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Fishing boat progress report

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David Meier29/08/2011 10:31:55
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205 forum posts
81 photos
In response to Ashley's gentle nudging on another thread to get cracking with building boats, Here is where I have got to with my fishing boat. It has spent a lot of time sitting, between short spurts of building.
 

White undercoat, I have just placed the fittings into their positions for the Photo.
 

Being my first scratch build I have made a lot of mistakes along the way and will do things differently next time. A classic one was gluing the window frames and doors onto the cabin before finish painting them, now I have a lot of fiddly painting to do. I also should have been more careful setting up the frames as the hull is not quite symmetrical and I have had to fit the gunwale / hand rail carefully to disguise the fact when you are looking from above. I have done some more sanding and top coats since these photos were taken.
 
David.
ashley needham31/08/2011 13:57:41
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David. Dont worry about a bit of cheating now and then. no one will notice.
 
Nice hull shape, great bow... prop looks a bit small?? or just a temporary job.
 
remind me of the dimensions. i should like to take a boat like that on the sea !
 
Ashley
David Meier02/09/2011 09:04:39
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205 forum posts
81 photos
Hi Ashley.
The model is 700mm long at 20 - 1 scale. The hull shape is from the plans of an Italian fishing boat that I found on the web, but the above deck structure I just made up as I wanted it to look more like the type of fishing boat you used to see around NZ years ago.
 
It is funny about the prop. I made a 4 bladed one at 35mm dia and was wondering If it would give enough thrust. When I tried it in the ballasted hull, at full speed it was doing its best to plane and the bow wave was higher than the sides of the boat. So I made a 30mm dia prop and that was still too fast, finally made a 25mm dia prop and I even had to tweak the pitch back on that.
 
I am using a small brushed motor running on a 7.5V battery coupled to a 2.5 to 1 gearbox that I made. I don't know what the motor is though. Here is a picture of it.
 
May be running a bigger prop on a lower voltage would be better. What do you think?
 
David.

ashley needham02/09/2011 13:04:00
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7645 forum posts
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A bigger prop gives more "bite" for good acceleration and stop, and will sound much less busy that a toddy one thrashing away underneath the stern, although ultimately they may probably give the same sort of top speed
 
given that there is a 2.5 reduction, the motor you have fitted must be a revvy thing..
 
I would just put the 35mm one back and use less throttle or fit a 4.8v battery ?
 
Years ago I bought. 3 x 45/50/55 mm plastic 4 blade props with quite a fine pitch...and have never found a boat to use them on. Thrust was disapointing, although they look the part in their gold paint.
 
The biggest props I have are on the Fantome, at 50mm brass three blade, on an MFA 800 motor. Wow..the thrust from THOSE babies!
Ashley
David Meier04/09/2011 00:57:17
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205 forum posts
81 photos
You are right Ashley it does sound very busy when it is going along, I will reduce the pitch on the 35mm dia prop and try it on 4.8 volts as you say.
Things are progressing, the hull and fittings are now painted and I have made a mock winch for the derrick.
David.
ashley needham04/09/2011 17:15:33
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7645 forum posts
159 photos
David. If it is about 27mm in diameter (or whatever a speed 400 or 380 is) it may be that fitting a cheap 385 motor (3-15v sort) would fit the bill. On a 7.2V battery it wont be revving anywhere near as much as the-presumably-380/400 motor you have, it will be a straight swap and you can use your existing battery.
 
I have a high regard for the 385. On 12V it is a very adequate performer for something quick-ish, and I have a number of models with 385`s on 6V and brass 35mm props which run no problems. It may be they are slightly overloaded, but the current draw is very small to start with, and they dont get hot...so must therefore be running ok.
 
BUT....on the TBD, which had a speed 400 and 35mm "s" 2 blade plastic prop (couldnt find a smaller one) on 7.2V...this WAS getting very hot..and so I fitted a 480 which only got fairly warm, until my mate Chris came across with a 32mm prop and now everthing is sorted. The TBD goes like you wouldnt believe and the motor only gets warm.
 
Ashley
 
.
 
 
David Meier06/09/2011 00:19:27
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205 forum posts
81 photos
Thanks Ashley, I will keep a 385 motor in mind. In the mean time I have reduced the pitch of the original 35mm prop and put it back on and will try it on 4.8 volts as you suggested earlier. I am just finishing a few detail bits on the boat and hope to give it a try out on the weekend.
 
David.
ashley needham06/09/2011 19:13:02
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7645 forum posts
159 photos
As an aside, while I was initially starting the Island OPV ( in my album) only 25 or so years ago, I tried various motors, one amongst them was an MFA 850 (the earlier slightly thinner one).
 
I learnt from this that an 850 will indeed power a 50mm prop with no problems, and a displacement hull will not go very much faster with lots of power, but rather the stern sits down and the bow wave increases to heroic proportions.
 
Picture a 36 inch craft going across he lake with a veritable sheet, nay, DUVET of water issuing from the bow, and the stern bulwarks actually sitting BELOW the level of the lake, and at a fair lick. Lacking motor control, only rudder, i managed to arrest it with a well placed welly on the nose as it headed straight towards me on the bank.
 
I should have realised something was wrong when I tested it besides the bank prior to setting it loose, as the plume of water issuing from the stern almost emptied the lake. But what the hell I thought, in for a penny, in for a pound.
 
 
Ashley OK, so I exaggerated a teeny bit..
 

David Meier07/09/2011 10:05:27
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205 forum posts
81 photos
I bet every one was keeping well out of your way until you captured it again. It must have been a bit scary having no motor control when it was hooning around that enthusiastically.
 
Well I am calling my boat finished today and am going to take it to Henley lake tomorrow to give it a whirl. I can still add more details from time to time as I feel like it in the future.


I have even managed to get my head around and get it running on my new cheapie 2.4 Ghz radio.
Now I can get started on the long awaited sailing scow build.
 
David.
David Meier08/09/2011 11:42:57
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205 forum posts
81 photos
Henley lake was to windy even for the 1 meter yachts so we changed to Queen Elizabeth park to give my boat its first serious run.
Everything went well with no hiccups.

The pictures show it running at about half throttle with the reduced pitch 35mm prop, Ashley.
I think that I will leave it like that, as it gives a bit in reserve for getting out of trouble if needed.
I have concentrated the lead ballast at the bow and the stern in the hope that it will give a more realistic effect when going through waves.
It only goes forwards at the moment as I bought a cheap Turnigy 20 amp brushed aeroplane ESC for $4.95 US, with the idea of making a reversing switch which will run off the 5th channel on the transmitter. This still needs doing.
 
David.
 

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