

[bearridge]

Legs on a good Beowulf table gotta be 6"x6". I reckon ya caint really call a 9' table a Beowulf table. That iz a Mini-Beowulf table. Mebbe a reloadin' bench fer geezers who dont have many local pals ta drop by in the evenin' ta consume fermented 'er distilled grains 'er cactus, tell tall tales, eat meat jest cooked on the grill, plan expedishuns, yada, yada? Mite even have some targets set up close by so it kin be a shootin' bench too? [Elvis used ta shoot off hiz patio at Graceland.]

Even if a fella haz the room, e-visits dont count. Ya caint put e-feet up on one. Mebbe I wuz jest born too late.......without a castle? [smile]

regards
bearridge
still dreamin' after all these years

You can train a cat to do anything it wants to do.  Solomon Short

 

[tx river rat]

I am going to get this back on the gap or no gap,I see one advantage of the spacers ,with a filet you can round the outside corner without getting into the grain of the ply much easier. It is way harder to do if it is a flush fit .
If you are going to paint it or put graphite over it I dont think it really matters much.
I coined a phrase on another forum ( Location sensitive) I feel like this is one of the most important things on building a boat and the choices you make in construction techniques and material choices.
I have built 10 boats so I am not an expert ,but I am pretty knowledgeable about what it takes to survive in my world of paddling.
Weight I want under 50 lbs,carry up down to many steep places.
Got to be tough,I drag my boats,run rocky rivers, and not to gently I might add,the formula thats seems to work for me is laun 3/16 thick 4mm full glass and cloth inside and out, after running the race a few weeks ago I was amazed at how the boat took the punishment I dished out. It doesnt need to be built any heavier
I make the inside heavier than outside because of the stresses applied and the fact that several of the folks that go with me will be on the plus side of 300 lbs.
Seedticks boats are awesome looking and tough I am sure ,but thats where the location sensitive deal comes in ,they wouldnt go where I go,now my boats might not perform in his area.
All small paddle craft are a comprimise and do some jobs better than others,personaly I think sitting down really listing what you want a boat to do and what kind of conditions it will be used in is the most important phase of the building a new boat that will be satisfactory to the builder.
Ron

 

[beekeeper]

tx river rat
Thanks for putting this thread back on subject. I apologize if my questions hijacked it. Every one's input was helpfull to me. Any other questions or ideas I have along these lines will be put in a new post. For me this one is" what it is is what it is".

beekeeper