Model Boat Mayhem

Dry Dock / Shipyard: Builds & Questions => Pleasure boats, Sports, Race, Power and Leisure Boats: => Topic started by: HS93 (RIP) on April 12, 2007, 01:21:51 AM

Title: Water inlet scoop
Post by: HS93 (RIP) on April 12, 2007, 01:21:51 AM
I have heard that on F E people use a scoop in the bottom of the hull. Ive used the type behind the prop but this is for a fast scale boat and I would like to hide it, from what I have been told they put them at about 70 Deg from the flat plane of the hull ,has anybody got any pictures or drawrings etc of how its done??  thanks Peter
Title: Re: Water inlet scoop
Post by: glennb2006 on April 12, 2007, 01:43:08 AM
Hello Peter,

have a look at this link for an idea of how to do it:

It is of course possible to do your own version using something as simple as copper bonded into the hull at the angle required and flushed back to the hull to keep drag low. And make it work.

Are you looking to cool an IC motor or an electronic speed control and motor?


Title: Re: Water inlet scoop
Post by: HS93 (RIP) on April 12, 2007, 01:49:38 AM
  This is the type of thing I'm after,  Its for a couple of brushles motors I would like to do it in brass or copper as I think it would be a better job ,do they work ok ?

Title: Re: Water inlet scoop
Post by: martno1fan on April 12, 2007, 08:04:26 AM
those inlets work great acording to the americans who use them on large cats to cool zenoah engines but id say either get a large one or try two smaller ones ,one for each could also as glenn said make your own from brass or copper.brass would be my choice as copper does tarnish quickly in water especially if you run in salt.just remeber they will need to be very close to the transome to work or they will spend most of the time in fresh air  ;).what boat are they going on do you have any pics as we like pics  ;D cheers .
Title: Re: Water inlet scoop
Post by: glennb2006 on April 12, 2007, 10:40:58 AM
Hi there,

they should work fine made from tube and bonded to the hull and cut to the angle so they are flush.

I saw one fella who had made some from aluminium, they were turned on a lathe so there was a "shoulder" to bond them into the hull flush, and then they were drilled at an angle to get water up and into the holes, to which on the rear side were tapped water outlet nipples to take the silicone tube. It looked really neat and would be easy top fit with just one hole to drill in the hull.

Title: Re: Water inlet scoop
Post by: John W E on April 14, 2007, 07:09:44 PM
hi all

Reading the topic, I know basically what you are after, a water inlet tube set at an angle to the bottom of your hull,however, whilst having the same/similar problem of wanting to disguise the water intakes on HMS Leeds Castle (which I built a few years ago) I came up with this system of a water intake.   It's not as efficient as the water scoop, directly behind the propellor, as in this system the water scoop forms part of the 'A' frame that supports and is also in front of the propellor.  However, it does scoop up sufficient water to allow water circulation around the motors and overboard when the vessel is at 3/4 to full speed.   

I thought the idea might be worth experimenting with for you lads with the fast boats  ;D no doubt you would be able to increase the size of the intake slots.

john e
bluebird e

hope this is of some help - food for thought  ;D

I hope my sketch turns out okay.  ;D
Title: Re: Water inlet scoop
Post by: martno1fan on April 14, 2007, 07:49:57 PM
those inlets would work fine on a scale ship or fast scale boat like a patrol boat etc but they wont work on a surface driven boat,just a thought  ;).
Title: Re: Water inlet scoop
Post by: omra85 on April 14, 2007, 09:00:40 PM
Hi Peter
The scoops I use are pieces of copper tube bent (using the groove of an old flywheel) in a compound curve wherever in the hull you want them to exit.
Buy some copper brake tubing from your local brake tube maker (friendly garage) then cut off the required length + 50mm.  Heat is up with a blowtorch until it changes to a lightish pink colour (you will have to move along the tube bit by bit), then let it cool (this is called annealing).  The tube will now be soft enough to bend with your fingers.  Put the tube in the groove of your flywheel about 50mm from the end (hence the extra 50mm) and bend it to about 45 degrees.  This will give you the bit that sticks through the hull.  I then usually run the tube along the bottom of the inside of the hull to the point where I want the inlet.  Remember that the bit you've already bent will be pointing forwards then just bend the rest in the direction you want to go. Pic 1 below shows two tubes going forward from either side of the shaft to the engine bay (excuse state of boat, I don't run that one anymore)).  Pic 2 shows the positions of the scoops under the hull.



The inlet needs to be positioned where it will be in the water ALL of the time (unless you're doing salmon impressions) ;D usually towards the transom, but work out if anything will be in the way first.
Leaving enough room for the bend in the inside, drill a SMALL hole in the hull (I use a 3mm drill) then turn the boat hull upwards. Using a round needle file at 45degrees to the hull (hole pointing forward remember) ;D, open up the hole until your tube is a snug fit.
Insert the tube and tape the inside piece to the hull bottom (not at the exit hole though) and glass the tube in at the exit point.  glass the front end in and leave to set.
When thoroughly set, cut the inlet tube as close to the hull as you can at about 80 degrees (not critical, for less drag, I've seen them cut flush with the hull, but as your's is not so critical, I'd err on the side of caution)
Job done ;D
I like to put my OUTLET so that I can see the water jet when the boat is running, then I know it's not blocked, but that's a personal choice.
Pic 3 is the slot in the rudder type which is just as efficient (at high speed) but more fiddly ;) and is usually built in to the rudder.


Hope that helps


Title: Re: Water inlet scoop
Post by: CalicoJack on April 18, 2007, 02:52:22 PM
what boat are they going on do you have any pics as we like pics  ;D  cheers

Do you have any pics so we can see what boat and motors are being used? I presume it's a fast boat of some sort?