Michael Storer Boat Design 

FAQ - Fixing up old and antique plywood racing sailing dinghies for fun or serious racing - International Cadet, Sabre, Sharpie, Cherub, Heron, Snipe, Lightning, Windmill, Fireball, TS16

Home Page - Plans, dozens of articles on building setup and sailing



Links
Boat plans sail paddle row motor fishing storerboatplans.com oz goose simple to build boat fast family boat club racer opengoose.com sailmaker inexpensive and nicely finished. Lug Gaff through to mylar sails canoe sails a specialty reallysimplesails.com



Contacting me

FAQ on Boat Building

BOAT PLANS LIST

A super simple and a classic plywood canoe how to choose ... storerboatplans.com

Goat Island Skiff, simplicity performance and stunning ... storerboatplans.com

Taal Plywood Stand Up Paddleboard SUP ... storerboatplans.com

Oz Goose simple to build, excellent performance, family or sailing club ... storerboatplans.com

Quick Canoe Electric Trolling Motor boat. Light roofrack super easy build ... storerboatplans.com

Beth sailing canoe. Quick build classic canoe with modern performance ... storerboatplans.com

Dayboat launch 23 or 27ft simple build plywood ... storerboatplans.com

Handy Punt simple to build plywood fishing boat roofrack ... storerboatplans.com

Free Paddle and Oar Plans

Free plans for Canoe and Kayak Paddles and Rowboat oars and sweeps
On the Oz Woodwork Forum one of the members picked up a rundown International Cadet to fix up for his son.

This would apply to many similar racing boats.

Also have a good look at my FAQ if you are looking for actual methods.

General Epoxy Methods - saving time and materials
Originally Posted by meerkat

We've picked up a cadet Mk2 to fix up for our son to compete (and be competitive in) next season. The hull is in good nick but the deck needs replacing.

What is the best way to proceed ?

eg take the deck off as whole pieces to use as templates for the replacements etc.

the foredeck is in 2 pieces should we do the same or make it one piece (if we can get a sheet big enough) etc.

I'll be getting some piccies to show the progress shortly.

Thanks
Andrew

Howdy Andrew,

First thing is to have a look at the class rules to find out what you can get away with.

http://www.cadetclass.org/documents/

For a competitive boat you should use premium materials - gaboon plywood for the decks

Any framing to be replaced should be Western Red cedar - or the cheaper and lighter Kirri/Paulownia.

Glue and sealing the panels before fitting to the boat - epoxy. With coating make sure it is rolled out thin so it doesn't add too much weight - three thinly applied coats - but don't thin the epoxy - see my FAQ.

Also see my boatbuilding FAQ for info on wet-on-wet epoxy coating to save some labour and use of cordless screwdrivers for holding everything together while the glue sets up.

Am in a rush now - but will put more info up later.

oh, yes - deck sheets are best of one piece as far as possible - but can be scarfed or have butt blocks under (we had to repair a sheet on the Puddle Duck Racer thread - scarfs are 6 times ply thickness, butt straps are 20 times ply thickness.
   
Originally Posted by meerkat
hi Mik

I read through your FAQs (might I say quite interesting and well put together) and I have a few questions.

Rather than using 2 pt polyurethane you recommened using epoxy with a poly topping (1) is this right ? The coats of epoxy are as thin as you can get them.

So i'm thinking....
the deck has 2-3 coats of epoxy with a coat of poly

inside has the 2-3 coats of poly (unless the epoxy is good there too). The problem with the inside is that there is some drips of epoxy that has been left there from a previous attempt to repair the deck as well as some black lines going across the boat and up the sides(why I dont know). so I'm not sure how that will come out.

The hull will be painted.

Oh yeah, after removing the lid there are a lot of holes left by screws, copper nails and yes even steel nails that have rusted & expanded and left holes like what screws do !

Whats the best to fill these with and will that affect the nails going back in ?

thanks
Andrew

Hi Andrew,

You probably don't need to put any nails back in. See the FAQs I gave the links to previously about
Cordless drill and,
Eliminating fastenings.

As far as gluing you just need to hold things together while the epoxy sets up - no need for permanent nails or screws.

As far as drips etc on the inside remove them by sanding - random orbit sander is good here - about 100 grit paper - be VERY careful not to cut away at the plywood veneers!!!

Look at Class Rules to help you decide if the boat is a keeper or a short term proposition

Before committing yourself to lots of epoxy coating it may be worthwhile reading the rules about what is a and what isn't counted in the hullweight and then weighing the boat in that condition.

Also read whether lead (metal) correction weights are allowable and checking whether there are any fitted - remove them before weighing.

The decision tree goes a little like this.

