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Fisher 34 motorsailer

R/C near scale yacht

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Tim Rowe02/04/2021 09:28:18
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564 forum posts
562 photos

Hello again

I am intrigued about your keel. I couldn't work out how it is fixed to the hull?

Tim R

gecon02/04/2021 12:05:07
461 forum posts
387 photos

Hi Tim, I have just re-posted photos of the keel (from my album) for Chris -on the previous 'page' (20).

The full size Fisher has a heavy enclosed keel built in. This is of course not good enough for model purposes. Therefore the extra keel I have produced is bolted on with two bolts, through the models keel which is filled with about 3kg of leadshot and tiny iron spheres which I bought from Krick. There's also two motors in the bilges and two 5000mAh battery packs. 

The through-keel bolts are actually made from 5mm threaded steel rod with a locknut on each end. The ends of the threaded rods have been sawn over to enable engageing a flat-head screwdriver to hold the rod while turning the nuts. (ouch!) This is starting to sound a bit 'exotic' so I'll  stop the detail discription!

I would not even dream of trying to mould a keel so mine is the wing keel sold by Krick for the Comtesse yacht. The galvanised L-irons used to attatch it can of course be lengthened/shortened to suit. And extra 'leg-metal' can be added later if needed. On a yacht without a Fisher-type keel the legs could be let into the hull and boltet inside -and could even be made adjustble/retractable!

George

Edited By gecon on 02/04/2021 12:38:39

gecon02/04/2021 12:28:39
461 forum posts
387 photos

Clear and bright weather today but the freezing cold wind from the north means I'm staying home. Will test the battery trouble at home for the time being. Try to provoke a low batt warning in comfort.

I read on Google that others have reported on 'low receiver battery' verbal warnings from Graupner telemetery systems.

My Graupner speed controllers are suppose give a BEC supply of 5v and max 5A current. Have not yet tried to think through all the available info, so I'll use Easter and days to come to find out as much as poss.

I may connect up two identical Rx batts 2000mAh / 4.8v in parallel but first I'd like to see the if the problem comes up with just one Rx batt.

George

Tim Rowe02/04/2021 12:32:59
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564 forum posts
562 photos

I still can't work it out George.

Could you show a picture of it bolted in place. That looks like a lot of hardware to drag around.

Tim R

gecon02/04/2021 12:41:15
461 forum posts
387 photos

OK, take a photo and post it asap.

G

gecon02/04/2021 12:46:56
461 forum posts
387 photos

20210402_134312.jpg20210402_134251.jpg20210402_134231.jpg

gecon02/04/2021 12:56:43
461 forum posts
387 photos

Yes Tim, it's a lot of hardware but it's all keel-weight -and adjustable -and removeable. I had no idea when I started the build of how much keel weight I needed. Letting it hang well below the waterline means less total weight and higher level of effectivity/efficiency.

The main thought at the beginning of the build was that I did not want all this work to 'turn turtle' in a breeze. I have not yet tested it properly either...but I can lengthen the legs if needed and get more effect for very little extra weight.

I don't care if it doesn't sail too well so long as it's not keel-upsad.    The whole project could be described as 'a lot of hardware' -which it is.smiley

G

Edited By gecon on 02/04/2021 12:58:28

Tim Rowe02/04/2021 19:57:01
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564 forum posts
562 photos

Thanks for the photos George

To be honest I was worried about all that weight bolted onto a short section of your main keel. Now I have looked closely at your album I see that the whole inside of the keel is filled with lead shot and epoxy. I am less concerned now but remain just a teeny bit worried because a boat of that displacement can generate quite a lot of energy.

As for hanging it below the waterline, there is a balance between a reasonable and safe amount of stability and a boat that behaves like a lighthouse.

I have to be a bit blunt. For keeping the boat upright I am confident you have cracked it. As for efficiency however, I fear it will be disappointing. Those two flat plates will interact and with the holes and bolts will be very draggy. It will be interesting to know if it goes to windward and how well it might tack.

For me, the keel lacks the finesse you have achieved on the rest of the model.

Good luck anyway with your next trial.

Tim R

Colin Bishop02/04/2021 20:30:41
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4927 forum posts
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408 articles

As someone who has owned a twin keeled yacht I am not convinced that George's arrangement will make all that much difference in practice at model size. It is not intended to be a performance boat. Motor sailers are not noted for their sailing qualities anyway. By their very nature they are compromises.

At full size that sort of arrangement might well be inefficient bit not necessarily so much at model size. I don't think the holes will make any practical difference.

Colin

Edited By Colin Bishop on 02/04/2021 20:31:40

gecon02/04/2021 23:59:45
461 forum posts
387 photos

I agree with Tim that the keel unit is indeed an ugly contraption. I think I wrote last year that only the local trout will actually see it.

When I get the chance to do so, I'll have my Comtesse on the water at the same time and compare relative perfomance. The very round bilge hull of the Fisher is known to roll willingly and my main concern for the time being is to keep the whole show upright....just like a lighthousesmiley yes

I have been churning the grey cell about my low battery voltage warning and it may be that (in addition to the fact that I have three large winch servos) the tensioning springs on the in-hull sheet runs are also contributing to unecessarily high current drain and thus causing a voltage drop in the BEC system. I'm not sure how the Graupner system is set up but it may be that once the voltage drops below the ca. 4.5v level over some seconds that the system starts an irreversible shut down.

My Comtesse yacht has the same BEC supply and same type of winches and rudder servo but one less winch servo BUT the winches have enclosed drums and NO in-hull sheet runs and therefore NO spring tensioners.

The weather report for the next 10 days at least suggests relatively high winds so I'll use the down-time to do some 'refinements' below decks.

I will also probably fit two identical Rx batts in parallel and not use the BEC at all. Changing more than one thing at a time will mean that I may not know where the remedy lies, but that's not going to bother me so long as I can get it all to work.

I have some other thoughts on all this but I'll 'go away' for a while until I have something more concrete to share.

All comments/observations/criticisms are very welcome and appreciated.

George

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