A pressurized tank is not required for gas engines since the carburetors have a pump to pull the gas in. I would go with a vented tank. If you're worried about water ingestion, there are ways around that: for example you make a few loops in the vent tubing...this creates an air trap and prevents water from entering the tank in the event of a flip. Others I've seen use a small container on the vent tube to create the same kind of effect. The tank should be vented for sure. Imagine what will happen when the tank is just sitting with even the slightest amount of fuel in it...especially in warm conditions...the fuel will vaporize and pressure will continuously build up...we see this very clearly with I.V. bags. Also, you would have to empty the tank often to make sure there is an air cushion in it, otherwise, it would instead create a vacuum as you draw fuel from it, making it harder for the carb to pump fuel in... it's just a bunch of headaches waiting to happen. The only tank systems that work well without a vent are the blatter types (such as I.V. bags) because they can collapse as the fuel is drawn and you do not have to trap air in the tank...which is another problem...as this will create air bubbles in the fuel with the vibrations of the boat...another headache! As for the pressure changing the mixture settings, I don't think that would be too much of an issue only the pressure exceeded the popoff pressure of the metering needle. My suggestion: go with vented tank or blatter style...definitely.

Thanks Marc.

Good advices as yours is the gold I am digging for in here!
I think I will go for the solid vented tank with double security: An air container with double loops on both sides. Seems to be good common sense.
Nothing much more to say than THANKS, Marc!

Cheers!

Woodie.

So far I have ordered heaps of inside hardware for about a billion from different europe retailers.
And I found (but did not buy) this:
"Radio box plug, fuel tank bung ".
Look to "PT90" at the site: www.prestwich.ndirect.co.uk/hdwraccs.htm
Looks nice. But can anyone tell me about the purpose of this gizmo? Will I need it?
(Remember I'm danish)

Cheers!

Woodie.

Ah! the old bottle stopper plug.
These are mainly used when the onboard radio switch is inside the radio box rather than being able to turn them on from outside.
Also good for running the charger jack in to charge the batteries without having to open up your radio box.
I personally use a NARVA toggle switch with a waterproof boot mounted through the side or top depending on the box, just put a small amount of silicone on before mounting to be 100% sure its sealed in.
Its all personal preferance really as I like to remove the lid when my boats are at home to air them out.
Any small amount of moisture in the radio box especially if running in salt water will make it sweat which can lead to some major corrosion issues with batteries and radio gear.

Ozpulse.

Thanks. I think I will go for a waterproof external switch (if available), and do like you: Open the lid on the radiobox after each run. Anyway the boat will need a good caring service (oil, grease, cleaning and adjustments) in the end of the day. Actually I think this will be half part of the fun in boating.
About the counter rotating MHZ drives, I am still in my Thinking Box. If Thinking Box is no worky, I will turn to my Shouting Box hoping to find the answer in there.

Cheers!

Woodie.

(And now off - yeah still trying to fit the engine rails even better to the bottom)...

Hello guys!

No pics so far. I am still fighting to make the Blata and an exhaust in Harley-Davidson size fitting into the hull together with a servo box, gear box etc...
It's like trying to fit a huge swollen foot into a much too small shoe! This takes much time and even more pain.
So as told before: This will be a really tight fit!
The outcome will not be a boat. No Sir!
It will be a sailing engine room.

Pics will follow soon - I think.

Cheers!

Woodie.

Here is some pics of my "floating engine room."
(Let's hope it will float).
I am still into fitting all of the hardware into a too small hull filled with annoying spants and profiles.
Nothing easy about this!

In this phase there is NO room for mistakes, and thats why things are "advancing" slow an close to backwards right now.
The setup on the pics is just an overwiew with the hardware thrown in. I will not glue anything in place before I get it all totally correct and working.
For now I am at constructing homemade aluminum fittings to support the dual gearbox. Made by hand, but intention is for sure a CNC-look.
Next step will be designing a servo box in 2,4 mm birch plywood. The right engine rail will be fitted to this, plus a small rail on the keel in the middle will be needed to support the box.
Servos are ordered and those VERY RARE MHZ sterndrives are pre-ordered and will follow some day in march - together with a couple of high quality 4-blade props - all polished and balanced (not my expertise so far).

Enough small-talk. Here is the pics:

Woodie.

Niiiiiiieeeeeece,
Good stuuf Woodie, I don't have to tell you this but did you make everything easy to replace?
Again nice.

Thanks Moofy.

It will be a very tight pack once it is finished. But the tank, the engine, the servo box, the exhaust, the gear and the flexicables should all be accessable and replaceable within a few minutes. (Well... thats the plan)
Anyway every step in this part of the build demands some good consideration, simply because there litterately is no room for mistakes.
Right now I am fiddeling with some homemade aluminium fittings to support the dual gearbox. They will be designed to give easy access to the gearbox.
(And hopefully in CNC-style). I use 3 mm plates glued together to 6 mm shaped plates, using epoxy metal glue. (That is VERY strong stuff! You have to work fast and watch your fingers).

Cheers!

Woodie.

Nice job Woodie!!!! I just hope that hull is big enough for that BEAST!!!! Keep it up Buddy. That is super nice!!!