HI Paul
Glad to hear you are still pushing the limits on speed. Missed your open day last year but hope to make 2016.
dave 😀

ok,

I have actual facts, check this out, its my 48" Deep v Huntsman, single screw, its not a case of it looks fast etc, you will read that I use eagle tree data logging so everything is factual. I know these are different boats to yours, but the info regarding electrical setup might help, 25mph for a 6kg ply boat is pretty damn quick, it has beaten ic Huntsman boats

http://www.modelboatmayhem.co.uk/forum/index.php/topic,21584.0.html

Also, for twin brushless set up, My 4 foot crashtender is pretty much the same speed, this can run on 5 cells per motor, so 10 cells in all. its in the build blogs on this forum.

All testing, prop choice, lipos, motors, cooling etc is in these forum threads.

Any questions, just ask, I'm no expert, it took a long long time to research and test, so hopefully this will help. I don't come on here that often, but will respond.

Paul

Those pulsejets are insane. I've seen a few up in the air up north wher I lived up until the last few weeks. One guy I had to stop and make enquiries with - his jet was almost 3m long and the exhaust from his custom-built pipe fit my fist half. The intake was bigger still than 'wrapping' my fingers in a circle... Needed some sort of launch platform - lost me from that point to be honest. I thought 60mm EDF F-15E's were incredible haha!

Back on topic though...

Unfortunately, given the advice that has been coming from all angles, it really looks like I will be sacrificing the full scale of what I want people to SEE for something that I can AFFORD.

The hull initially was going to be a little shy of £100 - painted, primed, laser cut and glued together. All my own work of course.

So let's say £100 for the completed hull.
£200 for the new electronics
£100 for the upgraded batteries for when I eventually feel brave enough to risk the power (bear in mind it's only 2mm ply!!)
Plus roughly another £80 - £100 in bits'n'pieces.
Add on top of that, the 3D-Printed MiniCat that I'm just waiting on new nozzles for...

Will update after the weekend, as I'm about to call it a day - ice cold beer in the fridge and Breaking Bad for me. Tomorrow I start cutting. Will update later in the day.

Enjoy your weekend gents,

Dean

😁

Big fast boats need big EVERYTHING laughs and I would recommend full spec radio gear.

RX needs to be mounted as high as possible. My days of go fast are a memory now and were using IC engines ( ask me about tuned pipe setups and monoline control line speed).

Now I like models that give me time to react ( and banks STILL jump out at me).

if I had a place to run one I keep looking at the twin engine IC outriggers and droooooooooling. But there is always an itch to try and go ballistic

http://www.hobbyking.com/hobbyking/store/__34247__Hobbyking_Pulse_Jet_Gasoline_Engine_34_Red_Head_34_with_Ignition_System.html

grins need I say more?

Don't know if Haverlock agrees but, big fast boats need big lakes with 2.4 sets I've found the range can sometimes be less than 27 or 40's. I try to keep the reciver as high as possible in the boat. A Hovercraft I have (see my harbour)has all the electrics under an alloy spine. I had range problems until I installed a receiver with an amplifier antenna.
If you're building from scratch it could take a while. if you haven't tried fasty's before. Can l suggest an off the shelf ready to run joysway supermono x. Around £100 once you've bought the battery. Great fun, fast, self righting. The only problem Ive had with that is, concrete lake sides and recently the flexI shaft snapping (motor needs alignment). Shafts £3.70 ish. Cheap fun. Think Xmas present!!!!!

Sorry its the RX lead from the ESC I was talking about.

Each ESC has ( for brushless) 3 wires to the motor and 3 to the receiver.

if the ESC has BEC then that feeds through the receiver lead. Now if you have two or more ESC each having BEC you need to disconnect the BEC for all but one. Failing to do so will result in a fried receiver and potentially fried ESC(s). Removing the red lead leaves signal and earth to the ESC which allows it to function but prevents a voltage being fed to the receiver.

Remember that BEC supplies voltage to the receiver/ servo system since the ESC has its own power from the batteries.

And while on the subject of batteries what battery ESC connectors are you intending to use?

http://www.rogershobbycenter.com/lipoguide/

Go to the end and there is a write up on the common connectors.

On the subject of ESCs make sure they have a LIPO cut off voltage to protect your battery packs.

The list of dos and don'ts just gets longer and longer.

Haverlock,

I thought the BEC's require their BEC individually? There will be two, and they'll both have a motor?

Have fun laughs make sure its water tight and this is not being silly. if you have never seen fast boats in action



You need to be able to adjust thrust angles and will probably need trim tabs. Setting up a fast boat starts with science and ends being a "black art" figure on it flipping on a regular basis.

Get a prop balancer and sharpen your props before balancing them. Flexy shafts seem to be the "must have" drive train.

http://www.cornwallmodelboats.co.uk/acatalog/fe-hardware.html

http://www.cornwallmodelboats.co.uk/acatalog/race-rudders.html

Not the only supplier but gives you some ideas as to the kinds of hardware you need to be looking at.

if your wedded to a twin setup then you need to consider contra-rotating props so you minimise torque effects.

if you use BEC from your esc(s) CUT THE RED LEAD from one esc. else you WILL fry something.

