I see your Schwartz is as big as mine!

Thanks everybody for the replies. It really did help give me some direction with this one and I think I've come up with a good solution. I am going to forge ahead with this hull. No matter what it will be a great test platform and I will certainly get it on the water sooner this way. My goals for the project are going to change a bit though. Instead of trying to make a great boat on the first shot I'm going to try and make a functional boat and learn as much as I can without spending too much time and money on this hull. This should let me cut a few corners and get onto the water much sooner.

Carbon skin - GONE
Internal carbon reinforcement - GONE
Perfect smooth finish - GONE

This will be a total test hull for learning the building techniques and getting the overall shape right. I intend it to be very underbuilt and expect it to last only one season. I better include some major buoyancy bags though. Plus, without any carbon skin of any kind, Mothball One MK 1 will be a super fast flying woody! Ahh, Mel Brooks would be proud.

Also, got my sail from the UPS guy today. A used Bladerider 8x thats in very nice shape. Thanks Bora!

Day 1- Part 1

The Mothball One project started this weekend and all in all it went pretty well, to a point. We learned a lot and had some great successes. But now I’m at a decision point. Keep reading and give me some direction as to what I should do next.

Step One- Cut and Connect the Plywood

We did this using a puzzle joint and it worked great. It took a bit of time to cut out the puzzle ends, but the finished product was fantastic. Totally smooth and very tough. Well worth the effort. This won’t ever come apart.

I would totally do the puzzle joint this again, but there was one small problem with it. You need a big solid flat place to lay the plywood on to let the joint cure. The best choice for this was the garage floor. The only issue was that the garage floor is cement and it was pretty cold, which massively extended the cure time of the epoxy. Not a huge deal, but it did mess up the construction schedule. We put the joint together at 9:00 AM and weren’t able to start working with the wood till almost 2:00, even with a heat tent. This is not a huge deal, but I would have preferred to have started the day before with this and let it set overnight.

Step Two- The Plans

After the epoxy cured I was able to draw on the plans for the hull. This was done by overlaying the paper plans and then punching holes through the paper into the wood and then connecting the dots. Went quite well actually.

Step Three- Cut it out

Cut along the lines using a jigsaw. Easy, good results. You also need to groove the plywood where you intend to fold it. I used a circular saw set so the blade only cut 1.5 mm of wood. Also filleted some of the joints so they would come together better.

Here was a good trick. Use clamps to connect the wood together with some scrap pieces when moving or flipping the wood. This helps prevent breaking the ply. We also attached some stiffening rails to the edges. These were attached with epoxy and screws which would be taken out later. We were done with this step by 5:00

Step Four- Form the Boat

Started again after dinner and began to form the boat. This was done using some water and my mom’s clothes iron (shhh, don’t tell). It went exactly as planned. It took about an hour to go from a flat piece of wood to a nice boat shape. Check it. Only 14 pounds at this point. Right where I wanted to be.

Step Five- Connect the Joints with Carbon Tape

Easy. Just apply epoxy to the wood, lay in the tape and smooth with your gloved fingers. It’s now10:00 P.M.

Now Walk Away.

Damit, I said walk away.

You just couldn’t walk away could you.

So here is where things got a bit weird. In an effort to flatten the bottom a bit before the carbon cured I put some weights in the boat help make the correct bottom shape and then went to bed. When we got up the next morning things had changed, for the worse. Over the night the weight in the boat had slowly collapsed the V bottom under the support. This looked very bad. Luckily the epoxy hadn’t totally cured and with a bit of extra tape and some heat we were able to bring it back into shape. Mostly. With a bit of fairing I could probably make it perfect again.

But now I’m at a junction. The project has actually gone quite well so far except for the one major screw up on my part and we have learned a lot. But there are already some things I would change and I need to decide if I want to just keep going with this hull or start over again and make the changes before I invest any more time and effort into this boat. At this point I only have one day, 1.5 sheets of plywood and 30ft of carbon tape invested.

What would I change? Well not that much, but it may be significant in the long run. First I’d change bottom profile of the boat. It’s not bad, but the transition from the V bottom to the flat bottom is not as good as I’d like. I’d also maybe make the bottom a bit flatter. Secondly I’d let the hull flair wider when I tape in the first joints. This is supposed to be stressed plywood and it didn’t take much stress to get it into the final shape at the end. The added stress would make the whole hull stiffer. I’d also make the stiffening rails a bit smaller to reduce weight and use some supports on the stern to keep the ply from bending too much initially. These problems combined with my screw up on hull make me want to start over completely, but it’s not that bad and I could certainly salvage what I have now and make a functioning boat.

What do YOU think? Leave a comment.

How Do You Build It?

