Miss Britain 3 information

[harry smith 1Participant @harrysmith1]

Hi All

Looking for info on this boat as I have a plan which is 724mm long, but, resizing to 905mm.

I have a few 175mm crew which require a boat !!!

Spares from my SG&K 1920's Gentleman's Runabout.

The plan has the motor up front, so I am looking where the CG is for the boat?

This is so I can plan out the radio, ESC and mainly battery positions.

I have a few 3 and 4S Lipo batteries, a 60 and 100 Amp Hobbyking car and boat ESCs and a spare 3648-1450 kv 1600watt 35mm brushless motor

[harry smith 1Participant @harrysmith1]

[Ray Wood 3Participant @raywood3]

Hi Harry

What do you need to know about her ? I'm only down the road from the Maritime Museum where she is located, you will need to source an aluminium tree for this one

Regards Ray

[Dodgy Geezer 1Participant @dodgygeezer1]

I would expect to find it slightly behind the step – but note that model boats often require a different balance to the full-size article. Unless you want to do calculation on Froude numbers, you would be better off making the boat and experimenting! These links might help:

**LINK**

**LINK**

**LINK**

**LINK**

[harry smith 1Participant @harrysmith1]

Hi Ray and Dodgy

Thanks for the reply.

Looks like getting the battery up around the CG is going to be a bit of a problem.

I think I will get the plans up to size and use a piece of wood the same length.

Add the motor etc.in the approximate positions to see what goes!!!

If I can get the bits so the CG is about right with a inch play each way, it maybe a future project.

I copied a few photos for the boat from the internet and save these with MWSnap( a free screen capture program).

Ray, I will kept you in mind, if I require photos, thank you for the offer.

Harry Smith

[Paul TParticipant @pault84577]

Harry

The simple and straightforward method is to build the boat and install the fixed equipment [engines, shaft, rudder, ESC] then float the boat and adjust the position of the batteries to suit.

After doing this you will know the best location for the batteries and then you can fix their positions so they don't 'flap about'.

Job done.

Alternately you could send all of the information to a designer who will calculate everything for you, but be warned that this option will prove to be expensive.

Paul

[harry smith 1Participant @harrysmith1]

Hi Paul T

As I have not had the plans resized, I tested my idea with a plank of wood.

With the gear I have I sat the bits on the plank and with the motor and ESC up front and the battery across the boat behind the crew cockpit.

I had the CG about 25mm behind the main step.

Also add the crew and still got a CG with a bit more playing the same.

As the step on the sized up boat is from the bow 406mm the plank is heavy to the rear at 499mm, so I have room to move the battery around.

NOTE THIS IS PLAN A ONLY !!!

Harry

[ashley needhamParticipant @ashleyneedham69188]

With fast craft such as this my limited experience is that it is the dynamic c of g that's important. I have unfortunately several craft that sit very oddly in the water at rest, are even more odd at low throttle openings, but suddenly assume the correct attitude at their full speed, and this is where you want to be.

​​Ashley

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by ashley needham on 09/09/2017 17:32:50:

With fast craft such as this my limited experience is that it is the dynamic c of g that's important. I have unfortunately several craft that sit very oddly in the water at rest, are even more odd at low throttle openings, but suddenly assume the correct attitude at their full speed, and this is where you want to be.

​​Ashley

The CG should not be dynamic- unless you don't tie the batteries down inside the boat! It's going to be the centre of pressure and the various force lines that are going to be dynamic.

At rest the boat floats because of upward pressure from the displaced water all around the hull. On the plane, and particularly with a skimming craft like a hydroplane, the boat sits on a few points which are reacting with the water surface…

[harry smith 1Participant @harrysmith1]

Hi All

Had the plans up size by 30% to 950mm (37 and 1/2&quot x 270mm(10 and 5/8&quot.

Because of the shallow hull I added the other 5% for a bit of room.

On the plans the motor rescale to 40mm from 28mm.

The only problem is that it's sixth in line project as I wish to clean up my other project before starting again.

To add to this my mate and I would like to build a pair of RAF 60 foot Pinnacle boats to sail together.

Lovely boat at 1021mm(41 and 1/4&quot and so many original boats to pick from!!!!

Harry

[Author]

Posts