This morning I unclamped my mast blank, only to find that I had not put enough tape into the corner. The blank had adhered to the aluminum angle. Ugh!
After some work, I was finally able to pry it off, but in the process had ripped a pretty good sized chunk out of the blank. However, after milling it down, I was able to cut that all off and now have a nice stick to use.
I also learned that I should have paid more attention to the bow in each strip, and flipped them alternatively to try to take that out. My mast blank has a slight bow to it. It will be easy for the upper and lower shrouds and spreaders to take care of, but it would have been nice to not have it at all.
In my previous boats, I've always used an aluminum mast (and a carbon fiber one on the Tippecanoe T37). For this Vintage Marblehead High Flyer Sun Wind II though, in keeping with the tradition of the 1940's/1950's, I thought it would be fun to attempt a wooden mast. This is my first try!
People on the innertubes seem to agree that spruce is the best. So I went to my local lumber yard (NOT a big box place either... but one that knows wood better), and bought two sticks of what they said was spruce. However, once I started milling it, I'm now not totally sure what I bought. I think that it probably is spruce, but after reading online about the differences, it may actually be pine.
Even if it is pine, at least one smart guy online says that he prefers it for his mast anyway. So... whatever! I'm calling it spruce. It has some very small knots in it, and is very whitish. The pine I've used in the past has been a bit more yellow.
Here are some images for various ways that you can use rubber bands to clamp down the planking when making a model wood RC sailboat like my Vintage Marblehead (VM) "High Flyer" Sun Wind II.
Start with a fairly wide strongback. Mine is 8" wide 3/4" MDF.
Then drive tacks or even small finishing nails, into the outside edge of the MDF in line with each frame. MAKE SURE THAT YOU ARE LINED UP WITH THE FRAMES! If you do this in-between the frames, you will warp the planks.
Then get yourself a couple bags of various sizes of rubber bands.
To clamp down a plank, just be creative! There are many ways you can use rubber bands to exert pressure on the planks.
Here are a few examples:
The Sun Wind II is coming along. It'll be a while though before the planking job is finished. Phew...
Pretty straightforward job tonight... installed the outer sheer rails and the stringers.
The stringers were just a matter of milling the proper sized wood - 1/8" square stock at over 50" long. Then I epoxied them into the notches. Easy.
The outer sheer rails weren't much harder. Painted on some clear epoxy on the inner sheer rails, and then some slightly thickened epoxy on the inside of the outer sheer rails. Then laminated them together and clamped them very well.
In the picture above, you can see the use of the rubber bands. Simply drive a tack or nail into the strongback in line with each frame. Then you can attach any number of rubber bands in any manner, so long as you hold down whatever it is you wish to hold down. Works so well!
Only one job to be done tonight, and that is to install the inner sheer rails. I couldn't also install the stringers because the rubber bands that are clamping the inner sheer rails need to use the stringer notches.
The sheer rails are composed of two laminated strips on both sides of the hull where the hull meets the deck. The frames have notches for both the inner and outer sheer rails.
The idea is that you epoxy on the inner sheer rail to the notches on the frames one day and let it cure. Then the next day you run epoxy down the entire length of the inner sheer rail and then laminate on the outer sheer rail. It's the lamination of the two rails that adds so much strength to the hull. The lamination also permanently holds the two rails together in the proper curve.
Later on during planking, you will actually add, essentially, a third sheer rail when you laminate on the first plank.
In this first picture, you can see the inner sheer rails on Frame 0. They are held together by…
Got the keel braces epoxied in. They butt up against the fin to transfer the load of the fin onto the frames and hull planking. The entire 10 lbs. of the fin bulb will put a lot of leverage on the top of the fin, which only extends into the hull less than 2". What the braces do is to lock the top of the fin at the edges of the slots so that the top of the fin is completely anchored to the frames. There is little chance of the top of the fin now breaking from the frames.
I'm hoping that the three doubled frames with additional keel braces is enough to transfer that load. In the bilge, frame 5 is now 1/2" thick! And frames 4, 4.5, and 6 are all 3/8" thick.
At this point, I'm actually quite confident that this arrangement will work. It also leaves the interior wide open, except for the mast support column, for the servo tray and lines.
The keel braces added about 2 oz. but I feel that they are worth it.
Big step today! I assembled and epoxied the frames for the Sun Wind II RC sailboat!
First, I drilled out the rudder tube hole with a 5/32" bit. The gap that is designed into the aft rudder tube keel assembly easily guided the bit through the slot and simply widened the sides a tad. You can now see that the rectangular opening is now a circular hole. The 5/32" brass rudder tube will easily epoxy into it later on.
Then started on the frame assembly by epoxying the frames down onto the strongback. Then added epoxy to all the slots on both the frames and on the fin and keel assemblies. They all slipped together pretty well after a little adjusting and persuasion.
Here is how it all looks while it cures.
In this image you can see a rubber band holding up the half-frame (Frame 4.5), otherwise it would slip out. The planks clamped to the sides are to keep Frame 4.5 aligned with the other frames.
In this image you can see the first use on this boat of the rubber band clamping syst…
Tonight I only had to finish the aft rudder tube keel assembly, and then add Frame 0 to the forward keel piece. Easy jobs.
