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Old 18-07-2017, 15:33   #31
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Re: Wharram Narai MK lV .

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Originally Posted by Cavalier MK2 View Post
Hey, make sure it is all fir and not hemfir as hemlock rots easily. The japanese like it for wood working because of the whiter color but you don't want it on a boat. For cdx fir ply the 3 lamination 1/4" /6mm size isn't a bad risk as you can fill any voids in the outer 2 laminations. Voids in ply are a trouble spot in the marine environment as they can allow moisture vapor to collect and pool starting a rot spot. Often meranti marine ply like Hydrotek and aquatek is cheaper than marine fir. For sure the grain is often better.
Honey Badger is in Australia. He should be using marine ply to the Australian Standard which is probably Hoop Pine.

Edit: he says he has got "exterior CD" which means it will probably be radiata, hoop or slash pine.
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Old 18-07-2017, 17:50   #32
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Re: Wharram Narai MK lV .

I have no idea about Australian ply, our domestic construction grade can be pretty variable but it depends on the mill. Marine is to international ratings BS1088 being the best followed by BS6566 I think it is. 6566 is still pretty decent. I've heard ply in OZ can be pricey. Cheap and cheerful beats not launching. If a guy could only get a few sheets of the good stuff the place to use them on a Wharram is actually the beam troughs which tend to stay damp and have rot issues.

It might be worthwhile to look into the Wharram beam lashing plan packages that use the Tiki style beams. Still the Classic stuff works.
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Old 19-07-2017, 17:08   #33
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Re: Wharram Narai MK lV .

Quality ply is expensive, but we're flooded with Chinese garbage just like everyone else.
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Old 19-07-2017, 20:34   #34
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Re: Wharram Narai MK lV .

I own a Narai MK IV that I refit here in Martinique. I spent 7 years to do it, and 7000€ epoxy. I made a big mod so it doesn't look like a Narai anymore.
How can we send pics here?
Trying...
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Old 20-07-2017, 10:28   #35
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Re: Wharram Narai MK lV .

Jules the lines of your boat are good. I have seen some awful mods done to these boats.
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Old 20-07-2017, 10:32   #36
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Re: Wharram Narai MK lV .

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Quality ply is expensive, but we're flooded with Chinese garbage just like everyone else.
Redreuben I have been cutting out some of the 1970's ply on the boat.The quality is streets ahead compared to today's stuff from Asia.
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Old 20-07-2017, 10:35   #37
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Re: Wharram Narai MK lV .

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Originally Posted by Cavalier MK2 View Post
I have no idea about Australian ply, our domestic construction grade can be pretty variable but it depends on the mill. Marine is to international ratings BS1088 being the best followed by BS6566 I think it is. 6566 is still pretty decent. I've heard ply in OZ can be pricey. Cheap and cheerful beats not launching. If a guy could only get a few sheets of the good stuff the place to use them on a Wharram is actually the beam troughs which tend to stay damp and have rot issues.

It might be worthwhile to look into the Wharram beam lashing plan packages that use the Tiki style beams. Still the Classic stuff works.
Cav. My mate had a look at that cheap ply.Turns out it was pretty gnarly and had heaps of staples in it.
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Old 20-07-2017, 10:43   #38
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Re: Wharram Narai MK lV .

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Honey Badger is in Australia. He should be using marine ply to the Australian Standard which is probably Hoop Pine.

Edit: he says he has got "exterior CD" which means it will probably be radiata, hoop or slash pine.
Spot on mate. When I built my first wharram I used beautiful hoop pine ply for the first hull.
Along came Julia Gillard and " building the education revolution" architects had specified hoop pine as some sort of interior cladding for the school halls. Result? Hoop went thru the roof and I built the second hull out of Asian hardwood ply often called pink ply.
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Old 20-07-2017, 10:46   #39
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Re: Wharram Narai MK lV .

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Old 20-07-2017, 14:54   #40
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Re: Wharram Narai MK lV .

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Jules the lines of your boat are good. I have seen some awful mods done to these boats.
Thanks,
You know, it's not an easy task, since you are always between 2 choices: the lines and the seaworthness of a boat, and the liveaboard matter.
Since we are living onboard 100% of the year, there is not really choice...
Narai from that period(mine was started in the early 80) at list mine, where made of good ply.
The only thing I would like to warn you is about borers.
I had 3 months ago to take the boat onshore in emergency, 150 holes at the flot line and underneath the boat. Big, huge ones! I hited a wreck that took away some paint and wood, and they entered...They love any kind of wood, even ply.
At the float line that was my fault, not enough protection and when I cleaned the hull I left, mini holes they entered through(sorry for my English)
If I would start again today, I would use glass, but that would cost, with the epoxy, a lot more.
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Old 20-07-2017, 14:59   #41
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Re: Wharram Narai MK lV .

I don't know a ton about Wharrams, but weren't they designed specifically to have wooden crossbeams for flex? Is the additional stiffness of the metal crossbeams going to cause issues? What about stress on the crossbeams themselves from the hulls flexing? Doesn't metal weaken more than wood when it's subjected to that kind of repeated stress?
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Old 20-07-2017, 15:31   #42
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Re: Wharram Narai MK lV .

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I don't know a ton about Wharrams, but weren't they designed specifically to have wooden crossbeams for flex? Is the additional stiffness of the metal crossbeams going to cause issues? What about stress on the crossbeams themselves from the hulls flexing? Doesn't metal weaken more than wood when it's subjected to that kind of repeated stress?
Hi,
Yes you are right, they are designed to be flexible. I asked J.Wharram for my mod, before. He did not want to validate since this is not his philosophy.
When I sailed my boat I found that a cat undertake huge efforts on the structure, espécialy underneath, where the waves splashes hard sometimes.
Underneath, some of the wood broke, because the flooring mooves and the wood(how do you call these sticks?) stays stiff. So they broke lenthwise...
That's always the point: if you have a hard spot, it becomes the "maillon faible"
If every thing move the same way, no problem. Moding a boat is a lot of guessing. I wanted at first to use aluminium to make the junction between hulls but I'm glad I didn't. You really have to know what you do and be conscious of the forces involved: after, while sailing, it's too late, and sometimes you might loose your boat, even worst.
Most of the time the glue won't break, but the plies of the plywood would delaminate, near the filet...it happened to me, with Indian plywood I bought here in Martinique.
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Old 20-07-2017, 16:14   #43
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Re: Wharram Narai MK lV .

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Attachment 151943Three of these 6m aluminium scaffolding planks welded together will make replacement beams.No more rot.
Don't want to be a nay-sayer, but you might want to tread carefully here. Aluminum is much less fatigue resistant than wood and could be prone to failure in this application. My guess is that JWD would not endorse it. Might want to run it by a naval architect before committing. A good timber beam would not be too expensive or difficult to put together. Best of luck.
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Old 20-07-2017, 16:30   #44
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Re: Wharram Narai MK lV .

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Originally Posted by mikereed100 View Post
Don't want to be a nay-sayer, but you might want to tread carefully here. Aluminum is much less fatigue resistant than wood and could be prone to failure in this application. My guess is that JWD would not endorse it. Might want to run it by a naval architect before committing. A good timber beam would not be too expensive or difficult to put together. Best of luck.
I agree whith that. And, also, there are different nances of aluminium, that do not react the same way.
Anyhow, it's better to have a coherent setup: wood or aluminium, but not both, at list for structural matters.
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Old 20-07-2017, 16:43   #45
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Re: Wharram Narai MK lV .

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Hi,
That's always the point: if you have a hard spot, it becomes the "maillon faible"
The weak link in english.

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