D&D's Mean Machine Sport

[D&D]

I decided that I wanted to build an Aeromarine cat boat again and the community that requires only electric boats of any kind. I have 13 years experience of building nitro cat boats, but zip nothing about eletrical anything. I looked around and first ordered the $60 MM from Aeromarine, then sent it back and ordered the MM built by Areomarine with extra carbon fiber. There are pictures of the completed boat in my D&D FE MM Cat album on this site.

I decided to aim for "Fluids" 61+mph even though I was not going to purchase as much motor he was running so here is my build:

Boat: MM Cat (American version)
Motor: NEU 1515 1Y
Controller: Castle Hydra HV 180 (set at "normal"/2 setting)
Radion System: Futaba 3PM-X FAAST
Servo: HiTech HS -5445MG
Hardware: SpeedMaster sport 20
Battery: Turnigy 4S2P, 5000mAh, 35-45C

My first runs using a X440-3, X442, & X445 props set from one-quater to three-eights of an inch up were all in the range of 54.4 to 55.5mph. I tried these props and strut setting based on what I read in this site but did not understand the almost identical speeds with that range of props.

This morning I decided that I was going to go how I always did on my nitro boats, the struct was always set even with the botton of sponson (no positive or negative) and I sized props and or modified props to work at that setting. I did that because I felt the boat handled best and all I did was race.

This morning I ran the strut as stated above and my first run with the X440-3 was 57.3mph. My second run with a X442 was 56.4mph, but the COG was too far back and it crashed. It seems as though this motor like higher rpm and smaller props. Your comments and recommendations please.

[Fluid]

The 61 mph I achieved was just goofing around, I never considered it to be a setup I'd run much at all. That speed with this boat requires smooth water and no wind!

Your results are stellar. Yes, the 1515/1Y is really a hydro motor, high rpm and smaller props on large draggy boats (non-hydros). You could try advancing the timing another five degrees using the CastleLink, that could give another mph or two, just watch for heat issues.


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[D&D]

Fluid, thanks for your reply.

I remembered from your post that you would not race the boat with your 61mph setup and I agree, I was flying on the edge with the X440-3 at 57.3mph. However, my racing days are gone (just can't stand to go slow) and I only intend to run for my own sport, but I still believe that there is more left in this boat. A little tweeking with the X440-3 and maybe even try a smaller prop and do some work with that. My Castle Link, as I rmember, only had four settings (timing/etc.) I am currently on two or normal and Castle told me that 3 was for SAW and 4 was almost for certain a melt down. I prefer to work with the current controller setup and play with props, strut, and Cog. I may not reach 60, but hopefully I will have fun and protect my investment.

[ReddyWatts]

Try a Y537/3. Smaller diameter with more pitch than the 440/3

[Fluid]

The newer CastleLink software allows you to set the timing at any value, so you could step up one degree at a time....or not. To go faster you will need more pitch like Ready said. For extreme speeds a v937/3 is the ticket, but that prop will require a different setup - lower strut setting angled up, CG back a bit, maybe 10-12 ounces of lead at the CG too. A 'similar' setup went well over 70 for me some years ago.


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[ReddyWatts]

Be careful with a V937/3. It has a huge jump in pitch from the 440/3

X440/3-- 2.198
Y537/3-- 2.279
X442---- 2.310
X637---- 2.368
X445---- 2.478
X640---- 2.512
X447---- 2.590
X642---- 2.640
M545---- 2.655
X448---- 2.660
X450---- 2.758
V937/3-- 2.812



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[Fluid]

Like I said, for extreme speeds...

BTW the 37mm props are not as efficient on that hull as the 40s and 42s so they will usually have higher slip values. At least they did on mine.


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[ReddyWatts]

I did see a little more slippage coming out of the hole in this hull using a Y537/3mm prop than an X440, but also saw more top end speed. Might get you over the 60mph barrier without stressing any components.

[D&D]

I'll have to look at those props (Y537-3 & V937-3), but I will be leaving for my home town in Indiana in a couple of days and don't have enough time to get them delivered. I will be home for 30 days, but there is a lake within my small town city limits and I plan to continue running there. Maybe I can order the props after I get home and work on them there. Thanks for the advice.

Today I plan to pitch up the X440-3 for a test run, I'll see how that goes. Also, when I get to Indiana I'm going to try detongueing the X442 and work with it too.

[DISAR]

You can also try bigger diameter props, 642, 645 better acceleration too. I think your amp draw is probably low with your setup. You can first try the 642 and check the temps after 1 min run. I run my MM with 1515 1.5Y, 6s2p, 646/3, 250A esc. everything is cool
Or you can go with 5s on the 440/3 or 442 (I run the 1515 1y on 5s with a 442 with turnigy 180A in a Maritimo)

[ReddyWatts]

Disar, what is the top speed with your setup?

[DISAR]

You know what, I can never achieve the speeds mentioned here. I always have 10 mph less, run in sea water with some chop always
I have achieved 52 mph, so in USA is probably more than 60. The 646/3 is the best propeller I have tested for the MM (440/3, 442, 445, 645, 646, 447, 648, 220, 225, 235), the 646/3 is the winner

[ReddyWatts]

That is interesting that top speed is with a 3 blade prop.

[DISAR]

and the 646 was very good as well, both props detongued, fast acceleration and best top speed.

The MM is a great boat, easy to build with your instructions and very very good handling

[Fluid]

Dimitri it is not at all surprising that your speeds in rough salt water are different than in fresh. The density and surface tension differences in the salt fluid are well known; full-scale racers seldom use the same props or setups in both fresh and salt water for example.

The fastest speeds with most any boat will be in calm conditions on flat water. The rougher the water the slower the boat for several reasons. Every time the hull hits a small wave it slows down a bit. The hull does not ride at a consistant aoa to maximize lift through air compression. The prop is never at a constant depth so its thrust is never optimal. With my smaller SAW cats I see higher speeds on flat water than on a ripple. Most of my SAW cat records and fast passes were with three-bladed props like the v937/3 and the x450/3.


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