Watercraft magazine "Cordless Challenge"

[Jeremy]

Having just tracked you all down to this splendid looking new forum, I thought I'd risk starting a thread on the cordless challenge.  As some already know, I've been tinkering around with efficient electric propulsion systems for a couple of years now, and, with luck, should have my completed electric Winsome on the water this spring.

One consequence of all this tinkering is that I've acquired a fair stock of left overs from various experiements, some of which may well be reasonably well suited to having a go at the cordless challenge.  Obviously I don't want to give away any secrets that may give me a winning edge, but there is some general stuff that may be of use.

As some will know from discussions on the Yahoo group, a reasonably fit person can deliver around 100 watts or so of power for fairly long periods of time (good athletes can more than double this).  This gives a pretty good baseline for working out how long a cordless drill might power a small boat.  

Assuming that the boat performs acceptably when rowed or paddled by one person, then it's reasonable to assume that it needs around 100W or so.  Assuming that the cordless drill propulsion system total losses (the sum of electrical losses, propulsion efficiency losses and frictional losses) are broadly similar to the efficiency of rowing or paddling (probably a reasonably fair assumption), then we can work out how much battery capacity is needed to get around the course.

My guess is that it might take ten to 12 minutes to get around that course, including manoeuvring time at the start and finish, so say around 1/5th of an hour.  If we need 100 watts of power, then the power drawn from the battery in 1/5th hour will be about 20 watt hours (100W x 0.2).  This is pretty close to the usable battery power of quite a few cordless drills, so competitors will need to choose their tools carefully.  For example, my very old Bosch cordless drill only has a battery capacity of about 21Wh, so would probably struggle to run for long enough to complete the course at rowing or paddling speeds.

Battery capacity in watt hours is just the product of the battery voltage and the battery capacity in amp hours.  For example, a typical mid-range 12V cordless drill may have a 2Ah battery pack, giving a total capacity of 24Wh.  In other words, it will deliver a theoretical (when new, fully charged, at the right temperature, all the Gods smiling at once etc) 24 watts for one hour, or 48 watts to half an hour or 96 watts for 15 minutes, assuming that the drill is up to it.  In practice it's unlikely to deliver more than about 80% of this capacity, for a whole host of reasons, not least of which is that manufacturers are notoriously optimistic about these ratings.  Such a drill may struggle to deliver the same power as a rower or paddler for the time required, which is worth thinking about when planning your entry.

Jeremy

[gmatkin]

Now that's a useful piece of analysis.

Just don't drop your expensive piece of kit in the water!

Gav

--- On Fri, 14/1/11, Jeremy [via UK HBBR Forum] <[hidden email]> wrote:

From: Jeremy [via UK HBBR Forum] <[hidden email]>
Subject: Watercraft magazine "Cordless Challenge"
To: "gmatkin" <[hidden email]>
Date: Friday, 14 January, 2011, 8:18

Having just tracked you all down to this splendid looking new forum, I thought I'd risk starting a thread on the cordless challenge.  As some already know, I've been tinkering around with efficient electric propulsion systems for a couple of years now, and, with luck, should have my completed electric Winsome on the water this spring.

One consequence of all this tinkering is that I've acquired a fair stock of left overs from various experiements, some of which may well be reasonably well suited to having a go at the cordless challenge.  Obviously I don't want to give away any secrets that may give me a winning edge, but there is some general stuff that may be of use.

As some will know from discussions on the Yahoo group, a reasonably fit person can deliver around 100 watts or so of power for fairly long periods of time (good athletes can more than double this).  This gives a pretty good baseline for working out how long a cordless drill might power a small boat.  

Assuming that the boat performs acceptably when rowed or paddled by one person, then it's reasonable to assume that it needs around 100W or so.  Assuming that the cordless drill propulsion system total losses (the sum of electrical losses, propulsion efficiency losses and frictional losses) are broadly similar to the efficiency of rowing or paddling (probably a reasonably fair assumption), then we can work out how much battery capacity is needed to get around the course.

My guess is that it might take ten to 12 minutes to get around that course, including manoeuvring time at the start and finish, so say around 1/5th of an hour.  If we need 100 watts of power, then the power drawn from the battery in 1/5th hour will be about 20 watt hours (100W x 0.2).  This is pretty close to the usable battery power of quite a few cordless drills, so competitors will need to choose their tools carefully.  For example, my very old Bosch cordless drill only has a battery capacity of about 21Wh, so would probably struggle to run for long enough to complete the course at rowing or paddling speeds.

