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Help getting the right brushless motor and prop

Old 12-20-2015, 08:07 AM
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eranomo
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Default Help getting the right brushless motor and prop

Hi all,
I made a 1000mm flat bottom airboat hull (I'll upload the pictures soon), the hull weight about 4lb.
I have a spatial paintball cannon that weight about 7lb that I wish to install on top of it (so total weight is 11lb without electronics and batteries), I also want to push this baby at 25mph, I need advice about motor & prop.
Can someone please refer me to such parts for this setup?
Old 12-20-2015, 10:49 PM
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crispyspa
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Motor:
http://www.hobbyking.com/hobbyking/s..._60_Glow_.html

ESC:
http://www.hobbyking.com/hobbyking/s...ler_OPTO_.html

Waterproofing ESC:
https://www.youtube.com/watch?v=cCfCsyDmK1g

Battery: 6 cells. You can go for a 6 cell, or two 3 cells in series. The larger MaH rated batteries will run longer but are heavier.
http://www.hobbyking.com/hobbyking/s...SortOrder=desc

Prop: Probably a 15x8 two blade APC. The combo I gave should get about 10,000 RPM and up towards 25mph on a fairly heavy boat. I left room for expansion. The ESC will take up to 12 cells though you won't need that many. The motor is only rated for 7 cells, but you can go over that as long as it's kept cool and not overworked. Get a watt meter and check your set up before heading out. See what the system is pulling. If you are on 8 cells but only pulling 60 Amps, you should be ok.

Hope this helps.
Old 12-20-2015, 11:43 PM
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eranomo
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Thanks a lot Crispyspa...
I will go for what you suggested, just to make sure - are you sure its ok to take a chance with the ESC (12 cells) and the motor (7 cell)? also, the hull is pretty heavy with my cannon (11lb) and the prop you suggested is large – I don’t want the motor to get too hot or have it replaced after 20 runs…

BTW - saw that HK/TH have many waterproof ESC (Aquacraft makes most of them), wouldn’t it be better if I just get one that designed to get wet instead of taking chance with silicone?
Old 12-21-2015, 04:26 AM
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It's okay to use a motor designed for less cells than the ESC. It's NOT good to go the other way around. As in a 12 cell motor using 12 cells and a 10 cell ESC. If you can find a waterproof ESC capable of 100-120A, so be it. You're gonna be moving a lot of weight and that's gonna require some power draw.

Personally, I'd trust what crispy is telling you.
Old 12-21-2015, 05:16 AM
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eranomo
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Hi,
I miscalculated the total weight, it is 15lb not 11lb..is this changes anything (the parts you recommended)?
Also - how long would i be able to run it before the battery runs out of power?

Last edited by eranomo; 12-21-2015 at 07:27 AM.
Old 12-21-2015, 10:00 PM
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crispyspa
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If you've found waterproof air cooled ESC's. that's good. Link them here so I can get me one. Stick with a higher amperage one, pay attention to the input voltage and never max it out. If you find a 6 cell ESC, I wouldn't run more than 5 cells, just to be on the safe side. Unless you have tested the system and have plenty of wiggle room with amp draw. Also, get any available programming card and reduce the timing as far as it will go. It will increase run time and reduce heat.

+1 on what 2.5r said.
It's okay to use a motor designed for less cells than the ESC. It's NOT good to go the other way around. As in a 12 cell motor using 12 cells and a 10 cell ESC
Run time depends on a lot of things. Mostly the Mah rating of the battery, as I said before. A 5000 Mah will theoretically run twice as long as a 2500Mah but the 5000 will weigh lots more.

I guess what I would do is build the hull, add all the component weights together, including what battery you want to run and do a float test with dead weight. My feeling is you have plenty of displacement to handle the 5000Mah batteries, but it's best to test before spending $$.
Old 12-22-2015, 01:24 AM
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eranomo
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Hi
About the ESC - It is 200A and It says that the PCB is 100% waterproof):
http://www.hobbyking.com/hobbyking/s...rless_ESC.html

I will do as you said about the floating tests....
I did not undertand what you wrote about reducing timing on the ESC with a programable card.... I never programed ESC, why changing the "out of the box" values?

