occume vs. cedar strip
steve
Does anyone have experiences with using occume plywood vs. epoxy/glass
sheathed
cedar in the construction of small craft? I'm curious about durability,
maintenance, weight, total cost, difficulty, health risks from dust etc.
If I wanted to build a small design that would be suitable for either
method, which would be better and why? Specifically, I am looking at
building a small rowing craft that would be suitable for either a smooth
hull (cedar strip) or a lapstrake hull (glued
4mm plywood with little or no framing)
Any thoughts from those with actual experience with both would be
appreciated.
Thanks
Steve
Glenn Ashmore
the same thickness might be slightly more impact resistant. The weight
difference will be so slight that you wouldn't notice. Cedar strip will go
together a lot faster and look better. If you rip and mill your own strips,
cedar will be a little less expensive but if you buy strips it will be more
expensive. Laying a light glass sheath on cedar strip would be easy.
Laying it on lapstrake would be close to impossible.
steve wrote:
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
steve
lapstrake. He states that the 4mm plywood he uses will last 20 years. Also, he
does
not reccommend sheathing the topsides with anything. Rather, just paint it. Is
occume THAT durable? From your response, Glenn, I gather it is not. Certainly
with no epoxy sheathing, the plywood would be lighter than an epoxy/glass
sheathed
cedar hull (well) mabey. I'm thinking that eliminating all that epoxy and
sanding would go a long way toward building an ecomomical boat, at least as far
as labor is concerned even though the occume
must be gold plated for what it costs. I assume also that not all occume is
created
equal.
William R. Watt
of plywood. secondary advantage is plywood is sanded by the manufacturer.
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steve
eliminated.
Glenn also mentioned that the cedar boat would look better. I guess that
is subjective and I probably agree but I've seen some awfully nice looking painted
boats with a little natural (bright) finished trim.
Glenn Ashmore
boatbuilding is that it is light weight and uniform strength. It all comes from
within a 700 mile radius in Gaboon and is sold in 3 grades. Construction is the
lowest, is not certified and is not imported to the US. The boat building grades
are 6566 which has thinner face veneers and 1088 which has more plys of even
thickness. If you store it under good shelter and painted and fix all the
scratches promptly it will last but it will require much more maintenance than
cedar. If you eliminate the epoxy encapsulation, you may be asking for trouble.
With just a varnish finish, cedar strip will be far more durable.
steve
that lloyds of london warrants the stuff for marine use. From what you are saying,
its not that good.
steve
brittle and more subject to cracking.
Glenn Ashmore
firm. I didn't say it was not good for boatbuilding. It is probably the most popular
plywood for that because as I said, it is light and uniform strength. You just have to
recognize its limitations. I have used almost 40 sheets of 4, 6,12 and 18mm on my boat.
Virtually all the deck, cockpit and interior sheet goods are okoume. It is also all
covered with at least 3 coats of epoxy and all exposed areas have 6 oz of glass..
Epoxy will make it stiffer and all plywood face veneer in exposed applications is
subject to checking. A layer of 2 oz glass will prevent that without adding significant
weight.
steve
gather from what you are saying that it would be unsuitable
for my use. Coating with epoxy an/or glass would negate any cost or labor advantage. That
would make cedar strip the way to go. Wouldnt you say?
Meindert Sprang
news:3B71E265...@sover.net...
> Ive been reading Tom Hill's book on Ultralight Boatbuilding using glued
plywood
> lapstrake. He states that the 4mm plywood he uses will last 20 years.
Also, he
> does
> not reccommend sheathing the topsides with anything. Rather, just paint
it. Is
> occume THAT durable? From your response, Glenn, I gather it is not.
Certainly
> with no epoxy sheathing, the plywood would be lighter than an epoxy/glass
Steve, I think you're missing something here. As Glenn said, sheathing a
lapstrake hull with glass/epoxy is almost impossible. But you can still
cover that ply-lapstrake hull with epoxy only. That will give you that 20
years. The glass mainly reinforces the epoxy, which is not so important for
(ocume) ply. Ply has layers of veneers in 'horizontal' and 'vertical'
directions, which give ply its strength. A hull made of cedar strips has the
wood grain in only one direction, the glass adds strength in the other
direction.
Meindert
Meindert Sprang
> Is Brunzeel plywood the same thing? or is that a trade name for ocume? I
read once
> that lloyds of london warrants the stuff for marine use. From what you
are saying,
> its not that good.
>
ply. The latter is supposedly the best you can buy for marine applications,
but also most expensive.
Meindert
Meindert Sprang
> I had hoped that it was usable without coating with epoxy, and be
reasonably durable. But I
> gather from what you are saying that it would be unsuitable
> for my use. Coating with epoxy an/or glass would negate any cost or labor
advantage. That
> would make cedar strip the way to go. Wouldnt you say?
