discussion boatman's 1/72 HMS Tiger C20 build

[boatman]

Chris, this may be a totally stupid suggestion, however if you were to lengthen the rudder, not depth but length toward the rear, would that perhaps extend the rudder sufficiently far into the wash of the props, when turning, to give you better steering?
Looking at your build I think that extending the rudder rearward would make it protrude out beyond the stern of the ship, which may not be acceptable.
Just me thinking outside the box.
ATB
Garry

AN HI Garry no it not a stupid idea as ive been thinkin along the same lines but my idea may not look very nice but im thinkin of cuttin off the back part where the rudder is an modifyin it to take 2 rudders an yes make them bigger like you say an if i can do it fit two rudders behind the outer props but they will be a very weird shape so they can turn in towards the hull an these new props at 45mm will nearly touch the hull so its goin to be a close run in an i may have to drill out all 4 prop shafts an A FRAMES an reset them all to take them monster motors as well so a lot of thought goin to happen an may take another couple of yrs before i get to try her out again an that blasted wind always gets up at norwich pond an sheringham but i cant do anything about that Aaaaaaccccchh
ATB AN PS EVEN MY BLOOMIN P/C IS AGAINST ME NOW AS I HAVE NOW TROUBLE POSTIN
chrisb

 

[boatman]

Quite a haul there Chris. I hope you luck turns soon.

If It was me I would have started with a fuse to each motor to see if there was one of those kicking off.
Swapped out the two "odd" motors to the ones that you would rather of had. Or more likely fitted 4 new low speed high torque motors with matched speed controllers.
If the ships speed was still an issue I would then have a look at the props. They do look to small. Even going from 33mm to 45mm will be a help. (Maybe going from a five bladed to a more modern ships six bladed high speed prop will be better still).
Steering wise to get a boat that length to turn quick you are probably going to have to have a not to scale solution. Either a huge rudder that will cut into the prop wash. (will need a high torque servo) or install two rudders that will cut into the wash of two props. Eventually with a mix on the radio that for example with a turn to port the rudder will turn to port, the the port motors slow and the starboard speed up assisting the turn. Maybe add the bow thruster into the mix and turn on a sixpence.

AN HI Ian yes so do i but dont think its gonna happen but will give it the good ole college try
1. now regards this fusein bussiness thats cured now as it one of those ole grupner motors causein that so i can tick that off the list
2.an yes im now goin to fit high touge motors but they are heavy an may make her sit lower in the water so more hull drag ? but wont know till i try her in the pond
3. yes today im hopein to order them x4 45mm props as cant go any bigger or they will hit the hull
4.AN them new fancy 6 bladed scimitar bladed props are to exspensive so i will have to stick with the normal 5 bladed props
5.yes Ian im thinkin of alterin the hull to take two rudders at the back an maybe two rudders on the outer props so all in 4 rudder like i did on my nimitz carrier but goin to be a big job an take quite a bit of work
6. an i treid a mixer on my nimitz carrier so that the props slow down on one side an the other side props speed up but it dint make any difference as remember im workin in the same medium water as the real ship an the real ship has maybe 12ft props so they will make a difference but as they say you can scale the model ship but not the water so no go on that but thanks for your intrest an info
7.AN regards the bow thruster Ian well it will only have effect when the model is still so it will push water left an right but when the ship is movin in hull speed the water will just stream past the outer ports so not good for steerin the bow if you see what i mean sir
chrisb

 

[boatman]

AN Ian if you note here is where ive fitted 4 rudders to my NIMITZ carrier an these turned her lovely an she was bigger than tiger but the hull shape on tiger is rounded so that will make it more difficult to fit in more rudders if you see what i mean
chrisb

 

[scottie3158]

Chris,
Sorry to hear the tales of woe continue, but you being you will overcome and sort it.

 

[boatman]

Chris,
Sorry to hear the tales of woe continue, but you being you will overcome and sort it.

HI Scotty nice to hear from you sir an well just me bein me wont cure the probs if i cant get the right gear as i have been on a boat site to get them 5 bladed props but its so complex i cant make out head nor tale of it an neither how much these props are as i want 5 bladed 4 mm thread an diamiter 45mm an even treid to send them a email but my p/c wont send so im waiting for them to phone up
an pic of props x4 below

 

[Guest]

Quite a haul there Chris. I hope you luck turns soon.

