New project 41 inch mono

[Old School]

I am considering a new project based on a 41 inch mono hull from Hobbyking. The unit comes fitted with 4 mm drive and a 4074 2200kv motor. The recommended ESC is a 180 amp model. I can utilise the 4mm drive on a current 70 cm mono hull project and no doubt my son would find a use for the 4074 motor.

Now my intention is to gut the motor and driveshaft/stinger, reinforce the hull interior and fit a 5692 1340 kv motor running on 6s with a 220/240 amp ESC and 450 prop. Obviously, the drive will need upgrading. Would it be overkill to fit a 1/4" drive or would a 3/16" drive be suitable please? I would retain the existing rudder setup.

[martin]

Im assuming that you are talking about the 41" Osprey from HK, if so the boat comes with a 3/16" (.187 ) drive. HK specs are wrong stating 4mm drive ( HK famous for getting specs wrong ). 3/16" flex will be fine on a 56 series motor.

[Old School]

Many thanks. I am surprised that they would get that wrong. The motor still looks like a Leopard Hobby item.

[ray schrauwen]

I ran a 40" mono on 6s2p, an SSS 5684-1200kv motor, sf240 and big props like 55mm range. Fun boat.

Sold it because can't handle large heavy boats anymore.

Took in Qmono at the FE Nats in Michigan a few years back.

[Old School]

Many thanks. When you state 6s2p, I assume that this is two 6s packs running in parallel to give more amperage draw potential and possibly increased runtime. I am new to this lipo game.

[Fluid]

An option for power is a smaller format motor. Several years ago a couple club members build a couple 41” DeltaForce monos powered by Neu 1527/1Y motor’s on 6S. Performance was outstanding in these lightweight hulls, which were not dissimilar to the OP’s hull. A lighter weight option which has proven performance.

Running 2P means twice the run time and the potential to safely draw more amps. It is common for larger hulls, and smaller racing boats too.


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[Old School]

An option for power is a smaller format motor. Several years ago a couple club members build a couple 41” DeltaForce monos powered by Neu 1527/1Y motor’s on 6S. Performance was outstanding in these lightweight hulls, which were not dissimilar to the OP’s hull. A lighter weight option which has proven performance.

Running 2P means twice the run time and the potential to safely draw more amps. It is common for larger hulls, and smaller racing boats too.


.

Would a more suitable combination be a 4092 1390kv running 6s and around a 47mm prop, please. I would most likely replace the stock motor mount if choosing the 40 series motor. I am not after a speed record, only something that gets up and moves. The 56XX series are heavy anchors.

Not necessarily a Leopard Hobby motor but just considering the amperage draw - LBP4092/4D 110A 26V

[CraigP]

That's a good voltage, kv and prop combo to start. I bet you could end up turning a bit more prop, but certainly wouldn't start there. A sport boat should work with a 180a ESC. Nothing wrong with a Leopard motor for a sport boater. Keep the rpm's no higher than 35,000, should be very reliable! I have a 20" Mono running 6s with a 3674 1400kv motor and it just flies, running a M445 prop. Some put 40mm motors into these hulls, but I got to tell you, I'm impressed with the 36mm!

[Bp9145]

you can certainly use a 4092 1390KV motor but still keep the 220A or 240A esc. . .will be easier on gear and you can use bigger props. .50mm and up. Just remember if you want to get that longer run time you desire a 2 blade prop will give you a longer run time than a 3 blade prop just in case you were also thinking of a 3 blade. Although, a 3 blade prop has it's advantages as well. Are you set on 6S? If your 220A or 240A esc can handle 8S then you can experiment with 8S. It's a slightly hotter setup, a little higher rpm with the 1390KV but with the right prop, most likely a smaller prop than if you were using 6S, it can be done with good results.

[Old School]

Many thanks gentlemen. I would prefer to keep with 6s. I was thinking a two blade prop but do have a liking towards a three blade.

Is there any advantage in stepping up to a 1/4" drive, still retaining the 4092 motor idea? I can utilise the stock 3/16" drive from the Osprey in another smaller mono hull, which I still need to purchase a drive for. The stock 3/16" drive will need to be removed to beef up the hull interior. Does a 1/4" drive consume more power to drive over a 3/16" drive shaft (less runtime)?

[CraigP]

Yes, there is higher friction with the larger flex shaft. How low no do you think the flex will be? The wind up is related to length. If it's over 15-20" in length, then I would be considering a 1/4".

Never mind this, I thought it was a 4092... if it's a 4074 or 4082, then 1/4" is probably not necessary.

[Old School]

With the 4092 motor on a revised mounting I think that there will be a minimum bend in the stuffing tube, so flex will be minimal.

[rol243]

normally with surface drive set up monos , there is a very minimal bend in the stuffing box so there shouldn,t be hardly any drag in the flex drive atall.
Old School , Hobby Supplies Melbourne have the high quality Aeromarine Flex Shafts in stock if your chasing a good one.

[Old School]

Many thanks, I just saved the Aeromarine webpage for products. No more expensive than anywhere else. I assume that they do postal orders.

[rol243]

Yes Tony from Hobby Supplies ships worldwide also his national postage is very quick and priced well too.

[martin]

Im afraid HK are renowned for incorrect specs, even if you inform them of incorrect specs they still don't up date their site. Even the Pursuit specs say 4mm drive shaft which is also totally wrong. Re shaft size 1/4" is over kill, 3/16" is more than enough.

