[MHml] Advice please

[Diane Selkirk]

Allied wrote:
> I think I will need to get this fore - aft profile fitted and shaped, then 
> make foam ribs at 200 mm apart? 
Probably overkill - for a 600mm extension I'd just use a single frame 
say 300mm aft of the transom and let the 300mm stick out past this.  
Maybe a 2nd frame to give you a bit more control of the shape.  Just 
screw a "keel" to the existing transom and attach the temporary 
transverse frames to that.

> Which will give me a frame, much like 
> building a hull from scratch. Then using foam with groves to allow bending 
> to cover these ribs. 
Boat building foams like Herex, Corecell and Divinylcell will all bend 
enough as straight strips - no grooves required.  Multihull hull shapes 
are pretty gentle.

> Do I make these ribs wide enough for butt joints, of 
> the outer foam, to go over them? Do I need to do one section at a time, so I 
> can glass inside as I move aft? What about areas impossible to get to? What 
> happens about the void space left behind, leave void, or fill with expanding 
> foam?
>
>   
I'll send you a picture.  You're making it too complicated I think.  
Unless your stern is very narrow you should be able to get in and glass 
the insides and do it all in one step.
> With the flat panels, it seems that best, is to make the basic shape out of 
> say 20 mm foam and butt join where necessary, putting a complete skin over 
> this first, then add a flange round the outer edge and ribs, glassing these 
> first, then gluing on and glassing again. Am I on the right track?
>
>   
Most is correct, except I'd skip the flange around the outer side - just 
leave bare and then you'll glass it to the existing hull right?  If not, 
round the edges and glass the edge over later with a separate piece of 
glass.
> For all my previous boat building and repairs, I have used a general purpose 
> epoxy, currently West Z105 resin and Z206 hardener, for gluing and filling. 
> Do I need to change this to anything else, for use on foam?
>
>   
West is pretty expensive, but it works fine for foam

Evan Gatehouse