Construction of Two Portuguese Style Dinghies (Small Boats)

This project covers the construction of two rowboats that are primarily constructed with three sheets of plywood. The design is not mine. I used a design by Hannu Vartiala, a very generous boat enthusiast who has graciously provided boat plans free of charge on his website.

This project can be found at:
http://koti.kapsi.fi/hvartial/dinghy1/simboii.htm

This is a step-by-step documentation and explanation of the project found on that site. I've tried to simplify some of Hannu's steps for laymen like myself. You will need to refer to that page as you read this Instructable. I won't repeat Hannu's instructions step by step since this is really his design. I'll just explain how I did it, what problems I ran in to and how I got around them.

If the link to Hannu's website ever changes (I discovered that it had) please Google Hannu Vartiala and his new website should come up.

This project tool me about 3 days for the first boat and 2 days for the second.

I will also include tips for oar construction, which Hannu did not cover in his project.

I purchased 1/4" exterior plywood in 4x8 foot sheets.

With the first sheet of plywood you can cut out two side pieces and two transoms (the back end of the boat). Measure carefully and you'll be fine. Refer to Hannu's diagrams for dimensions. The first boat I made was the larger of the two.
I used a skill saw and sawhorses to cut the sides and transoms out of the wood.
Since I was already cutting, I used the last two pieces of plywood to cut the sides for the second, smaller boat sides. I kept the larger remains of both sheets of ply to cut the bottom of the boat from.

To save yourself some time in the long run, I suggest you order your oarlocks now. By the time they reach you the boat may be ready.
I found a decent deal at www.shipstore.com, specifically this item:
http://www.shipstore.com/SS/HTML/ATT/ATT91463.html

This turned out to be the only real hardware I couldn't make myself.

Cut a piece of 1" by 1" wood (I used 1" or 3/4" trim I found a Home Depot...in the TRIM section) to run from the bottom of the side piece to the top.
Align the front edges to the piece of trim. I used 1" drywall screws to screw from the outside of the sides in to the trim piece.
I had also set the side pieces propped up on my sawhorses.
The side pieces are almost at a 90 degree angle from one another. Align them as well as you can as this is one of the most important joints you will make.

Cut three pieces of wood to be used for "ribs" that will help you shape the boat.
I cut scrap 2X4s I had in half lengthwise.
The short rib for the front of the boat is 34", the center rib is 46" and the back rib is 43". Hannu suggests angling the cuts to help fit them in to the boat. I did not do this on the fist boat, but tried it on the second. If you know how to cut angles, give it a try. Might make things easier.

I set the two sides on the ground for ease.
For this first boat, I was alone when trying to bend the sides. Bad idea. Get someone to help you out. In this case I used these straps I had. I looped them over the sides so that as I tightened them the ends of the boat would come together.

Also note that in the second boat, below, I soaked the sides in water for a while before doing this step. I highly reccommend doing that. Hannu also has ideas for how to bend wood using a heat gun.

Now you're prepped. The next step is adding the ribs and bending the plywood.

This is the most difficult step.
Mark the locations on the sides of the boat where you will be screwing in the ribs. The first rib, E, will be 30" from the bow. The second, F, will be 56" from the bow. the third rib, G, will be 80" from the bow. (See Hannu's diagrams)
Mark the locations on both sides of the boat.
I screwed all of the ribs to one side of the boat. To get them started. Use long, strong screws. I think I used 2 1/2" wood or drywall screws.

*Note: At this point I want to note a tip that may help you in the long run. I did this on the second boat. Screw in more wood where the transom will end up. I.e., rip a 2X4 in half and attach it verticall to the back ends of both sides. This will end up giving you something to screw the transom to once you get to that point. Otherwise, I have no idea how one is supposed to screw the transom to the sides of the boat.

Now. Carefully bend the side in. Start some screws on the exterior of the boat, and as you tighten in the sides, screw in rib E. Repeat for ribs F and G. They get progressively more difficult to bend in.

After you get the last rib in place, you put the transom on the back and screw it in as well.
You'll note in my pictures that I ended up adding the blocks of wood to the end of the sides as I noted above in order to get something to screw the transom to.

Once you get that transom screwed in, the boat is pretty well stuck together.
I added in some pictures of where my hull started to crack and splinter along rib E. I figured I could sand it down and repair it with fiberglass. Again, soak your wood as I do in boat #2.

