Maine Downeast Lobster Boat

[John Green]

I'm a newbie at building rc, just finished my first fiberglass boat and need help choosing a propeller. Dimensions are: 48" LOA, Beam 17", Draft 4" (in stern) weight 25 lbs. Powered with a Leopard 5698 - 910 Kv 2Y motor 56mm x 50mm, ZTW Seal 200 amp ESC, (2) 4S 5000 70c batteries. Will run them in parallel at first, may hook them in series if all goes well. The shaft is 1/4 inch and it can swing a 3.25 inch propeller. Needs a full submergible propeller. I will take all the advice I can get, Thanks, Johnboat 3.jpgboat 3.jpgboat 2.jpgboat 2.jpg

[fweasel]

I can't help you with the prop unfortunately, but anted to say that's a beautiful first build you've got there.

[John Green]

Thank you, I've got a lot of research and hours in it, but it's been fun! Can't wait for sea trials when things thaw out here in Maine.

[Peter A]

You will not want to run it 8s. On 4s you have just under 13,500 rpm. That is a lot for a submerged prop of such size. With a 1/4" shaft you are in the bigger sizes. I would suggest something with low pitch as possible and two blades. Of course it does depend on your expected speed and runtime goals.

[John Green]

Thanks for your input. I was hoping to get 20 - 30 mph out of her but it will depend on how stable the Hull is at those speeds. Run time in the 30 minute frame would be fine. I could always use a step down tail shaft. Right now it had a prop used with 26cc gas motor, 2.6mm dia 1.7 pitch, I have no idea what that will do.

[Youngbuck]

Awesome to see another Mainer here on the forum, I?m right outside of Bangor and more into the speed boats, I can?t help with your prop size but I?m always looking for other RC boaters to run with. Maybe after all this ice melts we could get some runs in. Good luck with the prop choice.

[Sailfish#1]

Very nice! Im building something similar with a leopard 4082. Please let me know what propeller works for you!

[dasboata]

OSE has some chopper props in stock , but you have to get a stepped down to 3/16 shaft,,,,,,,,,,,, https://www.offshoreelectrics.com/pr...4-chopper-4bld

[John Green]

I have been running a 2714 3 blade and I think it is still to much pitch. It goes good about 20 - 25 mph at 50% power and the speed control get warm but at 75% power the speed control gets to hot.

[John Green]

Hi there, beautiful prop you sent me but I think I need to try less pitch, it heats up above 50% power. As you said I may need to step down to 3/16 shaft.

[Sailfish#1]

Thanks, can I know who makes that hull? Love it.

[Peter A]

I have been running a 2714 3 blade and I think it is still to much pitch. It goes good about 20 - 25 mph at 50% power and the speed control get warm but at 75% power the speed control gets to hot.

It is not the pitch but diameter IMO. A 2714/3 is a gas surface drive prop.
A suggestion would be
https://www.offshoreelectrics.com/pr...4-chopper-3bld

Or an octura X452/3, 455/3, 455, 457

Ulitimately you will need to change/machine the end of your prop shaft to 3/16" or go lower kv on the motor to get this to work as you want.
Where is your water pickup? The best position is right behind the prop on a submerged drive. The esc will not like running 1/2 or 3/4 throttle under load and will get hot.

[tebby2]

Attachment 173276

I have three Downeast hulls that are 42.5" long X 13.75" beam. You did not indicate whether your Downest is hard chined like a Wesmac or round chined. My Hulls have round chines and top out at 26.5 mph. The green hull runs a Leopard 4092 700KV motor on 4S , the red hull runs a Leopard 4092 970KV on 3S and the blue hull runs a TP Power 1050KV on 3S. I have run the blue hull up to 26.5 mph with 4S on a 6511/3 Prop Shop Standard Scale prop that pulled 140 amps. All of my hulls become very erratic above 22.5 mph, so these days I am running with 6011/3 props on 2S and 3S lipo packs to keep the rpm around 10,000 and the speed at 18.5 mph. Simon Higgins at the Prop Shop can bore his props to just about any size as long has the hub has a large enough dia. The Standard Scale prop is a fully submersible prop that will give consistent slippage of 23 % or less below 12,000 RPM

Your longer and wider beam DE hull should provide higher speeds, and a chined hull will do even better.

Good Luck,

[tebby2]

20170422_102834.jpgSuzie Q - 1.jpg

[tebby2]

Down East Lobster Boats - Fwd Stbd Qtr.jpgDown East Lobster Boats - Aft Port Qtr.jpg

[John Green]

Hi there, those are nice looking boats. Thanks for the info, I haven't had any time to fine tune mine lately but the last time I ran it at 75% power the speed control got quite hot. I am guessing it was going in the 30 mph range and was stable if you turned slowly. The chines look very similar to yours. How and what kind of water cooling inlets are you using? I will send you some pics in the near future.

Thanks

[tebby2]

I'm using a 12 volt diaphragm pump connected to a Octura streamlined water pickup. The pickup is installed aft of the propeller, just to the starboard side of the centerline, and forward of the rudder. Natural unassisted water flow was insufficient to maintain satisfactory temperatures (<115F motor/ESC at 75F sea temps). I use a buck-boost voltage regulator inline with the pump to maintain its 12 volt supply - which also allows for different voltage battery packs. Also keep in mind that high amperage loads generate lots of heat. It is always more efficient to use a low KV motor and use a higher voltage battery pack. A slower turning motor can be coupled to a larger prop which is always more efficient that a fast turning smaller prop.

I also have an Aeromarine Challenger 43 that is powered with a TP Power 4070 440Kv motor on two 10,000 6S Lipos in series (12S) and does 50+ mph, This boat pulls less than 70 amps to get on plane, and cruises at less than 30 amps. Natural water circulation cools the motor and ESC to less than 100F with 75F sea water temperatures.