Veldas Lifeboat.JPG

[Chris PearceParticipant @chrispearce30862]

Guess What,

Thats right I found the leak, it was a fracture in the hull, I have poured in some resin araldite and wonder bah… no leak .. back went the 400s and shes off like a gooden, now for the brushless motor in the commander…!

CP

[DuckyParticipant @ducky]

rnli shop model

[David SeerParticipant @davidseer16625]

Hi All,

New member here. I did a RTR Severn conversion alomst 2 years ago, and thought I'd ad my two-penneth. Like just about everyone else, I wrangled with the weight issue, and the truth is that it's just about impossible to get absolutely right.

The poblem comes from the fact that in its' unconverted form, the model is too light for it's size. This is due in part to the size and weight of the RC gear and powertrain originally installed, as it's far lighter than would be any proper RC and propulsion / steering gear (remeber also that the model originally had no rudders or steering servo). To compensate, the designer(s) made three simple, but significant alterations to the original design.

Firstly, they altered the underwater profile, substantially reducing the deph of immersion at the transsom, threby reducing the displacement.

Secondly, the first mod was only partially successful, so they proceeded to paint the waterline quite a bit lower down, particularly at the stern – the unconverted model floats noticably higher by the stern than does a full size Severn.

Then finally, they positioned the exhaust ports about 10mm lower on the transom to make the model look right.

All this adds up to a model which when converted is invariably a little overweight, and goes stern down when full power is applied. You will all be glad to hear that mine is no different (!), and in reading the "Baby Severn" threads on other forums, I came to the conclusion that even a 380 motor was going to be too heavy. So initially I went the same route as Ashley, with a pair of 25mm brass props on M3 s/s shafts (from Raboesch), driven by a pair of 280 motors, running from a 7.2v 2200 mAH Li-Po, through a Viper marine ESC, and Hi-tec Zebra 3 RC gear (40MHz), and a micro servo for the rudders. This gave great speed, and good endurance, but on only the second outing i melted the backs out of both motors ! – Back to the drawing board !

Anyway, after much headscratching and surfing of the interweb, I found a great compromise between the power of a 380, and the weight and efficiency of the 280 – a motor that IMHO is too little talked of outside heli circles – the 370: Only a few grams heavier than a 280, with a steel back, ventilated can, and quite happy at 7.2 volts.

Will post some photographs towards the weekend.

[David SeerParticipant @davidseer16625]

Hi again All,

 

First lot of piccies. Will post more later.

Edited By David Seer on 17/02/2012 10:40:29

[David SeerParticipant @davidseer16625]

More photographs and details:

1). Setting out info for semi scale propulsion & steering, including a plastic jig I made for setting the correct height and angle for the propshafts, and a demensioned profile of a rudder.

2). An extract from a CAD drawing showing how to set out stern details. The datum lines for this are the models' centreline (vertical) , and the centre of the lower belting at the outboard end (horizontal).

3). Motor specification.

I have more to upload on a different PC.

Cheers

DS

[David SeerParticipant @davidseer16625]

Hi again,

Stacks more photographs in my album.

Cheers

DS

[David SeerParticipant @davidseer16625]

The photograph above shows the original layout, where I used the aft part of the RC compartment to brace the stern tubes, and mount the steering servo. However, after I managed to melt the backs out of the original 280 motors, I decided I wasn't happy with the weight or trim of the model, so I altered it as below:

I removed the remains of the original RC compartment, fitted a duplicate structure about 45mm further aft – this was about as far back as I could go, whilst still having clearnce between the underside of the motors and the inside of the hull. This gave far better static fore and aft trim, whilst lowering the cenrte of gravity and lightneing the model through commensurate shortening of the propshafts, stern tubes, and steering pushrod.

The battery that I ended up with (quite by accident) fitted the original battery compartment (substantially shallowed, with a new bottom) like a glove, and allows room for the leads which connect to a deans plug, bonded into the side wall. The compartment stays almost completely dry, and even if it does get flooded, does not allow water into the bilges. It also means that I don't have to remove the suerstructure to recharge. As regards the height at which the battery is mounted within the model, I can confirm that the model corners flat at all speeds when not planing, and even when I sent it out on Fareham Reach in a blow (with chop!), although it was a real cow to keep head to wind, even with the wind and waves abeam, the model showed no signs of being anywhere near capsizing.

Then, to complete the working side of the model, I made the original on/off button waterproof, and reisnstated it, so that there is no need to remove any covers to switch the model on or off.

[Keith LongParticipant @keithlong89920]

Hi

Can anyone please tell me if these RNLI models are still available? I looked on the RNLI shop website and couldn't even find one actaul sailing model of a lifeboat of any sort – looks as though someone may be missing a trick somewhere – quite possibly me!

Keith

[David SeerParticipant @davidseer16625]

Hi Keith,

They were discontinued some time ago. You do still see unused ones in their original boxes on e-bay, but people are now beginning to ask more for them than the £50 that they were originally retailed for ! I'd buy a used one – usually available for £25 – £30.

Cheers

DS

Edited By David Seer on 18/02/2012 22:38:42

[Keith LongParticipant @keithlong89920]

Thanks David – I'll have to keep a look out.

Keith

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