I’ve been off all week bustin’ hump on the boat. I have most of the inner hull faired out – twice! I should have all the sanding done tomorrow and bag it Sunday. Now that it is bogged out I pulled out of the mold to check for sharp edges in the mold and hull that may rip the vacuum bagging material. Took these pics and updated the web site.



Update from this week:
http://www.themanshed.net/tms-20-trimaran/update-8-7-09-fairing-inner-hull.html

Mike

One more Pic

great lines!

Interesting lines. Do you call that a soft chine?

Thanks DennisMe

Mary – Soft chine would work or maybe a graduated chine it goes from nothing to very pronounced in the stern. That would be thread of great debate? Name that chine.

My goal was to add a few inches of wiggle room to the inside of the hull but not increase the wetted surface of the hull. At first I was looking for something more in an “S” shape. I had in my mind what I wanted in form and function and Kurt Hughes put it to a line drawing with his twist.

I’m glad you like it. It will be something different now that is what I'm about, and it is made in Florida not China.

Mike

This is the original design.

I had the cabin area flared, which resulted in the chine and made it less angular and more "free form". It was designed to be cylinder molded in 3mm ply (interesting method developed by Kurt) and I took it to the next step to be composite strip with a carbon fiber skin.


10825

Mike, nice job!

Now, a question, I have zero boat building experience or knowledge, so when you lay up the foam strips onto the frame, what type of "glue" do you use to:

1. attach the strips to the frame and

2. attach the strips to each other on their edges?

And if the original plans called for 3mm ply strips, was the foam a newer, better option now available but not back when the plans were first developed? Is the foam lighter, cheaper, and/or easier to work with than 3mm ply strips?

Thanks Timbo it is a work in progress questions and encouragement are always welcome.

I am using West System Epoxy. The name system is really true you can mix and blend, as you need. To mix the epoxy I use 105 resin, then I have two different types of hardeners 205 (fast) and 209 (tropical super slow). The hardeners have different mixing ratios but with West System you buy metered pumps so the pumps meter the amount to make it a proper mix with a one to one pump. That gives you the basic glue.

Now you can add fillers (powder) I have 4 types of fillers on my shelf and I use 407 for most of the work. I use 407 for the adhesive and “bondo” qualities it’s easer to sand then the other fillers with good laminating properties. But no way does it sand like auto body putty it is much harder. The other fillers I have are for bonding qualities. The fillers are used to make a paste.

I tried different methods of gluing the strip together. One goal is keep the glue off of the side of the strip- you just want it on the edge. (It will make huge pay-off when you fare out the strips glue and foam sand at different rates) I started out with a caulking gun type of system from West worked well but was expensive. I got like 4 strip at a cost of $20 for a tube. Next I tried to putty knife and scooped a mix of epoxy paste into the cove cut of the foam took a lot of time. I read about mixing up the paste clamping strips up side-by-side and painting the paste across the surface. I did most of strips this way. It was a little messy but saved time. The last method and the method I will carry forward to the rest of the boat at this time - the turkey baster. I was in Publix and saw the baster and knew that would work great for a delivery method of un-thickened epoxy.

The foam strips are attached to the frames with drywall screws. The frames and screws are not part of the finished boat. The strips are cut on a router with a cove and bead edge and the glue is applied in this groove. The website shows cutting the grove.

Kurt’s cylinder molding method uses full sheets of plywood with scarf bevel cuts (8:1 to 12:1) to join the plywood sheets side-to-side forming basically one long continuous sheet. It is a brilliant method. His thought is why take a sheet of plywood cut it up and then glue it back together? Use very thin plywood and mold several sheets thick to form a continuous curved surface. So the original design has more angular curves and is not “free form”. Kurt’s trademark method of building is the cylinder molding that is what initially drew me to his portfolio. It would have been easier, cheaper, and faster to build the boat this way to the original plans.

Is foam better then wood? Foam has been improved. Foam is not cheaper then plywood about 4 times as much, Carbon fiber is about 6 times more then the E-glass (white), and West is about 4 times more then polyester and that is at the discount rates that I get some discounts up to 50%. But I learned many years ago in my first project you do get what you pay for and the total sum of the cost in a completed boat is small. To save a thousand or so is less then 10% of the building cost and perhaps 5% of the total value is just not worth the loss of quality not to mention the many hours of free labor.

Foam composite is lighter then wood and stiffer plus it does not rot. Foam does not need longitudinal stringers in the hull. Foam is easier to work with, make compound shapes, and more buoyant. The foam / carbon fiber glass boat will be lighter, stronger, have more room, carry more sail, and should be faster. I think my design improvements will help in the above and give it a modern look with a classic twist.

Thanks for the great explanation Mike, now do you have time for one more question?

I was looking through all of your pictures, saw the foam 4x8 sheets prior to being ripped, couldn't you have used them much like Kurt uses the 3mm ply, that is, rather than cut them apart into small strips, then glue them back together, how about cut them into much wider strips, to save time and effort? It looked like the foam was more flexible than ply would be, so couldn't it be -bent- around some of those corners without having to rip it into small strips? Or is it much stiffer than it looks?

Timbo good question.

As a 4 x 8 sheet - the foam is stiff and a sheet of ply would bend more. The foam would shape with pressure or heat. They also have foam that is scored into about 1 inch boxes with a scrim. Having said that you cut the foam in a thin enough strip you can take an 8-foot strip and wrap it into a loop.

You have to select a starting point to begin and build from that point. The obvious point for me is the chine. The strip at that point bent on two axes rounded out and rounded up. There is not a straight or flat line on the hull. I found a 1-3/4 inch strip to bend well in all directions except for last foot of the stern. I wanted the maximum size strip that would fit well and lay in the curves. Wider strips would have more faring and fill, to make round.

The other thing to consider is the set-up. The saw is not too bad. The router is another story, it has 4 adjustments and they are pretty exacting. Once it is dialed in I don’t like to change the setting. At about $100 a sheet of foam you don’t want a lot of waste.

The Ama’s may use wider strips as they are a traditional shape and don’t have compound curves.

If you notice the black mold in the background pictures of a 34-foot hull you could use full sheets on that type of mold so it also depends on the type of mold you build. A male mold or mold with longitudinal runners in it could use the sheet style. So there are factors to consider when looking at designs and selecting building method and medium. The strip foam method is pretty popular for a “One-Off” boat. Are you thinking about building a boat?

Now we're on to stripping I have a question for you TMS.
Did you evaluate the Farrier vertical foam strip method? If so, why did you choose to go with longitudinal stripping?

In the case of the TMS-20 the strip method I used better suited the shape of the hull. The vertical mold is a bit more complex. One method is not better then the other. I would have had to heat the foam to get it to bend in such sharp angles and I'm not in favor of that. When I build the 34' cat I'll use the vertical method.

Part of it is the builders preference and how complex is the shape of the part. I have compound curves that bend on two axes that is pretty hard to do in just one plane. Try to do that with a piece of paper then think of a more ridged material as a 4 x 8 sheet of material. What are you comfortable working with, how elaborate of a mold, the shape of the part you are building are factors also.