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Author Topic: What's the smallest practical RC yacht?  (Read 6270 times)

Little Rascal

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What's the smallest practical RC yacht?
« on: September 09, 2010, 03:25:50 PM »

Just wondering if anyone has tried this and with what results?

I know smaller yachts run into scale effect problems and the smallest RTR types are often considered not worth the money.
Is that just because they are built too heavy and have a poor ballast ratio? Or is it intrinsic to their size?

I was considering using some small components (6g rx, 5g servos) and building really light in balsa to build a sub 1kg yacht around 16-18" but trying to achieve decent handling and performance. I could go smaller still (into the realms of indoor flight rc equipment) but probably won't on the grounds of cost.

Would mini/micro servos cope with the sails?

Is it worth it? Has it been done?
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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #1 on: September 09, 2010, 03:58:10 PM »

there are tons of footies out there and they onkly use small notmicro material... look here:

http://footy.rcsailing.net/

there are plans for several boats too. Footies sail well and are a lot of small on very small ponds :)
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #2 on: September 09, 2010, 04:07:26 PM »

Hi Meatbomber

Funnily enough I hadn't even thought of footies, though I knew of them...!
Sort of the mini-transat of RC!
Enjoyed reading your build threads by the way.

Thanks for the link

Jon
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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #3 on: September 09, 2010, 04:29:19 PM »

Thanks mate :)

btw. there is a micro boat forum on rcgroups where there are several people building really small boats. Most are powered but one guy did a 8in sailboat :)
i`d like to do a cutter with the Spektrum AR6400 (or rather the 4channel version from the parkzone Vapor) after the Plank on edge Cutter "POETRY" in this forum with about 6 to 8cm length... maybe that will be the smallest i build :D
The Vapor RX "block" (including RX, RSC, and 2 small linear servos) can be bought for 45 USD so it`s not at all that expensive, infact one is hard pressed to get a receiver and 2 servos with a BEC for that price... the 1S LiPos that go with it are also only about 8USD..

So how about a Build off :)
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #4 on: September 09, 2010, 04:46:36 PM »

I'd looked at vapours for aircraft but not thought of it for boats...

Build off?
Ha ha, pretty sure you'd win that!

Thanks for the info.

Jon
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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #5 on: September 09, 2010, 07:15:36 PM »

yea thats what i did with them before too (tho i never owned a vapor ;)) i thought with a stolery powerlever it should have enough oomph, besides small sails don`t really excert much force :)
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #6 on: September 10, 2010, 11:06:36 AM »

The micro boats forum is awesome!

Do you have a link for your POE?

Im struggling with batteries to power the rx/servos.
3.7v lipo?
I wonder if anyone has tried 3.6v lithium watch batteries? Less than 1 gram!
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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #7 on: September 10, 2010, 02:54:37 PM »

About the micro POETRY...


I decided to give it a try and made a mokup of teh hull with a bit of 6mm depron and carbord.
And here is Micro-Poetry :) she measures 8,5cm on deck and a maximum beam of 2,5cm and drought of 4cm.
I sprayed her with some silver paint to protect the cardbord from the water for a quick displacement test..

POETRY displaces a whopping 33,5g on her design waterline :)
The brick and battery weight only 9g together, i guess the whole boat when completed will weight depending on what material is used (foam or plywood/balsa) about 8-10g, leaving 14,5g of ballast. That should get her plenty stiff for such a small rig :D 
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #8 on: September 10, 2010, 05:13:17 PM »

Lovely!

The POE seems to have perfect proportions for scaling down! Will you put a false keel on her?
What battery do you run the brick off? Volts/mAh?

