composite construction, strip canoe plans

Composite skins get their strength from a combination of the skin and
the core. The distance between the skins provides some of the strength.
Laying up in kevlar only will give you plenty of impact resistance but
I'm not sure you'll get enough stiffness. A very good explaination is at
<a style='text-decoration: underline;' href="http://www.oneoceankayaks.com/Sandcore.htm." target="_blank">http://www.oneoceankayaks.com/Sandcore.htm.</a>

I've often also wondered if what you described could work though.

For your offsets, why bother with that small of a change? You're talking
about 3/16" difference. But I can understand if you want to be precise.
Especially if you're looking to sell these later on. You could assemble
a small piece of skin with lamination you propose and simply measure it.

--
Matt Langenfeld
JEM Watercraft
<a style='text-decoration: underline;' href="http://jem.e-boat.net/" target="_blank">http://jem.e-boat.net/</a>

sebastian wrote:
 > thanks to the folks who provided feedback on my lofting question.
 >
 > Im going to build the ranger {15'} instead of the prospector (16')
 > canoe, and im going to construct it with a kevlar-carbon layup instead
 > of wood strip. Can anyone suggest the best way for me to adjust the
 > size of the stations to accomodate the thin, uniform thickness of the
 > composite layup compared to the wood. I'm going to use 3 layers of
 > 5oz kevlar and one or two layers of unidirectional carbon so im
 > guessing it will be about 1/8"-3/16" thick max. how thick is the wood
 > stripping and is it relatively uniform in thickness ie can i just add
 > 1/2" to all my patterns and have a decent work around?
 >
 > also i would like to not use foam core in my layup for simplicity and
 > minimizing weight...but will the canoe sink like a rock if its swamped
 > if its just kevlar/carbon/epoxy? I am wondering if i should use a
 > 1/8" atc core cell between layers of kevlar...for buoyancy and
 > stiffness.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: composite construction, strip canoe plans 

whoops. Meant to say flexural strength not stiffness.

Matt Langenfeld wrote:
 > Composite skins get their strength from a combination of the skin and
 > the core. The distance between the skins provides some of the strength.
 > Laying up in kevlar only will give you plenty of impact resistance but
 > I'm not sure you'll get enough stiffness. A very good explaination is at
<font color=purple> > <a style='text-decoration: underline;' href="http://www.oneoceankayaks.com/Sandcore.htm.</font" target="_blank">http://www.oneoceankayaks.com/Sandcore.htm.</font</a>>
 >
 > I've often also wondered if what you described could work though.
 >
 > For your offsets, why bother with that small of a change? You're talking
 > about 3/16" difference. But I can understand if you want to be precise.
 > Especially if you're looking to sell these later on. You could assemble
 > a small piece of skin with lamination you propose and simply measure it.
 >

--
Matt Langenfeld
JEM Watercraft
<a style='text-decoration: underline;' href="http://jem.e-boat.net/" target="_blank">http://jem.e-boat.net/</a><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: composite construction, strip canoe plans 

To build a canoe in 1/8" Core-Cell sandwich, I don't think it's be practical
to build it as a strip boat, where the order of constructions is:
- plank over station molds with strips, edge-glued
- fair the strips
- apply out glass (or ??) skin, set in epoxy
- remove from station molds
- fair inside
- glass (or ??) inside

For a thin foam core boat with this approach, I think you'd need to use
station molds spaced less than 6" apart. Without that, the strips would be
wayward and would lack the stiffness to stand up to the fairing step. This
becomes a MASSIVE lofting job.

Instead, the way that commercial foam-core boats are built involves a full
female mold in which the boats are built from the outside skin inward. Some
builders might be infusing these days. THis takes an investment in tooling
which is not practical for a one-off boat.


sebastian wrote:

 > thanks to the folks who provided feedback on my lofting question.
 >
 > Im going to build the ranger {15'} instead of the prospector (16')
 > canoe, and im going to construct it with a kevlar-carbon layup instead
 > of wood strip. Can anyone suggest the best way for me to adjust the
 > size of the stations to accomodate the thin, uniform thickness of the
 > composite layup compared to the wood. I'm going to use 3 layers of
 > 5oz kevlar and one or two layers of unidirectional carbon so im
 > guessing it will be about 1/8"-3/16" thick max. how thick is the wood
 > stripping and is it relatively uniform in thickness ie can i just add
 > 1/2" to all my patterns and have a decent work around?
 >
 > also i would like to not use foam core in my layup for simplicity and
 > minimizing weight...but will the canoe sink like a rock if its swamped
 > if its just kevlar/carbon/epoxy? I am wondering if i should use a
 > 1/8" atc core cell between layers of kevlar...for buoyancy and
 > stiffness.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: composite construction, strip canoe plans 

kevlar canoes are not stiff. they have lots of bulky foam core ribs on the
inside so the boat will keep it shape. the ribs are a bother when trying to
kneel and paddle. most "kevlar" canoes are a combination of materials with
kevlar in the places where its most beneficial

I've seen a book in which a one-off female mould was made by laying strips
of cheap foam over station moulds and fairing with some kind of putty. Then
the resin and glass were laid up in the nomral way.

