Delta Force build (bought part build

[MrBennett]

Hi folks

I just bought a part built Delta Force which I believe is a Cyber Storm because it looks identical but when I've seen those advertised they have the hull length at 825mm and mine is 810mm so I'm not quite 100% certain. Sure looks the same though.

This one came with the stinger and fins/rudder etc assembled and hull has a kevlar layer added inside and some noodle up front for bouyancy etc, but nothing else assembled. I have a feeling the hull has been used previously or if not has been bashed about as there's a few places underneath where it's been patched a bit with badly colour matched topcoat.

Anyway, I have basically all the hardware to finish building it (it included an aquastar 3974 2200kv and 120a hobby king ESC and mount), but before I start figuring out the correct positioning for the motor mount it came with, I have a question about the stuffing tube. The motor is a slight annoyance as it's only rated for 5S and I want to run 6s as I only have lots of 3S packs and lipos are difficult/costly to ship to where I am.

It's a 3/16 (4.75mm) flexidrive, and there's a teflon liner with it, but the actual brass stuffing tube is a super loose fit over the teflon tube, so I'm not sure if the previous owner had the wrong stuffing tube for it, but I don't know if that really matters much since I will be using a liner?
I realise I could use silicone sealant or something to seal in the teflon liner but if the stuffing tube is the wrong size then obviously I'd rather order a more suitable one first.

You can see from one of the pics here the gap between the stuffing tube and teflon liner, so I'd be grateful if people could advise if that's defo an issue or nothing to worry about if I seal the liner into it? Doesn't intuitively seem good to me though being honest.

Second question I have (or concern/observation) is about the positioning they have done with the stinger. When I look along the keel line the front part of the stinger is lower than the line of the hull, which to me says not as streamlined as it should/could be and will offer resistance to the water, or drag basically. I have an untrained eye for such things as this is my first boat running a stinger, but to my mind I would thing this should be a few mm higher so it does not protrude below the line of the hull as you can see in one of the photos? Again, appreciate input on this. I can easily move it if required.

The guy has put loads of silicone sealant around all the stinger base hardware. Is that a common thing to do?

Thanks anyway folks, appreciate any feedback about all this. :)

IMG_2551.jpgIMG_2537.jpgIMG_2464.jpgIMG_2553.jpgIMG_2456.jpg

Other boats I have btw are a 50" gas Apache, some smaller cheap electrics in different states of disrepair, a few scale tug type models etc, but this is my first proper fast electric with a glass hull and brushless etc.

[eehess81]

That stuffing tube looks way too oversized for the driveshaft. Is the prop stable when you spin it or is there a lot of play? If so that will probably cause a stability issue. As to the prop being lower than the hull line I think that may make your boat more stable but slower (others correct me if I'm wrong) and also put more stress on your motor.

[MrBennett]

Thanks, I have now ordered some brass tube that is 6mmID which the teflon liner should fit perfectly in.

Re' the prop, it wasn't so much about the prop itself being low, but the issue I see is that the very front most part of the stinger, just behind the transom, sticks down and will interrupt smooth flow of water so I just want to lift that by 3-5mm I think so it's not an obtacle.

I need to establish whether the propshaft hole being offset to the left like it is is a good thing though, before I can do much else. I think the prop direction is what makes a difference for this but I don't know if most of the props likely to be used are all ones that run counter clockwise like this one?

[fweasel]

A 3/16" flex cable typically goes in a 9/32" brass tube when used with a teflon liner. There are thicker walled, metric sized liners that can be used in a larger brass stuffing tube, but because it's not already epoxied in place, you're free to choose the proper sized tube now.

No part of the stinger should extend below the hull. In fact, the stuffing tube hole is typically drilled well above the keel to improve stability, around 3/8" or more depending on the hull size. All of the silicone sealant was probably to combat the incorrect sized stuffing tube and liner in use. The brass tube will be cut flush with the exterior of the hull transom, and the teflon liner can extend out into the stinger, providing a flexible joint when trim angle is adjusted. The continuous run of liner, properly sized for the brass tube, will prevent water from entering the hull.

[Peter A]

You need to move the stinger up on the transom. A good height for the stuffing tube centre is 10mm - 3/8". The trim tabs need to come up as well, about 2mm, and the turn fin mounts need moving up and out. All those parts are going to drag. The Aquastar motor is a 4s motor and a 120A esc will not hold up on 6s. My suggestion would be a 4074 motor around 1600 kv and an OSE Raider 150 esc on 6s, don't over prop, start at around a 442 and I think you will find you have a fast enough boat at that and you can adjust trims, cg etc so that it handles well.

[Johnc]

don't know anything about stingers, but shouldn't there be a gap (at least 3/16inch) between drive dog and stinger?

[eehess81]

Should have a gap as wide as driveshaft for flex

[MrBennett]

Thanks very much for the replies folks, that's mega useful and confirms what I thought that it did not make sense for any of the stinger hardware to protrude lower than the keel line.
Great to have suggestions like that for the height that it ought to be set at too thanks, that's a huge help.

