At the end of 2018 I posted a power cat hull build. Upon completion of the two hulls, they were picked up by the owners and taken home to Maine to build the crossbeams and cockpit, as well as fit engines, electrical, etc. I’m happy to report that the resulting boat looks spectacular, and the owner/builders say that the shakedown cruise went well, with a smooth dry 20 knots. stock props.
Ten years ago, most visqueen used to be of fairly high quality and it wasn’t hard to walk into home depot and walk out with a roll of plastic good enough for bagging. But at some point cheap, porous, recycled visqueen took over the market, which is fine for most uses but ridiculously bad for vacuum. Good polyethylene sheeting will be somewhat transparent, and smooth texture. I recently ordered a roll of Xpose Safety 4.5 mil through amazon, and it was inexpensive, and excellent. i bagged 7′ x 18′ curved foam roof panels on a 3cfm vac pump and got a nice hard vacuum with not much attention to detail. https://www.amazon.com/gp/product/B07PBXHWFB/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
I think that I have tried every kind of weatherstripping to seal door closures or wet hatches. This model, called Rubber seal, ribbed, seems to be the best I have ever tried. All are adhesive backed. The ribs allow one part to deflect, without distorting the whole seal like a square section would. The black one is 3/8″ thick, from Grainger. https://www.grainger.com/product/TRIM-LOK-INC-Rubber-Seal-10D149
The white one is at Home Depot. They don’t carry black. I think is 5/16″ thick.
I recently had to review a chainplate on one of my COI cats and send a note to the USCG.
I see from the X-Ray report that the Aolani chainplates were not steel, but composite as I thought they were.
These composite plates are immune to corrosion, unlike metal ones.
I assume the builder used my layup schedule as I have sent earlier. I see no reason to doubt that.
They are easy for the builders to build in a huge safety factor.
Instead of being fastened onto a hull, these synergistically combine to both strengthen the hull and the chainplate.
Unlike the metal plates, these have some resiliency so make all the parts longer lived.
Any delta in the parts from the loads would show up immediately and early by cracks in the paint. Unlike metal plates which usually are not painted.
Attached find a picture of one of my other catamaran designs with composite chainplates. Note that he lifts his entire vessel with only the three chainplate locations.
I took on the job of building a set of hulls for Kurts 28’ power cat design which we stretched to 31’ by adding about 2.5 inches to every station. We upped the stringer size by 30% and glassed with 8oz rather than 6oz but otherwise stuck with the plan and laminate schedule. We used multiple layers of 8 and 10oz to make up biax tapes, i find it makes for easier fairing and allows for tapering the buildup. We did a half-way-to-yacht quality fairing job, primed with 545 and installed cleats, hatches, fuel tanks, and fuel fills. There will be lightweight 25 hp engines mounted on rear transoms. We finished both hulls and shipped to the owner in maine, who is going to build the cross arms and center cockpit over the winter. I really can’t recommend committing to building a boat over the summer in sarasota, florida in a non-airconditioned space, but, in the spirit of running a marathon, and other ridiculously painful ways to enjoy yourself, we did it. Total build time, including purchasing, hardware, and mounting on a trailer for shipment, was in the neighborhood of a thousand hours. LOTS of pictures after the break-
I got the GPO-3 fiberglass sheet from Online Metals dot com. I hoped to substitute it for the more expensive G-10. Looks like it worked. It is smooth like G-10 though in the picture above it looks rough.
This 2 foot by 2 foot sheet was $10. Picked it up myself. Compare to same size G-10 at McMaster Carr at $47 plus some $20 shipping.
The red probably means it is phenolic. Both of these are fire resistant.
The panel looks like it was made with chopper gun, but it will be used for low load applications, so no worry.
They did used to be a friendly neighborhood supplier. They have been bought by Thyssen Krupp and have a new corporate bureaucracy feel now. Good prices though.
VHB tape is wonderful stuff to stick things together. It was created for attaching windows to things, with no fasteners. However, I just had an illustrative example of when not to use it.
I was very impressed with the VHB tape on the lunar lander dome. It had a steel frame to stick to. Straight and smooth.
Maybe out of inertia, I also put it on the little triangular windows of the lunar lander. Later I realized the tape looked too wide on those tiny windows and I vowed to trim it back when I bought a tall enough ladder to reach.
I got the ladder. It turned out that all I had to do was push a bit and the windows folded back in. So I could then remove the tape.
Two lessons. For VHB tape to work well, the contact surface must be both flat and smooth. Many of you can do that. I seem to not have that skill nor ability in hard to reach places.
The second lesson is the VHB tape must be kept dry. Due to no ladder, I could not protect it with my caulk.
My triangular windows are now stopped in and bedded with caulk. The caulk can span the sketchy surface and gaps.
If you can do and flat, fair and smooth contact surface, go for it. If not, use adhesive caulk, like the System 3, two part polyurethane.
In contrast, I have a solar powered motion light stuck above the front door. It was stuck on with a couple of strips of VHB tape. Turns out the light is defective and won’t work. I not only can’t remove it, I can hang from it. And swing. Gonna take a chisel maybe.
These bearings seem like a big improvement over what we usually have to do for the unstayed rotating masts. In the past builders have had to machine a bearing out of a giant chunk of slick plastic. Most of the plastic was ground off and wasted and the cost ran into thousands. http://www.glidebearings.com/
Spherical bearings like the Tides units would have been perfect, but were not nearly large enough. Bendy materials like carbon fiber require spherical bearings to keep from binding under load, or as Rob Denny does, have a very loose fit.
These kind of are of the loose fit variety. I see the bearing having a fairly close fit to the round mast, but deflecting with the mast. I have not detailed this yet but will. The bearing will need a fiberglass sleeve around it to protect it and keep it round. I see this whole unit captured in a looser fit.
Contact Tim Creighton at Glidebearings firstname.lastname@example.org