Hydro-bat by Vic Smeed: engine probs

The past weeks I tried to figure out how te make a light and good working rudder linkage. Originally, the rudder stock is extended above the rear deck and the linkage is above the deck with an idler to connect to the servo in the RC compartment. I think this was to preserve the watertight compartments on both sides of the pylon.
I don’t like this exposed linkage and shortened the rudder stock. The horn will be mounted at 45° otherwise it hits the transom.  The fact that the rudder is at an angle gives a funny circular movement of the rudder horn: left to right but also up and down. I first tried to mount an aluminium bent horn and a 0,8mm piano wire but the piano wire is to stiff. This makes it to move too much sideways. That way the push rod could not slide into a fixed tube.



I then wanted to make a quadrant, operated by 2 wires connected to the servo. But this is complex, a bit obsolete and heavy. I found out that the cable which is lead out wire, is strong enough on its own to push/pull the rudder horn. I came up with this:







The rudder horn is made of 1 end of a tie wrap and the cable runs in a thin brass tube trough the watertight compartment. This should work with the servo in place.

After a summer break, I continued building the Hydro-bat. I sheeted the central top starting from the transom. Before finishing, I glued an aluminium front bumper that is about 2mm more forward than the hull. The aluminium plate was covered with scrap balsa and sanded flush.











After sanding, I cut out a templet to mark where to cut out the hatch for the radio compartment. The hatch will not be flat but curved and therefore, the canopy that is fixed onto the hatch has to keep this panel in shape. I decided to not make the Vic Smeed canopy but to use a plastic hemispherical one. After marking, I cut out the top to fit.











After trial fitting, I removed the canopy again to fit the dashboard. I copied the dashboard out of a 70's Jaeger car dashboard catalog. There are pictures of it on the internet and there is a large choice.
Made to the wanted size, I cut out the pic of the dash and glued it on thin balsa. The dashboard top was cut out of a black sheet of drawing paper.

roddie wrote:Lieven, I believe that your angled rudder-pivot will cause the transom to lift on the turning-side. That's not good! Because the pivot is angled; the rudder is not only deflecting water from side to side.. but also "down" when turning. Is it too late to make a wooden-wedge stand-off for the transom, to mount the rudder-tube against? That would solve some issues.. One; it would allow for making the pivot-angle perpendicular.. eliminating the "lifting" forces.. as well as simplifying the linkage-geometry. It would also allow more space for mounting the horn parallel with the transom. I fear that the exposed part of your flex-cable could flex during pushing (turning port) directional-input. If you only run the boat in a clockwise (right-turning) circuit.. it would be less critical. Have you considered installing a rubber-boot pushrod-seal? It allows angular-movement of the pushrod.. while keeping water out of the hull.

I pack the inside of the pushrod-seal in my boat, with petroleum-jelly. It doesn't leak.

Note the distance between the rudder's pivot-post and the boat's transom. You could replicate this with a stand-off wedge-mount that's closer to vertical. I love the inward transom-angle styling on your model.. but it just doesn't afford itself to the function of a conventional rudder-mount unless modified.

Roddie, I read about the influence of a tilted rudder. But this is really in ideal conditions. This boat will jump up and down and I don't know what else. I think that when the water is pushed down by the rudder blade, it willkeep the nose down. Initially, I thought of installing one of those Hong Kong aluminium rudders. I got 2 of them. They are well made and look good. But it's all about the joy of making things myself. Thanks for thinking of all that!!

The next things to do will be the canopy rear fin and cover both sides !

Lieven

Thanks for your comments. The radio is not in there yet. After covering, I now have to cut out again a hatch to have access to the radio compartment. I like the bubble canopy too. It comes from those kids toys you get out of a distributor after you put in a coin. You could also use fishing floats from the make BULDO. I think the plastic will be a better quality.

http://www.buldo.com/index-en.html

To keep the curved shape of the hatch, I need to make a fin behind the canopy. At work, i get carried away and I make scetches of what I could make. I end up with antennas of different sizes. I will probably copy the shape of the pylon. That will be the most practical.



Today I fixed the engine and the boat weights 195g with the tank

Glad you like it!! No Phil, I've never read those comics. It's the first time I see them. They do come from a creative mind. And Roddie, I know I repeat myself but it's just an easy thing to use.

What about this:

I started covering the top sides. on the proto, those were covered with short pieces of 3mm balsa with the grain crosswise.



That is rather difficult to accomplish with immediate good results. None of these pieces are rectangles. And it needs careful sanding to get the curve back lengthwise. I made a pattern from paper for 1 side and cut this out in 1,5 mm balsa. That way, I save some weight and also, the sheet bends easier.











The sheet was cut to size at the transom and the edge was shaved and sanded at 90° to the bottom. sheet. There were some gaps of 0,5 mm or less due to inaccurate cutting of the sheet. I made tapered strips that I inserted with glue in these gaps. After drying and sanding that gave an all wood finish.

Near the pylon, I made some mistake in cutting the fore and aft member. The top sheet sagged and that bothered me since then. To remedy that, I glued another sheet on top and sanded it down. That gave the proper surface. On the pictures, the brighter wood is what's left over from the glued on sheet.

roddie wrote:Can you devise a small fixture for sanding the 45-degree angles into the edges of the deck and the side-sheeting?

I suppose you could. It'll have to be a bit universal and adjustable maybe? On this particular model, I don't know what the exact angle is and also, the angle varies from front to back. When the panel is glued onto both frames, front and transom, it is in fact twisted.

This is for Fred:


https://www.youtube.com/watch?v=pI2j4KEPQI4

The hull is finally finished.