Would you guys offset the propshaft to the side at all to counter prop walk? It was drilled offset to the left when I got it and a counter clockwise prop on it. No idea if that is correct or not but I was planning to centralise it as it seems like a lot of fast boats now don't have them offset anyway?

As for the motor, I'm just going off the hobbyking website which states this for the 3974:

Specs:
RPM/v: 2200kv
Poles: 4
Max voltage: 18.5V (5S)
Max Current: 100A
Max Watts: 1200w
Resistance: 0.0094ohm
No Load Current: 2.9A
Can Diameter: 39mm (actual motor diameter)
Can Diameter inc. Water Jacket: 49mm
Can Length: 69mm
Shaft Size: 5mm
Weight: 415g

So it says it's 5S at least but maybe they don't deal with 5S very well?

The ESC has these details:

Specs:
Constant Current: 120A
Burst Current: 150A
Battery: 2-6S Lipoly
BEC: 5.5v / 4A
Motor Type: Sensorless Brushless
Cooling: Watercooled
Size: 109 x 45.5 x 22mm
Weight: 166.4g


The prop with it is 37.5mm diameter, so maybe it's an octura X438 but who knows. Can barely make out any markings on the back of the hub to know really.

[fweasel]

offsetting the propshaft probably wont be necessary, but when it is done, the hole is offset to the right of the centerline when spinning a single prop counter clockwise. not surprising to see the previous owner got that wrong too.

[MrBennett]

Thanks that?s good to know.
I did read an article the other day about prop walk and the way the water pushes one side of the hull based on prop direction, was quite interesting really.

Can?t wait to get this done now but I?m still waiting for some parts anyway.
It?ll be slow to begin with though as I will have to run it on just 3S.
I hope that?ll be enough power that it can plane ok so I can at least experiment with the setup and handling.

[MrBennett]

Hey folks, finally have an update about this after doing quite a bit of work on it.

Peter A, I followed your suggestions about the turn fins and trim tabs, and the positioning heightwise of the stinger (which is also centrally positioned now).
This was all awkward as anything since the previous owner had used tons of silicone sealant over all the fittings in the transom inside, and all along the back edge of the badly applied kevlar layer they'd added, so it was a real chore to remove it (or as much as I could).

I've bonded in the motor mounts and stuffing tube after buying the correct size stuffing tube, and then added temporary fittings for the servo and lipo etc (I don't want to add permanent fixtures until I have tested it all successfully and made sure I'm happy with balance etc).

So tonight I went down to the beach after setting up radio gear and doing a float test in the bath etc to check for leaks. A small amount of water does get up past the flexi shaft in the liner. If I understand correctly people don't use any grease when using a liner do they, as I think that's basically the point of using a liner yes? I hope I'm not wrong but would rather know of course if that's wrong!

There was thankfully no disastrous sinking or boat fire, nor runaway etc, but it's not acting right, some sort of electronic issue it might seem.

It works perfectly for a few seconds, maybe 4-6 seconds at full speed, then drops suddenly to maybe 30% or 50% power/revs. I have no idea why.
Since it was only a few yards away I just turned it then and brought it back as quick as it would go, then popped the hatch and checked everything. ESC is ambient temperature, Lipo ambient (and still full of power), the motor ambient temp etc.

I did have a power meter attached and it shows that it managed to pull 46.8 amps max for the brief period it ran at full speed.
But nothing at all warm, and I found when I detach the lipo connector then connect it again and re-launch it would do the same thing, full speed for a few seconds then go slow mode.

So the spec again is the Aquastar 2200kv motor, 120A hobbyking ESC, 38mm unknown prop, and I was using a 4000mah 3s 45C Lipo. I know obviously it's not going to go fast with a 3S (and it didn't especially), but nevertheless I presume it still should be able to maintain whatever full speed that voltage supports while it can supply enough current etc, and there was no real indication of anything getting remotely warm.
I suspect this prop is absolutely fine too since it's quite small, and it certainly did not draw huge amps either.

Very grateful for suggestions on what could be happening here? I can easily swap out radio gear, and I have some 6000mah 60C 3S packs I can try, but I do not have any other marine ESCs I can swap out to see if it is an issue with that.
It did occur to me that it's possible that this ESC maybe needs some sort of setup/programming? But then if it did, why would it run fine for a few seconds still?

This is the ESC it is using:
https://hobbyking.com/en_us/hobbykin...___store=en_us

I can't see a programming setting that would cause it to misbehave like this. The ESC was still sealed in a pack when I got it with the boat for what it's worth.

Thanks!

[Peter A]

Turn off the lvc on the esc and time your runs. A really good esc is the OSE Raider 150.

[eehess81]

Definetely sounds like lvc kickin' in. I use grease with my liners, prevents water from getting in and takes pressure off of motor. I remove the shaft and reapply every few runs. Without grease the motor may be struggling and pulling more juice than batteries can provide. I'd use grease and try your bigger battery. Can always turn off lvc like Peter said..should fix issue if it's not overheating.

[MrBennett]

Thanks guys. I will try those suggestions. I wasn't using grease as in all honesty it felt like the combo of short stuffing tube and the liner there barely seemed to be any noticeable friction but I know of course there is 'some'. I will defo add some grease now though thanks and it should help prevent water ingress hopefully too.

