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[triumphjon]

ive a slight overheating issue with a small huntsman 28 running twin 400 motors so wish to fit some water cooling . having been away from needing cooling i need a reminder as to the best location under the hull to scoop the water up ? please ive already cooked a pair of speed 400 s !

[Lord Bungle]

Ouch mate, I think I will need to know this as well as got twin speed 700's in my Huntman. Will 1 pick up be enough or should I use 1 for each motor?

[gregk9]

From what ive been told in the past, its best to place the pickups so they get some jet wash off the propeller, so basically needs to be inbetween the propeller and the rudder, so it does not foul rudder movement, but gets sufficient water forced towards it off the propeller when going ahead. Obviously, astern gets not water cooling, but you are not about to go that fast backwards !

The only other way to do it, if due to the fixed locations of props and rudders is to mount the water pickup wher you can  and then have to plumb in an electric water pump to circulate cooling water around the motor coils and then through the exit/return pipe.

[TomTheKraut]

Hi there,
... on a motor yacht type boat like the Huntsman I wouldn't go for the propwash position.
I'd rather have the Graupner "Water inlet & outlet", one per motor, put in the hull bottom - nice and symmetrically to the keel line. (http://www.cornwallmodelboats.co.uk/acatalog/water_cooling.html and scroll down past the silicone tubes).
These gadgets work twofold, while moving they act as ram-intake at the front end while the venturi effect at the rear end supports the water flow by suction.
The additional water resistance is near negligible at your type of hull.
To keep a 400 size motor cool, the smaller version should be sufficient.
For a 700 size motor the bigger pickup should work.

[phillnjack]

The best place for water inlet is offset to the right of propwash.
You want it as far as possible to the outside diameter of the prop, and about 1/4 inch away from prop.
This will give you maximum amout of water and pressure from the prop.

1 piped will be sufficient for your motors, do not use a y piece as one motor might not get enough and the other
get over cooled etc.
This water colling can also be used for you batteries and esc etc after leaving the motors.

By having a pressurised water cooling system, you can have either very cool to cold motors or t-off and cool other things as per needed.

There is another was of water cooling the motors called keel cooling, but this would involve using a pump and having pipes underneath the hull.
Personaly i would opt for the traditional ic method of pressure cooling from the propwash, but might also consider a small electric pump for
when the boat has stopped moving etc.


My understanding is that the cooler the electric motor the better (could be wrong) if so ,then pressure is definitely best way to go



phill

[Circlip]

Given that the prop and shaft/tube Assembly is making the undersides of the hull aerodynamically "Dirty" anyway, Hanging a bit of forward facing tube behind the propeller arc ain't going to slow it down much.

  In the "Olden" days, we used to mount the tube facing the front of the boat, hung down from the keel with the tube bore covered by the tip of the propeller arc. This was of course in the Diesel days and as soon as the boat was placed in the water, even before letting go, water was circulating through the cooling system.

  Regards  Ian  

[Shipmate60]

If the 400's are overheating (overworked) why not just fit larger motors.

Bob

[triumphjon]

if i could fit larger motors i would have done initially , ive built a 1/12th scale huntsman c/w its twin shaft set up , from the firewall to the stern ive got both motors , the rudder servo and the drive battery

i intend to have one cooling pipe per motor

[phillnjack]

Larger motor =more weight = more power= more money etc etc

just a bit of old fashioned cooling should do the trick. !!!

and by using a behind the prop water scoop you wont be causing hardly any drag as its in the propwash.

I think this twin set up should go very well, and definitely give atleast scale speed if not a lot more

another way if you dont want anything that dont look scale, is to fit your own trim tabs, and build in water scoops in each one.
It could be done very simply,by using the trim rams as dummys that are infact tubes for the intakes ??? this would keep everything
looking true to scale etc and would cost much to fabricate at all.
just a thought for appearance !!!


and could always go the fan cooled route with a small brushless and prop with funnel directors, but that would be
more battery again.


phill

[BigA]

On my MFA Piranha, I found the Graupner inlet/outlet single unit ineffective, with very poor water throughput - this could be down to location, of course, but I'm pretty sure the position was optimised, with the unit being underwater all of the time, on a free-flowing part of the hull - I think these need a really good turn of speed to work. I did use the smaller version, so perhaps the larger version would work better.

In its stead, I made up my own assembly comprising a short section of 5mm diameter aluminium rod (inlet) superglued to the bottom of the transom - a section of silicone tube was routed from this to the top of the transom, where another short section of aluminium tube sent it to the cooling coil and outlet. This worked much better.

