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Author Topic: Wasabi 900e running gear ( Fast electric )  (Read 17619 times)

pompebled

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Re: Wasabi 900e running equipment
« Reply #50 on: July 29, 2017, 01:01:54 PM »

I'm unsure of drive shaft size and prop size I should get, so any help there guys will be gratefully received.
Hi Grant,

The front of the prop should be between 10-13% of the hull length behind the transom and having the rudderblade next to the prop counteracts propwalk.
When the boat is on a flat surface, the prophub should have 2-3 mm clearance of that surface.

You can use a solid shaft (2 mm wire drive with a 4 or 5 mm endpiece) which would have to be very long (500 mm, or more depending on how easy the CoG at 28-30% can be acheived), the motor would sit in the front, with the lipo's behind it on the left of the center line on the floodchamber wall.
A wire drive runs very smooth and requires very little maintenance.
Use the height of the floodchamber wall as a reference on which size Lipo's to get, having them upright makes life easier for the selfrighting.

You can also go for a flexshaft, with either a strut or a stinger/power trim, like this:
https://www.modellbaucenterlorenz.de/en/drives/powertrimm/mtc-powertrimm-5-lange-ausfuehrung.html
A rudderboom like this:
https://www.modellbaucenterlorenz.de/en/rudder/ruderanlagen/mtc-ruder-3-ausleger-95mm.html
With a rudderblade of your choice:
https://www.modellbaucenterlorenz.de/en/rudder.html
I'd go for a long blade with water pick-up: https://www.modellbaucenterlorenz.de/en/mtc-ruderblatt-2-lang-mit-wasseraufnahme.html
They also have the (3/16") flexshaft and the stuffing tube:
https://www.modellbaucenterlorenz.de/en/drives/flexwellen.html

My appologies for the prices in these links, but quality has it's price, I've used Chinese hardware, still do, but once you've used the German made stuff, you know why you pay more...

Here's a link to a topic regarding wire drives versus flex cable, croll down for the pictures showing the various options:
https://forums.offshoreelectrics.com/showthread.php?26887-Spartan-wire-drives

I'm sure Mart can provide links to UK suppliers, I'm not that familiar with those.

A flexshaft needs proper maintenance; the flex should be pulled after every day of running, cleaned, dried and put aside until the next run, when it's re-greased and installed in the boat.

Regards, Jan.
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #51 on: July 29, 2017, 01:13:41 PM »

Nice one Martin, I've searched everywhere for wasabi 900e and YouTube only came up with a few,but not this one.


Grant
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #52 on: July 29, 2017, 01:19:41 PM »

Cheers Jan, a lot to take in and a log of new names to research just so I know what bit your talking about , but I do Thank you for your time.


Grant
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pompebled

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Re: Wasabi 900e running equipment
« Reply #53 on: July 29, 2017, 01:21:01 PM »

Not sure if youve seen this ?.The motor hes using is the one i wanted to link but HK dont seem to have them .
https://www.youtube.com/watch?v=ulhNJEZy7Qs
That's a weird build...
The motor is a short can and very light for a hull this size: https://hobbyking.com/en_us/turnigy-aquastar-3660-2050kv-water-cooled-brushless-motor.html
When you build very light you may get away with it, but the boat is never going to be very fast.
The rudder on the left is also unusual, as it doesn't do a lot to counteract propwalk as on the right, next to having a less efficient rudder when turning right (as the rudder sits in the turbulence of the propwash)
Proof of the pudding:
https://youtu.be/MPRNiVbPoTA
A boat like this is driven with one thumb on the steering stick, the throttle is put at full and you can stick that hand in your pocket until the battery is depleted...

A smaller version, but speedwise more like it:
https://youtu.be/z-vbH0jhkis
Or this with a full size 900:
https://youtu.be/K7Q_TeI4XzQ

Regards, Jan.
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #54 on: July 29, 2017, 01:39:25 PM »

I would imagine he has set out the same as me wanting to take on a project build but where I seek advise and help he hasn't. There motor he has was the same brand I was looking at, I want to build it and do it right so it's going to take a bit of time go get the electrics I shall continue to research the internet. From what I can see on the video I've already made a few changes like a flood and float chambers.


In relation to the flood chamber, should it run from transom to the front or only to frame 5 ?