If the boat is much more than 5kg over - it is a short term boat - it will be pretty well impossible to get it down to the minimum. Clean it up just as much as you need to get it on the water. Your son will race it for a year or so and then will start to have enough experience to make a better boat go well. Don't spend too much money on this type of boat.

If the boat is only a kilo or two over it is a good boat if it is ready to go in good sailing condition. Just patch up to keep going, you can't afford to add much weight in epoxy (or anything else) so just two very thin coats. Bote Cote have a product called TPRDA that thins epoxy out without destroying its capacity to protect the timber - use it to the max allowed - roll the epoxy out well spread. Adding thinners to epoxy is not cool for boat use.

If the boat is under weight by a kilo or more - you're in luck. Provided the hull is stiff and fair (the chines and panels have nice geometric shapes - nice even curves, no hollows and bumps) this is the sort of competitive boat that is worth fixing up and giving the full epoxy treatment to.

So weigh it and see what you've got.

The relationship between epoxy varnish and paint and where to do each

2 pot polyurethane is only really for finishing the decks off - it gives a very strong surface with a good appearance, you would need 3 coats minimum. As an alternative you can use a good spar varnish as an alternative or paint the decks with a marine enamel.

YOu wouldn't use any of the above inside the bouyancy tanks as their purpose is to give a good appearance..

If the boat is two or more kilos overweight an alternative for inside is to use Everdure - a couple of coats. It is nowhere near as effective in keeping water out of the wood (see this) as using epoxy, but it doesn't weigh as much.

Epoxy coating is good from a wood and weight preservation perspective, but it will add a couple of kilos to the hull weight - even if you are careful.

If the boat is going to end up being pretty competitive with that added weight (ie no more than a kilo over minimum) then epoxy is a worthwhile investment - depending on how much labour is involved. Or just add the epoxy as you do work on the boat.

How much to spend, how much work to do on an older boat
The most common pitfall is that someone in your position gets all excited about fixing the boat up. They lose track of the fact that the boat is probably pretty close to sailable now. I would suggest doing the minimum you can get away with until you find out how commited your son is.

Another thing is not to overcapitalise an old boat unless it can be competitive - ie close to minimum weight, fair and stiff. Don't add new sails, new masts to an old clunker. Maybe pick up some second hand sails from some of hte top sailors in the class if the ones you have are shot. Replace other things as necessary. Then see how enthusiastic your son is after the first season.

A cheaper and a better way to get a fast boat is to buy a good second hand racing boat that is doing well in its fleet than to completely re-outfit an older boat with new sails, mast, rigging and fittings.

So weigh the boat and inspect it so you know whether it is a goodie.

If it is a bit heavy or out of shape - just do the minimum to keep it going - after the season sell it for what your bought it for and get a current competitive boat.

Big performance jump without spending much money - foils

One labour intensive but very effective way to lift performance is to make some highly accurate and smooth foils - rudder and centreboard. They can then be moved onto a new boat when the time comes.

Shape is important so you have to use templates - contact me on
storerm@ozemail.com.au
if you are after templates and an instruction sheet.

More on weight targets and restoration methodology - how much epoxy coating?
Andrew's hull ended up weighing around 7 lbs LESS than the class minimum

You have done very well with selecting the hull! It sounds like a keeper!

Epoxy is the go and will give it a good racing life without adding much weight over time.

Best Plywood choice for lightweight - Gaboon (okoume, gabon, occume)
Fit Gaboon ply decks in the thinnest allowed by the rules.

The join in the decks (along the centreline) is in the right place for most economical ply and the foredeck mid stringer is wide enough for both to land on.

Replacing fibreglass tape on chines
If you are removing the paint you'll probably have to replace the glass tape on the chines too. See the puddle duck racer thread for where the bottom was coated and the glass tape whacked down at the same time. All happens in one process - wet on wet. Glass tape 50mm wide. Don't round the chines too much - existing amount will be OK - but you want the last 3ft of the chines and transom corners dead sharp for clean water release - best to have a round there for the fibreglass tape to go on and then bog it out to a sharp edge with epoxy/filler powder mix.

Sounds like the hull is a good basis for improvements of sails and rig later on - but the first season with the existing ones.

Where to put the fittings on the boat.
There are probably some Cadet tuning guides on the net that may have things that you can do at this stage and also things like fittings placements on deck. You may need to work out where fittings will end up and glue the smallest possible pieces of 9mm ply (gaboon as well) under the decks to screw the fittings down to where you can't use bolts (all bolts should be Nylock heads - it costs a bit more but adds hugely to the realiability of the boat.

Any screws or bolts should be dipped in epoxy to prevent water getting into the hull and it also increases the grip of the fastening manyfold (to remove an epoxied fastening you just heat it with a soldering iron for a couple of minutes).