Battery capacity in watt hours is just the product of the battery voltage and the battery capacity in amp hours.  For example, a typical mid-range 12V cordless drill may have a 2Ah battery pack, giving a total capacity of 24Wh.  In other words, it will deliver a theoretical (when new, fully charged, at the right temperature, all the Gods smiling at once etc) 24 watts for one hour, or 48 watts to half an hour or 96 watts for 15 minutes, assuming that the drill is up to it.  In practice it's unlikely to deliver more than about 80% of this capacity, for a whole host of reasons, not least of which is that manufacturers are notoriously optimistic about these ratings.  Such a drill may struggle to deliver the same power as a rower or paddler for the time required, which is worth thinking about when planning your entry.

Jeremy

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[Gizzle]

When reading about the "Cordless Challenge" it really got my attention but I'm not going to be around for the event this year.

I wondered if the cordless drills have to be powered by their own batteries?  I had a thought about fitting some "comedy" paddle wheels to each side of a dinghy, each one powered by it's own cordless drill but as the batteries are useless each one could be run off a spare 12V truck battery I have in the garage.  Would that be outside the rules??

I very much doubt the above idea would be fast but it would be fun to try it!

Cheers, G

[Jeremy]

According to the blurb: "To make the whole Challenge more about invention than buying power, the cordless tools must use the batteries they were supplied with – we'll provide recharging facilities between races – and their total equivalent new value should not be more than £400." it looks like external batteries are out.

Interestingly, the blurb also goes on to say: "Some readers will be regular viewers of Scrapheap Challenge on tv. Others may have visited Power Tool Drag Racing. I should stress right here that our Cordless Canoe Challenge will have few similarities with either."   which is interesting, because I have a little history with this sort of thing:

 


There also some other clips from that show on Youtube, including the race at the end, where I got to drive the infernal machine around the lake at Laguna Park, near Reading:



Jeremy

[Gizzle]

Thanks Jeremy, you are quite correct external batts can not be used.  I guess that restriction does make sense but also does restrict an entrant to using new "good" power tools that I'm not sure I would want to risk on the water.

Looks like you had fun on Scrapheap Challenge!

[alopenboat]

On 14 Jan 2011 at 4:18, Jeremy [via UK HBBR Forum] wrote:

>
>
> According to the blurb: "To make the whole Challenge more about
> invention than buying power, the cordless tools must use the batteries
> they were supplied with - we'll provide recharging facilities
> between races - and their total equivalent new value should not be
> more than £400." it looks like external batteries are out.

Does it rule out changing batteries? I rarely buy a tool with
rechargeable batteries without buying a spare (so I always have one
that is charged). Swapping to a fresh battery part way round would
not cost much time.

--
Hoping for calm nights

Alastair Law,
Yeovil, England.
<http://www.little.jim.freeuk.com>

[Jeremy]

I share that concern!  I've got three to choose from, of varying ages and performance, and, as luck would have it, the one best suited happens to be the newest and most expensive one..................

My plan is to try and make sure that the drill doesn't get wet, although I'm well-aware, from bitter experience, just how challenging it can be to keep anything truly dry on a small boat.

Some propulsion system options are less likely to result in the drill getting wet than others, though.  Although it sounds daft, an aircraft-type propeller can be a pretty efficient way of propelling a low powered boat and would allow the drill to be kept clear of the water and around the middle of the boat somewhere.  The human powered speed record boat, Decavitator, used a large diameter, low rpm, aircraft type prop to good effect: http://lancet.mit.edu/decavitator/

The paddle boat approach isn't as daft as it may at first seem, either.  Large diameter, low slip ratio, slow turning paddles can be up to around 80 to 90% efficient, better than a lot of boat props, which often struggle to get better than around 65 to 70% efficient.  It's another configuration that could be arranged to keep the drill up high and amidships, too.

Jeremy

[Michael Rogers]

Jeremy, having sampled your erudition on these matters elsewhere (ie the Swallowboats website forum), I think it would be only fair for you to start after everyone else in this forthcoming race, or to have to tow a sea anchor, or something.

Only joking. Go for it.

Can I ask about the relative efficiency (or inefficiency) of a fan or aeroprop (or whatever you call it) vis a vis a submerged propeller? I wondered about a catamaran propelled and\or steered by a hovercraft-type of propulsion unit. Steering might best be done with a paddle, if that's allowed. Scrutineers would have to be alert to possible illicit yuloh-ing disguised as steering. There's going to have to be a rule book, you know.

Any hope for a paddle wheel (or two)?

