A speed boat by anyother name

[Phil Winks 1Participant @philwinks1]

the challenge is to make a small boat go as far as possible in four hours with as few bty changes as possible

[Phil Winks 1Participant @philwinks1]

Every year our club run a four hour challenge event. The rules are pretty simple the boat (for practical reasons) needs to be reasonably small and agile. Must be battery powered. And well thats about it really. A course is laid out that must be followed and if you exit the course you must re-enter at the same point. ie: if you come inside a bouy then you must circle it to rejoin. Bty changes are allowed and the trick seems to be to have a good lick of speed along with good longevity of battery. the winners usually change bty’s about 6 times.

 

Despite notching up 300 laps last year with a rather fast ish tug I came nowhere the winner (a 500 mm copy of a huntsman.( well designed DM.)) notched up over 400. So for this year I thought I’d set out my stall (so to speak) a little earlier and build something specificly to address the challenge. I chose a 435mm x 145mm(120 on water line) grp hull as the low beam to length ratio should reduce drag and make her a little slippy in the water. Max displacement is 726g so reasonably light and a 385 low drain motor on 8.4v  should provide enough grunt without draining bty’s to quickly (my aim is only 4 bty changes max) electricery will come from some 2450 Mah (or possibly bigger) AA NiMh  cells (7 per pack)

 

The pics are of progress so far

Cooling of the esc is quite important given that its working at close to full stick for 4 hours so pickup and outlet have been fitted

The 385 motor and a simple motor mount I will be fitting some cooling fins to this

Quite a narrow wetted area! the rudder is to be fitted on the transome looking like a dummy outboard thus leaving loads of space for the water scoop

Edited By Phil Winks 1 on 12/03/2010 18:52:13

[ashley needhamParticipant @ashleyneedham69188]

Phil. good luck.

 

just a thought.. why not dispense with the esc altogether??  no esc=no power losses=max battery life!!  or is the course as tricky as to demand some slow speed running??   

if it is, how about no esc, but a slightly lower voltage battery for slightly less speed and more full power running???

 

Ashley

[Phil Winks 1Participant @philwinks1]

Nice thought Ashley however, and DM will no doubt confirm or otherwise, modern esc’s do not create significant power loss, and certainly not in the order of the mech ones that used to, still do for some, warm the inside of the boat. Plus yes the course requires some level of control esp in the tighter corners, and there’s the other boats to avoid, so a reasonably  good level of speed control is a must. Technically without an esc its an rg boat (radio guided) and  the rules do state RC I can just hear the mutters of Bloody Hooligan from here and the challenge is in Sept lol and hey I’ve never been that much of an “all or nothing kinda guy” just don’t tell any one

[Rick DevonshireParticipant @rickdevonshire]

Hi Phil,

It’s good to hear of some new ideas/thinking on the subject of types of competition to be run. I haveoften thought about pepping up steering events for the faster motor boats, MTBs etc. rather than just plodding slowly round the marker buoys.

While keepnig the points for scale aspect would it be possible to lay out more of a ‘slalom’ type of course to be run against the clock?

Who knows in time this could foster a new type of craft specifically built for the purpose – ‘Fast Craft Scale’ –  FCSc.

Rick.

 

[Phil Winks 1Participant @philwinks1]

Hi Rick. I think what we do is pretty much on those lines, we don’t have a max size or bty definition in the rules yet but the possibility is there. Although we do compete for a trophy it is still very much an informal event aimed at allowing as many in the club to compete/have fun as possible. The length of the event does tend to self regulate the top speed of the vessels as to get “hooligan” speeds tends to mean high amps so producing short bty life/multiple changes which in turn defeats the gains made by the high speed, also the tightness of the course makes it near impossible to go to fast. About 400/500 mm seems to be the norm usually of the “swordsman” style. ie: quick and nimble, the big trick seems to be to get it real light thus saving huge mounts of bty power pushing it round. Last years winner displaced a measly 800g hopefully mine will come in well under 700g (currently weighs less than 200g but  still has superstructure btys esc rx and servo to be fitted) the other criteria I perceive is survivability as collisions are somewhat inevitable so a level of swamping must be acceptable hence I’m building with large airtight cabins fore and aft. Also the centre area will need to be easily accessible for speedy bty changing. A little secret weapon in case of a bump against the bank (Concrete in parts) is the front 50mm of the bow is a solid GRP plug with strengthing bars glassed into the inside of the hull running fore/aft back to the midpoint. Some rubber along the gunwhales should help too

[Phil Winks 1Participant @philwinks1]

Progress continues I’ve sorted the heatsink for the motor (glue setting as I type) and I’ve started on  the rudder! I may well disguise this as an outboard? not sure yet.