>
wood. That can be done with different stuff. If you use epoxy, you can leave
the boat in the water. If you use 2 comp. PU coating, it will be almost as
sealed as with epoxy, but you can't leave the boat in the water for more
than 72 hours, according to the manufacturer. Than aigain, read Iain
Oughtred's excellent book about lapstrake boatbuilding and discover that he
'hates' PU, discourages the use of epoxy for coating and gets really excited
about oilfinish like Deks Olje and Varnol. In another part of his book, he
describes a boat that is left in the water for 3 months, untreated! It then
gets a couple of coats with oil, while nailholes are filled with matches.
After 7 or 8 years in the water like this, they hauled the boat, stripped
the outer veneer off and slapped some paint on it, and 'she was good for
another few seasons'.
Meindert
Backyard Renegade
it. It is sitting in my backyard here in the Northeast US for almost
two years now, bare wood. With rain, snow, and sun there is no
checking, no warping, no signs of water damage anywhere even on the
unprotected edges. I could sand this boat tomorrow and paint it up, no
problem.
Okoume is Okoume, NOT! I have seen different "grades" from different
suppliers all marked BS 1088 but you can see and "feel" the difference
with different suppliers. I have found the most consistent to be
marked with a Blue and Yellow sticker that says "Joubert France" on
it.
As far as encapsulation, that is "old school". Remember, Epoxy is not
waterproof and once the water gets in (and it will) it has a hard time
getting out. After much R+D I have abandoned the idea of
"encapsulating" wood with resin and have reverted to the old ways of
painting a boat for protection. The old salts knew what they were
doing, let the boat breathe.
Scotty: So how do you glue wood to wood?
Professor: You don't glue wood to wood, you glue wood to glass...
Scotty: But what if you have to glue wood to wood, say in a butt joint
or a scarf?
Professor: Include a layer of glass with your Epoxy...Resin is for
filling Glass... Glass is for holding resin... and they should always
be used together.
And while we are talking about joinery, I saw a post here a few days
ago where an 8:1 scarf was mentioned. I imagine that it is an attempt
to justify using a 2" scarf on 8"2" (really sold in metric measure)by
1/4" (6mm) sheets of Okoume. This way you could use a 2" scarf
(8:1)and still end up with a 16' board. This is in my opinion
cheating, the accepted figure for scarfing in marine construction has
always been 12:1, see books by Payson, Gardner, Monk, etc...I know it
seems silly to have to buy extra wood for 1", so probably the best
thing to do would be to shorten the boat by 1" and use a 12:1 scarf
like you are supposed to.
Remember if you skimp on building a porch and it fails, you are
embarrassed, if you skimp on building a boat and it fails, you are
dead...
Scotty, The Backyard Renegade, flame suit on....
arbarnhart
My $.02...
I have decided to go the GLP (Hill) route because I like the look and the
method. However, I will be using Meranti instead of Okoume due to lower cost
and higher rot resistance at the cost of some added weight. I think it is
very subjective and either method can produce a long lasting boat, but cedar
would probably require less pampering (or withstand more abuse) over time.
My opinion is based more on research than experience.
"steve" <jax...@sover.net> wrote in message
news:3B71D9A4...@sover.net...
Tom Bloomer
theory this makes their plywood more rot resistant. You can get Shelman
occume from the Harbor Sales company http://www.harborsales.net - it is
probably the most expensive occume you can buy, but the product quality is
outstanding. I am not recommending occume as the way to go. In fact I
agree with Glenn - cedar looks better and is easier to work.
--
Tom Bloomer
Hartly, DE
"Glenn Ashmore" <gash...@mindspring.com> wrote in message
news:3B71DE73...@mindspring.com...
William R. Watt
problems bending the plywood to the shape of a boat you are designing okume
would be the one to consider. if you are building from plans then the designer
will already have determined what plywood is suitable.
arbarnhart
Most of the boats I am interested in for GLP are modern adaptations of older
traditional lapstrake designs which were built of 3/4" hardwood planks (or
similar). The ply is much easier to bend with either wood choice.
"William R. Watt" <ag...@FreeNet.Carleton.CA> wrote in message
news:9kum0g$a40$1...@freenet9.carleton.ca...
M. Walsh
boatbuilding. It has a real tight grain like maple, it is very hard,
finishes nicely but is fairly expensive and moderately heavy.
Meindert Sprang
5), moderate resistance against marine borers. Sipo is slightly better and
the best is honduras mahogany.
Meindert
M. Walsh <micw...@hotmail.com> wrote in message
news:mnHc7.3735$ym4.1...@iad-read.news.verio.net...