If It was me I would have started with a fuse to each motor to see if there was one of those kicking off.
Swapped out the two "odd" motors to the ones that you would rather of had. Or more likely fitted 4 new low speed high torque motors with matched speed controllers.
If the ships speed was still an issue I would then have a look at the props. They do look to small. Even going from 33mm to 45mm will be a help. (Maybe going from a five bladed to a more modern ships six bladed high speed prop will be better still).
Steering wise to get a boat that length to turn quick you are probably going to have to have a not to scale solution. Either a huge rudder that will cut into the prop wash. (will need a high torque servo) or install two rudders that will cut into the wash of two props. Eventually with a mix on the radio that for example with a turn to port the rudder will turn to port, the the port motors slow and the starboard speed up assisting the turn. Maybe add the bow thruster into the mix and turn on a sixpence.

Ian , I'd have set fire to it by now

 

[boatman]

Ian , I'd have set fire to it by now

yes John an give her a vikein furneral lol but im not givin up just yet gonna fit some bigger props on her an try that as that may have been the probs all along as thats the trouble with a workin model you just dont know what its goin to take to get it all right an i think ive been veryl lucky with all my other ships that i got them all right but as they say there is always one that will cause trouble an it seems like its this one lol
chrisb

 

[Jim R]

..... gonna fit some bigger props on her an try that as that may have been the probs all along

Lets hope your right :smiling:

 

[boatman]

Lets hope your right :smiling:

yes Jim well it seems that it gonna be complex as on model boat mayhem ive got several guys all sayin something different about what props to spend a 100 quid or more on as it seems that the ones i was goin for have not got enough thrust an are not coarse on the prop pitch so i think i'll leave it a while an find out more info before i buy as these props are so exspensive x 4
cheers sir chrisb

 

[Ian M]

yes Jim well it seems that it gonna be complex as on model boat mayhem ive got several guys all sayin something different about what props to spend a 100 quid or more on as it seems that the ones i was goin for have not got enough thrust an are not coarse on the prop pitch so i think i'll leave it a while an find out more info before i buy as these props are so exspensive x 4
cheers sir chrisb

I was wondering why the guys that have R/C boat shops in England couldn't be a little more helpful. 4 x 45mm would get my chap o er here out the chair and doing the mathematicals!

 

[Ian M]

Try here.
https://raboeschmodels.com/product/148-5-blade-metric/#iLightbox
45mm brass 46.1 pitch. only 4mm shaft though. About £21 each.

 

[boatman]

I was wondering why the guys that have R/C boat shops in England couldn't be a little more helpful. 4 x 45mm would get my chap o er here out the chair and doing the mathematicals!

WELL Ian it may be that they are not sure themselves as to how corse a pitch them props are as i dont know as the one i put on here looks great but accordin to a guy on mayhem he says they are not corse enough so not as much thrust as i need so it a case of buy an try an if not right send them back for more corse a ones but the shops will only do it a couple of time an it costs to keep sendin them back an forth so for the moment i'll wait till my boaty freind comes back from his holl an i will consult him an see what he says
cheers sir
chrisb

 

[outrunner]

I feel for you Chris as it looks a bit like the "suck it and see" method at the moment. I would imagine there are guys out there with the knowledge you are needing but finding them might be easier said than done.


Andy.

 

[scottie3158]

Chris,
I'm sure you will get it sorted. Hope your mate can sort you out. This is just my thoughts but will a coarser pitch make the motors work even harder pulling more current?

 

[boatman]

Try here.
https://raboeschmodels.com/product/148-5-blade-metric/#iLightbox
45mm brass 46.1 pitch. only 4mm shaft though. About £21 each.

OH Gosh Ian many thanks for lookin here an i was lookin at the pitch of the props an i havnt a clue TBH so as i will say wait till i talk to my boaty mate as i dont understand how this pitch numbers work is it the higher the no. the corser the prop pitch on the blades ? cheers
chrisb

 

[boatman]

I feel for you Chris as it looks a bit like the "suck it and see" method at the moment. I would imagine there are guys out there with the knowledge you are needing but finding them might be easier said than done.