You will have gathered, and probably already know, that I don't really know what I'm talking about. Also I personally suffer from a slight dearth (actually a complete absence) of surplus-to-requirements cordless power tools. So, if anyone has one to spare, can I borrow the one with the HUGE battery capacity, please? Thanks.

[Michael Rogers]

I do apologise, I'm still trying to find my way round this undoubtedly impressive forum format. Which is why, at the time of penning (or pecking) my offering of just now, I hadn't dug out Jeremy's contribution which answers the two questions I had asked - about aeroprops and paddlewheels. I'm actually rather chuffed that maybe my musings are not quite as idiotic as I had thought they might be.

Still a bit concerned about covert sculling. Perhaps the rule book will have to define a rudder and restrict entrant craft to those.

[Michael Rogers]

I'm being a nuisance, but things keep occurring to me.

Presumably the 'tool' bit of cordless tool will require some clarification. For example, does my brand new cordless mower count as a 'tool'? - a bit heavy, but FAB battery capacity! And has a crewless craft radio-controlled from the shore also been excluded?

[Jeremy]

I like the idea of the cordless mower - lots of power and lots of battery capacity.  I suppose the only snag would be the weight, I have a feeling that they tend to be a bit heavy.  It's a pity I don't have one to hand to play with, though................

The only mention of crew in the "rules" seems a bit ambiguous to me.  There's mention of the crew being "as many or as few as you think necessary", which implies that "few" could be none, I suppose.  However, the rules also go on to say that "at least one member must be an adult" which implies that the minimum may be one person, which would rule out a remote controlled boat.

BTW, a catamaran may be stable, but will have a higher low speed hull resistance than a monohull for a given waterline length.  As it's likely that all these boats will be running at speeds where viscous drag dominates over wave making drag, anything that reduces viscous drag (high L/D ratio, low wetted area) will give an advantage.  Decavitator (the air prop driven MIT HPB) used a catamaran layout because of the low speed stability it gave, but at speed it lifted on foils to reduce wetted area and hence total resistance.

Looking at the dogleg shape of the course, and remembering the layout of the lake around the beer tent promontory, I think that the ability to turn quickly and accurately, with minimum loss of speed in the turn, is also going to be fairly important.

Jeremy

The problem, of course, is that having announced our 1 May deadline for entries in the Amateur Boat Building Awards and the Cordless Canoe Challenge, both in the last issue and on our website, inevitably everyone now leaves their entries until then! Which makes organising anything at all ahead of time all the more difficult.

However, as I write we have 3 real entries for ABBA and 6 serious-sounding enquiries for the CCC. We have also had sort-of-interested noises emanating from two tv programmes. Also had an offer of sponsorship from another major power tool manufacturer if Makita get bored!

We have appointed CCC stewards (see the new issue), blown the cap-ex on a megaphone and (thanks to the EBA) organised banner flags to mark the CCC start line and the Stewards' tent.... About which... You'll recall some time back that Water Craft agreed to pay for a tent beside the amateur boatbuilders line-up where the UK-HBBR will provide a Backyard Boatbuilders Advice Clinic. It would be great if it can double as the CCC Stewards Tent; would you guys mind?

Two main items still to arrange at this stage...

1) We need 2 marker buoys for the CCC course. Hopefully Beale has some; we don't really want to have to bring buoys + ground tackle up from Cornwall.

2) CCC entrants will need to recharge their cordless tool batteries but we just learned last week that Makita have discontinued production of their portable generators. We are guessing wildly but we reckon we'll need at least two. Again, we don't want to have to lug them up all the way from Cornwall.

I look forward to any bright ideas

[LASER41420]

I have a buoy I could bring if you like

Steve

--- On Mon, 14/2/11, [hidden email] [via UK HBBR Forum] <[hidden email]> wrote:

From: [hidden email] [via UK HBBR Forum] <[hidden email]>
Subject: Re: Watercraft magazine "Cordless Challenge"
To: "LASER41420" <[hidden email]>
Date: Monday, 14 February, 2011, 14:58

The problem, of course, is that having announced our 1 May deadline for entries in the Amateur Boat Building Awards and the Cordless Canoe Challenge, both in the last issue and on our website, inevitably everyone now leaves their entries until then! Which makes organising anything at all ahead of time all the more difficult.

However, as I write we have 3 real entries for ABBA and 6 serious-sounding enquiries for the CCC. We have also had sort-of-interested noises emanating from two tv programmes. Also had an offer of sponsorship from another major power tool manufacturer if Makita get bored!

