Construction methods for O-1

[Willallison]

Thanks for the link Brian.
Having read through the (very informative) Duflex brochure, it would seem like the logical choice for O-1, or if the boat is to be designed with a number of different materials choices, then this (or something similar) should be one of them.
Construction is simple and not so dramatically different from plywood construction that it would scare off the amateur builder. It is light, strong and judging by the variety of different boats built with it, very versatile.
The only thing I couldn't find any reference to was the construction of radiused corners - say a nicely rounded joint between the cabin top and sides, for instance. I'd also like to hear from a few people who have used it, as to what's involved in the fairing and finishing off process.

[b_rodwell]

If you use 100% flat panel the boat looks awful. If you introduce (let me call them) cornices it can look very good and you need to look quite hard to determine that it is flat panel.

The solutions that I have seen to date, utilise strip planking for the cornices. This is fairly labour intensive. I saw one build where the strip planks were placed on the main male mould, glassed on the outside, taken off, glassed on the inside, returned to the mould and taped.

My proposal is to select, say, 3 standard cornice radii for the design and use them for all the flat panel transitions. The cornices are made in advance from Corecell.

Cut the Corecell into the appropriate strips
The cornice moulds (you will need male and female)
are made from PVC pipe cut longditudinally
Place the strip in the moulds with a weight to give pressure
and heat in an old fashioned boat building steam box
When complete glass the inside of the cornice

Not a huge amount of trouble to dramatically improve the appearance of the craft.




____________
Brian

[tom28571]

Brian,

I know what a cornice is in a house but have never heard the term used in boat nomenclature. Can't be the same thing so what is it?

[b_rodwell]

I am not familiar with what it would be called in boat building. In house building it is used to describe a concave fairing between (usually) a wall and a ceiling. In this house application there is no removal of the wall or ceiling material.

I use the term in boat building to describe a convex fairing between two surfaces. The shape is a longditudinal section of a cylinder. Two obvious areas of application in a composite boat are the hull to deck joint and the cabin sides to cabin roof joint. In these cases there is removal of the material of the surfaces being faired. In fact I would probably sequence the building by putting the cornice in first and then fitting the panels to the cornice edge.

Let me know if there is better boat building term for what I am talking about.



___________
Brian

[duluthboats]

I can't find a price list for this Duflex. But I suspect it is on the high end. Brian have you seen anything that compares cost with other materials.
Gary

[b_rodwell]

I expect Duflex would come out at the top end of the price per square metre compared to non-exotic alternatives that have been discussed. I don't know of cheaper materials that have the same properties. There is always the option, however, of making up your own panels and then cutting the shapes. This would be cheaper but you would loose these advantages:

factory formed panels
(presumably at optimum pressure and temperature)
(should be lighter or stronger than own built panels)

shapes pre cut

the panels with 'Z' joints so that when joined you get accurate
boat length shapes

If you price your own labour at zero you would probably consider alternatives. I don't consider my own labour at commercial rates but I do put a price on it. Another way of looking at is you can get your boat afloat sooner.


Another consideration is the weight. Duflex flat panel construction is an easy way for an amateur builder to get a very light hull and this leads to a lighter boat. Perhaps the engine and trailer can be slightly lighter. A lighter hull has a compound effect on the total weight and cost.


One other point that has been mentioned in this forum is the possibility of having alternative methods of construction for the project. I think this could work sometimes but needs to be approached with caution. In general, I see the hull shaped partly dictated by the method of construction. I would propose a (at least slightly) different design for the different materials that have been mentioned to date. The designers task is to prepare a proposal that makes the best use of the proposed method of construction. A general purpose design could involve significant compromises for each of the possible construction approaches. I would design for one approach and then evaluate whether other construction approaches would work. If so it would be bonus.








___________________

Brian

[Willallison]

If we can make the decision that we adopt flat panel construction - ie incorporate developable surfaces - then the hull shape need not vary according to construction material. You could build in aluminium, foam core or plywood without compromising the design as far as external hull shape is concerned.
It would be in the support structure that differences would occur. Foam core for instance, would have a thicker skin than aluminium, so its support structure would require different offsets - and maybe a different structural layout altogether. That just means more work for the designer.
But it also gives O-1 extraordinary flexibilty. A potential owner could choose building materials according to intended use, personal preference, his or her building expertise - or that of the local boat builder, and of course budget.
I think the possible gains of this approach far outweigh any negatives.

[Nomad]

I vote for Core Cell, with vinelester res. and Trevira after the skin coat...............Sorry am I getting to far ahead?