JetHobby Dolphin

[SG Villain]

Hi,

I start this thread to find out more from fellow RC Boater with regards to this RC boat from Jet Hobby. It is a EP fiberglass V hull - Dolphin. I bought it as a Christmas present for myself and has ran it for the past consecutive 3 weekends. I am facing some problems with set up. I am not getting the speed I want (without going into brushless).

As such I would like to invite fellow RC Boater that have this boat to contirbute their valuable experience and tips on these areas:

1) Brushed Motor & ESC combination
2) Brushed Motor and Propeller combination
3) Tips and improvements to the handling
4) Any Problem area

Thanks

Thanks

[SG Villain]

Let me start off with my boat's maiden run:

Set up:
7.2V / 6cell GP3300
Motor: Kyosho 13T Rev Super Marine Motor Type-G
ESC: ProBoat 50A ESC
Prop: Stock Plastic Prop
Others: Motor cooling, ESC cooling and floatation foam on the nose.



1st run:
The boat almost sank on its first run if I had not put foam on the nose! The boat took in alot of water when turning!!!!! I did not put any hatch tape on. Forgot to bring. So Hatch tape is a MUST MUST!!!!!

Boat's speed is so so. Maybe it is the weight of the additional water that seeps inside Not as fast or as brutal as my Traxxas Villain EX. Hull resistant is surprising little. Boat can glide a distant before it comes to a complete stop. As usually,will spin out on hard turns. So far no porpoising. Trim tab is working or maybe it is just not fast enough At max speed, a lot of hull is still in contact with the water...dunno how to improve on that

Problems:
Hull is rather thin on certain area. You won't be able to notice where. When my foam expand, it actually tore through the bow:



I repaired it with super glue and epoxy. So far so good

[SG Villain]

2nd Run

Set up:
Batteries: 6cell GP3300 & 8.4V 7cell GP3300
Motor: Tamiya TZ 23T Super Stock
ESC: ProBoat 50A (Same)
Prop: Stock Prop, plus some other sizes.
Others: Brush cooling, Motor cooling, ESC cooling. Foam sealing on the hatch, Blinking lights, universal joint for the motor shaft to the prop shaft and auto bailer at the rear.


My first attempt at making a brush cooler very messy soldering

Boat is slightly faster than my first run. Maybe my Kyosho 13T is old tech liao and not spining as fast as I want or maybe ESC not strong enough to power it. Motor alot of stress, runs very hot. Open hatch got steam comes out!!!!

Tried many propeller, different sizes and so far all dun work. Original size is 42mm X 1.4 pitch.
Tried Jet Hobby's Plastic 2 blade 45mm and 3 blade 48 - both cannot.
Tried Octura 39mm - OK la but stock still faster.

8.4V is faster but only a little. Boat handling same as first run.

[SG Villain]

3rd Run

Set up:
Batteries: 6cell GP3300 & 9.6V 9cell GP3300
Motor: Tamiya GT tune 25T motor
ESC: ProBoat 50A (Same)
Prop: Stock Prop and retry all the other props from my second run
Others: Usual Brush cooling & Motor cooling. Add on two thrust bearing. One for the motor and one at the stuffing tube.


My second attempt at making a brush cooler, getting better


My batteries placement. 6cell across the hull and another 3cells at the side. The 3 extra cells are held in place with sponge stuff into the compartment.

Boat is significantly faster on 9cells. Run time is great too. Still no porposing... Handling as usual.

Re-Try the propellers:-
Jet Hobby's Plastic 2 blade 45mm - faster than stock by a little bit only on 7.2V but no acceleration. Took a long time to on plane.

Jet Hobby's Plastic3 blade 48 - perform better than the 2 blade

Octura 39mm - slower

Conclusion: Better buy a few more stock props just in case Jet Hobby runs out and I hit a turtle

Problems:
My boat original paint work begin to bubble at the nose. Dunno why. When I peel it, there were no liquid. Seems like accumulation of gases causes these bubbling. Spotted a few more along the bow....

[dirtdynamics]

possible the seams where your hull is joined is taking too much heat inside the hatch and the glue is melting and paint flaking ?

[Mad Armour]

Here's my 2 cents. IMO, before you start to play with different motors, batt combinations and props, you'll need to setup the boat right first.

From your description of the Dolphin not porpoising and rather wet hull, it looks like the CG is too far forward. I suggest you place the batt a bit back. As for the trim tabs, adjust it 2 - 3 degree upwards. Here, I mean 0 degree being the imaginary line of the bottom of the hull.

Move the batt slowly until a time when the starts to porpoise. The spot just before the boat starts to porpoise will be the sweet spot.