[Phil Winks 1Participant @philwinks1]

Some more WIP pics! only 3 days on this so far and its sure taking shape the weights looking too with only 30g off ESC 20g off RX and bty’s to fit she now weighs a spritely 420g so if the rest of the superstructure and bty’s come in under 240g (which they will) she will be under design weight (a good thing ) The bty’s will be fitted on the cockpit floor with a box over possibly held to steel strips with magnets to allow them to be shifted forward/aft to trim and making them easily accessible for rapid changing. the rest of the superstructure will be minimull (to keep weight and aerodynamic drag down)

The heatsink hiding the motor is adapted from an old ESC, and doubles as the clamp for the motor.

The rudder may appear oversize. this is intentionall I need manouvrability and it can always be cut down if she’s too sensitive to it. I still need to reinforce the transome at the mount point.

[Phil Winks 1Participant @philwinks1]

OOps forgot I’d posted those pics and moved them in photobucket  ah here they are again may be the techies can repair the old links and remove this post

There I believe they’re in the right order

[Bob Abell 2Participant @bobabell2]

The heat sink clamp is a good idea, Phil, and being clamped to the motor should make it work well too!

 

Our club comp this year…….. “The Commodores` Challenge”…..is for a powered boat going round a course and NOT being powered by sail, steam or electric………..Looks like a lacky band job then?

 

Bob

[Phil Winks 1Participant @philwinks1]

Right now on to the WIPP’s the basic deck and cockpit are complete and with every thing on board bar the esc she is weighing in at 580g so loads of spare before she hits max at 726g. When I 1st started this I was thinking along the lines of the boat from the “Gaviscon” advert but as she progresses it starts to look more like a miniature OMRA vessel (Not sure about that being a good thing aesthetically) although if I fit the dummy exhausts purloined from a toy truck the OMRA hooligan look may well persevere.

 

[Phil Winks 1Participant @philwinks1]

Hi Bob sorry to hear about the potentially duff P98 I take it they’re both running on the throttle channel and one of the RX plugs isn’t reversed??

 

The heat sink should be good esp as I have a self adhesive heat transfer pad between it and the motor. (The sort of substance that you will find in between esc fet’s and their heat-sink) I’m going to risk and air scoop on the deck with spray deflector of course and a vent rearwards between where the windshields are to go. sort of inspired by the cowl on your Slo-Mo-Shun.

[Phil Winks 1Participant @philwinks1]

Some more WIPP’s this one is moving along quite quickly I now need another coat of red then gloss lacquer, then refit the hardware and make a windshield, purchase and fit bty’s/esc and the testing can begin so it may get an outing easter  sunday at a fun sail/easter egg hunt in our local country park

The tunnel on the foredeck acts as both air scoop and warm air outlet.

I’ve chosen a simple colour scheme and a classic hooligan as the skipper

 

[Bob Abell 2Participant @bobabell2]

How about fitting a working Slo Mo fin and rudder?

 

It might give you an edge?

 

Another great idea from ………………………..Up North!

 

 

Bob……..Full of it!

[Phil Winks 1Participant @philwinks1]

 not a bad Idea that bob quite easy too ! I’ll have to give it some thought. maybe some retractable wings to allow it jump over any unfortunate that gets in the way  well it is mutley at the helm!!

[Paul TParticipant @pault84577]

Hi Phil

 

Try a hull like the flash steam boys use, long and thin with little sponsons to keep it upright, this will give the model a great ‘swim’ just like a canoe….lots of forward speed for very little effort.

 

I like the little dog.

 

Paul

[Phil Winks 1Participant @philwinks1]

Hello Paul really chuffed to see you back on here mate I do hope your as well as can be. I do like that idea really do. and is food for thought should this not perform as hoped.

The initial motor run tests on this one went well this morning the motor out of the boat draws .1 A on 7.2v and in the boat with the prop on but  out of water draws imeasurably more so I guess the motor / propshaft line up is good. put it in the test tank and best guess is that it will move swiftly (very swiftly for app 2.5A so considering 2900Mah bty’s I should get my planned hour at a good rate of knots. 

 

Phil (a very happy bunny)

[Phil Winks 1Participant @philwinks1]

I’ve just ordered the ESC and Batteries for her and so now its sit back and wait for the snail mail to fetch my goodies. given one item is coming from hong kong it could be 10 long slow days  however for applications such as this I rate the ESC I’ve ordered slightly over kill as its rated 50a fwd and 20a rev With  a Voltage range of 6-12V having said that once had one in an off road buggy and it never failed despite my grandson constantly stalling it (Prob 80A’s) trying to climb rocks, also they are 100% waterproof and testement to that was the same buggy (a 1/8 scale 4wd job) driving through many puddles, often slowly sometimes quickly, that where deep enough to completely submerge it. the esc was strapped to the chassis so no protection there. finall testement is the fact that said abused esc is still performing faultlessly in the SS Tonendale So yes a good piece of kit well worth the £20 average that I spend on them on ebay generally they just won’t let one down and this one will be my fourth, I’ve got 2 others powering tugs.

