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[andrewh]

Welcome to Andrew's instant trial brushless boat

The raw materials:
Motor - home made using CDROM motor bits
ESC - aircraft, unnamed, cheap chinese, no adjustment, forward only
Boat:  footy racing yacht hull (of course)
drive:  2mm propshaft and graupner 28mm carbon racing prop


Motor with rotor removed (they are only held on by the magnets) - observe my first attempt at winding


Templates for the hull and running gear

the hull is styrene - a) because I have it and it is free
b) its very quick to construct


The bits of styrene are the punched-out middle bits from a vacforming machine - too short for the sidewalls of the hull, but I will splice a bit on

The footy is actually "razor" by Bill Hagerup.  Plans for this and others freely available at http://footy.rcsailing.net/plans.php
I used Razor because I was looking for something small, hard-chine, simple and with a good Vee-bottom


construction begins - the parts are taped together - glueing/welding comes later when everything is together and square
more later
andrew

[andrewh]

I think I should explain the motor with its great big blue cylinder attached 

This little brushless is producing a lot more power than a S400, and I wanted to be able to interchange it with a S400 (7.2) SO
the boat comes equipped with a hemicylindrical "bed" of packing foam with a cutout for the S400 motor cut in it.  When I use the brushed motor it is held in place be a rubber band.

The Brushless, as is fairly common, has a tube attached to the stator which pokes out backwards,  I cut a cylinder (OK, NEARLY a cylinder ) the same diameter as a s400 (use an old motor case with the end sharpened) and poked the BL mounting tube into the cylinder.

Its MEANT to be not quite straight so that I can adjust the best motor/shaft alignment.  The blue foam cylinder also is rubber-banded into the "bed"

At these powers silicone tube couplings are perfectly adequate, and readily available


hull comes together

I use insulting tape because its more elastic than masking tape - and it removes better
BTW - don't forget to remove the felt-tip markings/lines before assembly - I use meths (alcohol)



bonding in the transom - cack-'anded as you see

This is how I left it - total time so far about 1/2 hour
The hull will be good and hard tonight when I get home - can fit the running gear and inwales. 
She is going to be decked like a racing footy - with mast step and all - I want to be able to sail her as a Q-ship

With nearly 100 watts this little beast shoulld shift
Must lash up create a reversing switch with a couple of microswitches and the smallest servo I can find
andrew
 

[andyn]

Looking good, you say you get free depron, where from? I use tons of the stuff and have to pay through the nose...

I also have an experimental brushless boat on the go, but with what I'm putting in it it will be classified more as an experimental aircraft...

3.7 gram servo for reverse switch (second one down)
http://www.servoshop.co.uk/index.php?pid=XYMS44SS&area=Servo

[andrewh]

Andy,

I hope I said styrene, as in vac-forming HIP sheet, so the same stuff your plastic models are made of.  The free comes from having worked in a Vac-form place for a while - they throw tonnes per week of roll-ends, punchouts, etc

I've got lots of depron, since Mark, the head Aeronut used to buy the stuff in bales - you might have a look in B&Q - they do 6mm greemn depron for about £11.00 per stack for wood floor insulation.

Show us your boat - if it touches water it must belong here
andrew

[andyn]

You did say styrene yes but i took it as depron from the pics.

Boat and supersonic (literally) motor I have for it

[andrewh]

Andy - that can do nothing but fly!  Can't see which Feigao that is but it has the aspect of a 400 replacement  - THAT will spin the prop!

And I have an apology for you, hawkeye Andy.  The picture you looked at did indeed show depron parts - I had cut them a while ago to make a Depron razor, but at the time my ZapO was getting old and didn't want to set, so it hasn't progressed any further.

However the brushless trial boat certainly has - it awaits its maiden flight


the hull is seriously light, so i have stuffed it with computer foam asa flotation aid before adding the deck




I am about a day behind with the photos - but have been able to make my BL reverser, and tested it


More details, circuit and discussion in BLBasics
Trials of BLTrial soon
andrew

[andyn]

The one I have for it is the 7800kv one, yes, 7800, which doing the maths means 57,720rpm on 7.4v and 86,580rpm (potentially) on 11.1v

Hoping for at least one touch of the water per ciruit...

'Tis looking good, got wet yet?