We have appointed CCC stewards (see the new issue), blown the cap-ex on a megaphone and (thanks to the EBA) organised banner flags to mark the CCC start line and the Stewards' tent.... About which... You'll recall some time back that Water Craft agreed to pay for a tent beside the amateur boatbuilders line-up where the UK-HBBR will provide a Backyard Boatbuilders Advice Clinic. It would be great if it can double as the CCC Stewards Tent; would you guys mind?

Two main items still to arrange at this stage...

1) We need 2 marker buoys for the CCC course. Hopefully Beale has some; we don't really want to have to bring buoys + ground tackle up from Cornwall.

2) CCC entrants will need to recharge their cordless tool batteries but we just learned last week that Makita have discontinued production of their portable generators. We are guessing wildly but we reckon we'll need at least two. Again, we don't want to have to lug them up all the way from Cornwall.

I look forward to any bright ideas

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[Paul H (admin)]

Pete,

Bright sparky idea#1

Many on the HBBR Thames Raid starting from Beale will have electric outboards that need charging. So if we borrow or hire a genny for the Thames Raid a generous donation to running costs could mean said genny is made available for the CCC.

We could go the silent route and use the HBBR outboard batteries with 12V chargers or an inverter....recharging the outboard batteries at a convenient time. That kind of gels nicely with the spirit of the CCC I think.......especially if we pull the stops out with the Electric Boat Association (EBA) because they have members living along the Thames who offer battery charging to other members.

So that means CCC, HBBR and EBA all collaborating on electric boats, which has to be good.

-Paul

PS. Perhaps the "Environment Agency" (oxymoron?) could also join in and tell us why there are so few charging points along the Thames! EBA would love to hear their reply

[Phil H]

---

From: adminHBBR [via UK HBBR Forum] <[hidden email]>
To: Phil H <[hidden email]>
Sent: Mon, 14 February, 2011 19:59:18
Subject: Re: Watercraft magazine "Cordless Challenge"

Pete,

Bright sparky idea#1

Many on the HBBR Thames Raid starting from Beale will have electric outboards that need charging. So if we borrow or hire a genny for the Thames Raid a generous donation to running costs could mean said genny is made available for the CCC.

We could go the silent route and use the HBBR outboard batteries with 12V chargers or an inverter....recharging the outboard batteries at a convenient time. That kind of gels nicely with the spirit of the CCC I think.......especially if we pull the stops out with the Electric Boat Association (EBA) because they have members living along the Thames who offer battery charging to other members.

So that means CCC, HBBR and EBA all collaborating on electric boats, which has to be good.

-Paul

PS. Perhaps the "Environment Agency" (oxymoron?) could also join in and tell us why there are so few charging points along the Thames! EBA would love to hear their reply

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[LASER41420]

Something like this one?
http://www.hss.com/g/41101/Generators-625w-To-750w-Petrol.html
Steve

[LASER41420]

Or buy this one?
http://cgi.ebay.co.uk/BRAND-NEW-PRO-USER-850W-PETROL-GENERATOR-240V-850WATT-/200576213308?pt=UK_BOI_Industrial_Tools_Generators_ET&hash=item2eb346213c

[Jeremy]

I was tipped off by Pete that there was a segment on BBC South West's Spotlight news programme with one of the contestants boats plus the "stalking horse" entry from the stewards.  Thanks to the joy of satellite TV I managed to tune to Spotlight a few minutes ago to see what the competition are up to.  

It was a good item, great fun and illustrated something that I mentioned a while ago in this thread - battery life on cordless tools is key to getting around a long course!

I'm glad that I'll have two 18V, 3Ah battery packs with me...................

Jeremy

[Timmo]

Jeremy's Cordless rig is so beautifully crafted that I couldn't resist offering a contrast:



Drill drives a reduction gearbox (thanks e-bay) with cranks that push the wooden legs that work the Mirage Drive pedals. Very Heath Robinson made of ply offcuts and odd bits of metal clamped to each other with hose clips.

Works on dry land, no idea how well it will work on the water. Not even sure I'm entered for the CCC. sent my e-mail in a day late and haven't heard back so I suspect I missed it. I'll bring the gadget along just in case, but it's not getting any more sanding or sorting!

Tim

[Jeremy]

Neat idea, Tim, isn't ebay a great source of bodging parts?  The right angle gearbox in my unit is a much-modified drill right angle adapter that was an ebay purchase.

Did you get an email from Pete yesterday, regarding arrival arrangements, passes etc?  I can't see your name on the list, so maybe a quick call to Pete might be in order.

Jeremy