Blimpy

In the last post there were a couple of photos of the mold for the new mast head float.
My friend Brandon, the genius who runs Turn Point Design helped me design the new float and then cut a half-mold from light foam with his CNC machine. I glassed and finished the foam mold before covering the mold in teflon film and then attached it to a flat panel. From the mold, two halves were made as shown below

Because I wanted to install a radar reflector inside the new float it had to be made out of fiberglass, not carbon. The weight of the float is critical as it lives above the masthead, so I used S-glass cloth for the laminate. S-glass is not very popular because it costs almost as much as carbon yet is not as strong. It is however quite a bit stronger than regular E-glass and it was interesting making (and breaking) sample laminates.

 With production molds and methods one would use different technology to make this part, but I wanted one good masthead float with the least investment in time and money.
I knew that with thin laminates, vacuum bagging is not necessarily beneficial as it makes the laminate so much thinner. Stiffness is related to thickness, so I hand laminated the parts without bagging.

I was faced with the interesting challenge of how to laminate multiple layers on the mold at one time. It was difficult to make the cloth conform to the shape even with the cloth dry and able to slide around on the mold.  It was obvious that putting a dry layer of cloth over wet cloth wouldn't work.

I found from testing that if the mold was warm, multiple layers could be wet through at one time, so the first three layers of cloth were fit to the mold dry as shown above and then saturated in one step as shown below.
This was possible because I was using West System Pro-Set laminating epoxy (which is quite thin) and because the mold was warm when laminating, making the epoxy even thinner.  A temporary oven was built to warm the mold and to cure the first three layers before adding the final two layers.
All five layers of cloth and the fill coat were applied in one day to insure good adhesion between the layers.

To make the laminate stick into the inside corners, the cloth was lifted and a small bead of epoxy thickened with 406 Colloidal Silica (mixed very thick) was syringed into the corner before wetting the cloth out on to the flange area with a brush.

I used Microlight filler mixed into epoxy at about 50 percent by volume for the fill coat.

The foam rollers won't spread a thick fill coat  evenly, so I used a brush (and some heat from a heat gun) to meter the thickened epoxy evenly over the surface. A roller was then used to make it really even.

The laminate consists of three layers of 5.7 oz S- glass and a layer of 3.7 oz on the inside and outside, making 5 layers total.

The parts were easily removed from the mold.

Had I been content to have the joining flange on the outside (as was the original float), I could have skipped the next step of making an inward-facing flange.

A plywood flange mold was cut and covered with plastic tape. This mold was clamped to the outside flange as shown.

Multiple layers of glass were laminated to form an inward-facing flange. The strips of cloth were pre-saturated and placed into the inside corner. This was not a fun part of this project, but necessary because of my limited mold investment.

Removing the plywood flange mold shows the inward-facing flange (the glossy part).















The perfectly good outer flange was hacked off with a jigsaw and the remainder was trimmed off with a router screwed to a strip of plywood The photo below shows router from underneath.

A large router table would have been better suited for this job.
The beauty of using the router here is that the edge is easily and accurately trimmed square to the centerline making alignment of the two halves much easier.










The mast head float rotates on an axle protruding from the masthead. The float has a tube running through it that the ball bearing races fit into.
I had to make a light fiberglass tube with a 1 5/8" ID. The bearing races are 1 5/8" OD.

My new favorite tube making method is to lightly wet cloth out on plastic taped tightly to the bench and roll the cloth tightly onto the waxed mandril. The cloth can be wrapped very tightly because the cloth on the plastic can be pulled against while rolling.
The mandril and tube are then "cooked" using a small heater blowing warm air into a box, starting while the epoxy is still wet. The finished tube should slide right off the mandril after cooling, but only if the cook was hot enough and long enough and if the metal used for the mandril has a high thermal expansion rate. Aluminum is great for this purpose, copper (shown) worked well, steel is not so good. Putting the mandril and tube in the freezer can also help with removal.

With the two halves of the float taped tightly together,  a hole saw was used to cut the holes for the tube.
Epoxy had been piled into the inside corners to allow the pilot bit to stay centered while drilling.









The tube fits snug in the hole which will help with the next steps. The brown ring inside the tube is a stop for the bearings.

The loads incurred when the float whacks into the water are considerable, so it seemed important to attach the tube into the skin of the float in a serious way.

Here the tube has been wrapped in plastic tape and hot-melt glued in it's place. The scrap plywood flange molds are also taped on their lower surfaces.

This is what it looked like from underneath with about half of the laminate in place dry.
These layers of glass were placed with the fibers at 0-90 and + - 45 degrees and are shown dry because the laminate wasn't visible after saturation.










The area was primed and beads of thickened epoxy were squeezed into the inside corners before applying the laminate.