 

 

Phil (looking for his patient head)

[Phil Winks 1Participant @philwinks1]

Posted by The Fat Controller on 19/03/2010 14:02:35:
Hi Phil
Try a hull like the flash steam boys use, long and thin with little sponsons to keep it upright, this will give the model a great ‘swim’ just like a canoe….lots of forward speed for very little effort.

 

Just one problem occurs here Paul the rules apparently state it should be semi scale so next question is there such a vessel type in the real world some research called for here me-thinks.

 

Any way on with the progress on the little speedboat I received the bty’s today 12 Vapex 2900Mah AA cells to be made into two custom 7.2v packs. 1st shock was that they are somewhat heavier than anticipated. Being chemically denser bty’s I expected them to be heavier than the 1500’s I possess however 33% heavier was a big surprise the packs  each weigh some 198g as against the1500’s at 135g. that may not sound like much but that puts her final weight at about 800g which is creeping into significant figures above target weight of 726g.  however a float test with all this on board shows her to be a mere 2 or 3 mm above the planned measly 25mm draught and no significant trim issue so perhaps all is not lost. so when the esc arrives and I’ve completed the little things like bty strap and touched up paint she should be set for water trials and possible disappointment. however at worst I expect to end up with a fun little boat that’ll prob see much thrashing about the ponds, rivers & canals of Somerset.

 

Finally  the WIP pics

The bty packs

 

The water cooled shelf is for the ESC

The battery in position still need to fit strap/cover. the string attached to the deans connector is to facilitate removal

Edited By Phil Winks 1 on 23/03/2010 18:21:45

[Phil Winks 1Participant @philwinks1]

The ESC arrived from hong kong today and so it’s full steam ahead on sunday.

 

 

Personally I feel the performance, speed wise, will be satisfactory, and duration wise prob a little disapointing. this is based on the fact that I’ve exceeded the target weight of 726g by nearly 150g, ooh er thats a lot, however in the domestic tank her response to a 1/2 throttle blip is to jump onto the plane in about a foot, swiftly caught by my waiting left hand I might add! So I’m hopefull all is not lost, and she may even stand a prop  size reduction to extend bty life.

 

If nothing else I’ll have a fun little boat and some valuable experience under the belt.

 

 

Phil (praying for dry weather this Sunday)

Edited By Phil Winks 1 on 30/03/2010 15:16:18

[Phil Winks 1Participant @philwinks1]

Well she got her water trials and the exccess weight was her down fall she wants to plane and prob would/will if I could lighten so I guess its back to the drawing board but not before I rip the decks of and rebuld in 1mm plasticard or similar lighter material to try and shed as much weight as possible The dog may have to go overboard to.on a positive note the esc motor and bty combo worked faultlessly and 30min running only knocked 75% of the bty capacity out so lighten her and so get some more speed and who Knows?????

 

Phil (in hopefull mode)

[Bob Abell 2Participant @bobabell2]

Oh dear!…………….Back to the drawing board, hey!

 

Sounds like the trials and tribulations, I`m having with my Slo Mo!

 

Keep up the good work……….There`s plenty of time before the big day

 

 

Bob

[Phil Winks 1Participant @philwinks1]

Hi Bob yes I’m guessing its exactly the same issue a tad to much weight however I don’t have the option to up the power, I don’t think so anyway,

 

That 385 motor is a pretty close fit!

 

however as its not a superb example of scale engineering its not too soul destroying to tear it apart and start again.

 

Phil

[Phil Winks 1Participant @philwinks1]

Here we go then in a moment of bordem I took this one off the backburner and ripped the heavy balsa/grp deck and the forward bulkhead out and replaced it with depron. basically styrene foam. I also moved the esc back to just forward of the rear bulkhed. all this has reduced the weight to a tad over the target weight.

 

The effect on performance isn’t stunning. she still sits a little low at the rear and top speed aint sparkling. edurance is though nearly 45mins at 80% throttle on one bty before any serious degridation of speed. so to lighten her further I’m looking for a lighter esc (current one weighs in at 50g) and then add a cell to the bty packs and then fingers crossed eh

 

Phil

Edited By Phil Winks 1 on 27/04/2010 19:31:59

[Author]

Posts