These two shots are just showing what the boat looked like after it was all screwed together with the ribs and transom.
Do you arms hurt yet? Mine sure did.
Note the blocks of wood at the back. Again, rip a 2X4 in half and screw it to the sides. That'll give you a place to screw to. (See boat #2)

Place the sides and ribs on top of the excess plywood you have. Trace out the bottom of the boat on that ply and cut it out with a jigsaw.
As you can see with this boat bottom, I had a very hard time making my boat symmetrical. One side is almost straight. I was pretty concerned at this point. But pressed on. I mean, what could I do at this point anyway? The reason this was so skewed was because of the cracking earlier when I bent the sides around the ribs. Again, soak your ply and you may avoid this problem.

Flip the boat over and start using 1" screws to screw the bottom to the bottom of the sides of the boat. I started from the bow and worked my way back.

For some reason the first boat was very easy to do this to, but the second boat was a pain in the neck.

For this boat I spaced the screws fairly far apart so that I could fiberglass between the screw heads, let that fiberglass dry, then take out the screws and finally do a second pass through to fiberglass over the places the screws had been. (next step)

I should say, the Messy World of Fiberglass. This step has several parts to it and a lot of notes.

First, use duct tape (our favorite tool) to tape the seams on the INSIDE of the boat. This will keep the resin from oozing in through the seams. Gives it a nice flat surface inside too. Don't worry too much about big gaps between the bottom and the sides of the boat. The resin will fill in gaps.

Always use good gloves when working with fiberglass resin. And wear a long sleeved shirt and pants when dealing with the cloth. I used these black, rubberized, gloves I found at Home Depot. They worked great because I could handle the resin directly and I could flake off the dry resin from the gloves between batches. Thin rubber gloves tend to rip apart when smoothing on the resin.

Ok. Hannu's instructions explain to use "Glass Tape". I think that means fiberglass tape. (European style?) After searching the Internet for "glass tape" I figured it didn't mean much but fiberglass. So. I went to Home Depot (Homer's) and bought two 128 oz fiberglass resin kits (has the fiberglass and hardener) and two big packs of fiberglass cloth.
Two 128 oz. kits was too much. But you will need at least 1 of those. Probably more. So either plan to make multiple trips or buy more than you need, keep the reciept and return the unused stuff later.

Also, buy a few of the plastic measuring cups that Homer's sells in the paint department. They have ounces on the side. The resin has a certain, tiny, amount of hardener to mix into the resin. I used one cup only to measure the resin in to. I used 2 or 3 others to pour the measured contents in to then to mix and use. I had several of the mix and use containers because that stuff hardens FAST.

I used a plastic shot glass to measure the liquid hardener in to.

First I pre cut lengths of fiberglass strips. Long ones. About 2 or 3 inches wide. I put them where they would be resin'd into place.

I mixed my resin in 7 oz. batches. More than that and it would harden before I could use the whole batch. My recipe was 7 oz of resin and 98 drops of hardener. (MY_NOTE: use your "hardener measuring cup" aka my plastic shot glass or some other disposable, clear container and put in 98 drops, which is 7 drops per ounce according to the instructions, into that. Then make a mark on that measuring cup so you know where 98 drops comes up to. Then reuse that cup over and over only for hardener.)
Make sense?

So now you have 7 oz. of resin in one cup and 98 pre-measured drops of hardener in a smaller cup. Pour both in to a third cup.

Now. Mix that stuff up. Then, add FLOUR. No kidding. Thicken the resin up with either sawdust (which is what I used in the first boat) or flour. And mix. I found that sawdust was too granular. You can see in this first boat that the seams are brown. The sawdust paste was too chunky and was a pain to smooth out and sand. With the second boat I used flour and it was so much smoother. Use flour.

Order of fiberglassing:
Outside first. After taping the inside of the boat, glob on the resin on the seam on the outside. Lay the fiberglass strip in to the resin, and cover over with more resin. Smooth it out.
Once you have finished all exterior seams, then remove the inside duct tape.
Then glob on resin on all seams inside the boat and lay fiberglass strips in to those and cover those with resin and smooth.

You will notice that the resin hardens pretty quickly.

That was pretty verbose. On to the next step.

After all of your fiberglassing is done, you are ready to sand and it smooth.

Because your fiberglass is now hardened and holding the boat together, you can now remove the ribs. If necessary, take out the screws and patch the holes with little pieces of fiberglass.