 

[triumphjon]

using 4mm od copper tubing ive now installed a pair of scoops see photo , what have i done wrong please as they dont pull anything up the pipes ?

[phillnjack]

well the only thing i normally do is have the pipes sticking out the bottom then bend them slightly to make a sort of
upside down j and also slash cut them like you have to get elongated entrance for the water.

when you say they are not working,do you mean nothing at all ? and is this just a test in the bath ? or on lake etc ?.

i use 7mm outer diameter alloy pipe, and thats for 15cc glow, believe me i get tons of water ,that much that i have to
restrict it in the colder months slightly to stop over cooling.

have you blown down the pipe work to make sure no blockages ? if you cant blow easy then something is very wrong.

here is a pic of mine, its very similar to yours
.



hope you find the problem,


phill

[Circlip]

The ends need to be within the prop arc John, what happens is the prop actually pushes water through the scoop so you need to extend the amount sticking through the hull so the end is covered by the sweep.

  Regards  Ian.

[Arrow5]

 You should also consider more turns on the wrap arround coil on the motor but dont cover any air outlets.

[Lord Bungle]

thats given me plenty to think about :)

[triumphjon]

the scoops are within the diameter of my props , all of my pipework is brand new copper with the silicon joins so i cant see a blockage . ive tried the boat in water ( both open and our trusted test tank ) but nothing is being emitted from either tube ! if the location of the inlets is fine then maybe it needs a larger diameter pipe ?

[Arrow5]

Triumphjon, your centre picture looks like the inlet is  a bit short, also it should be on the up-going side of the disc for best results and closer to prop. Try short additions using silicon tube to get best position then make a permanent fix.

[triumphjon]

arrow ive just checked , the scoops are fitted 3mm from the tips of the blades on the upward stroke , the tubes extending 10mm from the hull , my props have been change to two bladed 31 mm .

[Lord Bungle]

I think I have found a use of that 5 channel switch on my huntsman 
does anyone have a good sugestion on what is the best pump to use? I was thinking a car winscreen pump, but not sure if it would burn out or drain the battery. Boat will be running the 700's on 12 volt each so will need cooling, but on the plus side plenty of power to run pumps

[phillnjack]

No diameter is ok.
i think your not getting enough water due to pipes not having slight bend.

Here is a diagram. ( i know its pretty poor but might help) of what your realy after.
(the blue is the boat by the way,  )



Now if your scoop is like this then it will give water cooling  for sure unless thereis a restriction.
The flow from the prop will force water up the pips, diameter will only affect the amount of water.

with my 1/4 inch internal pipe and i could easy sink the boat within 5 mins if i took the pipe off inside the boat.

what sort of revs are the props turning at ?



car windscreen washers are great, if you get one with 2 pipes, i.e 1 for front window 1 for rear, then you
can always use the second pipe for bilge pump, or water cannon etc


phill

[triumphjon]

having now removed the original pipes i have some which are 1/8 id copper brake pipe , which will be installed tonight ! hopefully i will be able to make a running test tommorrow weather permitting , as the tide is just after lunch this week !

[triumphjon]

thank you gents for your sugestions , ive now fitted a new pair of 1/8 bore scoops just behind my props , and after a short test in the home test tank im getting a good flow of water from the exhaust tubing ! now hopefully i wont be cooking my motors ?

[phillnjack]

glad to hear its working at last.
Once the boat gets underway it will work even better.
If the motors are not getting cold enough, the first thing to do is have the warm water exit the
boat as near as possible to the motors.
This gives the scoops less pressure to work against, but hopefully it will all be fine down at the waters edge.

once the boat has been running for a while, put your hand under the water comming out from the exhaust to
see just how warm it is.
If its still cold then wrap a bit more pipe around the motors as suggested above, it could help a lot.


phill

[phillnjack]

Here is  a suggestion for security of pipework in your boat in your boat.

I allways put a doubler on the ends of my sillicone pipe in every boat, it keeps the pipes from
comming off and that stops me filling a boat with water i thought was being used for cooling etc.

Just get a piece of silicone the same diameter that your using and cut a piece 4 mm long.
us e apair of long nosed pliers to stretch it over the silicone pipe before attatching to metal pipes or nipples etc.
This still allows the silicone pipe tp go onto your metal pipes, just with a real good flexible join thats better than tie wraps.

its easiest to see pics below to understand what i mean.


.

.

.

.




hope this helps understand what i mean



phill

[RaaArtyGunner]

Are your outlets (hot water) located under water at the stern?