Northwind 40 Conversion

[Psycho1]

Hello, new to the site.
I'm currently converting a oldschool Northwind 40 mono to FE. I'm new to FE boats, so need some advice on which motor would work best for what I'm looking for. I'm planning on running 4S most of the time, with occasional short duration speed runs on 6S. I think I have the motor narrowed down to a Leo 4074 or 4082 2200kv, and will start with a M440 or similar prop along with a 640 and work my way up from there while monitoring heat. My question is how much more power would the 4082 use compared to the 4074 if the prop, esc hull etc remain the same? Would the 4082 really tUrn that much bigger of a prop to be worth the extra amp draw and weight? How big of a prop should the 4074 usually be able to turn without overheating it, would it safely tuirn something like a M645 3? Here's some pics of the boat, it seems fairly heavy to me, but my little 3650 5700kv was able to get it up on a plane on 2S for about 4 minutes before finally melting the battery connector off the + wire between the bat and esc lol. The blue and red boat is the Northwind (32" long 15" beam at the transom, the black boat is a one off all wood scratch built hull my dad designed and built for me for my Xmas present last year. That project will be next in line for completion.

John

[Peter A]

If you are running a sub surface drive then the M440 is probably going to be plenty. I run a M445 (TP 4050 2050kv) on my pursuit for heat racing (surface drive). You will need to go lower on kv for bigger props and keep the pitch down for sub surface or surface piercing, higher pitch and three blades are going to load the motor more and create heat. Run times will matter also.

[Fluid]

Since you are new to FE, the above post is probably gibberish to you. I haven't seen a Northwind hull for over 35 years, they were great nitro hulls in their day. As I recall they had a wide, flat vee with a flat ride pad for lift and turning stability - characteristics we abandoned years ago. But it can still be a great sport boat, which I assume is your goal.

Few of us run submerged drives so there is not much of an experience base to help you. A motor with a 2200 Kv on 4S is too hot for submerged drive on this wide hull, and the 4074 motor would be boarderline IMO. I suggest running the 4082 with a Kv around 1900, this will swinga bigger prop fully submerged and be easier on the amp draw. Amp draw is really related to the load, not the motor size. If loaded heavily enough the 4074 can draw 200+ amps, believe me. The larger motor will run cooler and be faster with the same amp draw.

I would start with an x440 to be safe. The 4082 will probably spin a 45mm prop okay, but try a 2-blade first. Expect speeds in the 40s, which is plenty fast for this hull. Good luck.



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[Psycho1]

Thanks for the responses. Yes the Northwind is being set up strictly for playing around at the glass smooth pond around the corner from the house with the grandkids. I remember my dad telling me that the Northwind was fast enough back in the late 70's that they forced them to race in the Hydro class at Legg lake for a while at least. What determines if it is a surface or subsurface drive? I only ask because this was built using a short hydro type strut, leaving the prop centerline only about 1/2" below the transom (pic 4 above), so the blades on a 40mm prop are long enough that they are higher than the bottom of the hull. Once on a plane wouldn't this technically help unload the prop a bit and be a surface drive? I know with the old Fox 60 engine my dad tried to run in it, it would propwalk so bad at 1/2 throttle that it kept spinning out, which eventually led to it being shelved before ever getting a single clean run lol. My thought on the problem he had was he had used the hydro style prop, which had way too much lift. Will definetly go for the 4082.

[Fluid]

A surface drive has the prop centerline even with the bottom of the boat. I guess yours would be called semi-submerged. The big prop and flat ride pad were the causes of the boat spinning out - nothing to hold the boat in a straight line except the rudder, which many cut too short. Today a longer rudder and a turn fin would help a lot along with a prop no larger than 45mm. That big .60 must have swung a pretty large prop!


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[Darin Jordan]

Today a longer rudder and a turn fin would help a lot along with a prop no larger than 45mm. That big .60 must have swung a pretty large prop!

I have the .21 version of one of these hulls in Kit form here, and I had the 40 size at one time (traded it for the .21 size kit).

They show skags on the plans, similar to a Cracker Box.

[Psycho1]

I have the .21 version of one of these hulls in Kit form here, and I had the 40 size at one time (traded it for the .21 size kit).

They show skags on the plans, similar to a Cracker Box.

Yes this has a turn skeg about 1 1/2" or so long right around the CG, I believe about 2" forward actually.

[Psycho1]

Ended up buying a TomCat 4074 2000kv motor to try in the boat. I was going to wait and get a Leopard 4082 with a little lower kv, but the TomCat was on sale at the time for $49.99 with free shipping. Made a cooling coil with 3' of 3/16 brass tube and have everything mounted up nice and solid and aligned very straight. I am going to try a 1616 frp prop (1.6 pitch 40.6mm 2 blade) and see how that does, I still have the frp 440-3 to try too if temps are too high with the 1616. Still working on my sponsor (aka the wife lol) to get the ok to pick up a couple of 4S batteries to get things going. While I was waiting for the motor to come in, I went to the local hobby shop and picked up 2 packs of the Castle 6.5mm bullet connectors to go between the batteries and the esc.wired those in to positive on the battery cables will be a female plug, negative using the male plug, so I can connect in series later if I decide to connect 2 packs together for 6S. I know 6.5mm bullets are overkill for my needs, but the lhs didn't have 2 packs in stock in the smaller sizes. Has anybody else ever tried these TomCat motors? They seem to be pretty nice quality from the looks and feel. Very smooth running too.

http://www.banggood.com/TomCat-Brushless-Motor-4074-2000KV1050KV-395G-RC-Car-Motor-p-1062201.html

Battery ordered http://www.chinahobbyline.us/product...01607/533.html