I have a little Ryobie orbital sander. I used 40 grit paper...a LOT of it, to sand the seams of the boat. I think I used at least 6 packs of the stuff between the two boats. Probably more.

When sanding fiberglass, please always use the following safety precautions:
1) Wear a respirator. You do NOT want microscopic shards of glass in your lungs. Very bad.
2) Wear goggles. You don't want it in your eyes either. Here, I sport Wonka goggles.
3) Wear long sleeved shirts and pants. I figured this out the hard way. You'll itch for days if you do not do this. It's quite uncomfortable.
4) Wear gloves. Same reason.
5) In this picture, I have my jackhammer ear protectors on. the sander is quite loud on 1/4" plywood. I reccommend this.
(Incidentally, I have retrofitted these ear protectors with headphones. I listen to audiobooks when I work. www.audible.com is a great resource for this.)

Ok. Safety taken care of. Sand away. Just make all the seams smooth.

Right about where the middle rib, E, was I inserted my seat.
I cut a 2X4 in half lengthwise and screwed each half to the side of the boat, rounding the tops for effect.
Between I screwed a piece of 2X4 across the span. The top of that 2X4 is about 5 1/2" from the bottom of the boat.
The seat is two 2X6's I had laying around (note the new deck....leftovers.) I had no pieces long enough to go all the way from front to back, so I screwed the 2X6's into the back transom and into the 2X4 seat cross beam. They kid of float out beyond that. I figured that's ok since I'll mostly be sitting right in the middle anyway.

The 2X6 seat planks are about an 1 1/2" apart to "provide comfort for the coccygeal bone". And it does work.

Also note in the pictures that I added those holes in the corners near the transom for handles. Those were rather tricky and I improved on those in boat #2.

That last picture has the beginnings of waterproofing. I had leftover deck waterproofing. I slathered a coat of that on to the wood. May have been superfluous though. I think pain and polyurethane might have been sufficient.

Everywhere I added screws I had to also add fiberglass patches and sanded those for waterproofing.

I used 1" drywall screws to screw in the 1" X 1" trim all along the top lip of the boat. Again, soak this stuff thoroughly in water before you try to bend it. Mine did crack some. It looks great and adds some strength to the boat.

This part took some time. I mean, what colors are we painting this thing?!
I used regular ol spray paint. Blue outside, yellow trim and green inside.
I put a layer of polyurethane all over it to give it a nice glossy look and to water seal it.
Because I live in Colorado, I doubt my little boat will get too much use. I think if you were really going to use this thing a lot you might look into more durable paints. I had a really difficult time even finding any information about "boat or marine" paint online.
Any ideas anyone?

Safety:
Use a respirator and gloves. Goggles won't hurt either.

This is an odd step.
First off, I didn't order my "oarlocks" or "oars" until I was about done with the boat. So I'm noting to do that in step one or so. Here, I'm trying to imagine how they'll fit...while listening to an audio book.

For this step, I'll just say that you shouldn't buy cheap oars. I bought some $16 Sevylor oars that telescope. They're pathetic. Save the cash, folks. I bought these, and then made my own. (Which is later in the instructable.) The home made ones worked a million times better. The little ones kept unscrewing and loosening. Had no leverage. Too short. They didn't fit the oarlocks either, therefore I tried to bulk them up with hot glue and rope. 'Twas ok, but still pathetic.

Anyway. I used another half a 2X4 and screwed it to the side of the boat about where I thought the oar should be. They're about 12" from the sternmost (the back of the boat) edge of the little seat crossbrace. A hole in the top of that block of wood holds the oarlock.

Make sure you attach that block of wood really well. That's where you'll be pulling all of the force of motion on to the boat. If that thing breaks off in the middle of a lake, you're going to have a heck of a time getting to shore. I used screws and liquid nails.

I had pretty much finished the first boat. Now it was time to make one for my wife. ;)

Of course the second time around it's much easier. And faster.

Note here I SOAKED the wood in water. (A tarp held by scrap wood.) for a while until I was ready to begin. Helps a lot!

We both pulled the sides over the ribs together and got a very nice bend to the wood. In the photos below you can see how I outlined the bottom on the extra 1/4" ply.

Also, this boat is the "smaller" design from Hannu's plans.

Note I added the 1" trim to the back of the sides to screw the transom to. Much easier.

In this boat, I used all 1" screws and left them all in. In Boat #1 I took the screws out and fiberglassed over them. Here I left the screws in and fiberglassed over the heads. The advantage is that I didn't have to make 2 passes witht he fiberglass, just went over it all at once.

