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Broad Ambition - The Model


grendel

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today the motor was fixed down and tweaking began.

 

 

 

well there we are - consumption down to about 1A, the cv joint (from a model car) the bit sticking up was a steering arm, I will make up a bracket from the bulkhead to this to allow me to fine tune the angle of the joint for the lowest resistance. I also found a tiny bit of packing under the stern tube locks this in place and reduces the current consumption. also seen here is the 35mm prop.

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Today we went to the boating pool, the speed is a lot better with this motor. the added bonus the motor barely gets warm. while I was here I also had a test of the motor on the 6v ballast battery - very slow.

I took my ammeter along to measure current draw in the water 1.1A at 6V, 2.6A on 12V.

thats about 2 1/2 hours on full speed. a good cruising speed is obtainable at about half to 3/4 stick travel. I did encounter a few problems with leaves wrapping around the prop, cutting the speed dramatically 

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nearly a week with no updates - shocking I hear you cry - yes I have taken a short break, whilst I have been  getting the workshop sorted. add to that a couple of days (friday and saturday) feeling seasick, as a mild bout of labrynthitis struck.

hopefully now I have just about got there I can proceed with the boats particularly model #2.

the next step is the prop shaft support and the rudder.

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this evening two small bits of work, firstly one of the storage cradles has cracked, and needed repairing, so this was brought into the workshop, glued , reinforced, and clamped.

secondly the stainless steel strip down the bow of Broad Ambition was added, this was done with the chrome pen, and will be tested for durability in the water, this may be replaced with a real stainless steel strip if it doesnt last.

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this evening the fitting of the prop shaft support started, I didnt want to fix it solidly into the skeg end, as I wanted to be able to remove this, so I devised a method that would allow the bracket to sit in a slot in the skeg, the solid lump will be soldered into the skeg.

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28 minutes ago, grendel said:

this evening the fitting of the prop shaft support started, I didnt want to fix it solidly into the skeg end, as I wanted to be able to remove this, so I devised a method that would allow the bracket to sit in a slot in the skeg, the solid lump will be soldered into the skeg.

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I really do like to see a craftsman at work. 

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31 minutes ago, grendel said:

this evening the fitting of the prop shaft support started, I didnt want to fix it solidly into the skeg end, as I wanted to be able to remove this, so I devised a method that would allow the bracket to sit in a slot in the skeg, the solid lump will be soldered into the skeg.

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I really like to see a craftsman at work.

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tonight the block was soft soldered into place and the skeg replaced, motor tests done, no noticeable increase in current draw - still at 1.7A as before I fitted the support, when installing the prop shaft and associated parts, keeping the current draw low means everything is well aligned.

You can see the skeg has been slightly angled down to accommodate the 35mm prop, this is 5mm bigger than model #1. I actually have 40.5mm clearance now - not quite enough to go up to a 40mm prop. next the rudder will need to be fitted.

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so tonight I decided to see if I could custom build my own rudder, to enable me to give the model a bigger surface - more in keeping with the real thing, the first job, cut a slot along the centre of a 3mm shaft, over a fair distance, how to support it while I remove a fair chunk out of the middle. 

So a bigger chunk of brass had a 3mm hole drilled through it, then a carefully cut slot in the bigger bit, then using that slot I fitted the shaft in and cut a slot, slowly feeding the 3mm shaft in from the back.

success.

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I think they just come to me - one minute I am looking at something - the next i am trying to work out a better way of doing it, just for the challenge I guess.

that rudder shaft was the third one I tried, the first was on a v block on the bandsaw, that sort of worked, but I had trouble keeping it straight, the second was the first attempt at a sawing guide, but I didnt get the saw cut properly aligned with the hole, then this was the third attempt.

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a good example was the rudder, having widened the gap for the larger prop, the rudder I had ready looked a bit small and weedy, so I looked how it was made, and thought to myself, I can do that, so set about slotting the 3mm brass rod - the rest followed on from there, I will cut some brass sheet to make up the rudder and solder the whole together. the net result is I have done the slot and have a guide tool if I ever feel like doing another.

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tonight it was cutting out the rudder blade, this was cut to the shape  of the gap, but clearance was left in case of weeds. Then I soldered the blade into the pivot axle ,the rudder isnt a lot longer than the stock one, but has a little more in front of the pivot, and some depth.

this should give a bit better turning performance.

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