--
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 >> Stay informed about: composite construction, strip canoe plans 

I'm not clear how you plan to support the kevlar during the layup.
Usually such boats are made using a vacuum bagging technique in a female
mold...way too much work for one canoe. But I have seen descriptions of
building a kevlar canoe where the kevlar and resin is layed up over a
male mold that is built from strips fastened to section molds. See the
book "Building Your Kevlar Canoe by James Moran". I think that this will
work ok if you don't mind a canoe that isn't quite perfect on the
outside of the hull. Personally, I think wood strip consruction, though
it also has its drawbacks, produces a very beautiful boat. Unless you
are really looking for something really light weight, wood strip seems
like the best method. But you may have different ideas.
I believe that the materials cost of building a kevlar canoe would
exceed that of a wood strip canoe but the resale value would be less.
That may or may not be a factor for you but keep in mind that once you
build one, you will want to build another.
And to answer your question about wood thickness, most canoes like you
are talking about use 1/4 inch thick strips but I have built boats using
3/16 inch strips to try to save weight.

sebastian wrote:
 > thanks to the folks who provided feedback on my lofting question.
 >
 > Im going to build the ranger {15'} instead of the prospector (16')
 > canoe, and im going to construct it with a kevlar-carbon layup instead
 > of wood strip. Can anyone suggest the best way for me to adjust the
 > size of the stations to accomodate the thin, uniform thickness of the
 > composite layup compared to the wood. I'm going to use 3 layers of
 > 5oz kevlar and one or two layers of unidirectional carbon so im
 > guessing it will be about 1/8"-3/16" thick max. how thick is the wood
 > stripping and is it relatively uniform in thickness ie can i just add
 > 1/2" to all my patterns and have a decent work around?
 >
 > also i would like to not use foam core in my layup for simplicity and
 > minimizing weight...but will the canoe sink like a rock if its swamped
 > if its just kevlar/carbon/epoxy? I am wondering if i should use a
 > 1/8" atc core cell between layers of kevlar...for buoyancy and
 > stiffness.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: composite construction, strip canoe plans 

 >sebastian wrote:
  >> thanks to the folks who provided feedback on my lofting question.
  >>
  >> Im going to build the ranger {15'} instead of the prospector (16')
  >> canoe, and im going to construct it with a kevlar-carbon layup instead
  >> of wood strip. Can anyone suggest the best way for me to adjust the
  >> size of the stations to accomodate the thin, uniform thickness of the
  >> composite layup compared to the wood. I'm going to use 3 layers of
  >> 5oz kevlar and one or two layers of unidirectional carbon so im
  >> guessing it will be about 1/8"-3/16" thick max. how thick is the wood
  >> stripping and is it relatively uniform in thickness ie can i just add
  >> 1/2" to all my patterns and have a decent work around?
  >>
  >> also i would like to not use foam core in my layup for simplicity and
  >> minimizing weight...but will the canoe sink like a rock if its swamped
  >> if its just kevlar/carbon/epoxy? I am wondering if i should use a
  >> 1/8" atc core cell between layers of kevlar...for buoyancy and
  >> stiffness.
 >
You won't be able to achieve a fair hull just using the stations
described in canoecraft. The kevlar will just lay flat between the
stations instead of springing out slightly like the wood does. If you
look at a factory built canoe you'll notice the ends are closed in
thats to create an air pocket to give bouyancy.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: composite construction, strip canoe plans 

sebastian wrote:

 > also i would like to not use foam core in my layup for simplicity and
 > minimizing weight...but will the canoe sink like a rock if its swamped
 > if its just kevlar/carbon/epoxy? I am wondering if i should use a
 > 1/8" atc core cell between layers of kevlar...for buoyancy and
 > stiffness.