I don't have a card for this ESC but I'll find the instructions online and see how to switch that off manually.
Will fit an XT60 to one of my better packs tomorrow and retry it with that. Really appreciate the input thankyou.

[MrBennett]

I see actually the instructions do refer in the troubleshooting section to potential low voltage protection and battery 'ability' so they sound likely.

Also I see there are settings for adjusting the motor timing but despite several land models with brushless motors I've never messed with timing on them. I have no idea whether that might be correct nor how incorrect timing would manifest itself so I shall do some research on that!

[MrBennett]

Hey guys, I finally got the chance to do a first proper test run today.

Setup with a 5S pack and on the fairly calm sea, my GPS picked up a recorded speed of 40mph but it subjectively looked faster. It was only running a few seconds each direction and I don't know if that was long enough for the GPS to pick up the full max it was getting to.
Only further tests on super calm surface will help verify that.

It did unfortunately end in a sinking which was my own stupid fault, after removing the temporary duct tape I was using on the hatch to let it cool before a second test run, it hadn't stuck down well on the damp hull, and when a too sharp turn flipped the boat, the hatch came off annoyingly.
Straight away rinsed in fresh water and blown out with air then left to slowly dry fully. All seems ok beside potentially my power meter. They're ?10 though so could have been worse.
I won't run it again until the proper hatch tape I've ordered arrives anyway!!! Lesson learned.

Anyway, I now am hoping for a further bit of advice.
The boat ran great for a first try, but the hobbyking 120A esc got pretty warm and I think went into thermal protect (limited speed until I left it a few minutes to cool).
What surprised me though is the power meter claimed it had pulled a peak of 179.31amps (it also displayed 2436.3Wp, 0.692Ah, and 8.1Wh).

Now the ESC is a 120a one with a temporary peak limit of 150a so I'm kinda surprised there weren't fireworks, and delighted it protected itself, but given the hardware I'm running I'm really surprised it drew so many amps since the prop is only 38mm twin blade and I understand that's not a huge size for this sort of boat/setup (going on other builds I've looked at for Cyber Storms anyway).

So just to recap here are the details, if any of you guys might be able to suggest why the amp draw would be so high as it is I'd appreciate the wisdom and experience thanks!

Delta Force Cyber Storm 33
Hobbyking 120A marine esc (rated for 3-6S)
Aquastar 2200kv 3974 motor (rated for 5S)
Some budget 5S 3000mah 30c pack
Prop - 2 blade 38mm diameter (14.5mm from front most point of blade to rear most point of blade if that helps to identify since I don't know actual pitch or type).

Max amps pulled = 179A
40mph max recorded speed.

Grateful for suggestions on improvements in respect of reducing that current drawer as it seems like an awful lot for a 38mm prop, but I don't know the spec of that.

Thanks!

[eehess81]

I don't think 120amp is enough for running 5s at 2200kv. That is about 41000 rpm..I wouldn't run that at over 4s. Try and bring rpms down to 35000 max. Or drop prop size to a 34 or lower to reduce motor strain. Surprised it only hit 40 with that high rpm..you may have triggered lvc quick and been running on half power. I have an external lvc I hook up to my battery so I can shut off lvc on my esc.

[eehess81]

My DF23 does 40 on 3s with 3000kv motor and 35mm prop on 90 amp esc. That's about 34000rpm. My lvc was kickin' in after a few mins..think my 2 25c 2200mah batteries aren't putting out enough juice.

[MrBennett]

Thanks for the suggestion.

I did wonder if it?s hitting more than 40mph but just not recording the full speed due to such short bursts and the gps lag etc.

It?s a shame I don?t have a means of counting the rpm in order to check to see if it is getting anywhere close to 41k.

I wonder if it?s possible that it?s not hitting its full rpm and a slightly smaller prop would allow it to, resulting in less load and amp draw but possibly the same or higher speed (if it did end up revving more than it currently is).

Worth a try to order a smaller one anyway thanks. I?ll have a look for a 34 or 36mm octura then run it again.

It still seems odd though as I?m sure I?ve read builds where people are running much bigger props but I assume they?re running on lower Kv motors.

So I wonder if something more like a 6s rated motor around 1600kv might be a more suitable option at some point?

[eehess81]

If you are gonna run 5 or 6s then yes I would drop the kv. Or you can keep the motor and try a 4s.

[eehess81]

If you were hitting 41k rpm with no lvc or thermal protection kicking in you would be probably hitting closer to 50 I would think. I'm guessing it's overloading. Lower the rpms and the 38 prop should be fine.

[MrBennett]

Ok cool thanks. Someone else suggested for something like this I should be using a bigger esc, but I feel like it?s an awful lot of amps for a boat this size so that?s not really the answer just yet.

I?ve orders some 4s packs and an Octura x436 so can try different combos of props and lipos and monitor temperatures and current draw etc.

Thanks!

[tebby2]

If I read your information correctly, you should be using XT90 plugs (not XT60) on your battery and ESC connections. The XT60 is rated for a nominal 60 amps and is not meant to handle anything close to 179 amps. The high amperage loading and LVC could be the result of undersized plugs.