flatpanel construction

Hate to tell you ....but that doesn`t sound too "friendly" to me.....

It`s one thing to make claims , but quite another to actually back them up.
You have only done the first. I actually posted this hoping to "learn something new" I only found vague claims.
Vague claims don`t build boats ( or anything else ) !
You seem to hint at knowing what no-one else does ....but you don`t actually deliver or share anything.
Now why would that be ?

Anyway , carry on....enjoy what you know , as to the rest of us mere mortals who " can`t learn anything new " I guess will just have to get by without your "secret knowledge " and carry on the best we know how......

Thanks everyone else too , for the help.

 

ask him a simple question and he replies with all that crap, i simply asked why you think ply and epoxy is no good in australia when there are lots boats built every year with that method. if you don't like questions raven, don't post. the 94% humidity might be sending you troppo.

 

I'm told the ply they put in shipping containers lasts like all heck, it might be an option for the bit that gets knocked around. It is hardwood, I believe. Heavy as, but some hardwoods have an extremely long life under water.

 

Sounds good Mr. Efficiency , ,

I have heard of this before , trouble is ,
where do you get it , and how do you know its the actual ( right ) stuff?

Are you talking about the bottom runners only ?

 

The plate FRP is known since several decades and it's called in France Placo Plastic. I made several boats with this method when plywood was not suitable because of several reasons (the most common in Mexico is non availibility and cost of importation)

The plywood is a "better" material for boatbuilding hard chined boats than polyester FRP. It's simply physics and structural engineering. In short words plywood has a better ratio rigidity/density than FRP. In other words a plate made with 12 mm thick Meranti marine plywood (density 600 kg/m3) is stiffer ( I SAID STIFF, or rigid) than a 5 mm FRP plate (1550 kg/m3) having the same weight by square meter (about 7.8 kg/m2).
Rigidity in structural calculations of inertia varies with a cubic ratio. In plain words a 12 mm plate will have a inertia ( or rigidity) of (2.4³) 13.28 times the inertia of the 5 mm plate.

Add the fact that for a one off boat in plywood is easier to use than polyester plates. Covered with fiberglass and epoxy a meranti plywood will last if correctly mantained.

FRP plates is far more complicated and ask for more tooling; a flat molding table of the size of the longuest plate by the largest plate has to be made. The table will serve to make the 3mm plates which will be used as supporting skin for further laminations, a good female jig has to be made for supporting and adjusting the plates that will be joined by the further laminations. In fact you make a female mold that will stay in the boat and will be used also as external finition.

It's the lone way to get a boat with an acceptable strength at the chines. Full thickness FRP panels are impossible to use for several reasons: impossible to to bend without introducing inacceptable stresses in the panels and worst in the joints, impossible to glue with polyester (polyester does not glue...) and difficult joints to make. And need for a very very strong female jig as the stresses will be of several tons.

So the method, if used with Nicacore or foam to get a good ratio weight/stiffness, is very tedious and asks for a knowledge or craftmanship beyond of the ordinary amateur builder. However when well made it gives good boats. In the States where marine plywood is avalaible, the FRP plate results to be far more expensive than plywood FOR A ONE UNIT MADE BY AMATEURS.

I do not know about avalaibilty and prices of marine plywood and epoxy resin in Australia. Make your calculations. Do not forget that if you take plans designed for plywood, you'll have to re-recalculate the scantlings for the FRP sandwich to get the same weight and the same strength. It's useles to try with monolithic FRP, it's impossible on a pontoon boat because of the deck surfaces involved.

 

Wow! Thank you for that!
This sounds even more complicated and difficult than I had imagined.
I had no idea.

Is there any possibility of making smaller ( maybe 8 ft long ) modular hull units ,complete with molded deck flanges ( not unlike a series of drums ) and bolting them together ?

It would seem to me that building a female mold for that could be "doable" ?

