Col

Is it possible to insert brass tubes through to the mast steps? These would be sticking out say 2 mm above the deck; when satisfied with their placement and the rake of the mast, drop a bit of CA on it to keep it in place.

Sand the section of mast that is the length of the brass tube allowing the mast to slide inside the brass tube easily.

The brass tubes will allow you to insert your masts without stressing that joint on the plastic.

@ColRay
Don’t give up, Colin.
Admittedly, an RC (radio-controlled) model comes with more challenges, so you could always fall back on static display models instead.
But if you stick with it, you’ll achieve excellent results with functional, navigable models as well.
It would be a real shame to quit now, especially after you’ve gained so much expertise in 3D printing.
And remember, in any case, you can always opt for a hybrid build, incorporating traditional modeling techniques wherever necessary.

@ColRay
Hey you were going down an experimental road. Yes, some people have 3d printed sailboats, but don’t loose your dream. It’s only a set back. Find the right filament to take the stresses .

Thanks for your comments

Fishercat It's a new learning curve Col

That's tough - PETG isn't stronger than PLA - it just doesn't creep as much under pressure and won't sag in direct sunlight.

The issue you have is likely weak layer bonding - which, sadly, is normal. 3D prints are notorious for being extremely brittle and easy to break between layers. You can increase the bonding a little by printing with as high a nozzle temp as you can without having it affect your prints - but it won't make a huge difference.

It's really important to orient your parts so the stress is along the layers and not between them. A 45 degree angle also works well. Also, giving yourself plenty of meat in any 3D printed part that is going to be stressed is a good idea. The stuff gets quite strong - even along the layer lines - if there's enough of it.

Also, you have to pay attention to the number of walls you have, and your infill. The slicer will normally produce a print that is OK only for light usage unless you increase the number of walls, or even print it solid. Note that increased wall thickness backed up by moderate infill is stronger than thinner walls and more infill.

I don't know what those specific parts were or how much stress they were under, but swelling wood can generate a LOT of force, so you might also want to build some room into your parts. Personally, if I'm doing something functional that has to take strain, I want at least 2-3mm of wall thickness (depending on how much strain) or even solid.