Vinnystoolbox

I have decided to build from scratch please ignore the first few posts about using the RTR hull it has gone back







Hi,
I have built rc cars before but this is my first boat as my son likes boats and i thought i'd join in

Ok so i'm not looking for anything super fast just a bit of fun for not too high a budget

So i was thinking of using the boat i've ordered till it dies then mod it to a single brushless setup with better radio gear etc.


I have ordered this boat to use the hull ==== http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWN:IT&ih=012

This esc and programmer === DYNAM : ESC-70A DYE-1007 - Program card DY-1014

This radio gear === Acoms Techniplus 2 channel radio, 27Mhz

And thinking about one of these motors === http://www.hobbycity.com/hobbycity/s...idProduct=4206

or

http://www.hobbycity.com/hobbycity/s...idProduct=5145

Not thought about batteries till i have picked a motor

I guess i need a proper prop and a way to balance it?


Also thinking of water cooling at least the motor, i have read up on this from a link in another post

Any thoughts would be appreciated thanks in advance

Vinnystoolbox

Ok so the boat arrived today and i'm glad i have real radio gear coming as the standard equipment is very chinese

Now i have the hull i can see it has a trim rudder fitted which may affect how i modify the boat as it might be best to fit a useable rudder in this position and keep the props where they are, it has a twin prop configuration as it stands.

Would it be too much to fit 2 brushless motors???

Fortunately i have some experience of glass fibre as i will need to strengthen the main parts of the hull, although the transom seems fairly strong as it has additional structures protuding from it.

wave waker

post pics please in and out of the boat.

Vinnystoolbox

Here are the pics

Think the wings need to go

Vinnystoolbox

I've charged and used it twice just to see what it can do and the battery doesn't seem to hold a charge properly as it has good power for maybe a minute if i'm lucky then gets slow and lasts about another 5 mins any thoughts?

pompebled

Hi Vinny,

How long did you charge it, with how many mAh and with what charger?
The battery needs to be charged and discharged (=used) up to five times, for it to come 'alive' and deliver the full charge.
If this doesn't occur, the battery may have been shelved too long and simply won't work anymore, get a refund or an exchange battery.

With 80 cm length, it's a rather big and (due to the plastic hull) heavy boat.

Normally I'd suggest an 800 (brushed) motor on 20 cells, but that would be way too heavy. A 700 on 12 cells would work, but still would be rather heavy and not very fast (compared to a lighter epoxy hull with the same motor, which would run about 30 mph).
I can't get your links to work, so I have no idea which brushless you've selected.
Could you repeat the links without the ****, or list the type and number of the motors?

Regards, Jan.

Vinnystoolbox

Hi,

It's a 1800 mah battery charged on a 0.5A charger for 5-6 hours as the manufacturer suggests

The boat has a couple of other issues including water leakage and endplay in one of the prop shafts so i have contacted the supplier regarding a refund

Sorry about the links i cut and paste them so i guess the forum did that

I was thinking of one of these motors

KB28-47-13S Hobbycity Product ID = 4206 Shaft Size: ƒ³3.17mm�~12mm
Motor Dimensions: ƒ³28mm�~48mm
Weight: 163g
Kv: 3000
Idle current: 1.4A
Resistance: 0.0248
Max Amp: 32

or

TR 28-45 3600kv Brushless Inrunner (WaterCooled) Hobbycity Product ID = 5145 Kv: 3600rpm/v
Required ESC: 40A
Voltage Range: 6-15v
No Load Current: 1.5A
Mas Load: 45A
Max Power: 300W/60S
Weight: 149g
Shaft: 4mm

Or would something else be better?

I've taken the specs from the hobbycity website hope that helps



If i get a refund where is a good place to get a hull, motor mount, prop shaft and prop etc from in the UK would be best

Also what would be the best hull size range, i'm not after a record setter just some fun

pompebled

Hi Vinny,

The first one is on the small side. the second one would need two of them, as it's a motor for a 20"hull.

