Building an Electric Classic Shovel Nose Hydro
By Chris Breen
Our 12 cell electric Hydro class is rapidly growing in popularity. I have always liked the shovel design from the ‘50s and ‘60s so I made a decision to build one. I also like a scale finish (or at least stand-off scale finish) to boats so I looked through the photos I could find on the web of shovels from that era. I liked Graham Doggett’s exposed Allison on his Miss Bardahl so I finally settled on the 1963 Harrah’s Tahoe Miss. The paint job is relatively straight forward, Orange-red deck and otherwise white There were not many pics but those I found were enough for a simplified "stand-off" scale finish.
I started off building a boat from balsa from scratch, but gave up eventually and purchased a Classic Hydro kit from High Performance Models in Whangaparaoa. These are excellent kits and are fully recommended. (http://www.classichydros.com)
Parts in the Classic Hydro kit
Don’t forget to also buy the scale driver (extra). For hardware I bought a Fullers mono hardware kit (also from High Performance) although I have used an Octura rudder I had knocking about.
Note, Fullers also make a hydro hardware kit. The differences are that in the Hydro kit the rudder includes a water pick-up slot and the prop shaft is stepped down from 3/16 to something smaller (don’t know exactly what diam)
In Tahoe Miss the flex shaft follows a gentle S bend and the strut is mounted inside the transom like the original shovel nose boats – None of this stuff sticking out the rear for me thanks
Speed controller is an AstroFlight I already had. Batteries are Intellect SHV 4200 (two stick packs from Offshore Electrics)
Cost so far (roughly): hull kit $150, motor $100, speed controller $150, hardware kit $150, driver $25, batteries $150, turn fin $30, paint $50, props $50, Deans type electric plugs etc $30 - bloody hell, already approaching $1000.
Construction of the hull is pretty well described in the instructions that come with it so I will not go into that phase in detail. But a couple of points to emphasise:
* Make sure that your waterproof the framing before gluing it in (I use Epiglass Everdure)
* Make sure you roughen the areas of plastic you will be gluing to, with fine sand paper
* DO use weights on a flat building board to make sure the hull builds straight without twists
* Block sand the frame assembly after you have glued it into the bottom of the hull so that the deck fits nice
* DO fill all spare cavities with foam before you glue the deck on
* DO take their advice and use lots of white electrical tape to hold the deck on while the glue
* dries DO a trial fit of all the bits to get CoG about 30 to 40 mm behind the sponsons BEFORE you glue on the
After completion I trimmed off the "overhang" around the edge and sanded the seam smooth. If you do a good job block sanding before you glue on the deck and then use a generous bead of epoxy and lots of white tape, you should not need much (if any) filling around the seam.
The flat floor of the hull is a little unsupported where the batteries lie, and where the stuffing tube exits the bottom so it is a good idea to glue in a few extra stiffening strips in these areas.
For paint I have used Dulux Spaykote Quick-dry enamel. This seems OK and seems to adhere well but after masking up for the white "bat wing" on the front of the hull and spraying I found the paint under the tape has been affected. I suspect this is the tape’s fault, because where the tape was overlapped and therefore double thickness, the paint is fine but it looks like the solvent soaked through a single layer of the tape even though I stripped the tape only about 30 minutes after spraying the white. I used a Scotch brand blue paper-based "low tack" masking tape for "delicate surfaces" – use with caution. (Bugger!)
The Allison engine is scratch built. Graham put me onto a site that manufactures balsa model engines and the site includes an image of the laser-cut parts – That is all we needed!!
The first sea trial was not a success but a change of prop soon fixed the problem. Then I had a problem with water entering the hull in spite of very carefully sealing on the hatch – Was it a leak?, coming up the prop tube?, a split in the brush cooling system?, a leak in rudder push rod seal? No it was none of those, it was a leak where my silicone goo around the stuffing tube was not adhering to the plastic. (Why is the solution always in the last place you look for it).
Finished 1963 Harrah’s Tahoe Miss
Well, last Sunday it went like a dream except the strut angle may be a tad too steep as it periodically nose dived underwater. Comparing to Graham’s Miss Bardahl I had a bit more angle on the strut. That is now adjusted – just need to wait until next week-end to re-test.