As for your hull splitting, it has been well documented that the pressure from expanding spray foam is high enough to split the joints so you'll have to use with utmost care. Perhaps it's moot point now but it's better to spray little by little, letting the previous spray have time to expand fully first before the next spray.

[SG Villain]

Thanks MA,

Yeah, lesson learnt on those foam. I only heard that they will split ABS hull, did not know that they are so powerful to split fiberglass hull too. Will not repeat them again

Battery position? Siow liao...where to put? Boat already no space, maybe my next run I will put the batt up instead of flat or put it on its side.

Will bend the trim tab and see how it goes on my next drive.

Thanks

[Mad Armour]

Thanks MA,

Yeah, lesson learnt on those foam. I only heard that they will split ABS hull, did not know that they are so powerful to split fiberglass hull too. Will not repeat them again

Battery position? Siow liao...where to put? Boat already no space, maybe my next run I will put the batt up instead of flat or put it on its side.

Will bend the trim tab and see how it goes on my next drive.

Thanks

Uhm....the radio box is sort of limiting the way you can adjust the batt placement.

[SG Villain]

4th Run

4th run last Sunday evening:

Set up was the same as the third run, no change. No time.

1. Ran some 6 cell, 7cell and 9cell. 9 cell is the limit the ESC can take. 8.4V is the limit the motor can take. Overall, 9cell is the best, good run time and good power. 6cell and 7cell difference is very little.

Problems:
1. Notice a few problems that I fail to spot in the eariler runs, maybe it is the angle I played, I was sitting down now, the boat seems to seat with a tilt to the left (when view from the rear) at rest and when it took off, it tilt to the right!!! Torque of the motor causes the boat to tilt right? So my boat now can ROCK! Any boat using the Yamaha and Volvo experience the same problem?

2. My motor is cooking! Even on 6cell, when on 7cell my motor is super hot! Boiling point to be exact! I hand itchy, pour water into the motor after one run and was suprise to hear "shiiiiiii...... " water is boiling / evapourating upon contact!!!!!! Any idea why is this so? The boat has stop about less than half a mins after a run. The motor temp was cool (at least luke warm) to the touch immediately after the run but the temp creep up as it rest longer! Creep up to the point of boiling!!!! I think my motor going to up the lorry very soon.

Some questions:
Any old bird boaters here have any recommendation for RC car 540 motor that is good to use on a RC boat. ESC should not be a problem for me, I can water cool and water proof a car ESC for use on boat. As I have many RC car motor and accesses to new motor is not a problem for me but boat motor is a headache to me. No brushless for me at the moment. Dun wan to spend additional $$$. Just wanna use what I have.

[Adrianli]

Problems:
1. Notice a few problems that I fail to spot in the eariler runs, maybe it is the angle I played, I was sitting down now, the boat seems to seat with a tilt to the left (when view from the rear) at rest and when it took off, it tilt to the right!!! Torque of the motor causes the boat to tilt right? So my boat now can ROCK! Any boat using the Yamaha and Volvo experience the same problem?

My Yamaha will seat evenly when still. But when running, its tilt to the starboard side also.

My motor already up lorry after various run wif 3S lipo pack.

[SG Villain]

My Yamaha will seat evenly when still. But when running, its tilt to the starboard side also.

My motor already up lorry after various run wif 3S lipo pack.

I am thinking of adding a gearbox / reduction gear. My friend's Blue streak still going strong and did not display any motor over heating problem, still as fast as my Dolphin on 6 cells. That is why me hunting for any used Kyosho boat to test out some theory: - Big torque, Big Props = Fast speed

[Mad Armour]

Overheating motors are usually due to overpropping. Perhaps you are asking the motor to do more than wat they are capable of. A smaller prop is the way to go. Or a bigger motor. Or a reduction gear.

[SG Villain]

Overheating motors are usually due to overpropping. Perhaps you are asking the motor to do more than wat they are capable of. A smaller prop is the way to go. Or a bigger motor. Or a reduction gear.

Hmmm......I thought it should not be as I am using stock prop (42 X 1.5) Anyway will try out 39 X 1.5 and 40 X 1.5 on the next run and see if the motor can still fry an egg.

[Mad Armour]

Hmmm......I thought it should not be as I am using stock prop (42 X 1.5) Anyway will try out 39 X 1.5 and 40 X 1.5 on the next run and see if the motor can still fry an egg.

When you use a hot motor on your on-road, you need to change into a smaller pinion, right?

[SG Villain]

When you use a hot motor on your on-road, you need to change into a smaller pinion, right?

Tamiya GT tune very hot meh? It is a 25T stock motor with advanced timming. RPM is only 19500rpm but I like its torque figure: 500g/cm yum yum!

Any recommendation for Car motor that is good to use on boat?