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[rathikrishna]

Hai friends...i am on my way to compleate my puffer, and done almost..but i am facing a problem, that is, when i increase the speed,the nose of the boat is droping in to water...as one instructed i replaced its final shaft from a steep position to 45 degree...still it bahaves like that, and if the speed is too high, it runs in to a zig zag pattern.what can i do to overcome this..?  help please...

[rathikrishna]

its prop made from a aluminium lid, and dia is 2 inch.it spins anti clockwise, with a rudder you can see in my photographs...i dont know what to do, and i am too sad, because of its erratic nature...

[Shipmate60]

The original puffer had a completely flat propshaft.
With your angle the thrust wants to jift the stern which will push the bow down.
All I can suggest is you ballast her down by the stern so when using a little power sh sits about level.
In real life these vessels regularly ran deep at the stern it allowed them to be beached and unloaded.

Bob

[rathikrishna]

Thank you sir...but i dont know to seal water entering in to the hull, while using flat prop shafts.so i always choose angeled prop shafts.so from your advice i will add more weight at stearn.i hope it will clear the problem...thanks once again..

[Shipmate60]

rathikrishna,
Do you have access to any waterproof glue or adhesives.
If you could tell us what you have we could tell you the most suitable.
Or you could use a non-waterproof glue but ensure that there is good paint coverage which will keep the water from the glue.

Bob

[pugwash]

Rathikrishna, Please don't forget these little ships would not have been travelling
very fast.  They were only capable of travelling slowly - at a guess perhaps
8-10 knots perhaps you are just using too much power and that is why the
bow is digging in to the water. Once you have sorted out your leak problem
try it out using less power and if the motor will not turn very slowly shipmate60
is correct about the propeller having very flat blades

Geoff

[DickyD]

rathikrishna,
Do you have access to any waterproof glue or adhesives.
If you could tell us what you have we could tell you the most suitable.
Or you could use a non-waterproof glue but ensure that there is good paint coverage which will keep the water from the glue.

Bob

Have to be very careful with adhesives Bob as the boat is made of polystyrene.

[boat captain]

Are you scared of water entering up your propshaft?  If so fill it with grease or thick oil.

 Joe

[Bunkerbarge]

From your description I assume that you angle the shaft so much to prevent the water travelling along it and entering the boat.  The first question is then do you have a bush or bearing at either end of the tube, supporting the shaft?  If not then you would restrict the water significantly by fitting them.  Also as has been suggected filling the tube with lubricant such as grease for larger ones or oil for smaller ones will also keep the majority of the water out.

The dipping of the bow is definately as a result of the fact that the shaft is far too steeply angled so working on sealing the tube and relocating it horizontally would be a better way forward.  If the bow is going from side to side then I think you are going tooo fast.  A puffer hull is not the most efficient so pushing it through the water too quickly will make it unstable.  This can go so far as to tip the boat over so stay well away from these conditions.  This is also as a result of the shaft being too steep and you are moving the centre of gravity too high when you lift up the stern so, again, back to getting the shaft level.

[LarryW]

hi Ramakrishna my puffer is made of mount board ,which is resin treated i also seal with poleyerthane varnish ,...............but do a test on materials first,...nice puffer though. cheers Larry

[Arrow5]

I think a radical re-design of the stern is required. You will be able to flatten the prop shaft angle plus there will be some protection  of the prop and rudder.  As others hve suggested a bush at each end of the prop shaft tube filled with oil or grease should stop water ingress.

[malcolmfrary]

Arrow is correct, the steep angle will not help at all, but another bad effect will be that the flow coming off the prop will almost totally miss the rudder.  Steep angles like that were intended for fast runabouts and ski towing launches such as the "Albatross", where the thrust pushed the stern up, but the hull shape encouraged planing, so when the boat went fast, it stayed level.
Have you found this site?
  http://www.towboatjoe.com/     
It has a section about home-made props and shafts.

[rathikrishna]

Good evening all respected friends..sorry for the late reply, i as in duty....i will do all the things adviced, and yes sure, i was pushing it faster in water....i will use less powered motor, and try to make shaft more flatter...hat a fool i am...i wasnt thinking about the grease...and oil...Hi...Hi....thanks for all once again...thanks...

[rathikrishna]

Thank you all...i have reworked on my puffer, and its compleated...its working nice...

[Shipmate60]

I am just glad such a nice model now works as it should.

Bob

[rathikrishna]

thank you all...it working nice in water...watch video here...http://www.youtube.com/watch?v=mNJubICxU2c