As I mentioned, this bottom was a pain to add.
It didn't want to bend...or fit. There were some large (1" large) gaps in the seams. But no worries, the fiberglass resin filled them in.

We've alredy covered the steps of mixing and applying fiberglass. Only note that this boat used flour and not sawdust. The result is a much smoother seam.

In this boat I made the seat a bit wider. A total of three 2X4s. Two in the middle and two halveson the outer sides. 'Twere the only scraps I had left that fit the bill. Same seat design otherwise as in boat #1.

This time, audiobook in ear, I did not prep the wood with deck treatment, but just applied paint. My wife wanted custom colors instead of spray paint.

Note in that second picture I used rope instead of wood for some handles on the back of the boat. Much easier to put in.

The oars I bought were pathetic. But I'm from Colorado (Denver). Not really a boating area either. REI didn't have any oars. I went to Outdoor World (Bass Pro Shop) and they didn't have any either, despite what their website said.

(Side note about Outdoor World. I was disgusted that they had so many dead animals all over their store. And they've taken the liberty of killing hundreds of year old trees to decorate their store. I don't consider myself necessarily an environmentalist or an animal activist, but this place is grossly using natural resources and indescriminantly killing animals only to decorate a STORE. A store like "Outdoor World" is the anthesis of everything nature and the outdoors is. They are consumptive and irresponsible to the outdoors and the life therein. Please. Don't shop at places like this. One glance at any Bass Pro Shop or Outdoor World will explain what I mean.)

Anyway. The process for making oars is thus:
Use a piece of paper ( I had some tar paper for roofing available) and fold some in half. My first set of oar paddles were 18" long. I suggest some a bit longer. I free hand sketched half of an oar shape. Unfold and trace on to 1/2" plywood. Cut those out with a jigsaw.

Then I ripped a 2X4 in half (sound familiar yet?) and cut a 1/2" notch in to it. Several inches up. Use your judgement. Has to be pretty strong. After all, this is another point of force and momentum. If the paddles break off the oar shaft, you're stuck in the middle of a lake.

Use Liquid Nails in the notch and put the paddle into the oar shaft. Then carefully put some 1" screws through both sides of the shaft into the paddle.

I then cut some of the corners off of the shaft to start making it round. I made a second set of oars, larger ones, and I cut the edges before I notched them. Either way.
After that I sanded the shafts and paddles with 40 grit sandpaper.

Then I sanded all of it with 150 grit sandpaper. That made it really smooth.

With the first set of oars I coated them all the way with deck waterproofer. That made the really smooth finish I had accomplished very rough. Unfortunately.

The second set of oars I made I only coated the bottom half of the shaft and paddles with deck sealant. the handles I left very smooth and untreated. I figure, as much as I row, those handles will not get wet enough to warp. And I'd rather keep them smooth.

I've not seen an Instructable this long before. This is the end. I promise. (My first Instructable)

First photo is a comparison of the purchased oars versus the home made ones.

The last weekend of June, 2006 we took the boats out to Stanley Lake in Denver (Westminster). I strapped the boats to the top pf the Jeep with those handy straps I have. (I have 4 purchased from JAX in Fort Collins...or any army surplus store. Thye have been handy millions of times.)

Got to the lake. I first tested my oars and they worked wonderfully. Nice, long, strokes. Got deep into the water and had a lot of thrust. I then tried the store bought oars. Total dissappointmet. In fact, I was out on the water and my oar lock was too loose. bloop. One of the nuts in the oar lock came off and sank to the bottom of the lake. I made it to shore and found some nice people with tools and a spare nut.

(Lesson: take some basic tools and spare hardware. This is a low tech boat, yet still has mechanical parts.)

We had a great time in the boats. The smaller one was intentionally made that way to nest inside the bigger for transportation and storage. I have some video I may put up later of the boats in action. The smaller boat did tend to be a bit unstable if you lurched to one side or the other. Just stay balanced.

That's it. Happy Boating! And thanks Hannu!

8/15/2011 - I will post any updates and notes on this step. 
I came across this via Make Magazine's Blog :  http://www.safarana.org/Safarana/Do_It_Yourself/Entries/2011/8/9_Wooden_outboard_motor_powered_by_a_cordless_drill.html The last time I took out my dinghies in July I swore I was bringing a trolling motor next time!  This looks like a great candidate!