Casting a tender

[EASLOOP]

I have been offered the use of a two part mould for laying up a 10' fibreglass tender/rowing boat. Are there any books/articles/papers etc that are trusted on how to cast such a boat? or does anyone have the knowledge that could be passed on to me?

Any info gratefully received.

 

[Perry]

http://www.gibbs111.fsnet.co.uk/grp.htm

Years ago we had a training session at Strand Glassfibre, not sure if they still do that but somewhere to start.

 

[EASLOOP]

Great intro. Thanks very much.

 

[William_H]

Although it is described as a 2 part mold it is most likely just a F/g female mold. You polish the mold with wax. Paint on a gel coat of resin with pigment then lay on layers of fibreglass in the form of chop strand mat or woven rovings with a layer of light fibreglass cloth on the last layer (inside) of the dinghy. My guess is the second part is a mold for seat or bow decking or floatation tanks. When the layup is hard you pop it out. Not always easy.

So what are the traps? You must design the strength of the finished boat by deciding how much fibreglass to put in different areas. ie Large flat bottom areas might need a piece of foam to make a rib which is glassed over to make the floor/bottom stiffer. Corner areas may need extra glass.
Usually with a dinghy the gunwhale needs to be stiffened often with wood or there is a roll over of fibreglass to help dinghy keep its shape.

The problem is that like me you probably want a light weight dinghy. Fibreglass is generally heavier than a comparable plywood or aluminium dinghy. You might find it worthwhile to price carbon fibre to use in lieu of glass for the composite. This is much stiffer but will still need areas of foam to provide more thickness hence stiffness.

So what I am saying is that the design of the internal structure of the dinghy is critical.(materials and thickness) Try to find a completed dinghy from this or similar mold and work out why every piece of structure is there. (and how thick it is)

Lastly when laying up the fibreglass it is easy to be a bit slack with working the resin into the glass. This results in tiny air bubles and can leave you with a leaking boat. Use a roller and work it until the glass is fully saturated then work it some more. But be carefull too much resin makes a heavy boat. It can be a lot of fun and very usefull experience for F/g work but try a small project first and really if you just want a dinghy buy a second hand old f/g dinghy. good luck olewill PS there must be books on the subject.

 

[snowleopard]

These people do mail order materials and have a lot of useful info in their free catalogue and information sheets.