How much epoxy (12 ft boat)
I would expect that you would use probably a little over 3 litres - so a 6 litre pack would make the most sense - or buy a 3 litre pack and be ready to buy a bit more as you need to.

You will need a kilo approximately of a powder modifier to add to the epoxy to thicken it into a gap filling glue.

Also some TPRDA diluent for where you use the epoxy for coating the ply - it will help spread it out thinly. Don't use the TPRDA in the epoxy where you are gluing or glassing.

I have also added a page to my site about what I did to get a geriatric Sabre in some sort of racing condition.
See here

If the class rules give minimums and maximums sizes for different parts

By the way - it might be worthwhile seeing if the class rules or class plans specify the minimum and maximum sizes of any of the solid timber parts. Use the minumum for everything except the width that the gunwales go out from the side of the boat.

The gunwale should be maximum to increase righting moment. In fact - it should be at the maximum from the shrouds to the back of the cockpit (where the crew will be - and minumum everywhere else to save weight.

Dealing with stained plywood
The Cadet had some stained timberwork - from water getting into the structure.  My mate Biting midge had a crack at a solution
Quote:
Originally Posted by bitingmidge
Other than sanding, I'm a great fan of cabinet scrapers, which is a flash word for a bit of tin(steel really) which has been "sharpened".

Hold with two hands and get all the stuff off in a pass or two.

If you need more info get back and I'll try to find a few web references.

Cheers,

P

Ah midge - I disagree - this doesn't happen often - so we can enjoy the novelty of it!!!

Plywood is made up of such thin veneers that the staining will go through the full thickness of the surface veneer. Scraping will make little or no difference. If it was a solid teak drawer fascia - I would be with Midge - but for ply - nah.

You can sometimes get a bit out with some oxalic acid solution. Don't make it too strong and rinse the area well - but it won't disappear. Oxalic is an acid so if you make it too strong it will weaken the wood fibres.

The only way to get it to disappear is to replace the panel :-)

So Meerkat - have a bit of a play but you have to know in your water that it won't disappear.

She is an old boat - and she will be a FAST old boat - but you can't make her new again without replacing more of her.

I need to tell you about boatbuilder's eye too. We all get used to eyeballing our projects from a distance of 6 inches. We know every nook and cranny, every mistake and defect. BUT NO ONE ELSE WILL EVER SEE THEM. They will be so impressed at the end result that they will never look over the whole surface from 6 inches away. You have to do a few projects before you realise just how oversensitive we all get to each one.

Let's just say she has a lovely patina for an old boat.

Getting the timber bits to look neat and fair - gunwales
There was discussion about whether a plane, a router, powerplane of belt sander would be best.

Midge pointed out that he'd seen me use a belt sander for a similar job.

WELL, I was going to say ...

The plane is the best choice for removing bumps in gunwales and other bits of trim.

I was only using the belt sander because I have a pretty good feel for the use of it - I can keep it pretty flat or even follow a bevel. And also the PDRs that Midge was watching me work on are boats to not be too precious about.

Still like 'em to look luvverly - but there is no timber trim to get on dead flat after the cleaning up with no changes in the glue joint width through crappy handling of the belt sander (which I CAN do on the right day as well!).

For goodness sake Midge - I'm not some sort of hand tool expert! :-)

My method is do a bit, stop and review - one thing I have learned over the years is when to stop!!!! Perhaps that is the difference between the amateur and the professional.

I tend to use the biggest fastest most monster tool available, but stop to change to slower, more accurate tools at (usually) the right time.

The router would be a slightly risky choice if there are any subtle changes in bevel or irregularities in the deck or glue drips down the face of the timber the ply is being finished flush to. With the Cadet the angle will vary the whole length a little bit.

But then I'm not a hand tool expert!!!!

By the way spend a bit of time getting the edges of the boat fair - get your eyes low and look along each of the edges you have created. If you see any bumps in the curve set a handplane to cut very fine and hassle the bit away - sight frequently.

When the gunwales go on the outside there are a couple of tricks.

Make the bits big only where they have to be and small elsewhere

The class rules will have a minimum and maximum size - they should be the minimum depth the whole length but width should be Max in line with the cockpit but minimum in line with the end decks. Check whether the rules require the gunwale to be a "fair continuous curve" in which case the transition between wide and narrow needs also to be smooth. If they don't say anything - you can have a stepped thickness - which will show the opposition just how serious you are!!!

Just about everything else should be pushed toward the minimum as far as possible.

MIK
(bottom of his woodwork class at high school)
__________________
Boats, Boats, Boats...
my boat pages



View My Stats