Andy.

YES Andy how very true what you are sayin but the point of it how much will i have to spend to get the right props thats the question
cheers
chrisb

Chris,
I'm sure you will get it sorted. Hope your mate can sort you out. This is just my thoughts but will a coarser pitch make the motors work even harder pulling more current?

Chris,
I'm sure you will get it sorted. Hope your mate can sort you out. This is just my thoughts but will a coarser pitch make the motors work even harder pulling more current?

well Scottie at the moment i dont think the current matters as i have heavy duty fuses an batts an same on ESC an same on them monster motors if i fit them an if i can get 15 mins worth of sailin before it flattens the batt it will be worth it as i can buy another batt so twice the sailin time as them batts are not to dear what costs the money are these props as they are a specialist item as when they are bein made they have to all be at the correct pitch on the blades an they must be finely balanenced or the prop will shake an break the bearins in the prop shaft then more trouble TBH I just dint realise how lucky ive been on all them other ships oh dear
cheers
chrisb

 

[Ian M]

Pitch is simply the distance the propeller would move in a line for one full turn. So a pitch of 46.1 the screw would travel 46.1 cm per full turn. (Ignoring slip.)
So the higher the pitch number the further the screw will travel.
Silly question but have you checked the rotational direction of the props, so both starboard props turn the right way. If you have a lefty and a right on the same side, that boat ain't going anywhere lol.
I know someone who did it

 

[boatman]

Pitch is simply the distance the propeller would move in a line for one full turn. So a pitch of 46.1 the screw would travel 46.1 cm per full turn. (Ignoring slip.)
So the higher the pitch number the further the screw will travel.
Silly question but have you checked the rotational direction of the props, so both starboard props turn the right way. If you have a lefty and a right on the same side, that boat ain't going anywhere lol.
I know someone who did it

WELL Ian after building an sailin 7 other big models i have never put a L/H AN A R/H PROP on the same side as its easy to spot i just look at the way the blades are bent so NO on one side there are two L/H an on the other side its two R/H PROPS goin in or out but IN OPPISITE DIRRECTIONS SO ALL GOIN INWARDS for forward thrust an maximum thrust through the rudder a very good qeustion all the same but one ive never been guilty of an as for pitch Ian i thought that the pitch of a prop was in the angle of the blades how far they are bent in to the prop boss from 90 degreess up angle ? as it shows that on mayhem pic
but many thanks for your help IAN as sooner or later we will get there
Chrisb

 

[Ian M]

WELL Ian after building an sailin 7 other big models i have never put a L/H AN A R/H PROP

The chap that did it had been building ships/boats for 50 years. Oh and he was a boat builder by trade... Anyone can make a mistake when they are flustered.

i thought that the pitch of a prop was in the angle of the blades how far they are bent in to the prop boss from 90 degreess up angle

It is but the distance that the prop travels per revolution is a much easier way to visualise it and it is infact how places like Mercury and Volvo/penta explain it.
If had just said that the higher the number the coarser the pitch, would you have been any wiser?
The pitch can be measured but is not that easy so I will leave that to your cleaver mates at Mayhem.

 

[boatman]

The chap that did it had been building ships/boats for 50 years. Oh and he was a boat builder by trade... Anyone can make a mistake when they are flustered.


It is but the distance that the prop travels per revolution is a much easier way to visualise it and it is infact how places like Mercury and Volvo/penta explain it.
If had just said that the higher the number the coarser the pitch, would you have been any wiser?
The pitch can be measured but is not that easy so I will leave that to your cleaver mates at Mayhem.

HI Again Ian an yes anyone can make a mistake an to be sure ive just nipped upstairs to my model room an looked at the props on my tiger an they are all fitted correctly so there is no L/H an R/H fitted on the same side so that is not the problem an yes i would have understood if you had said the higher the number the coarser the pitch of the prop so more thrust thats right isnt it ? so ive now learned from you sir on that as ive never had this prob but yes i know that i need bigger props an what ive learned from you Ian will able me to look at the list on the prop site an look for a higher no. but wheather the prop coarness will be enough will be pot luck if you get my meaning but thank you very much sir for this info
chrisb