[andrewh]

Andy

How disappointing, only 86krpm
Should sound and go like a turbine - if the water-prop is dull you could try either a waterjet or Electric Ducted Fan with the same motor - or both at the same time (or simulataneously).

I have been laid up for a week with flu, but now getting back into circulation - aim to test in the next couple of days.  With and without reverser switch

watch this space
andrew

[BobF]

Hi Andrew,
I may have missed something here, so help please.
Firstly as you already know, I know nothing about brushless motors.
What I understand from others, is that they are faster reving etc. and make FE boats go quickly!
So question, why would you fit one in a yacht hull. Won't the bow lift the stern dig in, and won't it try to turn away from straight when it reaches its displacement speed?
Please explain, as I would love one of these little boats to put a SAIL on.
I have re read the thread a couple of times, but can't work out the yacht hull bit. Help Please.

OK went back and read again, do you only do yachts
PS yachts are my first love.

[andrewh]

Bob,

No worries, and don't look for too much wisdom in my choices
I'm a Yacht person, too, and build and race Footys - 12 inch yachts, of which Razor is an example
http://www.rcsailing.net/forum1/forumdisplay.php?f=61
is where Footys are discussed and built - you will see that sunshine has also just built a Razor

The reasons for picking Razor for a test vehicle were:
Right size- I want this to be seriously fast
Shallow Vee bottom
Fast to build

But, as you say, Razor has a lot of rocker and is likely therefore to porpoise if she gets the chance - we will find out this morning if this is the case!

andrew

[andrewh]

WELL

What a silly boat!  It goes like stink, stood up on its transom in a silly posture!

In a short and very cold trial spin yesterday



The acton eventually stopped because the motor seized - I am investigating the reasons now, but rest assured that they are more to do with my assembly than anything about brushless.

What have I learned?
Well razor is the right size, but the wrong shape - I will move the batteries a long way forward
She steers well at all speeds (lots of rocker)
A little more development needed, but I think a different hull will be needed
andrew

[andyn]

How odd...

Can you put the lipo up the front? this will most likely solve it. Clever Trevor at our club is forever moving batteries about to get the right weight distribution.

It sounds like you need to rewire the motor, dont put any power throught it until you have, or your esc and motor will turn into two quite large and effective heaters...

[nick_75au]

Make the same hull but from the midpoint of the center of the hull should be straight to the stern(eliminate the curve from the midpoint) the side and transom shape will change as well but a bit of judicious cutting will fix that. this will give you a hull that will plane better.
Nick

[andrewh]

Nick,
thanks very much - I am sure that you are quite right. 
This little feller has far too much rocker for this application - although the trials showed that she rode very well over her wake, and did not do too much of the "demented woodpecker" imitation

I will try your suggestion in card first - pics to follow.

In fact the successor hull is being readied even now, even tho the boat parts are not the problem.

The BL motor is still sick, suffering from GOK.  I still want to diagnose and fix the problem, but fiirst I willl fit and try a commercial bell-motor in the razor hull.  This is a 10A motor, so we are looking at a max of 70 watts here, but I am sure that the KV is much lower, so my little racing prop will be the wrong one - I have bigger props with M2 threads and will experiment. 
The bell motor has a threaded shaft - same as GWS motors - I think is is M3 or m3.5. so I may need to adjust the polymer drive coupling (rubber tube)
andrew

[andrewh]

This is the next trial hack


its a Graham Goodchild design from a book of his I have - deep vee and designed to at least look like a speedboat

BTW - whatever happened to Graham?  He had a very productive spell in the 1980s and produced lots of attractive and fun designs and then disappeared from view.  I would like to contact him and express my pleasure with his designs.

andrew

[Martin (Admin)]

This is my brushless trail boat....
Haven't run it yet but will be runining it with replacement / normal radio first (fitted radio.... total crap!) and then
up the voltage on the fitted 385 sized DC motors until they burn out! 

[andrewh]

MARTIN!

You have been reading ahead in the book again!

Are you going to stay with the differential steering?  or add a rudder and be more conventional?

If you are going twin brushless  - and don't need the differential control it MAY (that's MAY) be possible to run two BL motors off a single ESC.  It IS done, people do it, many Twinstars fly this way!

