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[Lifeboatman]

Ok so I'm new to the world of building model rc boats. Have done a few car kits but not boats.


So any help would be more than grateful.


I'm going to build an rc model of the lifeboat I'm currently crew of, Dover lifeboat.


But this one is going to be a bit different as I'm going to use petrol power instead of electric. My day job is repairing garden machinery. So I'm going to use hedgecutter two stroke engines as one type of cutter engine already turns anticlockwise and another made by the same people (stihl) turns clockwise. So the turning of the screws isn't a problem.


What I'm going to have difficulty with the first the hull building, never done anything like this before so what's the easiest way? Sorry the best way to do this?


Getting any information from the RNLI is no problem at all. But I'm not a technical drawer so getting plans and reducing the size etc is beyond my capabilities.


This model will be twin props just like the real thing, what's the best way to seal the props so there is no water ingress?


The electrics are not a problem for me at all, I can handle those easily.


Any help would be very gratefull.


Richard.

[gingyer]

Hi Richard,
Welcome to the forum and well done on you for serving on the lifeboat.


I would seriously reconsider the use of the IC engines for power as it limits the places you can sail
But that's no to say its not possible. Have a look at Bills Arun class thread he used only 1 motor and
Gearbox [size=78%]http://http://www.modelboatmayhem.co.uk/forum/index.php/topic,24621.0.html[/size]


Hope this helps

[Lifeboatman]

Many thanks, the link isn't working for some reason, 


The only reason I'm looking at using IC engines is so I can take it and play with the real boat when out in the harbour. See if I can match the speed of her.


I can also see that cooling of the engines could be a problem aswell. Without air flow they will over heate in no time. So this will also need to be in the planning.


The real lifeboat has extractor fans above the engines to take away excess heat, but also water cooling. Was looking into nitro engines last night and water jackets for them. Was thinking this may work?


Rekon if I'm carefull I can get away with using it Down the local place if I limit my speed and don't put the power on.

[Tug-Kenny RIP]

The link had too many http's

Here you go

http://www.modelboatmayhem.co.uk/forum/index.php/topic,24621.msg242253.html#msg242253

Welcome to the club, by the way.  You sound an interesting member to have.

The  RNLI drawings can be re-sized easily by your local print shop as we've all done it.

Cheers

ken

[w3bby]

...I can also see that cooling of the engines could be a problem as well.....

.....The real lifeboat has extractor fans above the engines to take away excess heat, but also water cooling.....

It need not be the problem you envisage. A water jacket on the cylinder and a pump (if you want to sit still) should be ok. Biggest source of heat is probably going to be the exhaust.

[GAZOU]

Simply a coil in the cooling fins

[Lifeboatman]

A bit lost of coils on the fins.?


I'm thinking of different coils I rekon 

[Netleyned]

Ally or copper tubing wound between the fins with water circulating to act as a waterjacket.
Fed from water pickups on the hull or, if the model is to spend time idling then a circulation
pump would be advisable.


Ned

[Lifeboatman]

Ally or copper tubing wound between the fins with water circulating to act as a waterjacket.
Fed from water pickups on the hull or, if the model is to spend time idling then a circulation
pump would be advisable.


Ned

Ahh. Thank you. Get it now. I've got loads of copper brake pipe in the workshop. That would do it. Just a pump that would be needed. It would be perfect aswell, I'm looking at making exhaust flaps that actually work front he engines, so I could incorporate the water outlet in these aswell. Would look much more like the real thing.

[GAZOU]

you keep the cooling air. This for when the boat is stopped
When the boat is moving you in the circulation of water in the coil

[Lifeboatman]

Some good info already. Thanks guys.


Plans are being drawn, looks like my fiver year old has done them but getting there. Just working out how everything is going to sit,  no measurements on them as yet, waiting to get hold of engines first then working out from there.


Got the steering figured and where the props will sit, just the throttle control.


Been to local model shop and he said that counter turining prop shafts are not needed, just a L/H screw and R/H screw. Then the props will be turning the same way but the propulsion will be different. Does this make sense?


If it does it will make life easier as I won't need gearboxes to reverse one engine drive.

[Rottweiler]

Hi Richard,
have you thought of conventional brushed and brushless motors? These will give you ample SCALE speeds,but probably not as fast as the real thing.I'm not sure if I would want any model of mine to go that fast,it would look totally wrong,and very probably very difficult to handle.There have been a few builds on here using electric motors.
Whatever you choose is up to you of course,and as already said you will get plenty of tips and advise on here
All the best,
Mick F

[Lifeboatman]

Thanks mick.


The main reason I'm going to petrol is so I can make the exhaust system work to be honest.


I real miniature working model is what I'm after and having the exhaust flaps working with the water jacket ejecting spent water out them aswell will just look really cool.


I'm not interested in having a high speed on her, but its always fun. Just having a realistic as possible working model. Plus I'm going to strengthen the aft deck so it could even tow.


I was thinking about a working crane but that might just push it a bit too far. 


Well get the model mad wand then see from there, I can always remove the petrol stuff and replace with electric if it goes wrong I suppose.

