Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Lifeboats => Topic started by: Lifeboatman on August 12, 2013, 09:17:47 am
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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.
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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 (http://http://www.modelboatmayhem.co.uk/forum/index.php/topic,24621.0.html)[/size]
Hope this helps
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Many thanks, the link isn't working for some reason, >:-o
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.
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The link had too many http's
Here you go
http://www.modelboatmayhem.co.uk/forum/index.php/topic,24621.msg242253.html#msg242253 (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
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...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.
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Simply a coil in the cooling fins
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A bit lost of coils on the fins.?
I'm thinking of different coils I rekon {:-{
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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
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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.
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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
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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.
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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
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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.
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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
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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.
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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.
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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.
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Hi ya,speak to bill D203 as he done basically the same for his arun.baloo
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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 :D :D
Ned
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Hi ya,speak to bill D203 as he done basically the same for his arun.baloo
Bill ran a single shaft setup.
Ned
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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 :D :D
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.
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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
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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.
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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?
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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..........
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I think I'm starting to stumble.
This build is looking like its getting really hard to build. {:-{
I really want to build this thing and use the IC engines. But the whole drive system is looking impossible. I can build one that just goes forward and no individual drives, but I'm really thinking I need the reverse even to just stop the boat.
To sum up today, >>:-( >>:-( >>:-(
Why is this getting hard on the brain... I'm not stupid, I've got a degree in agri engineering for crying out loud.
Looks like I may have to just buy some IC nitro engines and buy the gearboxes to go with them. Would make life easy I suppose. And mean making some stuff easier,
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Ok. I've had a mini brain wave. Please bear with me.....
Ok. So I got electric motors for running. Easy, all the reverse problems sorted. Plus they can be independent..
But as I want the exhaust flaps to work I can use a small IC engine that will just run inside, that way if its effecting anyone I can shut it off and still use the model.
But next question. What motors? Water cooled brushless? What ones do I get and what ones to stay away from?
Looking at maybe going 3ft ish.
Plans are coming from RNLI soon. So how big does these plans make the boat?
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you can easily achieve that effect by having cooling rings around the motors that take water in through a scoop under the boat like ICE lads do, and then eject it out of the exhaust flaps at the stern.
and then you don't need the ICE which is the big blocker to sailing on most waters, as even one for just producing noise and water effect will probably not be allowed most places.
neil
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This is true Neil. :-))
But I do want some exhaust gas aswell. I know there are smoke generators but will one pump out enough to move the flaps.
I see the exhaust flaps all the time when I'm at the station, the water only just moves the flaps, the exhaust gas does most of the movement.
I have a load of electric stuff coming in soon from a crewmember from rc cars. So most of the servos and control boxes.
Going electric also means I can reduce the size of the model aswell.
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have a look at this video at around 2.18 on the video you can see the exhaust flaps on the arun with the engine sound and exhaust smoke operating them.....if you look further on youtube you can find others with similar effects.
neil.
http://www.youtube.com/watch?v=-sAWSanEZak (http://www.youtube.com/watch?v=-sAWSanEZak)
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If you are going to build a boat that is 7ft long it is going to be VERY heavy and you will need help to launch it.
All the answers can be found with the members of your local club at Dover and we will be pleased to help.
http://mba-dover.org.uk.freehostia.com/ (http://mba-dover.org.uk.freehostia.com/)
Regards,
Len, Scale Secretary.
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Can't wait now.
The plans have turned up today from the RNLI.
Just work that is going to get in the way next week. A busy week for me.
Going to start construction soon as I can. Havnt had a good look at the plans yet as I don't have a table big enough to spread them out on, so going to wait until I can get down the boathouse and lay them all out down there on the tables.
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Ok so looked at the plans, still am looking.
One plan, and probably the most important one is in 1.25 scale, the other two plans are in 1.20 scale.
I've read about how to re scale the drawing, but couldn't make head or tails of it. Could anyone give me an idiots guide to doing this. Or should I just find my local printers and get them to re print it?
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your print shop should be able to scale them for you.
But, you need to know either of two things
a. length you want the model, and the length of the original boat, then you have a scale to work with.
or
b. the scale you want to build your model, then using the scales of the plans work out the %age to print the drawings
simple.
Without either of these its all pie-in-the-sky, as I couldn't find any of these in your thread.
cheers
vnkiwi :-))
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Ok. I was going to follow the plans and go 1.20, but I guess I can't do that?
Was going to build the same size as the drawings.
I did say I was a novice. :embarrassed:
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yes you can.
you just need to enlarge the 1:25 plan to 1:20 scale.
That's a 1.25 times enlargement.
Any good print shop can do that for you.
Then everything should be the correct size on all sheets.
Go for it
cheers
vnkiwi :-))
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yes you can.
you just need to enlarge the 1:25 plan to 1:20 scale.
That's a 1.25 times enlargement.
Any good print shop can do that for you.
Then everything should be the correct size on all sheets.
Go for it
cheers
vnkiwi :-))
Thanks, had a small panic then. Will see if I can find my locl printers, there was a few in my area but not even sure of they are still going.