It won't necessarily sink, but it will float so low in the water that
you won't be able to paddle it. A foam core will not provide enough
buoyancy to make a difference. Either create sealed compartments (with
access hatches) or use float bags to provide the buoyancy you need.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: composite construction, strip canoe plans 

ah again helpful comments (except from the self proclaimed ass :0))

i thought i had procured a really good deal on 40 yards of kevlar but
the guy flaked out on me so im going to have to poke around ebay until
i can find a nice roll of the stuff cheap ...it can be had for <$5
yard if you shop around. if any of you have a roll of kevlar youre
looking to liquidate let me know...

ive been doing a lot of practicing making small layups with various
thicknesses of 5oz kevlar49. One thing that ive noticed is that a
single layer of epoxied kevlar is quite flexible but still very tough
so i was going to make a bunch of 1'x4' kevlar sheets by pressing the
epoxy impregnated kevlar between two boards covered with polyethylene
sheeting to keep the kevlar from sticking (maybe park my truck on the
boards to really squish out the extra epoxy). then ill use these
semi-rigid kevlar sheets to cover the the canoecraft mold stations.
the comment about the spacing being too far may be valid but with
sheer and keel cords on the sections i might be able to fudge it.
with that first layer of kevlar sheeting in place (held together with
5min epoxy) then i was going to layup more kevlar cloth on top of the
semi rigid sheets (with slow cure laminating epoxy) so that i can have
3 or 4 layers of kevlar total. Since kevlar is fuzzy miserable stuff
as a external surface, and not that stiff, ive got many pounds of 12k
high modulus carbon fiber roving and i was going to lay up one or two
layers on the outside all running the lnegth of the the canoe for
stiffness and also carbon is nicer/easier to patch than kevlar and its
god almighty light which is what im shooting for i really want my 15'
canoe to be no more that 30lbs. so the end product canoe will be 4
layers of kelvar with 2 layers of carbon fiber. i figure with a nice
stiff gunwhale maybe out of carbon fiber tubing (which i found an easy
way to make by winding roving onto metal mandrel) and some support
beams it might not fold up on me.

and the suggestion of making air chambers (sealed
hatches...brilliant)in the bow and stern is the way to go foam core is
going to be way too much hastle and ill have rigity from the carbon
fiber...

thanks folks...maybe ill post a pic or two if i make some headway on
the project...ive got the sections all plotted out with very clear
help from stevej...i just need to find a batten


rian Nystrom <brian.nystrom DeleteThis @att.net> wrote in message news:<grWec.26956$i74.536472@bgtnsc04-news.ops.worldnet.att.net>...
 > sebastian wrote:
 >
  > > also i would like to not use foam core in my layup for simplicity and
  > > minimizing weight...but will the canoe sink like a rock if its swamped
  > > if its just kevlar/carbon/epoxy? I am wondering if i should use a
  > > 1/8" atc core cell between layers of kevlar...for buoyancy and
  > > stiffness.
 >
 > It won't necessarily sink, but it will float so low in the water that
 > you won't be able to paddle it. A foam core will not provide enough
 > buoyancy to make a difference. Either create sealed compartments (with
 > access hatches) or use float bags to provide the buoyancy you need.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: composite construction, strip canoe plans 

sebastian (psr_94117@yahoo.com) writes:

 > so i was going to make a bunch of 1'x4' kevlar sheets by pressing the
 > epoxy impregnated kevlar between two boards covered with polyethylene
 > sheeting to keep the kevlar from sticking (maybe park my truck on the
 > boards to really squish out the extra epoxy). then ill use these
 > semi-rigid kevlar sheets to cover the the canoecraft mold stations.
 > the comment about the spacing being too far may be valid but with
 > sheer and keel cords on the sections i might be able to fudge it.
 > with that first layer of kevlar sheeting in place (held together with
 > 5min epoxy) then i was going to layup more kevlar cloth on top of the
 > semi rigid sheets (with slow cure laminating epoxy) so that i can have
 > 3 or 4 layers of kevlar total. Since kevlar is fuzzy miserable stuff
 > as a external surface, and not that stiff, ive got many pounds of 12k
 > high modulus carbon fiber roving and i was going to lay up one or two
 > layers on the outside all running the lnegth of the the canoe for
 > stiffness and also carbon is nicer/easier to patch than kevlar and its
 > god almighty light which is what im shooting for i really want my 15'
 > canoe to be no more that 30lbs. so the end product canoe will be 4
 > layers of kelvar with 2 layers of carbon fiber. i figure with a nice
 > stiff gunwhale maybe out of carbon fiber tubing (which i found an easy
 > way to make by winding roving onto metal mandrel) and some support
 > beams it might not fold up on me.

sounds like a good plan. if the boat is flexible when you try it on the
water you can always bend in and glue down some ribs to stiffen it.

boats have been made out of flat fibreglass panels laid up beforehand. I'd
buy a roll of vapour barrier plastic sheet as it is cheap and stiff. I've
tried plastic garbage bags on small jobs but they wrinkle and leave a
rough surface. I'd also staple the plastic sheet to the surface of the
form to keep if from moving. Vapour barrier plastic should also be stiff
enough not to distort if you want to squegee the resin on the cloth before
covering the layup and weighing it down. Weight should be as good a vacuum
bagging in this situation.

however I'd be inclined to use long narrow layups. a pair of sheers should
be able to cut the thin panels into narrower strips.
--
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 >> Stay informed about: composite construction, strip canoe plans