[Old School]

Many thanks

[785boats]

I used to run the Osprey with the Neu 1527/1y motor that Fluid mentioned in his post. There were a few in our club. I ran a Seaking 180 ESC with an X447/3 prop. Great speed & great handling.
But bear in mind we can only run 1P in our boats here in Australia, so with your 2P setups & a larger prop you will need the larger ESC too.
There was never a problem with the 3/16" shaft in this boat or in any of the other guys boats. Or any of the Delta Force monos either.
Keep in mind that the lower kv motors like the 1250kv 1527/1y will allow you to run larger, more efficient props

[Old School]

Many thanks

[Peter A]

I am running the Leo 4092 1390kv motor in a 42" mono with a V2 T-180. While there has been a lack of on water time recently, I have raced it sucessfully against the gassers in our club and it holds it's own. Currently up to a Prather 240 and GPS speed of 88 kph, with the hull running stable. The hull looks to have seducer styling in the bottom with a ride pad, so it can be somewhat flighty and tend to bow steer. I deliberately used a speedmaster stinger as it is height adjustable, with a flood tube. Lifting the stinger right up has taken out the chine walk and allowed bigger prop use comfortably. A few more prop tests yet to go. I use this boat just for racing so perhaps a little out of what you are wanting to achieve, but the motor you are looking at works fine in a hull this size, and if you aim for speeds in the 70-75 kph range you should get reasonable runtimes (esp. on 2P) and a boat the runs and performs well.
I have to say that what seems to have gotten lost lately is the recommended rpms for sport running and racing. Around 24K for sport and 30K for racing in general works well in keeping things reliable. Serious racers learn where they can push the boundaries, but for fun play boats 35K is just asking for trouble, not to mention excessive wear and tear on the running gear, ecs's and hardware. The old KISS principle! I see so many guys with the mindset that more power must make them go faster, sometimes it does, but at a cost. Learning how to tune a boat and find the right prop will get much better gains with a lot less wasted money.

[Old School]

Peter,
many thanks. I was concerned with the 3/16" flexshafts as there are numerous examples on You-Tube of stock boats with failed drives. However, these were all relatively inexpensive RTR boats and not purpose built race craft with obviously higher quality materials. The shafts could most likely have been the 4 mm shaft favoured by inexpensive RTR manufacturers.

I suppose it is the engineer in me that wants to build an indestructible boat that I favour a 1/4" drive, however as I have found, matching a 5 mm motor shaft to a 1/4" flexshaft is a no go. I have been unable to find such a coupler. Thus by default I either downsize to a 3/16" flexshaft and use the 4092 or I upsize to 1/4" and use a 56 series motor. Examples to date indicate that the 4092 is a more than capable motor in this size hull and most likely a 56XX series motor is simply wishful thinking.

[Peter A]

You will not have a problem with 3/16" flex and the 4092 motor if set up well. I run a TP 4060 1620kv in my Q hydro with a much longer flex and no problems, and I get my flexes from OSE, no breakages so far. Keep them well lubricated and looked after and they will last. Trust your engineering know how and build in the things that keep reliability. You should be able to drop the motor in the existing mount (just make sure the water jacket you get isn't too long) and replace the original flex with a better one. If you are not pushing amp boundaries, the OSE raider may be sufficient esc, there have been issues with the V3 t-180, so a SF220 would be the next stop.

[Old School]

I did intend removing the stock drive, including the stinger and replacing with better quality items. Many thanks for your guidance.

[Old School]

My HK "Osprey" arrived this morning. My first impression was that if the boat was not available from the wharehouse in my country then the shipping cost would have been unaffordable. Down to the nitty gritty. The boat as supplied has a beautiful almost blemish free gelcoat (several minute specks of dust in the finish). The motor is a Leopard Hobby 4074 with an aluminium water jacket (currently $80.00usd on OSE). The hardware is your typical TFL CNC clear anodised aluminium commonly seen on eBay. The immediate impression is that this is a well built extremely large boat. The hull is supplied with flotation in the forward half of the hull. The fibreglass cabin is designed so that locks could be fitted to the rear if needed. The transom is reinforced on the inner side with plywood. The stock propellor is a 2-blade 40mm brass casting.

Criticisms of the boat -
#The cabin moulding does not sit flat to the moulded recess in the hull opening and of cause tape would be essential
#The 3/16" flex shaft has a non-threaded end, thus the prop retaining "spinner" is secured by a grub screw only. A flat is machined in the shaft for this.
#The flex shaft is the dreaded two piece layout. This will find its way into the garbage bin.
#The motor mounts are fibreglass and do not inspire confidence in me. They look rather flimsy, considering the available power from a 40 series motor. Fibreglass cloth has been added each side of the mount rather than the usual epoxy fillet to hold the mounts in place.
#the stuffing tube terminates at the transom leaving an exposed gap to the stinger with just the teflon liner showing.
#The unstraked pad area on the hull occupies more than one-third of the hull undersurface. I am surprised that the strakes do not extend further aft.
#The "ugly" graphics look to be nothing more than printed masking tape and will be lucky to survive the maiden run. This will impress my son as his only criticism of the boat is that the graphics emphasise the toylike looks of the boat.


My overall impression is that this is a well built, well presented model that has a lot of potential for upgrading. It will provide an excellent canvas to start with. Over the next few months I will gut the boat, reinforce with carbon fibre and install a 4092 brushless motor, Speedmaster stinger and upgraded 3/16" flexshaft. The existing rudder, trim tabs and turnfins will be reinstalled.

The stock Leopard motor, no doubt, will find a new home in the future plus the removed stinger (and possibly the stock flexshaft) will be fitted to a current 70 cm mono I am rebuilding. Thus when the costs of these items is removed from the initial cost of the boat, the model represents excellent value.


Edit: as supplied the stuffing tube would have leaked like a sieve.