Converting the Touchwood K4 Blubird for Radio Control

Converting the Touchwood K4 Blubird for Radio Control

by ERNIE LAZENBY 2006

Disclaimer.

I offer the following guidance on the basis that I know it works having built this model however I cannot be responsible for any model not working as intended because the building of each model is beyond my control.

The owner of Touchwood and the owner of the ASTEC have my permission to publish this information.

These notes of guidance supersede my review published in MMI Magazine in 1995 because I have learnt much about this model and how to get the best out of it.

Hull modifications.

The model as supplied to me in 1995 had very little angle of attack on the sponsons being quite shallow and this caused some running problems particularly when turning. The photograph shows how I increased this angle by building up the bottom of the sponsons and the model now runs very well. I used plywood but P38 filler would do the job. Sharp edges are very important, particularly the rear edge of the sponsons but also the outer and inner edges need to be sharp otherwise the water will not break clean causing it to run wet.

Motor and Drive System

The cheapest method of powering the model and one I have used is a Graupner 8.4 7000 BB Turbo Motor correctly suppressed. The motor needs to be fitted with a cooling coil. 12 x 3000 Nickel Metal hydride cells. (2000 mah or 2400mhr ni-cads will do but will give less run time). I use an Astec 60 amp electronic speed controller. A purpose built flexi drive system threaded to take 4mm Graupner 2318 series carbon fibre props.

(Astec can make a drive system to order). A 34.5 mm or a 36mm are the most suitable. An Octura Hex Flex coupling for connecting the motor to the drive system. A Stainless steel rudder assembly (Astec can make this to order)

This needs to be well forward as shown in the photograph.The front of the motor casing needs to be 4.5cm forward of the transom and centrally located.

Bluebird K4 - close up of motor location.

The rudder servo

is not visible in the photograph being hidden under the deck on the right hand side of the boat. The centre of the rudder arm on the servo needs to be approx 15 cm from the transom however this is not critical and depends upon the length of the rudder actuating rod.

Cell position.

The ideal is 6 on each side of the boat and you will need to make a plate to be fitted on each side of the floor but raised up slightly to prevent water getting onto the cells. Use the cells to achieve a COG that needs to be approximately 5 cm rearwards from the back of the sponsons. Use self adhesive Velcro to hold the cells in position.

Water cooling

The photograph shows the water pick up on the underside of the boat. The exit is via a small pipe located in the transom overhang (as per the real boat) Astec can supply you with the parts needed to water cool the motor.

Close up side view of the strut and rudder on Ernie's Bluebird K4 Model

Running the model.

This model runs very much like the real boat. As it sets of the nose will rise quite dramatically, keep the power on and you will find the nose comes down as the boat starts to plane correctly. Don't try turning at full power.

Caution. It is not possible to prevent some water from getting into the hull therefore the Radio equipment and speed controller needs to be raised well up from the bottom and on my boat they are on the underside of the deck well out of the way.

It is possible to power this model with the new brush less motors however the amount of water that can get into this hull could lead to a failure of a brush less speed controller if it gets wet. I have found the 7000 BB Turbo to be very robust and all I do is lightly oil the front bearing. The flexi drive system needs to be removed after each running session. I dry it off then spray it with WD40.

To prevent the boat sinking mine has been filled at the front with buoyancy foam and also of part of the underside of the superstructure. Accidents can happen and you don't want to loose yours model if it flips over.

Final thoughts.

If you want the boat to run well then you must forget any thoughts of an exact scale drive system. The system I have suggested works very well and is efficient. I have tried the model with a scale system and it does not run as well.