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KeilKraft Mermaid

Eze-Build

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carl brotherton21/01/2021 20:06:03
34 forum posts
27 photos

I know nothing about model boats.

Although pre teens I built a KK Mermaid. which went remarkably well, other prior to finishing, that is unsealed/painted, I ran it in the bath. At that point the sheeted hull warped.

During lock down for a number of reasons I decided to build another, and yes a lot of water has flowed under the bridge in-between. That is about 62 years of it. In that time a lot has changed.

I now have a hull, the top slightly modified, just to make it less fussy and the hull detail has been amended to avoid the the warping (hopefully).

I now need to fit it out. I do not know if a 2mm or 4 mm shaft assembly is best suited to such a small model. Plus I intend at the moment to fit a 60w input motor on a 2s Lipo.(probably about 300-600ma) the Kv is approx 1200. In short I do not know what a good combination will be to provide a decent turn of speed, with a reasonable motor run.

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I have sealed the model with Water Based Varnish, about 4 coats.

Advice is needed intially on the prop and motor arrangements.

ashley needham21/01/2021 22:27:00
avatar
6920 forum posts
201 photos

Carl Have a look at the excellent “eezebilt.tk” site. A veritable mine of information.

The suggestion seems to be a 2mm shaft. Do we assume your boat is 14” long?A brushed speed 280 motor and 25mm prop would likely be more than enough for your boat unless you already have a motor as per pictures?

Ashley

Chris E22/01/2021 07:44:41
198 forum posts

You might care to have a look at this video.The model is powered bu a 180 motor!

Weight is a critical factor with a model like this.

KK Mermaid

Ray Wood 222/01/2021 09:26:49
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2232 forum posts
777 photos

Hi Carl,

The interesting part of the youtube video is the boat is fitted with spray rails along the chine line which helps lift the bow out of the water, these little boats were never envisaged to actually get up and plane with tiny motors and Ever ready torch batteries. Ashley is spot on with the motor size I always use 4mm shafts even on the little boats.

Regards Ray

ashley needham22/01/2021 09:28:59
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6920 forum posts
201 photos

Cor! Very small “in the flesh” as it were.

yes a 180 would seem to be adequate. J.Perkins do some aircraft style brushed esc that weigh 5g including wires!

..GWS -ics100

Ashley

Edited By ashley needham on 22/01/2021 09:32:42

Charles Oates22/01/2021 10:31:34
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597 forum posts
50 photos

Someone educate me please. I thought I had a reasonable grasp of the common brushed motors, but the model in the video has me wondering. I haven't seen a 180 motor for a long time, but I don't remember them as anything special, so I thought he meant a 280. The problem is that he's using 7.4 volts, and the only 280s I've used were either 6 volts max or 24 volts max. I presume there are variants I've never seen, or have I got something wrong?

Charles

ashley needham22/01/2021 11:11:47
avatar
6920 forum posts
201 photos

 Not looked up a 180, but all my 280s run on 7.2v and get a good thrashing. Not had one burn or worn out yet!

No doubt running a 280 for days on end at 7.2v will give it a slightly shorter life than using 6v but considering the briefness of model boating?

Ah the wonders of opening another iPad window whilst replying to a post... a well known component shop does a round 140 motor takes up to 9v andseveralothers.

Ashley

Edited By ashley needham on 22/01/2021 11:15:39

Chris E22/01/2021 12:56:48
198 forum posts

This is what I don't like about brushed motors. The specs are generally so imprecise. I note that Component Shop list 3 different spec 280's & I am sure that there are many more out there.

I agree that the motor in the video looks like a 280 but what spec? I note that Ray's Ferret is about the same size & also has a 280. Perhaps Ray will be kind enough to tell us which spec?

Ray Wood 222/01/2021 14:58:41
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2232 forum posts
777 photos

Hi Chris,

I get the feeling we have had this debate before on here many times ? the only specs I know about or the ones I wear the Ferret MTB had a Robbie Slow Fly 280 it was one of 4nr I bought for an aeroplane I never built 20 years ago. I ran the little boat on a 2 cell lipo giving 7.4volts.

I was frightened by the photo of the brushless motor and surface piercing/ flexi drive set up in in Carl's opening post !!

Regards Ray

Chris E22/01/2021 16:04:13
198 forum posts
Posted by Ray Wood 2 on 22/01/2021 14:58:41:

Hi Chris,

I get the feeling we have had this debate before on here many times ? the only specs I know about or the ones I wear the Ferret MTB had a Robbie Slow Fly 280 it was one of 4nr I bought for an aeroplane I never built 20 years ago. I ran the little boat on a 2 cell lipo giving 7.4volts.

I was frightened by the photo of the brushless motor and surface piercing/ flexi drive set up in in Carl's opening post !!

Regards Ray

Yes it is one of by frustrations in life!

The brushless motor frightened me as well. It looked much much larger/ than any I would want to put in a model aircraft as a 280 replacement.

Keep Well

Chris

 

 

Edited By Chris E on 22/01/2021 16:04:36

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