Grant
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #55 on: July 29, 2017, 01:47:40 PM »

Seen this motor going off what the motor ( 3660-2050) put out on the water, how well would this motor work ?
https://hobbyking.com/en_us/turnigy-aquastar-3974-2200kv-water-cooled-brushless-motor.html
I think I'm going to get a good servo and esc possibly the 180amp turning one and start half way up the power motor level and when I've got the hang of it and feel confident get a better motor.
What do you think to that guys?
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pompebled

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Re: Wasabi 900e running equipment
« Reply #56 on: July 29, 2017, 07:09:50 PM »

Hi Grant,

If you compare the specs, the Wattage of the 3660 is actually higher than the 3974 (1800 versus 1200W), so the bigger motor will give you more weight with possibly(?) the option to turn a bigger prop, but, it is a 5S max. motor versus the 6S you're aiming at at the moment.


Can you calculate what the volume of the floodchamber will be? Both versions?
Floodchamber size/position: the most common floodchamber position is forward to the front of the hatch opening (frame 5 in your build).
This makes the boat turn back up partly over the transom, due to the weight of the Lipo and the hardware (and the lead on the left outer side if required), which in general works best.

Having the floodchamber all the way forward into the nose aims at making the boat turn up over the side, as the water in the floodchamber will also anhialate boyancy up front.
There is an issue however; a floodchamber that long will be hard to fill entirely with water, as there's little to no weight in the nose to acheive that, as a result there will remain air in that section, not really helping to turn the boat back up...
Also, the extra lead needs to be more forward along the hull to help flooding the forward section of the floodchamber, this weight more forward and on the extreme left of the boat will compromize the running attitude when running the right side up.

In our Arowana's (my son and I each run one), the floodchambers stop at the front of the hatchopening and still had issues getting filled completely, leaving an overturned boat bobbing upside down...
The problem here was air trapped in the section closest to the bottom (which is the top when overturned) with the air having no place to go.

The solution was a brass tube from the bottom of the floodchamber front to the right side of the hull; now the air could get out and the floodchamber filled completely, allowing the boat to flip back up.

The tube can be seen in the picture of the interior in one of my previous posts (#36).

Which version to choose does not depend on the motor position: the CoG will remain in the same place, between 28 and 32% of the hull length.
The hull shape does; a long narrow hull will flip back up easier with a long floodchamber into the nose, a wide hull will flip back up over the transom easier.

Regards, Jan.
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #57 on: July 29, 2017, 07:46:00 PM »

Good comparison of flood chambers Jan. So from transom to frame 5. I really do like them German rudders etc.
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Re: Wasabi 900e running equipment
« Reply #58 on: July 30, 2017, 08:42:02 AM »

Good morning, on this YouTube video it shows the bottom of the boat with lines on, are these essential ? Does the boat run better with them?.

[size=78%]https://www.youtube.com/watch?v=ulhNJEZy7Qs[/size]
[/size]
[/size][size=78%]Grant [/size]
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pompebled

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Re: Wasabi 900e running equipment
« Reply #59 on: July 30, 2017, 10:39:39 AM »

Goodmorning Grant,

Yes they are, the strakes help lift the boat out of the water when the speed increases, omitting them, or making them the wrong size and shape, like Giancarlo's boat in the video, will make the boat run wet.

In Giancarlo's case his version of the 'turnfins', with waterinlets on them, makes matters (a lot) worse, the drag of a pipe, being pulled through the water, is huge, it's the main cause for this boat being so slow and ill handling.
A turnfin should only get wet when the boat banks into a turn. Your Wasabi only needs one (1) turnfin on the right.
Giancarlo has created a medium fast fountain...
There's a second video of this boat where it scares the owner by almost flipping, running over its own wake, which is something that can happen (the flipping I mean) but not at such a low speed...:
https://youtu.be/BtGTxX7n7Qk
Giancarlo is a skilled builder (and has the tools), but he has no clue on how to get a fast electric moving...
He uses the waterinlet behind the prop, which works fine with a scale model, but is totally out of place on a fast electric:
https://youtu.be/LnDPCPeW_qA
Watch what he wants to slow down this beautiful build cat with, at 1:11 :
https://youtu.be/8qm-1VLz71k

I added a picture of the strakes on my Arowana (top) and Jetchopper30 hulls, both 800mm hulls. Similar but not identical approaches on how to use strakes.
Notice the absence of strakes in the triangle that is the last part of the hull, strakes on that sectionwill cause lift, which will push down the bow, leaving you with a very bad behaving boat.
Having no strakes in the last part also helps the hull to turn when rudder is applied.