The tube was removed, leaving the flanges shown in the foreground.
The tube and flange molds have been moved to the other half for the same laminating process. The same, except there's no plastic tape on the tube this time. Better hope it's in the right place.

Flanges after trimming....















The radar reflector (a Davis emergency reflector that weighs 7.5 oz.) was bonded in place with small blocks of foam glued to the skin and reflector with G-flex.

Tiny little blocks were hot-melt glued around around the edges to align the two halves when gluing. After careful preparation, the two halves were bonded together with G-Flex.

Headed for the moon....

After trimming the tube flush with the surface and some sanding, the centerline joint was taped.

The taping was peel plyed and later faired in with a squeegee and then fill coated.

 

 The plywood cradles were removed and turned into a special Blimpy holder. Yes, that's her name, Blimpy.

The fairing was done with flexible sanding blocks of different stiffnesses. These were made from thin plywood of different thicknesses (very thin for fairing around the nose.










The tail fin was made from 1/4" foam with carbon skins. It was filleted and taped in place.
The whole thing was given a thin coat of 105 / 207 as a primer for painting.

The upper edges of the plastic bearing races were beveled to allow syringing un-thickened epoxy around the races to lock the bearings in place without worrying about getting epoxy in the actual bearings.










Blimpy weighs almost 4 1/2 pounds. The "dirigible" that blimpy replaces weighs just over 7 pounds.
With a bigger investment, the weight could be reduced, but this one seems light and it bounces really well when dropped on the floor. The old float rotates on a thin walled stainless shaft, this one uses a carbon shaft made by ICE. The new shaft is quite a piece of work and I don't worry about breaking it.

Meanwhile, the mast is very close to being finished. It has been quite a project. More complicated (of course) than I had imagined, but still fun. I'll post about that next....

New rig and other parts.

Well, I'm building a new rig for the G-32 and many other small parts as well. Of course I'm way behind on the blog, but that's the way it seems to go..

Designing the new rig and sail plan was done with help and advice from a number of people and took some time to accomplish. I started in the Fall working on things that weren't likely to change with changes in the rig design.

The spreaders were pretty easy to determine. They are short because they need to fit inside the fixed shrouds and they need to fit the mast section that I will be using.

I had thought to make hollow carbon spreaders, but instead shaped Sitka Spruce blanks and covered them with woven carbon.
My goal with the new rig is to make it as light as possible and to make it as aerodynamically
clean as possible. These spreaders will operate at high angles of attack because the boat heels so much, so I wanted a short chord length for as much of the span as possible.

The Spruce blanks were shaped with a grinder, block plane, and sanding blocks. The trailing edge had a solid epoxy fill applied before final shaping.

After more shaping, the ends had solid epoxy tips added before the final shaping shown below.

The spreaders were covered with three layers of 5.7 oz, (200 gsm) woven carbon, one of the layers being cut on the bias.

Pulling down hard on the bleed stack to prevent wrinkles at the leading edge when vacuum bagging.

After trimming the edges and sanding, the spreaders were cut away from the center of the blank. Notches were cut in the tips for the diamond wires to run through and holes drilled for seizing.

It shouldn't be long before the spreaders are bonded and taped onto the mast.

The G-32 storage boxes (behind the cockpit) were beautifully designed and quite light, but the hinged lids were right were I wanted to put hardware. The autopilot mount, traveller controls, and other things would like to be mounted right where the lids are.

So I built cored panels similar to the top surface of the boxes.
For storage, there will be mesh fabric bags underneath the panels supported by tent pole-like fiberglass tubes.

I knew that these panels had to be light, which meant they had to be cored, but I didn't want another mold to take to the dump, so I decided to use 3 mm Okoume plywood skins and use the lower skin as the mold surface.

Only the materials shown in this photo were discarded after making the panels.

The lower plywood skin was attached to the framework with double-sided tape (the type sail makers use) and a bit of hot-melt glue around the edges.
A light coat of epoxy was applied to the under side of the plywood first to prevent grain tear-out when removing the mold frames



To use the lower skin as a mold, it had to be completely airtight, so I applied two coats of epoxy, the first being squeegeed into the grain. The second coat was healthy and thorough and was lightly sanded after curing.
The core and top skin are shown here, the core being 5 pound foam (of two different colors).
The core and the top skin have corresponding holes to let air and extra epoxy pass into the bleed stack.

I was able to stretch the vacuum bag tight enough to pull the panel close to the mold surface before turning on the pump, keeping the peel ply and vacuum bag from creeping under the panel edges.

The panel was easily removed from the mold frames and cut into the final shapes using a template, skill saw, and jigsaw.

 

                                                                              Light carbon fiber cloth was applied to both sides and an extra tape was applied around the edges.

Carbon angles were bonded and taped to the aft edges of the platforms. These angles will be bolted to plates that attach to the traveller. 

