Oz Goose and Oz Racer and not buying crappy plywood

It is important to choose good building materials. We found some really cheap ply. Was it any good?

It was OK for most of the structure which was fine after 12 years. But we put our feet through the bottom.

So we got good 6mm ply for that!

The Story follows below with some useful takeaway points

Lightweight plywood construction with strength.

When we originally chose 4mm plywood for the OzRacer hull most people involved in discussions thought we were crazy as most were using plywood around 8mm and still having some structural problems with hull twist under sailing loads and excessive movement of the flat hull panels.

This is an article showing how well that workd
Article on making boats stiff and light through structural efficiency

Also our Australian tradition is based around hull weights of 8 to 10 pounds per foot of hull length. Even for the smallest of the skiff classes – the 12 footer that carries 240 sq ft in main and jib and around a 400sq ft spinnaker. We wouldn’t be stressing our humble boats anything like that. 120lbs of 4mm ply in the 1970s.

Ooops … we chose the wrong plywood for our boats

At least for the bottom

We were quite confident that the 4mm would provide enough strength. But we were a bit shocked when we saw the light shining through our bargain basement plywood (pic right – the sun is behind the boat). There was no middle veneer in some places. Red lines in the photo below.

The combination of the poor ply quality allied with its thinness resulted in Peter putting his foot through the bottom of one of the boats (he

Below is our original discussion BEFORE we ran into the problems above.

There are ALWAYS lessons for  lightness

Also see the Storer boats EPOXY and Boatbuilding FAQ for detailed information about the thinking and use behind the modern construction methods involved in the OZRacer

Regarding the thinner ply we are using in Australia – it was partly chosen because they were the cheapest true 8ft x 4ft sheets we could get locally on that day. Under $20/sheet.

Ply supply for boat building

A note for Australians – A lot of ply these days in is 2400mm x 1200mm – which is just under the imperial sheets but unsuitable for the OzRacer and Oz Goose as it would add quite a bit more labour and material wastage to get the 4ft width.

Using the thinner ply – Sides, bulkheads, decks and transom have turned out fine – quite stiff and strong enough.

With the current longitudinal bracing of the bottom it is OK (being fitted in the pic right), but making the bottom panel of 1/4″ (6mm)would have been better – but that would have doubled the price of one of the sheets.

In fact springing the extra $40 for the thicker bottom panel would have been a good idea – it would have eliminated the longitudinal runners I have just finished gluing to the bottom of the hull, for a labour saving and would only add an extra pound and a bit (0.5kg).

(and that was all written before Peter put his foot through the hull!)

Oz Goose plans