Printable View
I see a lot of puddle duck racers being built out of cheaper plywood. I have the oz racer mk2 plans and they say to use the more expensive stuff, but this is a trial run for me just so I can get out and sail. At the local lowes and home depot the wood seems really flexible and not really suited to boat building. I just don't understand how people can make usable boats with the stuff I have seen. Any help on using cheaper wood to build my oz racer?
Howdy Westky - and welcome!Quote:
Originally Posted by WestKy
You question is the most excellent one people can ask. Why build a boat out of cheap or why of more expensive materials.
First I will answer for most of the Western world except for North America (then I will get on to your situation). For most of us there is so little difference in cost between really poor plywood and the start of the good stuff that it is worth going for the good stuff almost any time. Also the cost is relatively high so it starts to be worthwhile to protect the investment by using epoxy for coating so the boat will be low maintenance.
For example in Australia
Poor quality Plywood $50
Good Quality Plywood $85 and up.
So the difference for an OzRacer is total $75 or a Goat Island Skiff maybe 150 to 220 extra. In Europe the difference is even less.
Now if we consider the USA or Malaysia or the Philippines (maybe South America) where cheap plywood can be quite good and the premium plywoods the same price as Australia it starts to be a more difficult choice.
Cheap Plywood good enough to build a boat $20 to $30 - USA and Canada
Cheap Plywood good enough to build a boat $10 to $25 - Philippines
Good Quality plywood $85 and up.
You can see it is worth looking at cheaper plywood in some countries for boatbuilding.
The way to select ply is that the faces should be smooth without any knots ideally, but sometimes a few small knots are OK but they shouldn't be at all loose.
You look at the edges of the ply in the shop and you see that in their stock there are very few or no gaps in the veneers in the middle of the ply - "voids".
Meranti can be cheap and a nice board
Douglas Fir is terrible plywood for boatbuilding - it gets lots of little cracks after a short time.
Exterior ply is the same glue as Marine. Marine is a guarantee that there are not so many voids in the inner layers. But if you look at the exterior ply edges as above and see not many or any voids then it is as good as Marine grade ply.
Then there is a second question about "flexibility".
The standard boatbuilding thickness of plywood for racing boats in Australia is 3/32" or 5/64" (5 or 4mm). I make my boats much more durable and trouble free by making the bottom of 1/4" or 6mm. If you can get a 1/4" (6mm) plywood for the bottom that is made of 5 layers of veneer that is totally ideal. But three layers is OK if it passes the tests above.
This is a boat built of 5/64" plywood. They last for a decade or more of hard racing if glued with epoxy.
http://yachtyakka.co.nz/wp/wp-conten...07/cherub1.jpg
It seems flexible and flimsy - with our first Oz Racers - five years ago now (?) we used really poor grade 4mm plywood all round but found that the bottom was too brittle - and we found the ply had voids too - the sun would shine through it :)
So I took the bottoms off and replaced them with 6mm (1/4") and not a single problem.
The PDRs, bless their cotton socks are not experienced builders or designers so they go through cycles of saying that 1/4" is OK to saying that you need 3/8" to get around certain problems - twist and "oilcanning" (a flexible bottom).
But it is just not having a standard method they can trust. Those of us who know racing sailboats know that the lighter plywoods have been successful for tens of thousands on tens of thousands of boats - so we think "if the structure is reliable of the lighter materials then why go heavier". It is only more expensive and makes the boat more heavy (bad for handling in and out of the water).
It is about structures - like closed off buoyancy tanks, continous decks and bulkheading in high load areas that make the structure stiff. Not the material. the sides of the OzRacer can be 5/64" (4mm) and are floppy before the framing goes on but incorporate it in a properly designed structure and it becomes completely rigid.
If possible I strongly recommend using epoxy for the gluing even if you decide not to coat. Those who have built several boats have found that epoxy is pretty much the same cost as the cheaper glues by the time that quantities are added up. If you use another glue then PL Premium seems the most reliable. But I would still recommend epoxy for the structure that supports the mast and glues the centrecase and leeboard case to the bottom of the hull and the deck. I've had a few (not many but a few) let go where alternative glues were used.
Also the idea of a boat as a trial run - two points.
A boat made from my plans will be a very good boat. Everything is done properly. Your first boat will be a good boat, built properly and lightly with nice finishing details. It is because the plans guide you through best practice. If you build a boat from the plan you will find that even experienced boatbuilders will be interested because of the detailing and the way it is put together. There is nothing complex there - it is just well thought through with clear aim of producing something nice.
If you are more interested in getting out and sailing rather than doing anything competitive then the OzRacer RV might suit you better. Did you look at it? If you want to swap over it is simpler and faster building than the Mk2. I would send you a plan if you want to go that way.
MIK
Every word above is true. If I have a problem it is almost always because I did not read the plan carefully enough. Build a good boat and enjoy it.
