rctruggy

Hi,

I have a 15CC CMB nitro engine and like to build a hydroplane. The length will be 150 cm, width almost 80 cm.

I wonder why rc hydros turn right while the real things take left turns. Is it because of the torque of the model engine? The right sponson is pushed down en the left sponson is lifted a bit. It can't be the turn fin because it can be mirrored and strapped to the left of the boat.

I have converted a PDF of the Atlas Van Lines from Gary Finlay to DWG and redrawn an scaled it up in Acad. What would be the right thicknesses of the parts?
I've choosen:
5mm for the sponsonformers
3mm for the bulkheads
5mm for transom (doubler included)
5mm for the bulkhead that takes the turn fin (doubler included)
2mm for the skin of the boat
all plywood

Is all the driving force taken by the strut and transom, I think so but not sure about that?

Will post some pictures of the engine and drawings soon.

Regards,

Leo

wave waker

it's one of a kind here if ever built...that's huge! keep it posted...and goodluck..

rctruggy

Hi,

It's so big I think I can't transport it with my own car. Have to rent a van to do it. But one of the goals is also to make something special.

And the real hobby of mine is to build it, not to drive it. I will however drive it to see if it works and if so, it will be placed against the wall I gues. I have a bunch of cars which I rarely use, for me the fun is to have it in a good condition. That's also (mainly) because there are really no places to drive them.

Leo

wave waker

as long as ur havin' fun without breakin' the rules that's fine....u need to have a van or pick-up truck or trailer the haul this giant, 2 guys to launch, big body of water.

how much is ur estimate gonna cost?

rctruggy

I already have the engine, need to buy the hardware and RC control. Really have no idea about the costs but I plan to run it about this time next year so I can spread the costs.

Maybe I'm wrong but I think it will not be that more expensive than a 1/8th scale boat and there are lots of them.

What rules are there to break?

About 13 km's from here there is a small lake but more than big enough to run the boat.

gooycheese

I will say if you have a 1/8 scale boat do 60mph and then you multiply that 60mph by 8 that equals 480mph. I would imagine at half or less power the scale boats could turn left pretty easy. This just a guess I don't know for sure.


Paul

Hydro Junkie

Okay, lets take this one step at a time:
1) Your 150cm works out to aproximately 1/6th scale, though it is about 5cm overlength
2) Use 5-6mm for all lengthwise framing, including sponson sheers
3) Use 10mm for all transoms as they will handle much more stress than any other parts of the boat
4) Use 3mm for all other cross frames and skin
5) All the thrust is normally transferred to the strut, so be sure to add at least a 5-6mm or getter still 10mm doubler in the boat's rear
6) Be sure to have cross frames every 10-12cm to support the skin. To go further apart will make the boat too weak
7) The right turn is preferred because of propwalk, not engine torque. You must remember that only the bottoom half of the prop will be under water while running at speed, causing a paddlewheel like effect to the left

I'm posting a picture of a 1/6th scale Pay N' Pak that's 144.78cm long. I tried to use stringers instead but found that to be not structurally solid enough

rctruggy

Hi,

Thanks for your answers. On another forum I am advised to scale the boat down to about 120 cm's. I think it's to small because of engine size. But this engine can handle a 145 cm boat?

How can I determine the shape of bulkheads to go between the "existing" bulkheads? This is my biggest question that stopped me from designing a boat myself. Now I have choosen to build this one but it's still is interesting and needed to draw the extra bulkheads. Can I measure dimensions from 2 bulkheads and take the mean values for the new bulkhead? I don't think so because the shapes are curved except on the aft ship, so they need to be slightly bigger I think. Seen from aft to front the gradients from the curves (aft to front and bottom to top) gets higher. Don't want the skin to "wobble".

What are stringers? Are those the square pieces of wood from the front to the aft of the boat?

Leo

Hydro Junkie

yes, stringers are the square sticks visible in the picture I posted. The easiest way to do the additional frames is to cut them to fit below the deck level but leave them oversized so that they stick up above the plan frames and out past the sides outside of the sponson insides. You can then sand them down to match the deck curve and nontrip shape

hydroracer11g

Hell that thing is going to be big enough to drive in, not drive from shore!

Hydro Junkie

Not quite, it's going to be about 59" long. I've got a 61.5" Valvoline/Miss Madison and 57" Pay N' Pak under construction so I can speak on this from experience. It will be hard to handle on the beach but, if built right, should be a decent runner