Working out a decent laminate for a rudder

[Zoro]

I will admit, I am itching to try resin infusion. I'm not setup for it... yet. It looks like a very clean way to get a great laminate.

 

[Zoro]

A couple of points to ponder; 4 plies of cloth will give you an implement you can fell trees with,its a bit heavy for a sheathing layer on a structurally adequate core.Second,given the curved leading edge,it won't be possible to wrap the plies as they will need darts cut to conform to the shape.Wrestling with slippery,resin coated cloth and manouvering the sticky whole over to work on the other side is no fun.Something so critical to the operation of the boat isn't an ideal candidate for a learning exercise in infusing but it might ultimately be a good choice of method.

Before reaching that stage I might suggest using biscuits to align the strips when gluing the blank together.Also keep in mind that adding half a dozen or so sash cramps may impose enough of a load to lock in a downward set if the support isn't carefully arranged.

I don't think that the Palowina alone is structurally adequate.

I've done quite a bit of laminating over the years, so I have a good idea of the joys that I am in for here. By no means professional, but I've built boats in the past. It has been a while, maybe I've got the Rose coloured glasses on, but I'm sure it will all come flooding bad once the resin is mixed...

Yes, I realise that the curved surfaces present a problem. I was considering using tape or maybe even chop strand down those edges first. I'd have to recess it, obviously. Still thinking that out.

As for resin infusion, I do want to learn the process first hand. I've watch untolded hours of other people doing it in various projects, but I've never had the need. I suppose this is a small project that will not break the bank if it all goes horribly wrong. I could be talked into it.

 

[Zoro]

finger sketch, 4 layer laminate, relieve core for overlapping section all the way around the end, stagger each layer 20mm min, one corner drawn, build 4, build upside down against drawing, set part on jig to allow wrap. If the laminate misbehaves doing it by hand, plastic wrap over peelply or laminate and wrap with masking tape and secure plastic to ‘bottom’, with 8 layers of glass on the end, you may decide 3x db1200 is enough and then the ends are still 6 …

wrapping the section will be a nightmare, as the glass will distort too much


View attachment 198329

OK. Thanks.

 

[fallguy]

Show us a 3 view drawing of the rudder, please, unless you did and I forgot, it is late here..

 

[Zoro]

There is no drawing of the rudder.

50-year-old one design class and the designer isn't with us anymore.

I might get around to drawing one in CAD in the future, but my CAD skills are not top draw, so that will be a project in itself.

 

[fallguy]

Just do a 3 view pencil sketch

 

[Zoro]

This is basically it... 50mm (2") thick...

 

[fallguy]

I would make the narrow or thin edge from G10 and laminate to it. I might also make the area where fasteners go from same, but I don’t know the fastenings details.

36x2” at 0.25” thick is $29/pc

It adds weight, but you can grind the thin edge without fear of blowing thru the laminate.

You just make a relief in your core on a tablesaw and bond it into epoxy putty, then you can sand the core down or however you want to make it work..this is basically like the laminate you showed crossways, but only needed on the thin edge. G10 is heavier, but nice to laminate to and the rudder won’t flex on the thin end under load.

https://www.professionalplastics.com/G10FR4SHEET

 

[wet feet]

The idea of an inset strip of G10 is sound,but given the curved shape of the trailing edge,the actual cutting of a groove will be less easy than a simple pass over a saw.A slotting cutter in router might be a way round this and clearly the G10 will need to be crescent shaped.Since the whole thing will be glass sheathed it only really needs to be a very thin strip as the sheathing will bolster it.You could use the same technique to insert ordinary biscuits to align the strips when gluing the assembly together and thus reduce the loss of material to skimming the blank flat.

 

[Tops]

Here is a simpler drawing. I would be more inclined to add extra layers of cloth and resin at key locations, sanding the wood back if needed, than to attempt slotting and letting in heavy G10 at the trailing edge.

 

[wet feet]

I don't know what prior experience you may have in making rudders so I may be assuming too little experience compared to reality.My choice of method would be to scarph a short piece of hard wood to the exposed ends of the underwater sections of the paulownia strips,as illustrated below (if the file appears).
The only way I would consider adding a groove for a tough insert strip would be with a router cutter of this style as the greater surface area of the face would give the router some stability.

 

[wet feet]

I had a bit of free time and wanted to see if I could create a CAD model of the rudder in question.It's a bit rough and ready but shows the useful features'You may need some suitable software to open it-most 3D software should cope with step format or if you don't have it,download Freecad which costs exactly what you might hope from the name.

 

[Zoro]

Hey guys, thanks for the efforts. I'm sailing for the next couple of days, season open down here, I will be back soon.

 

[Tops]

Hey guys, thanks for the efforts. I'm sailing for the next couple of days, season open down here, I will be back soon.

Enjoy your time on the water!

I had a bit of free time and wanted to see if I could create a CAD model of the rudder in question. It's a bit rough and ready but shows the useful features. You may need some suitable software to open it-most 3D software should cope with step format or if you don't have it, download Freecad which costs exactly what you might hope from the name.

Nice work on the rudder, I really like the transition between cheek and foil and the foil tip.

 

[Zoro]

I had a bit of free time and wanted to see if I could create a CAD model of the rudder in question.It's a bit rough and ready but shows the useful features'You may need some suitable software to open it-most 3D software should cope with step format or if you don't have it,download Freecad which costs exactly what you might hope from the name.

FreeCAD is my weapon of choice, what can I say... I'm cheap.

I should have time tomorrow.

Thanks.