Rober Branch II
It seems like the cedar strip composite method has not been heard from so
having built in it I'll offer comments on it. I build in cedar strip
fiberglass and cedar strip kevlar composite methods. The kevlar lets some
weight savings in if you can get cloth light enough. In 2000 the lightest
you could get was 5 oz, currently you can get a number of lighter weights...
tank armor plating gets the bulk of world wide production. But unless you
are building for ultra light weight there is nothing to be gained form
kevlar except it takes compound curves wonderfully. It cannot however be
sanded and if you want to finish to a smooth surface you must overlay it
with fiberglass as a sanding veil. Hit kevlar cloth with sandpaper and you
have a texture like your living room carpet and it will stay that way. nuff
said for kevlar.
The cedar strip method itself is fairly easy. Western red cedar is best.
Check lumberyards for someone who carries it for decks. In southern Michigna
Fingerle lumber in Ann Arbor carries it to 22 foot lengths... all clear,
perfect stuff. Its very light and soft and rips easily either with table saw
or bandsaw. Table uses more as saw dust, bandsaw gets slightly less true
strips.... but its pretty tough ripping long strips to get perfect
thickness... more on this later. THE KEY either way is to build full length
infeed and outfeed tables and really have excellent feather boards set up. A
thin kerf tephlon coated carbide blade for your table saw will give best
results, stabilizer discs help keep them from wobbling but a smaller diamter
blad helps just as well. You are only ripping a one inch board in most
cases.
You'll get alot of opposing opinions as to wether to bead and cove the
strips or not. What most who have not done it miss is that when you bead and
cove, the strips lock in place as they are placed. This controls the strips
tendencey to not lie perfectly on the molds in areas of compound curves.
Also bead and cove makes it so strips of differenct thickness (from the
ripping) lie still centered so you have only 1/2 of the thickness to correct
on one surface. Depending on your tools and what you are trying to do you
may want to run the strips through a planner after ripping. If you are
building to very high finish level inside and out, especially if you are
going to finish bright with varnish, rip the strips a tad thicker than spec
and then plane them. It eliminates alot of finish work later. Its not such
an issue if you are painting (yes Ollie, there are those of us who paint
cedar strip composite boats because we want a perfect painted surface
instead of varinsh everywhere.... perish the thought!) this is not as big a
deal since you can use fillers, but it still eliminates some work... and it
can be alot that you eliminate! BTW, finishing with varnish is much less
work believe it or not, especially if you are using high gloss finishes...
the wood grain hides a plethora of nonperfect surfaces compared to high
gloss paint.
The real key to cedar strip composite not working you to death is the
glueing of the strips. Most folks use way too much and the wrong type of
glue. Use very little... just a pin head wide amount between the strips of a
Tightbond II type glue. Its not going to water proof the boat, the epoxy
glass sheathing is. Its not going to hold the boat together, the epoxy glass
sheathing is. Its going to only hold the strips together during shapping and
sanding prior to application of the glass. Glue being squeezed out must be
removed and on inside curves, well that's a pain. Epoxy is too hard.
Remember, cedar is soft stuff, go to sand epoxy against cedar and guess
which goes away first?
Glueing is again where bead and cove helps because it contains the glue and
lets you put on a smaller amount. For the best discussion on it see the
builders section of Martin Step's website www.greenval.com
Martin also gois into stapleless cedar strip construciton. Which is
certainly a wonderful method, its just slower cause you have to let the glue
dry before you add the next strip. But his devices for positioning and
controlling the bending of the strips are a wonderful adjuct to any type of
strip construction. I can recommend them highly.
If you don't want rows of double holes, why not use single holes? The air
powered brad nailers that shoot rectangular brads control cedar strips very
well, only one hole is created per strip per mold, and you can align the
holes much easier than with staples. I will never use staples again.
After the hull is done I find a sharp jack plane does a wonderful fairing
job on the strips on the outside or you will go throught the soft cedar. If
you are a traditional boatbuilder who loves those long shavings you get
planning a nice chine, you can get addicted to planning western red cedar.
Just don't make an aggressive cut or you can wind up with daylight.
Well, there's the poop. Yes you MUST use epoxy, no shortcuts unless you want
the expense of building another boat a few years down the road and I thought
the discussion involved longevity so nuff said about polyester resin.
Glass is straight forward, finish straight forward.
bob branch
steve
Any idea who sells bead and cove shaper bits?
I once hand ground a pair and they worked....almost.
I 've used both tite bond and epoxy for gluing the strips together.
I added lots of microballoons to the epoxy to get it to roughly the same
hardness as the cedar. worked ok
Originally I was asking about the relative durability of occume lapstrake method
and cedar strip/epoxy glass and wondering wether the apparent lesser durability
of epoxy uncoated occume was worth the trade off of not having to sand all that
epoxy.
I still have not gotten an answer to that. Some said you cant leave an uncoated
occume boat in the water..others said it lasts forever almost with just paint.
Guess i will have to try out a plywood boat and see for myself.