I've done a couple of drawings and calcs and I'm thinking 9" lugger or Fifie maybe...
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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #9 on: September 10, 2010, 06:28:43 PM »

I run the brick of the original 70mAh batteries that are also used in teh vapor. Easy and cheap, and i have about 20 of these lying around here :D

I rigged micro Poetry quickly witha bit of Tyvek for sails, and some carbon rods, just loosely taped togther, to make some tests with teh hair dryer in the sink :) Displacement and rightening moment are good, so even at full power on the hair dryer she doesn`t tip too far over. But i found that the CLR and CE are not at teh correct relationship to each other with th rig i used. I moved teh mast forward a bit and it seems better. I also think that the bottom profile of the hull is too thick to give decent lift as a keel, so she has a lot of leeway if you can say anything about that with a hairdryer and a sink as your proofing ground :D
i`m gonna test some more... a new hull with thinner lower hull and maybe a styren sheet keel to get some more grip :)
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #10 on: September 10, 2010, 07:43:49 PM »

Looking good! She floats right on her marks anyway.
I think you might be right about the keel.

I wonder if its a scale effect perhaps too? I would think that the overall drag of the forward moving hull is pretty high relative to the lateral resistance...
Like the equivalent of high drag in aircraft at very low reynolds numbers?
Maybe sharpening the leading edge of the keel would help a bit?
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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #11 on: September 10, 2010, 07:55:37 PM »

I did all that... i give you POETRY II :)

The top is the same, teh bottom profile got much slimmer and i added a styrene sheet keel and larger rudder... now she has some serious grip :)
She no longer goes sideways but really straight ahead, afore the wind with the sheet fully out she is also going pretty straight, noting i can`t fix with teh big rudder... this hull can be RCed now that i know it will at least go straight :D
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tobyker

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Re: What's the smallest practical RC yacht?
« Reply #12 on: September 10, 2010, 07:59:42 PM »

Absolutely Brilliant!! and thanks for the namecheck. If you are starting a new micro-poetry class, maybe you should call her Ode or Haiku!
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #13 on: September 10, 2010, 08:31:05 PM »

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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #14 on: September 12, 2010, 01:05:09 AM »

Haiku it is then :)

i`ve installed the brick and hooked up the rudder.
Unfortunately i have tomount the brick at an angle so i`ll loose some travel for my sheet, as the whole brick is tilted up 20. oh well...
Tried the Rudder in teh sink and if she won`t sail then i can scull her at about hull speed :D the servo is very quick and the rudder very effective. next i`ll have to see how i do it with the sheet.
I found a different cutter sailplan i want to use. i`ll have to build the spars and mast extremely light.. and i want to use some thin film for the sails.
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meatbomber

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Re: What's the smallest practical RC yacht?
« Reply #15 on: September 15, 2010, 10:36:18 PM »

Haiku ready for maiden. So far no topsl i dont know if she can handlr it with the internal ballast only.
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dodgy geezer

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Re: What's the smallest practical RC yacht?
« Reply #16 on: September 16, 2010, 12:41:17 PM »

I wonder if micro but complex rigging is becoming the latest fashion? I've just put up Kiwi's plan of the Alma schooner-rigged scow as a footy on the EeZeBilt site for free download - http://modelboats.hobby-site.com/Scow.html refers...
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #17 on: September 17, 2010, 07:08:25 PM »

Looking good MB!

My lugger is on hold at the mo - got way-laid by wacky ideas for Footy designs  {-)

dg: I really love the EeZeBILT 50+ idea! You should persuade Meatbomber to design you an EZ-Brig...

I think that people are going smaller as the rc gear become more affordable (well their models are, not the people!) It opens up more and more opportunities! Just that boats are maybe a little behind planes at the moment.

Now if someone could come up with a tiny plug 'n' play ESC compatible with 3.7v 1S lipo batteries specifically for boats that worked in forward and reverse, I think they'd make a bob or two...
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Martin [Admin]

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Re: What's the smallest practical RC yacht?
« Reply #18 on: September 17, 2010, 09:50:19 PM »

Something I've been working on during my tea breaks.
 It's not RC yet as the glass sail winches are a bit too powerful......  %)
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dodgy geezer

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Re: What's the smallest practical RC yacht?
« Reply #19 on: September 17, 2010, 11:03:46 PM »

Wow!

Martin, where do you get needles that big...!!?
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Little Rascal

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Re: What's the smallest practical RC yacht?
« Reply #20 on: September 17, 2010, 11:17:43 PM »

Next to the tiny camel shop.
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