[Rottweiler]

I'm hoping to get water coming out of the exhaust on my Tamar,but using brushless motors,and either a water intake,pumping water out at the back, depending on speed,or using an actual water waterpump to give a constant supply.I have been toying with smoke also,but as you would mainly see that only on start up,it would be a little complicated.Working cranes have been done before,but if I ever get my severn built,it will be the Falmouth Lifeboat "Richard Cox Scott" and won't have a hiab at all.
Mick F

[Lifeboatman]

I'm hoping to get water coming out of the exhaust on my Tamar,but using brushless motors,and either a water intake,pumping water out at the back, depending on speed,or using an actual water waterpump to give a constant supply.I have been toying with smoke also,but as you would mainly see that only on start up,it would be a little complicated.Working cranes have been done before,but if I ever get my severn built,it will be the Falmouth Lifeboat "Richard Cox Scott" and won't have a hiab at all.
Mick F

Watch that space and hold off. If it hasn't had its refit yet it will come back with one on.


The exhaust will smoke on them on startup but to pickup speed they will dump a huge load out the back. I don't know how much you know or if you are a crew member but the new mtu engines burn a litre of engine oil an hour, so they will always be pumping black smoke out the back. Just not very visible unless its at standstill or revving up.


I rekon the two stroke engines will give it a very good going, if I use low smoke two stroke oil it shouldn't chuck too much out.

[w3bby]

Been to local model shop and he said that counter turining prop shafts are not needed, just a L/H screw and R/H screw. Then the props will be turning the same way but the propulsion will be different. Does this make sense?

This is a load of BS..... A right hand screw turns one way and a left hand the opposite to give forward motion, you need counter rotating shafts to achieve this.

Depending on the size of the boat you could possibly get away with just one motor and use a a one in/two out gearbox. These are available commercially but at rather a high cost.

[Lifeboatman]

This is a load of BS..... A right hand screw turns one way and a left hand the opposite to give forward motion, you need counter rotating shafts to achieve this.

Depending on the size of the boat you could possibly get away with just one motor and use a a one in/two out gearbox. These are available commercially but at rather a high cost.

Well that's what I thought. So one turning clockwise and the other counterclockwise. This gives even propulsion. That's the way I saw it. But you say its wrong? So I do need one engine to turn the other way.


Yes the size means it will be two



Has anyone for a link for an appropriate gearbox please.

[baloo]

Hi ya,speak to bill D203 as he done basically the same for his arun.baloo

[Netleyned]

W3bby is correct and so are you.
What sort of model shop did you go to?
Did it have ladies in the window and the
guy you spoke to was the 'manager'
Dover must be getting like Amsterdam 

Ned

[Netleyned]

Hi ya,speak to bill D203 as he done basically the same for his arun.baloo

Bill ran a single shaft setup.

Ned

[Lifeboatman]

W3bby is correct and so are you.
What sort of model shop did you go to?
Did it have ladies in the window and the
guy you spoke to was the 'manager'
Dover must be getting like Amsterdam 

Ned

Sadly its the only model shop in my sad little town. And not knowing thought he would be the best place to ask.


Right so I'm back to square one. I need to transfer one of the engines into reverse by wither turning it the other way and running a shaft underneath it. I have seen these on ebay from Hong Kong... Not sure about them. Or I could make my own.


Or a one in two out gearbox. Could also make one of these with the right gears. There is a lot I can make as I'm a qualified agri engineer. So making things like these doesn't phase me at all.

[Netleyned]

I thought you had a pair of stihls that ran clock and anti clock.
Are they the same physically so they will balance easily?

All you need then are a left handed and right handed prop to work OK.

Ned

[Lifeboatman]

I thought you had a pair of stihls that ran clock and anti clock.
Are they the same physically so they will balance easily?

All you need then are a left handed and right handed prop to work OK.

Ned

Yes your right I forgot about them. They are hedgcutter engines, one is designed to run opposite to others. I have one engine and I can easily use another from another type of stihl. They are the same size weight, so it can be done that way.


Means the engines will be on there side as such as the drive comes from the bottom when they are on the hedgecutters, this doesn't matter much as they are two stroke.


I'm going or start building all the bits I have tommorow at the workshop and plan them out on the bench then use a piece of hard board and fix them all in place to test if they all run together, before I go putting them in the hull, or even so I can see what space I have to play with.


A question on the props. Left hand and right hand screws, what one goes on what side and what rotation do I need on the shafts? Did say I was new to boat building.

[Lifeboatman]

Update on the build.


Nothing doing yet, got the engines sorted today and ran them up on the bench, they both run in on tach at 2200 rpm. On tickover. This is normal and happy they both run at same speed.


Layed out what I have and done some measurements. Looking like the minimum I can get away with is 2ft accross. So was thinking somewhere around 2 ft by about 7ft. Height will just come along as I build up superstructure.


Getting plans sent by RNLI.


Now I have been toying with the idea today do making a reverse drive gearbox, been mulling over how to do it. On a car its easy, just a shaft with an extra gear thrown into existing gears, but on a model its over my thinking, so what's they way to do it. Or can I buy one that will put up with the petrol engine stresses?

[Neil]

your best bet without thinking of reversing gearboxes is to buy two variable pitch propellors, which would allow the motors to run in their continuous direction, and the props, by altering their pitch would set the boat from forward, to neutral and into reverse pitch mode..........