Carbon angle will also be used to attach the forward ends to the cockpit area.

I needed a lot of angle, so I made a simple mold from plywood with a small bondo fillet in the corner and covered the mold with plastic tape.

10 layers of 400 gsm (almost 12 oz.) woven carbon produced a laminate 4 mm (almost 3/16") thick. 

It's easy to plan thickness with vacuum bagged carbon; each 100 gsm of laminate equals .1 millimeter of thickness.

A new mast head float is underway. It's slightly smaller than the old one and shaped differently. I had a mold machined from styrofoam which was faired, glassed, fill coated, faired again, and then gloss coated.

More on this later...

The mast is an Omohundro section built for the F-25. I bought two of them ages ago that were discounted seconds because there were flaws in the bolt rope track flanges. I built a rig from one of them at least 15 years ago and have been hanging on to the other ever since. The section is heavier than necessary, but I'll be able to have less rigging than the stock G-32 and the rig should still be lighter, even though it's a bit longer. The bare tube shown weighs 48 pounds, the G-32 rig weighs close to 75 pounds.

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The bottom end of the mast has about a third of the trailing edge cut away to make room for the roller furling universal joint, which will be covered later in the blog. Re-building this part of the mast was complex. This photo shows lots of laminate being bagged into the leading edge to reinforce for  holes that will go there.

To re-build the lower section of the mast, I had to laminate inside a very small space. I made a thin plywood pattern that covered the area and then chopped it up into sections about 4" long (after plastic taping the pattern). Patches of wet-out carbon were applied, one section at a time. These patches were overlapping, lapped down onto the mast walls and were located by draping them over a stir stick and then pushed carefully into place by hand.

This part of the laminating looked pretty good for having done it without being able to see what I was doing.

A piece of pre-preg carbon plate (mostly unidirectional) was then bonded to the mast as shown. 

After rounding the edges, a lot of laminate was vacuum bagged over the area using Pro-Set epoxy. This laminating was done in two steps to avoid wrinkling and has fibers running at 0 degrees, 0 - 90, and + - 45 degrees. Note that the lower two inches of the mast will be cut off after this laminating.

The next step was bonding on the new bolt rope track. I bought extruded polycarbonate track from Ted Van Dusen, who runs one of the first carbon spar companies; Composite Engineering. Ted designed this bolt rope track and it has been used it on many masts. 

The first step was to get the track glued on, which would have been easy if I didn't care if it was straight or not. The photo below shows a little jig holding a knife blade that is cutting the green masking tape to the width of the track. This green 3-M tape adheres really well if pressed down hard.

I cut a long strip of wood angled as shown and then cut the strip into little blocks. With the track taped in place using the green tape as a centering guide, the little blocks were glued to the tape every 6" with a little dab of hot-melt glue.

The track was glued on to the mast with West System G-flex, a toughened epoxy that seemed to stick to the polycarbonate track really well (after sanding). Plexus adhesive is usually used for attaching plastic track, but I wanted to use G-flex for the longer working time and because I will be wrapping carbon over the track, making the bond less critical. Plexus fumes are horrible too. 

I wanted to vacuum bag carbon fiber over the whole length of the track to make it reliable, but had to do something to keep the track from pinching under pressure and to keep epoxy from entering the track. A roughly 1/2" x 1/8" stick was milled, covered with plastic tape, and inserted in the track as shown. It protrudes slightly for reasons that will become apparent.

Because G-flex sticks so well to this plastic, the track was primed with G-Flex immediately before applying the wet carbon. This was a thin coat applied with a stiff brush.

The carbon strips were wet out on plastic taped to the bench (using Pro-Set epoxy) and then then applied to the mast. The strips were cut from the end of the roll of 5.7 oz carbon, so were a manageable length. I used three layers for the top half of the mast and two below that, except that both ends had four layers applied.

I forgot to take photos with the bag on, but this is what it looked like after the bag came off. There were vacuum lines coming in from both ends and plenty of breather to allow air flow.

Pushing carbon into inside corners is always challenging because the peel ply and perforated film are not stretchy, which means that they need to be pulled (along with the carbon) toward the inside corner while under vacuum pressure. I used two short lengths of plywood with the ends cut at angles and rounded to push the laminate into the corners from both sides at once as soon as the vacuum pressure started.

After post-curing the laminate with heat blankets, the laminate was block sanded away from the aft face, revealing the spacer. Then the spacer was pried up as shown.

A narrow strip of sail batten was tapered at one end and used with a hammer as a wedge to pry the spacer out in one long piece.

I'm much farther along with all this stuff now, but I'll have to catch up with the blog later. I'll do my best to do blog entries more often. This kind of work is fun for me and the really fun parts are still to come; the new mast head float, carbon hardware, etc...

We still haven't found the right name for the boat. Any ideas?

Happy new year!