In the picture below, you can barely see the hole for the rudder tube. The idea in this assembly is that the rudder tube fits in a gap created between "Keel piece #2" and "Keel piece #3". That gap is held open by two side pieces that are perfectly aligned by running 1/8" stock through the two alignment holes in back of the gap, and the three holes in front of the gap. In the picture below, you can see the stock protruding from the front alignment holes.
Then frame 9 will slip into the slot you can see just in front of the assembly. When planked, this rudder tube assembly will be extremely strong and yet relatively light. Much better than trying to carve a solid piece of wood and fit it to the bottom and then accurately drill a hole through it. Ugh... been there. This way, the hole is perfectly aligned, and perfectly straight.
This weekend I was able to get several small, but necessary, steps done on the full build of the Sun Wind II RC sailboat.
The three double-frames are all laminated, and the remaining frames are clear-coated with epoxy.
The fin was entirely laminated, shaped and fiberglassed.
The rudder was laminated but still needs to be shaped.
The aft rudder tube keel assembly was laminated. The three aft pieces are held in perfect alignment by two alignment holes that you stick 1/8" stock through and epoxy in place. I'll later sand them flush. The idea is that the keel piece that is just forward of this assembly will align to the forward three alignment holes and leave a 5/32" gap for the future rudder tube to go through.
It's upside down on the table so that the flat top edges can be used to help keep it in alignment while it cures.
Next, I still need to finish the aft keel glue-up, as well as gluing frame 0 to the forward keel piece.
A NOTE ABOUT GLUE: If you read some of my earlier posts regarding my mock-up test hull, you'll know that I often used Titebond II to glue things instead of epoxy. That was because that boat was never going to see water. This time I am almost exclusively using epoxy. This is the real deal boat and will be sailed, so a waterproof adhesive is required. Specifically I'm using WEST System 105/205. Read more about it here.
I started to laminate the fin tonight. Just the inner core made from 1/8" plywood, and then the first side of ply #2 made out of 1/16" plywood. You need to take extra caution on the first three or four ply's so that it remains really flat. The last few ply's you can stop using the 3/4" MDF form, but use it for the first several.
Use the excess epoxy: Then use the extra epoxy to clear coat some of the frames. Between laminating the fin and rudder, you can easily also add a thi…
Tada! Here's how my 6 laminations of 1/32" plywood turned out today when I took the clamps off...
Here's how it looks mounted to the servo and servo tray. Yes, I have some work to do on the tray, and especially on putting down some velcro for the battery and receiver. And I'll need to ziptie the wires too, but you get the idea!
I am using WEST System® epoxy for this boat, but I’ve also had great experiences with System Three®. Whatever brand you use, be sure to stick with it. Never mix and match resins from one company and hardener from another. Stick to one brand and follow their instructions.
Specifically, I am using WEST System® Group ‘A’ size cans of 105 resin with their 205 hardener. This epoxy uses a 5:1 ratio of resin to hardener; therefore, you’ll buy a quart of 105 resin and a much smaller tin of 205 hardener. They are usually sold together.
Using the WEST System® Mini Pumps: (They still actually put out a lot of epoxy!)
I use their ‘Mini Pump’ kit which includes measuring pumps for each can. They are easy to set up and use, and will dispense the proper 5:1 ratio.
CAUTION: System Three uses a 2:1 ratio, and some brands use a 3:1 ratio. Furthermore, each brand has its own ratios and you must follow them carefully! READ the directions closely for your brand. I assume you are using WEST System 105 resi…
Then last night I began assembly, starting with the servo tray. I'm still not entirely happy with it, even though it's now version 5 or 6. At this point, I think it will be a constant evolution. I'm torn between a simple board that mounts all the things, versus a board that tries to hide the cables and such. It's a balance that I haven't achieved yet.
Today I've started to laminate some of the doubled-up frames. Will continue tomorrow.
So it turns out that there is actually a very big difference between cutting the various types of 1/8" hobby plywood! I had no idea.
I bought my plywood from National Balsa. They offer three types of 1/8" hobby plywood:
1. Lite ply, which is very light but not too strong. Apparently it is made from poplar. Very flexible. I haven't tried to cut it, but would imagine that it cuts easily.
2. Regular, 3-ply plywood which is called birch, but seems to clearly be not as refined as 6-ply. Much stronger than Lite ply, but a bit heavier too. Cuts really well! Less reflective, fewer layers which means less resin to melt.
3. 6-ply birch plywood. This is actual birch. Very reflective, strong and solid. Tough to cut! 6 ply's mean lots of resin to melt.
They also offer both 1/16" and 1/32" birch ply.
So, the other day when I was laser cutting my frames, I was able to easily cut through the first two sheets…
Last night was spent avoiding the State of the Union address by instead working on the latest, and hopefully final, version of the Sun Wind II laser cut frames. Unless something obvious comes up, this is the file that I will shortly use to make the complete Sun Wind II boat from.
It's nine sheets. I know that someone out there could have puzzled this together better to make it fewer sheets, but whatever...
Six sheets are 1/8" plywood, and three are 1/16" plywood. There is a tenth sheet that can optionally be cut from 1/32" ply. The only part on it is a spacer for the rudder, but alternatively you could also just grind the edges off of the 1/8" rudder post to get it down to the 7/64" thickness of the actual rudder inner piece. Either way you run the risk of being slightly off-center with the post, but the amount should be so little as to be inconsequential.
More later when the laser cutting starts... hopefully next week!