 

Marine ply is readily available in Qld and lots of "Easy" designs have been sold that use ply as the build material - some laminate the skin ( sometimes inside and ) out with cloth & epoxy... Go and check out a couple of build projects....

DO NOT USE Polyester unless you have had previous experience with it, and can complete the entire job using only that one glue... using something like West System epoxy and tape for the joins, screw the parts together whilst the glue cures then REMOVE ALL THE SCREWS, and glue the other side and bog the holes - TOO EASY...

A record of most of my build starts here http://www.boatdesign.net/forums/boat-building/my-little-piece-peace-25962.html#post253723

 

Talk to the various ply suppliers, it may only be available in thicker material. Building the whole boat out of hardwood ply would have to be too heavy, you'd think. But it may have it's uses. Ordinary ply with epoxy/dynel should avoid the rough and tumble of use that exposes it to water penetration.

 

Hi Masalai

Actually our Hoop pine ply is better than most others , anywhere in the world. Very high standards and quality.Prices to match , but that`s ok.

Would never consider using polyester over plywood , never.

There are problems here with imported plywood .
Apparently there is "price dumping " going on , the place is apparently flooded with inferior rubbish plywood at the moment .
Buyer beware !

 

Speed, cost, strength, Weight! there is absolutely no comparison to ply. Full stop.
Try putting an axe through a 14mm sheet of any ply be it cheap or top marine. 'It'll bounce off' and hit u in ur swede!
Whereas FRP, GRP, Glass will almost go through, glass/foam/glass composite it will go through.

Another suggestion is to build in strip cedar gluing with Resorcinol - a dark brown glue that has gap filling properties, then, Kevlar laminate One 'layer' - (engineered weight) the inside and glass the outside all with epoxy.

As an apprentice boat builder some 100 yrs ago, repaired many boats with all sorts of damage.

I am currently building my own hull, using epoxy glass/ply/glass for it's weight properties mainly and secondly there's heaps of rocks out our way so will laminate Kevlar inside the hull.

 

Mmmmmm, Have you tried with the following process.

1, thin the un-waxed resin and saturate the timber/ply.
2, when set proceed as you would using epoxy.
3, use peel ply when laminating to make life easier (no itches sanding glass)

Really the same as if using epoxy.
You will be surprised just how good this is!
The epoxy system is superior, having typed that, I have 'peeled' epoxy'ed glass off boats before, think probably as the structure was not saturated before laminating later.

 

I've owned a couple of medium sized plywood boats here in Australia, one built new with epoxies and sheathed in the same. One a one design racing yacht. Both lived on a mooring.
The yacht when I first bought it had bare ply exposed in many areas below the water line and absolutely no lasting damage at all.
Proper marine plywood is a very rugged, forgiving material that is dead easy to build with, readily available and cheap. I'd own another
plywood boat without question, sheathed or not.

 

I agree Typhoon, anyone contemplating building ply, use top quality stuff, that does not mean you need to pay through the nose for it either, get quotes, or like I did, tell them you're now looking at importing the 'stuff' as it's cheaper!

Look for gaps in the ply's, overlaps compressed in the ply's, if it is cheap because they got scammed and these dud sheets were 'hidden' in the container, then go through the stack looking for the good ones. (it happens - Indonesian ply has these 'qualities')

I often get the sheets that have defects near edges, divide this area 'out' of the sheet to get a good price.
Barter everything!

 

Single layer glass left as flat panels does not provide the needed stiffness. Simply add layers and weight/cost go up faster than stiffness.

Add a core and add an inner layer and effort / cost go up. Glass on both sides of plywood is the traditional "core" that works pretty good in terms of good initial results at a reasonable cost. It is subject to problems if water gets through either skin.

Fiberglass that is initially laid out flat, but then lifted while soft and shaped into a curve is different. Simple curvature can be designed to add a lot of stiffness quick and easy. This is why the pre-made fiberglass panels for greenhouses are "wavy" and not flat.

 

Is that stuff still around ? I was told it was inclined to lose its properties after a good few years, but that is just hearsay.