In order to save weight I'd suggest a single motor like this one:
https://www.unitedhobbies.com/UNITED...hless_Inrunner

Running on 7 cells, 8,4V turning a 40-42mm prop (Graupner K series) should keep the boat light enough to leave you shaking at the maiden run.

This requires a 'proper' propshaft, prop and a seperate rudder.

Modding this hull will set you back several times the value of the original boat and it still won't perform as when you'd put the suggested parts in a lightweight epoxy hull...

The choice is yours, ofcourse.

Regards, Jan.

pompebled

Check out the links list at the bottom left of this site:
http://www.modelboatmayhem.co.uk/

You'll find a lot of UK shops also sell European hulls (like the H&M boats) ordering directly from the manufacturer is always possible.

Some other links:
http://www.modelltechnik-schnippkoweit.de/xtcommerce/
http://www.hydromarine.de/
http://www.mhz-modellbau.com/
http://www.jet-drive.de/cms/index.php
http://www.gundert.de/
Just to name a few...

Hull size is a matter of preference, what ever you like (and are willing to pay)
Keep in mind, that it's not the hull and hardware that will cost the most, it's the motor, ESC, batteries and required charger that can make the price skyrocket.

Regards, Jan.

Vinnystoolbox

Excellent thanks

What a lot of reading to do

Think i might go for something quite small, oh and jet drive that looks fun

I have radio gear and esc on the way which limits me a bit but i think they should do for what i want.

Vinnystoolbox

I must be cursed or something LOL

I received my radio gear ACOMS Techniplus 2ch 27mhz, opened the box picked up the transmitter and rattle rattle, more stuff to return what fun

Still nevermind it is all giving me time to decide what to do, i think i may have to get a real/composite hull and fit a jet drive sounds like a good challenge as i have Glass fibre experience.

Not sure what hull to get have seen a few, think i'll try to keep it small, well smaller than the original hull anyway.

Anyone gone brushless with a jet drive?

The drive suggests a 700 or 800 motor, i haven't got my head around working out what brushless motors numbering is all about yet

Ron Olson

My Feedback: (1)

The reason why you're seeing the ***** is because that site was sending members over to the R/C forums to spam the sites pushing theirs. They received store credit for doing that so a lot of forum sites have now blocked them, not just here. Since they got nailed for it, they have changed or eliminated the program.

Vinnystoolbox

I see that seems reasonable

Can someone please post a link to a post about motor numbering for brushless, as i've searched but can't find anything

Think i'm defo gonna go brushless, jet with around a 22-25" v/shallow v


Got my radio sorted popped to the shop who swapped it no problems shame they only do rtr boats, oh well the search for a shop near me continues

Vinnystoolbox

I have come across a hull design i think could be quite good for a jet drive, as it might help the inlet flow and also give some extra stability, the designer says he could adaptit to be taller in the rear as i think this might be a problem with the rear height fairly small


the specs are:- Length- 560mm
Width - 220mm
Height- 100mm front 60mm rear


Any thoughts from jet drivers would be great

pompebled

Hi Vinny,

With the hull in the pictures I see more problems coming from the very wide, flat rear end.
A jet intake needs to be in the water, that's why most hulls, designed for a jet have a fairly steep V-shape, to make them sink in sufficiently.

With that flat hull, you may be drawing air under it and in the intake, rendering the jet waterless...

Regarding the 700 / brushless issue; the 700 run's some 21000 rpm on 12 cells, when searching for a brushless replacement, aim for those rpm unloaded on the jet, more will just create cavitation and foan, no propulsion,

I wouldn't pack 12 sub-C cells in the hull you selected, 6 or 7 will be enough, adapt the KV rating to get the desired rpm (roughly 2600 - 2800 KV)
Power consumption in the 350W (for a 700 motor substitute).

A 56 cm hull is too small for a 700 driven jet, you'll need a smaller jet for that size boat.
Check on the Kehrer site for examples boat size/jet size.

Regards, Jan.

Vinnystoolbox

Thanks

The designer has come back to me regarding hulls and is now offering me something a bit special, first batch of a new design.

The hull in the pictures : i thought the front and sides would create a nice flow into the inlet but you are probably right, i'll have to see what this new hull looks like


Thanks again