I have built or raced 17 different PDRacers, and have built a MkII and built the prototype OzRV. This is what I have learned;Quote:
Originally Posted by WestKy
If creating a 'home designed' PDRacer, and just trying to flesh out some ideas, use whatever plywood you can get your hands on as long as it isn't Superply, Ultraply or luaun. This stuff will break your heart. It will rot out, delaminate and be too flexible for the bottom. You can spot it by the three plys, the outer ones are paper thin, and the inner is a thick, water sucking core most likely balsa.
If you are doing a trial run, build the Oz RV. It is easier to build, and more user friendly if you are sailing with children or a spouse (more room), or if you are *ahem* a bit larger. (wider cockpit)
How long do you plan to own this boat? In real time, you will spend at least a month or two building a MKII, and a couple or three weeks building an RV. I think either the longer you plan on keeping it, or the longer it takes to build, the better materials should go into it. I still regret not using better wood in my MKII, and as a result, after the third season I stamped out the bottom of the cockpit, and ripped out the mast step right off the plywood which destroyed the deck. (I sail really hard, and I am a big guy at 6'1" and 210lbs.)
My OzRV I built out of 1/4" fir plywood for the bottom and the airtank sides, and built the sides out of 1/8" 2.7mm mahogany doorskin. I am in my fourth season with this boat, and have had no issues as of yet. I actually won the 2010 PDRacer World Championships with it, as well as all the Canadian Championships so far. It gets used 50-75 days a year, usually practicing upwind...Very sturdy little craft.
Good luck with your build, I'm sure you will enjoy it.
Rick Landreville
Rosedale B.C. Canada
Hi WestKy, welcome!
I wasn't surprised by MIK's reply which was quite comprehensive for what on the surface seemed a simple question. It was really, really good advice. The structure is indeed what makes the boat stiff, not the materials. Epoxy is the best thing since sliced bread, so go that route as it will also save you heaps of time. With epoxy, you also don't need the high clamping pressures that other glues require, so you only need cheap clamps. I definitely wouldn't stuff around with any of the other glues, so don't be tempted by the blurbs on their labels.
The other tip that MIK gave was to to keep it light. Don't go the overkill route. Your boat won't be any stronger, just heavier, so harder to handle out of the water and slower. For example, on my Goat Island Skiff I made extensive use of of a timber called Paulownia. It is super light, but I trusted MIK's structure. It is still a very strong boat and by now well proven.
Rest assured, your first "trial run" with a Storer plan boat will be a boat you will be proud of.
I'll add when looking for suitable plywood, check the veneer thicknesses on each layer. If they are about the same, it'll be a reliable piece. If the outer veneers are paper thin, try another source. This is true of all low veneer count sheets, as you only have a single layer of cross grain "tie in", so the outer layers bear most of the loading. These outer layers need to be of similar thickness as the inner layers for this reason. Lastly, some Laun underlayment has been seen in the big box stores, with equal veneer layers. This stuff has a WBP glue and can be suitable, but select the stock carefully, as mentioned above.
You guys are awesome, thanks for the information. The RV might be easier, but I don't want to spend another 20 dollars for the plans. I also like going faster that's why I got the mk2 plans. Eventually I may build your Goat Island Skiff as it looks like a fun build as well. I'll think about getting the RV plans, otherwise I'm just gonna stick it out with the mk2. The RV would be better if I took another person or try and teach my niece how to sail as well... Blah! How would we go about swaping plans?
Who said anything about 20 dollars! :)Quote:
Originally Posted by WestKy
If you use one plan only I will send you the RV plan for nothing.
Best wishes
Michael
I am just putting the finishing touches on my RV build after a very leisurely (& therapeutic) build. When I was reading the thread I was thinking about how great the question and answers were. Before my build, I had the pleasure of visiting Rick and looking at his RV. I was amazed how well it was put together and how nice it looked even after some very heavy use he has logged. I decided to go the same path with the 1/4 fir on the bottom + internal faces of the tank + stern and 1/8 in door skin on the external tanks and deck tops. One thing that I will throw in as advice is to hold up the ply to the sun and look for voids. I was stunned when I realized my bow had 2 big gaps in the wood when I was prepping it for priming. Needless to say, I've decided to throw a layer of glass on the bow.
Hehe,with my old scow Moth out in the sun it's quite well lit when you peek through the hatches. The deck is 1mm 3ply, no glass :)
Sent from my iPhone using Tapatalk
Glad you are enjoying the build, Steve. "Therapeutic" is a good outcome ;)Quote:
Originally Posted by stevecanaga
With our first Oz Mk1 PDRacers (morphed into the non affiliated OzRacer Mk2) we found the same thing - there was a slight mismatch between the butt joins of the interior veneer. With the West sun hitting the boat bottom from the outside it looked quite like a red laser beam lighting up the inside of the hull - a sharp red line.
For the first minute or so I was looking West at the neighbours looking for someone playing a trick on me! Repairs4
MIK