So how do you build a moth? Well, there are lots of ways, some easier than others. My goal was to use a construction technique that would be simple and cheap and yet relatively tough and light. I really like Phil S’s technique using tortured marine plywood. But my design not only called for torturing plywood, but also creasing it. So how do you fold plywood? I wasn’t sure, but I had some ideas. These ideas needed to be tested before I finalized my design. I got several 2’x2’ sheets of 3mm Okoume marine plywood and began to test folding techniques. After just a few tries I found that plywood can be folded pretty easily. Here’s what you need to do, first you need to groove the plywood where you want it to fold and remove enough material from the back side of the fold so that it does not bind upon folding (about 60% of the 3mm ply for a 90deg bend) Then you wet the wood and heat it with a hot iron. After you do this you will find that it folds pretty easily. Let dry and then glue on place. Done. First obstacle down.

After working on the folding technique I went ahead and build a 1:8 scale model of the boat with the 3mm ply. Turned out pretty good I think. I was also able to use this model to estimate the weight of the basic hull (no internal frames or deck). 13lb. Not bad. Granted I still need to add a lot of stuff and the final hull weight will probably be +2x that weight, but it’s an ok start.

While plywood construction is pretty effective for a job like this, it will not be as light as a fully vacuum bagged carbon foam construction. Also, the raw plywood is not great on durability so I intend to give it a single layer carbon skin over the hull on the outside only. This will present some construction challenges and add some weight, but it’s probably worth it to make a boat that will last.

Next Time – Parts and Pieces

The Design

The hull on the modern Moth does very little. Unless the wind is low, the hull is totally out of the water. So other than aerodynamics and weight, the hull has very little impact on sailing. For this reason, you don’t need to have a highly specialized and evolved hull design. There are some important design considerations and you do spend some time with the hull in the water, but for the most part you can have whatever shape hull you want.

My hull design was based off of Phil S’s plywood moth design. The overall structure of the boat was reduced considerably from Phil’s designs to more closely resemble the newest generation of boats. I also wanted to put some pretty hard chines on the hull. Although a round hull is faster going through the water, a flatter hull with hard chines will plane faster and theoretically fly sooner.

Here are some pictures of the iterations of hulls shapes I created using cardboard. I tweaked each hull generation slightly until I got a hull that looked how I wanted it. I think the final result looks pretty good. After I completed my final design I discovered Doug Culnane’s moth Blog. Doug has been building moths for years and seems to know what he’s doing. His blog was nice enough to provide measurements at key points all over his newest boat. I started looking at these measurements and checking how close I was with my design. The verdict: close, really close, scary close, I-promise-I-did-not-copy-your-boat-design-Doug close. The reality is that Doug and I chose to do somewhat of a similar construction technique and that technique really lends itself to this boat shape. At least that’s the story I’m going with.

The only real difference the Mothball One will have from other modern designs will be the knuckle bow. This is a modification that I came up with which should have some good effects on sailing. The idea came from the latest generation of America’s Cup boats. If this design is used on the ultimate seahugger boats, then it should hopefully have some good effects on moth sailing when in seahugging mode, in theory. Also, it should improve the touchdown handling of the boat. The knuckle bow should impact the water all at once which will hopefully reduce the water entry speed and lessen the nose dive tendency... in theory.

Next Time – Construction Technique.

So Why a Moth?

Cuz they’re cool, that’s why!

But I suppose there is a bit more too it than that. I have never sailed a moth. But I have been sailing since forever and did a lot of windsurfing when I was younger. I purchased my first real boat in 1999, a penultimate International 14. It took me years to really get a handle on how to sail a high performance boat. I sailed the I14 at the Worlds in Long Beach in 2006 and had a blast. We did fairly well considering we had the oldest boat in the fleet and were not up the current rules standards.

In 2007 we had a little baby girl Megan. She is probably the cutest little girl ever, but it became really clear that Megan was not going to be sailing an I14 for a very long time. We also have a SanJuan 21 for a family/class racing boat, so the I14 sailing became pretty questionable and the concept of having a small one person super-high performance boat became really appealing. The Moth was the natural fit.

So why build a moth. Well, several reasons. First, cuz it’s going to be way cheaper than buying one. Secondly, cuz I can. I’ve done a lot of work with epoxy and carbon over the years and my background as a civil engineer gives me a pretty good handle on the structural part. Also, I have collected several sets of random carbon tubes which are the exact right sizes to build the racks, for a savings of $1000 or more. Building a boat from nothing is pretty appealing to me. It should be a great learning experience and is great for your sailing cred.

Next time, the design.

Step One

In compliance with Section 12.4a of IMCA rules, this is the official blog of Mothball One, the Montana Moth Project, Bobzilla vs. Mothra. This blog will be the full account of the construction of the International Foiling Moth, Mothball One.

Here are some links of Interest.

The US Moth Website

Spaceball One!

Stay Tuned for Actual Content!