As the water isn't scaled down, the strakes need to be wider and higher than on a fullscale boat in order to be something else than ornamental.

Make sure to glass the bottom first before gluing on the strakes with epoxy resin, as strakes need to be sharp to be effective.

Regards, Jan.
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #60 on: July 30, 2017, 11:21:03 AM »

That's brilliant cheers Jan. You don't have a profile picture to see the shape they need to be?. Why only 1 turn fin on the right as I've seen loads with them on both plus trim tabs, not that I'm bothered if not needed spend the money on a better motor.


So far got all frames cut out waiting for epoxy glue to arrive. Ordered a savox servo and looking at  a 180 amp esc.
Fibre glass ordered 24gsm/mtr
So we are getting there, I'm hoping to when done and complete and runs fine, putting a full build up post on including all parts needed bit like a shopping list for newbies like me who want to build one.


Grant
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pompebled

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Re: Wasabi 900e running equipment
« Reply #61 on: July 30, 2017, 11:50:59 AM »

Hi Grant,

When watched from the rear, or the front, the surfaces of the strakes are horizontal with vertical sides.
This means the triangular shape changes when going from the bottom towards the bow, as the angle on the hull becomes steeper.

A single prop boat will turn right much tighter (and spin out) than left, due to the propwalk (when using a counterclockwise rotating prop), hence the need for a turnfin on the right.
On the left, there's precious little room (floodchamber hole), or need for a turnfin, as left hand turns at speed will always be wider due to the propwalk.

Trimtabs are a bandaid for a poor set-up!
All the bling bling on the back of the commercially available boats are aiming at the newbies who have no clue (and/or the skills) to run a fast electric really quick, so the looks are important.
The fact that extra hardware isn't required on a sluggish RTR (compared to a fully dialed in competition boat) and only slows you down (both by the nature of trimtabs and faulty user adjustment) is lost on them.

None of my fast electrics have/need trimtabs.

Only when you're approaching the limits of the design, trimtabs will help to adjust the running attitude, as trimtabs elongate the hull and will counteract proptorque which will try to push the boat on its right side, which is not good when you're running well over a 120 km/h (75mph)...

I would not use epoxy to assemble the framework, but white woodworking glue, I use the quick setting waterproof type.
Epoxy is for laminating and makin fillets, etc.

Make sure to use a building board to keep things straight, avoid building a banana, it'll never run properly!
See picture.
The frames have 'legs' elongating them into one plane (the building board) just like the picture in this build:
http://www.modelbouwforum.nl/threads/wasabi-e900-setup.241965/

Regards, Jan.
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #62 on: July 30, 2017, 12:17:25 PM »

Very interesting you certainly have a vast knowledge even down to physics and mathematics. I look forward to building this boat to precision cause if it's anything less I won't be happy.


The majority of the vids you see they have the standard transmitter with the 2 sticks, is there a reason for this ? I would of thought  a 2 channel wheel controller would be easier?


One for martin, With regards to the fibreglassing would you put colour in the epoxy instead of spraying and what product would you use?


Grant
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pompebled

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Re: Wasabi 900e running equipment
« Reply #63 on: July 30, 2017, 12:24:50 PM »

Hi Grant,

Which type of transmitter to use is entirely personal, I 'grew up' with stick transmitters, I'm all over the place with a pistol grip....
A lot of boaters have more models and use the transmitter (with multiple memories and computer adjustments) for all models. The simple pistol grip transmitters are limited in this way, but the more expensive ones also have multiple memory storage capabilities.

Colouring the epoxy when laminating makes it harder to see flaws and air trapped underneath.
I would use clear epoxy, fill the weave with a second layer of epoxy and use filler and (two component spray)paint from there.

Regards, Jan.
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martno1fan

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Re: Wasabi 900e running equipment
« Reply #64 on: July 30, 2017, 01:03:12 PM »

Heres my opinion on strakes some designs need them as they need the lift some don't as it creates too much lift.For instance the mono i recommend you build the Prowler doesn't need them in fact when built smaller or when using more powerful motors be it electric or gas they get too flighty so i omited them on the ones Ive built.Cant speak for the one your building but personally id omit them and test the boat first.I def wouldnt have them going all the way back to transom id stop them short .The only thing you must add are chine or spray rails on the chine where bottom meets side.,Offset the rudder to right and also the drive 1/4" to overcome prop walk etc,turn fins are a must and i like them on both sides so the boat will turn well either way but right turns will always be sharper than left.You dont need much rudder to turn these boats so adjust your rudder throws at the servo or your boat will spin out too easy.
Radios i would commend a pistol grip makes life simpler as you have controll of the throttle while launching the boat with the other hand,flysky gt3c works fine for me.
heres a pic of my apache bottom strakes stop short and she has plenty of lift.
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #65 on: July 30, 2017, 04:34:37 PM »

