Slo mo Shun

[Phil Winks 1Participant @philwinks1]

Your right Bob you did say Wed and I did go to specsavers too. perhaps I should try puting them on lol

 

So Best of luck tomorrow mate

 

Phil

[Bob Abell 2Participant @bobabell2]

Results of the 5 th test……………….Sponson mod

 

It doesn`t look like it but it was an improvement……….I think more sponson tip would be even better

Slightly blurred piccy………..Notice the wave shape has moved round, from the front?

Just an action shot…….I was going too fast for the pressganged camera man!

 

The boat was quite lively at times, and light on the water………Hope?

 

Bob

[Phil Winks 1Participant @philwinks1]

Definately getting higher in the water mate that much is apparent just need to get some air under the bow. maybe flatten the ‘V’ of the 1st hull mod??

 

 the wave form on the last shot suggests it slides into corners with its tail. Is this so? if so that suggests the tail is plenty high enough!

 

Phil

[Bob Abell 2Participant @bobabell2]

Now thinking that the weight should be more aft………………to slope the hull upwards, to give the props something to drive up, like an incline plane…….must be a fine balance somewhere?

 

The motors seem powerful enough for my requirements……..just look at the propwash on the first picture above……..it`s very realistic too

 

Not giving up yet……………….Bob

 

…………………………………(Still got the speed up gears to try!)

[Phil Winks 1Participant @philwinks1]

You’ve got a real point about the balance Bob just like a plane!!

 

I know it’s more work but a flttening of the ‘V’ on the 1st hull mod at the step end can’t do owt but let the wave through and air in can it?? I feel she needs a tunnel again!!

 

when you get the gearing sorted don’t forget smaller finer pitch props.

 

I’m thinking maybe as much as 30% smaller and maybe the same in pitch. might be a good Idea to get a fast electric view on this!!

 

 

Phil

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

Can`t understand your second paragraph?

 

Bob

[Phil Winks 1Participant @philwinks1]

Typo error there Bob

 

try this

 

“I know it’s more work but a flattening of the ‘V’ on the 1st hull mod at the step end can’t do owt but let the wave through and air in can it?? I feel she needs a tunnel again!!”

 

where you’ve created a V in what was the tunnel why not remove the sect that protrudes below the original line of the sponsons?

 

you’d still have most of the extra bouancy it gives at slow speeds, and a larger tunnel section for that troublesome bow wave to pass through, instead of it trying to escape sideways around the sponsons.

 

 I’ll try a doing a working sketch for you later on mate.

 

Phil

[Bob Abell 2Participant @bobabell2]

I like the idea of re-introducing the tunnel….to get rid of the bow wave!….Good idea….Son!

 

I do it right away, then I`ll have a good reason for another test sail next Tuesday!

 

Thanks, Phil

 

Bob

[Len OchiltreeParticipant @lenochiltree67043]

Put a wing underneath as I suggested Bob.

 

Len.

[Bob Abell 2Participant @bobabell2]

Thanks Len!……………..You`re full of great ideas!

 

Congrats with your magazine cover fame!

 

Bob

[Phil Winks 1Participant @philwinks1]

Magazine cover fame eh Len Looks like I need to get the latest copy of MB and find out what the fuss is.

 

 

Phil

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

Can you recommend a pair of Brushless motors, complete with ESC`s, using my existing 12v batteries………..that would guarantee a planing performance for Slo Mo?

 

Let`s get talking!………………Bob

[Len OchiltreeParticipant @lenochiltree67043]

Hi Bob,

Does your Bank Manager know you are spending all this dosh?.

 

Len

[Bob Abell 2Participant @bobabell2]

Hello Len

 

We`re only talking at the moment!

 

Looking at several Brushless sites, the motors are about £45.00 each…….Hopefully!

 

I would have gone brushless at the onset…….Didn`t realise Nimins could power this type of motor………I was fighting shy of those LI Po`s really

 

Bob

[Phil Winks 1Participant @philwinks1]

Hi Bob suprising how many folks think brushless means lipo but any electrictry tank will do it’s just that lipo’s are so light.

 

Right you asked I’ll get of and ask some friends on the rumrunner thingy and a little research of my own the price you’ve mentioned above seems about right you may still end up with 2 bty’s in and 24v’s to get max effect for a shortish run (about 10/15min)

 

Any I’ll get you an answer asap (before the weekend)

 

 

Phil

 

PS check the video on the homewood thread mate

[Bob Abell 2Participant @bobabell2]

Thanks Phil

 

Looking at the webby…….these motors seem to run on 12 v anyway?

So, I would have two sets of batts to go at…………and with only two batts in the boat, it would be a lot lighter………….sounds good to me!

 

Bob

[Phil Winks 1Participant @philwinks1]

Your  right there Bob some however go all the way up to 30v+ (8+ lipo cells)

 

and often these are the lower kv (Revs per volt) motors so two of your bty’s in series (24v) will give the high revs that  you want.  and this would help keep the Amps to a managable level for a goodly amount of  watts!

