hi all,
i am wanting to construct a 1:25 scale pb 65 (which is really 70ft & worth iirc AU$5-6million [link=http//www.pbmy.com.au/range65_intro.html]Palm Beach Motor Yachts[/link] which is what i am working on at the moment) and make it a radio control boat. i have only made rc yachts so i am a total newbie to rc powerboats. i have worked out how i am going to build it, i've got all the stations printed up and the actual boat to go off so its just the running gear and electrical stuff that i really need to know about.
i am intending to use frames and balsa core with a layer of surfboard cloth over the top, with everything done in epoxy or polyester.
cheers
rob

What is it you need to know?.

its going to be 853mm long, and 231 wide. what kind of motors would i need, what sort of esc would i need, how to i wire these up to hitec reciever, how do i make a stuffing box. how do i do lighting inside and around the boat?
cheers
rob

Hi Rob,

Your link doesn't seem to work, at least on this end...

With a loa of 853mm you'll need to build rather light, if I remember correctly, the cloth for surfboards is rather thick, most likely too heavy for a relative small yacht.

As it's a powerboat, the lightest option is to go semi scale and only use one motor, givine you the benefit of less weight and the use of a single bigger prop, which is more efficient than two smaller ones (= more speed and runtime).

Basically the motor(s), batteries and ESC(s) are the only items you'll need to buy, all the other hardware can be homebuilt.

Read up on the scale forum on yacht builds, use the search function, you'll find most of your questions have been answered more than once.
If you don't find the answers let us know.

Like Toes said; 'What do you need to know?'

Regards, Jan.

Hi Rob
As Pompebled said, most of your questions have already been covered on these forums..

Motor / ESC selection depend on the style of hull and its weight... after selecting a prop to match the boats type and required speed.
Wiring an ESC to a Rx is easy, it just plugs in to the throttle channel on the Rx
A stuffing tube can be made from two brass tubes, one piece fits inside the other (as bearings at either end) and fits your prop shaft.... what size do you need and are they available comercially?.
What type of lighting?.. LED or incandecent?... number of lights?... again, we need more info as to what you are trying to achieve.

i was thinking leds. they would be harder (maybe) to do, but batteries should last longer? in full size, its a semi displacement hull, true wieght is around 18000kg's, 2x700 hp engines. should i scale this stuff down too?
ohh and thank you for letting me know that the link didn't work. should now work.
mmm i think at work we have 200g/sm plain weave glass. i am hoping the hull won't weigh over 500grams once its laminated, if i do a decent job of the balsa core and glassing, i was thinking of leaving it as that kind of finish, but i don't know if it will look that good for the type of boat it is.
cheers
rob

Hi Rob,

I got the link to work (actually google found it for me) and have taken a look.
There's not much to see, but I guess shipyards have to be careful about what they show on their websites in terms of line plans or clear photo's, showing the lines of the hull.

As the cruicial part of boating (the water) can't be scaled down, you'll have to compensate with the motorization.

To get performance in a relative small hull, you need to build light and slightly overpower the hull.
Weightwise, Lipo's and brushless motors would be the best option as NiMH and brushed motors would make the hull too heavy (mind you, it will perform, but it would sit much too deep at rest, as two 700 motors and 10-14 cells for each motor, is heavy).

Running a hull in semi displacement is torture for the motors and ESC(s) as they have to work very hard at over half throttle, making heat a real issue.
Running the boat as displacement hull would require substantually less power, but if you want to emulate the real thing, make sure everything in the drive train is 'properly' oversized, and very well watercooled, to avoid smoke on the water.

How fast does the boat have to get?
If you want to go for twin motors, two of these will certainly make the boat jump on the plane on 3S Lipo:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5146&Product_Name=HXT_36-56_2700kv_Brushless_Inrunner_(WaterCooled)

More sedate (and civilized) would be two of these on 2 or 3S Lipo:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5145&Product_Name=TR_28-45_3600kv_Brushless_Inrunner_(WaterCooled)

For each motor you'll need an ESC, the large motors require minimal a 100A ESC, the smaller motor need a 60-70A ESC.

The forward only brushless ESC are relatively cheap, the reversing type is a tad more expensive and hard to find.

Regards, Jan.

mmm, the boat is only just starting construction, we are making the molds and stuff for it at the moment. i have 1:25 scaled frames for it and the actual boat to work off so it should be easier for me than it would be for a lot of other model makers. hopefully my boat building skills will help me, if not i have wasted 4 years of my life lol.
i am guessing it would be smarter to make it plane, cooling wise?
i think i will be able to build it pretty light (i am a shipwright after all)
cheers
rob

Hi Rob,

The larger of the two motors will get the boat on the plane, no problem.

Depending on the total weight, even the smaller motors may be able to do that.

Problems arise if you try to run it for prolonged periods of time as a semi displacement hull, just before it will get on the plane; in this phase, the smaller motors will overheat and die, the larger will play along a little longer, but it's a lot of strain on all the components.

You can play with the set-up a lot and figure out which propsize will get the boat just on the plane, so you'll be close to full throttle when in 'semi displacement mode'.

Regards, Jan.