HI Jan, Martin can you confirm I've got this the right way to calculate rpm, is it  kv x battery volts ie..3660/ 1700 so it's 1700 x 22.2 on 6s lipo ?
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Re: Wasabi 900e running equipment
« Reply #66 on: July 30, 2017, 05:27:01 PM »

Looking at boat motors and came across this one ....

Turnigy XK-4082 1450KV Brushless Inrunner


It would need a cooling sleeve , but according to calculations it's not bad ? Unless I'm wrong  {:-{
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pompebled

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Re: Wasabi 900e running equipment
« Reply #67 on: July 30, 2017, 05:43:21 PM »

Hi Grant,

Way ahead of you...

I had hoped you wouldn't stumble accross this one, as I intentionally haven't linked to it:
https://hobbyking.com/en_us/turnigy-xk-4082-1450kv-brushless-inrunner.html

Reason is the relative low Kv of 1450, multiplied by 6S (22,2V) gives you an unloaded rpm of 32190 rpm, with losses ( x 0,9) that would be 28970 rpm.
To get the topspeed the higher Kv motors would make the boat run, you'll need a bigger prop, which means more propwalk and proptorque issues.
These issues could be counteracted by increasing the offset and putting the weight a bit more to the left, but the load on the motor would be high and with the specs giving 100A as the maximum Ampdraw, I expect high current/heat build up issues in future on 6S.

Running on 7S or 8S would allow you to reduce the propsize and bring the current down, but that would raise issues with getting the floodchamber to work, due to the bulkier Lipo's, or result in a reduced runtime if you were to slim down on the lipo weight by reducing the capacity, which in turn would be hard on the lipo's due to the constant ampdraw...

Regards, Jan.
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #68 on: July 30, 2017, 05:47:16 PM »

Ha there is a bigger of version of 2000kv which would do it, no  :(( {:-{ :o 
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Gaci4

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Re: Wasabi 900e running equipment
« Reply #69 on: July 30, 2017, 06:48:08 PM »

If turnigy xk4074-2000kv has a max current draw of 120amp would the turnigy marine 120A esc run together as it's continues 120amp but has surge protection of 720amp.


Grant
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Re: Wasabi 900e running equipment
« Reply #70 on: July 30, 2017, 07:14:32 PM »

Hi Grant,

In Reply #43, I commented on a similar motor.

Rule of thumb is to choose an ESC with at least 50% headroom, to make sure the ESC will handle the current spikes easily.
As I've explained before the specs are just that; the motor is happy to draw whatever current it needs to turn the prop at the rpm given by the input via the ESC.

Having the max of both devices match isn't a good idea.

Regards, Jan.
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Re: Wasabi 900e running equipment
« Reply #71 on: July 30, 2017, 07:17:03 PM »

Would you say the 4082-2000 motor was ok to run on the 180amp esc.
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Re: Wasabi 900e running equipment
« Reply #72 on: July 30, 2017, 07:19:31 PM »

I do apologise for all the questions , I've always run on gas with cars,hovercraft so electric is a bit novice bug we'll get there. Thanks For your help Jan.
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Re: Wasabi 900e running equipment
« Reply #73 on: July 30, 2017, 08:34:18 PM »

Hi Grant,

First of all, it's better to ask, than to muddle on and let out the magic smoke out of electrical devices such as ESC and motor, which is also hard on your budget...

A 4082-2000Kv motor can be handled by a 180A ESC, provided you don't overprop the motor and make the ampdraw soar, but it's a 4074-2000Kv motor you mentioned earlier, isn't it?

I would go for the Flycolor 150A ESC, mentioned in previous posts by Mart and me, for the price you can find these on line, they are hard to beat.

Regards, Jan.
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Re: Wasabi 900e running equipment
« Reply #74 on: July 30, 2017, 09:13:40 PM »

No I mentioned a 4074-1450 which you said was to low on the kv well they also do 4074-2000 which covers the loss and it's 6s. Don't mind th 180amp as the flycolour can't get in UK
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