It is something I was planning for a future chapter in BLB, but can accelerate if relevant.  How long will it take you to frag the existing motors?
BTW, I rather suspect that they are 3-pole, so more accurately 380 type and probably 6-volt (nominal) wound.  I would guess that they will have a brief but merry life at 12V, finally expiring with brushgear overheat

andrew

[Martin (Admin)]

Hi Andy,
This project on hold at the moment while my shoulder heals up, (wrenched it in the cold a couple of weeks back!  )
I'll get the boat going as fast I can with the supplied setup then ditch it and fill the holes and then fit my preferred drive line,
Graupner Hydrospeed surface drive strudder. I'll not be using differential steering as the boat always drops of the plane when
cornering so there is already fitted a small 'trip' rudder which I'm converting to the active rudder.

[andrewh]

OK, every day I learn a new thing!

The S700Turbo (p/n 3308) has a kv of 1562 (rpm/V) which seems modest.  No doubt because its a Turbo (5-pole motor), so if you want a brushless equivalent  - to match the prop you are looking for something in the KV1500 to 2000 range. 
No need to worry about the power - it will be very much more!

This motor is actually made for efficiency - hence the 5 poles and neodymium magnets.  I make the power 160W at max efficiency (16 Amps)

Something like a Scorpion 2215 -1860 sounds possible (max power is 320W continuous) and it comes as a kit, too for £21.15
http://www.micronradiocontrol.co.uk/scorpion_22.html#scp2215

But Naw, you wouldnt want to double the power for less weight
andrew

[andyn]

Martin, thats nothing compared to what Bills done to his, just you wait till you see it next year 

Trust him to do silly things to stuff

[andrewh]

Quick update of the BL trial boat

My home-made motor is still suffering from GOK, so I have grafted in the bell moter out of my park-flyer, and will give this a try.

I have not been able to find the original website where I bought it from, so I don't have the KV, but it is fairly low - 1200Rpm/V is what I remember.. So its a relatively gentle motor, and may well need a lot more propellor to work well

Watch this space!

Andyn - what is your little supersonic hull?  is it a moulding or a complete boat you have stripped out?
andrew

[andyn]

It's a moulding I bought at the Boat Show the other week. Cost me a fiver so quitre a bargain.

Unfortunately it's on th back burner at the moment because I'm building a MONSTER....

[andrewh]

Second trial run completed with:

21T bell motor* fitted to satsuma ply bulkhead.  This was made as a pattern in cardboard, cut in satsuma ply, then the motor fitted with a rigid tube to the prop shaft and the radial motor mount position marked.
Bulkhead position marked
The bulkhead was then hot-melted to position and the motor and coupling fitted

I howked out the flotation foam in the bow of the boat to enable me to get the battery well forward.

*If the motor had numbers it would be something like a 2508/21, 1200Kv

Bench trials  showed good controllabiility, and, it seemed, modest revs.
Trial flotation and power blips in the garden pond showed that would launch itself right out of the pond EVERY TIME
Canal trials then followed - performance (and attitude in the water) very similar to the first tests despite the forward battery weight

Up on her hind legs like a politician

Bow wave "wings" going sideways beautifully
Speed seemed the same as before - but with the forward battery position sharp turns at speed had the potential to turn her over


Conclusion:  Good trials, Wrong boat, both these motors showed the promise of making the right boat interestingly quick, if I can stop the bows from climbing!

I am going to return the hull to being a footy yacht, and make a replacement trial hull.  (or two)
Has anyone played with the Slingshot boat - especially the hull?  I suspect that it would be quite fun with this power-train fitted
I also can't wait to see how AndyN's boat goes with the Feigao inrunner - I have a sneaking suspicion it will need a small high-speed prop!  This is the kind of motor I would stick in a Ducted fan or waterjet!  Now there is an idea!

andrew




 

[andrewh]

Pics of the bell motor in TrialRazor

Close examination shows that he bell motor is marked 2509-21 so we know its 25mm diameter, 9mm stack length and 21 Turns
Memory tells me it is 1200KV, so on 8V (2s Lipo) it should be doing 9600 rpm, which is well less than a S400





I am about to slip this motor into my Hellkitten and hit it with 3S
andrew

[Subculture]

I had a couple of Silver machines when I was small. Nice little boats- used to really nip along.

Personally, if you want something really quick, have a look at some of the fast electric designs by Vic Smeed. Moccasin is a nice looking boat that should go like the clappers with a decent sized brushless motor and lipos.

Andy