I hope your pockets are deep enough cos going fast is EXPENSIVE ( divorce may be a cheaper option) .

Haverlock,

Thanks for such an in-depth post. Much appreciated - worry not about negativity; as you say - realism is the way forward and with the grief the wife is giving out, this MUST succeed lol!!

I've decided I am going to stick with the decision to bring the size down from 72" to 60" because I would like a decent cruising speed.

With the boat being the size it is, there's plenty of room. On which note, it's a V-Hull, scaled back to 60 inches, blueprint attached.

I've been advised that a suitable prop pair would be X465 Octura. They're huge!! Very excited to get this thing onto some water!!

25c batteries will I suspect be a limiting factor. if you run at a full 25c you can only pull 130A and that will lead to a much shorter battery life.

http://www.rchelicopterfun.com/rc-lipo-batteries.html

That's a pretty full treatise of the factors involved.
To daw 130A you would in practice need 50c batteries. if you intend to run the batteries for more that one or two times.

You WILL need a watt meter so you have some idea as to the actual current being used.

Using a watt meter you can then find out what a prop/motor combo draws static and thus have some idea of the way to go.
Sharpened balanced props are a MUST.
Really if you just want speed have a look at the outriggers. They seem to run at insane speeds and since they are raced they have to be fettled to do it time after time.



one example ( single shaft 60A ESC).



actual race footage.

The simple facts are the less of a boat in the water the faster it CAN go, this is independent of how much power you have. So hydroplanes are the faster hull type. if your intending to design your own I doubt you can better them for speed.

Hull design is paramount when it comes to speed, no amount of power will make a badly designed hull go blisteringly fast.

Sorry if I seem to be negative but I hate the idea of a lot of money and enthusiasm being thrown at a probable failure.

I can bring the boat down to 60 inches. This relatively solves my speed issues, especially with the dual motor setup.

However.. Application of power is where I'm a little lost.

Prop suggestions anyone?

I'm thinking of starting off with a mid range 38mm.

---

Here's where I'm at so far with the heart of this boat:

- Twin watercooled 4048 1050Kv motors
- 4S 25C 14.8v 5200 Battery to start off with: 6S if that all stays happy
- Twin watercooled 200A ESC
- 38mm Prop (like in the HK Osprey 1057mm)

Whilst this is on the shelf pending prop advice, I shall go see the fireworks!

Happy Guy Fawk's everyone 😊

Dean

Good things come to those who wait. in this case China, most of my stuff comes from there.
If I were you, I'd order separately. Sometimes the customs pick up on expensive orders. They often put the value on the package.
Note it says YOU do the waterproofing.

https://www.hobbyking.com/hobbyking/store/__65411__Turnigy_AquaStar_4084_1050KV_Water_Cooled_Brushless_Motor_UK_Warehouse_.html

http://www.ebay.co.uk/itm/171874401282

Looks like I found JUST what I need!!

Sounds like your wanting a BuggatI for Skoda money, ( I've got one) Skoda that is, the fast one.
I've measured my Avenger, its small. 970mm x 290mm. Water weight 490kg. Ni-mh 4600 mAh Max volt I run on is almost max speed control can take, 21.6v. Speed control big red brick 100amp, non water cooled like the motor. Single hull. Around 10 mins run time, and as I said earlier all just warm even after 2 runs. So I'm not pushing to its limit.

Have had a look at powerplant options.

Turnigy AquaStar T20 3T 730KV/1280KV Water Cooled Brushless Motor
SKYRC Proteus Water Cooled X520 730KV 1280KV Brushless Motor for Marine IM680

I like these as they can switch output power. Shame I'd have to bring the boat size down considerably to afford TWO of these!

Still looking for a reasonably priced 150A ESC.

Derek,

Thanks for your reply mate. I like the sound of your boat - pic looks pretty cool! I'm assuming just a single drive yeah?

My boat will likely be getting very warm, as I'll be hammering it if I can... (Ducks are quick to respond to RC boats these days).

Do you know exactly what you're running just now, that I may use as a point of reference?

If possible, your data I'd love to crunch consists of;

- Water-ready weight
- Battery mAh?
- Shaft/prop material? (Balanced?)

Cheers!

I'm no fasty expert, more of an all round experimenter. I have an old MFA Avenger (see my harbour).It around 3' and fibre glass. I installed a brushless out runner 5055 700kv.it runs on16.8v reasonably quick. Add another 4.8v and it lifts the front on start up, and quite a speed increase. Think it's going to be trial and error with yours, but these motors are quite reasonable on eBay, and you will of course have 2. I use 55mm x Prop. Motor only gets warm after a good hammering. No water cooling.
See what other ideas you get. Stopping a thing of that size quickly may require reverse good luck.