 

Ideally a highish kv (1500 +) motor that’ll run on 12v would be good I agree however that would still only get you 18000rpm so I think you’ll still be looking at 24v to get the revs.

 

a good target would I reckon be circia 30,000rpm with a small fine pitch prop

 

then you’d  still be at half the the bty weight your at now and the motors would also be lighter with more torque

 

Phil (still looking)

Edited By Phil Winks 1 on 20/04/2010 08:41:54

[Len OchiltreeParticipant @lenochiltree67043]

Hi Bob,

Here is a target for you, get this thing on the plane before this thread reaches 700!!!

[Phil Winks 1Participant @philwinks1]

Hi Bob sorry I’ve not got a difinitive answer on motors yet, been a hectic week one way or another and the good weather has had me outside at every opourtunity, never kowng if it’s the last good weather this year lol.

 

still the gardens upto scratch and no work till a week on Mon, fingers crossed I start a new job then!! so hopefully I’ll find a couple of hours to check them all out for you.

 

 if memory serves your currently at about 760w, are you not? any idea what revs your getting, or should be getting, from those motors?

 

Have you progressed any hull mods? and or had her on the water this week?

[Bob Abell 2Participant @bobabell2]

Hello Phil

 

The MMB900 Motors were about …360 watts each, running at 18000 rpm

 

I really need to get back to Bury and find out what motors were in that giant Aqua launch…..but unfortuneately….I never saw it run!

 

The hull is back as it was originally

 

There`s no rush at the moment……………..All the best with your new job!

 

 

Bob

[Phil Winks 1Participant @philwinks1]

Thanks Bob It all sounded seriously hopeful at the interview one of the two interviewers sounded like she wanted to give me the job on the spot however as it’s working around vulnerable adults. (building maintenance) they need the CRB checks back 1st (No worries there) and they had 2 others to see after me.

 

from those figures I’m reckoning you could do with something the region of 500w per motor min,  and hopefully I can find something that would spin at nearly double that speed. Requiring smaller/finer pitch props.

 

And as a bonus at that wattage and running two bty’s in series to provide 24v running both esc’s you’d only be drawing 42A so even on a sustained full throttle run you’d have a min of 6 minutes any less throttle obviously would extend the run period considerably making 15 mins achievable I think.

 

How do you feel about no reverse? many (but not all) esc’s in this range have a brake (to stop the props) but no reverse. also do you feel there is a good airflow through the hull? Just in case outrunners seem the best option.

 

(outrunners are where the armeture is bolted to the mount and the outer case holding the magnets rotates, they tend to have much higher tourque than traditional inrunners. However water cooling the motor is obviously often not an option here) 

 

Phil

 

 

[Bob Abell 2Participant @bobabell2]

500 Watts per motor…….don`t sound much to me?

 

I was expecting………………………3500 watts per motor!………5hp each?

 

It`s all going over my head at the mo!

 

I need to sit down……………….Bob

[Phil Winks 1Participant @philwinks1]

that at 24v would require 145A per motor Bob your 4800 bty’s would be flat in, er seconds

 

I would seriously question anyone who claimed that output from a bty driven motor in a 1.5m boat (they are available I think but not practicle) 

 

in all seriousness it would require 48v at least (to fetch the Amps down to manageble levels)  thats 12 lipos or 40 NiMh’s a serious case of way too much weight. and thats if you can find a motor that’ll handle the voltage!!

 

Phil

[Phil Winks 1Participant @philwinks1]

Here you go Bob

 

Big Boy!!! – 7000 Watts of Power for less than 100GBP

Model: XYH80-100-A
Turns: 6
Maximum Power: 7000W
Resistance: 17ohm
Idle Current: 3.5A
ESC: 150A
Input Voltage : max. 48V 
Kv : 180 rpm/V
Weight: 1750g
Shaft: 12mm
Voltage Range: 20-48v
Non Load Current: 3.3A
Equivalent: 60-80cc Gas Engine
Prop Size: 30×15

this is the sort of size they go to but this one aint exactly practicle 

 

mind you it’d get that beast on the plane if it were not for the 40 Nimh’s and 1750g of motor dragging her to the bottom at high speed and it’s a hundred quid give or take.

 

cables would also have to be enourmously thick to carry that current, about 6mm squared I reckon and it turns at a poultry 8640 rpm on 48V. mind you the prop could possibly be about 4″ maybe 6″

 

Maybe I’ll design a 1/2 size tug to take it eh?

 

If you go for 1/2 that size so you can have two in the boat the weight  issue is much the same if not worse.

 

Phil

 

[Bob Abell 2Participant @bobabell2]

Thanks, Phil

 

Wow!………………..That`s a biggun!………..said the Duchess!

 

It all proves the point, that nobody can recco a Brushless motor for a big Slo Mo!…………Because, it`s not been done before?

 

I`ll just have to weigh up what`s available, ask a lot of questions etc……..

 

The Club has got a charah trip to the Harrogate Show in May……..That should do nicely?

 

 

Bob

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