So I've been experimenting with my .60 4-stroke engine on my big Kamikaze... The problem I'm encountering is porpoising. The age-old wisdom (not that old, LoL) has been, AFAIK
, to have the prop at 1/3 the length of the hull measured from the transom. I have the prop in this location. 32 1/2" long hull, prop is at about 10.75" from transom. The boat weighs about 8lbs with engine, full tank of fuel, Battery pack, etc. Lifting by the prop, the boat is very bow heavy. Moving the engine forward any more than it is will involve raising the engine even higher so the prop clears the hull. Not ideal. Instead, I strapped my 8oz GPS on top of the fuel tank and this helped it balance much better, nearly perfect. It still porpoises. I had the same problem with my .90 2-stroke, but worse since that engine is a lot more powerful. There isn't much I can do to lighten the bow much except using lighter servos but that isnt going to save more than an ounce or two. Not enough to make a difference. So.. Since there isnt a How-to in the Jigs/how-to section, I ask here to find out from the veterans (if any of them still visit the forum) as to how I can correct the bouncing up front. The 4-stroke .60 weighs just grams less than the .90 2-stroke, and the original engine (bushed crank .65 2-stroke) was installed about 1.5" further rearward than the engine is mounted currently. What does a guy do? I can't get a good speed run if the bow is bouncing like a pogo stick... Need some input, please.
Empty fuel tank, but RTR otherwise:
Empty fuel tank, with GPS on top of fuel tank (+8oz) - sorry I cut off the rearmost section of the boat in this picture. You should get the idea though..
Static picture of boat as I ran it last.
This is an older vid from a couple months ago, but you can see and hear it porpoising. This is without the GPS on it, but a total of 12 Standard alkaline batteries in the radio box for ballast. 4 of which power the receiver and servos.
I dont really want to have to add that much more ballast... Is my only option to move the engine? Angling the prop up didnt change much. The GPS on the fuel tank helped some, but not enough.