Thanks

Last edited by eranomo; 12-22-2015 at 03:32 AM.
Old 12-23-2015, 01:34 AM
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That ESC is a water cooled model....plus it's an aquastar. Steer clear of Aquastar escs. Poor design makes them have a tendency to overheat

Lowering the timing advance will reduce the amp draw, increase run time, reduce motor/battery temperature, but may slightly reduce top speed and punch.

Just a tip for shopping at Hobby King: If you are a "gold" or "standard" rating, you can still get the platinum pricing discount by leaving the product page open for a while. A message will pop up saying "We've noticed you've been looking at this product for a while and would like to offer a discount".

You must add the product to your cart and order right away to get the discount. Do this for all the things you plan to order.
Old 12-23-2015, 08:24 AM
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eranomo
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It worked! thanks for the HK tip!!!

I ended up getting this ESC for my twin motor setup: http://www.hobbyking.com/hobbyking/s...r_Cooling.html
It has good reviews, it is cheap, it is 100% water proof and water cooled but I read that many people mentioned that this ESC can actually just get cooled by airflow and it almost never get hot if you do not use the integrated BEC that comes with it (connecting a UBEC directly to the main battery) since using linear BEC inside an ESC makes the ESC constantly about 20% hotter and drain your battery faster than external UBEC.
I thought that if I put that ESC on top of the hull on the open I can leave it covered with a small roof (against direct sun) and have it installed on a small mount about 10mm above the hull surface so water will cool it as the boat speed up and then fall back to the hull surface and in to the pond (As it is currently working on my Aquacraft Cajun commander Airboat).

I dont know if you can see from this picture but the ESC is installed 10 mm above the hull below the motor

What do you think?
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Last edited by eranomo; 12-23-2015 at 08:29 AM.
Old 12-23-2015, 09:21 AM
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Hi everybody, I am building a new 30 Inch cat and looking for Help on all electronics from motor (Single motor) to battery, And should I go for a watercooled system or not? I am new to this Hobby, most of the Wood work is done and I'm getting ready to fiberglass.Thanks happy holidays
Old 12-23-2015, 09:42 AM
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crispyspa
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Originally Posted by Smokey55
Hi everybody, I am building a new 30 Inch cat and looking for Help on all electronics from motor (Single motor) to battery, And should I go for a watercooled system or not? I am new to this Hobby, most of the Wood work is done and I'm getting ready to fiberglass.Thanks happy holidays
Hi Smokey. You should start a new thread. click here to start new thread

Last edited by crispyspa; 12-23-2015 at 09:52 AM.
Old 12-23-2015, 09:53 AM
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crispyspa
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Originally Posted by eranomo
It worked! thanks for the HK tip!!!

I ended up getting this ESC for my twin motor setup: http://www.hobbyking.com/hobbyking/s...r_Cooling.html
It has good reviews, it is cheap, it is 100% water proof and water cooled but I read that many people mentioned that this ESC can actually just get cooled by airflow and it almost never get hot if you do not use the integrated BEC that comes with it (connecting a UBEC directly to the main battery) since using linear BEC inside an ESC makes the ESC constantly about 20% hotter and drain your battery faster than external UBEC.
I thought that if I put that ESC on top of the hull on the open I can leave it covered with a small roof (against direct sun) and have it installed on a small mount about 10mm above the hull surface so water will cool it as the boat speed up and then fall back to the hull surface and in to the pond (As it is currently working on my Aquacraft Cajun commander Airboat).

I dont know if you can see from this picture but the ESC is installed 10 mm above the hull below the motor

What do you think?

Looks good. good find on that ESC. It's going into my wish list.
Old 12-23-2015, 10:08 PM
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Hey Guys, been a long time since visiting RCU. I'm new to air boats and I found this great thread via google and logged in.

First, I'd like to wish you all a Merry Christmas & a Happy Hanukkah to you and your Families.

Anyway, When the dust settles from eating, drinking, the gifts are open and, being VERY merry. I would like to come back and explain my set-up in full. Specs, watt tests on three props, etc.

It's really not an air boat per-se, as it has a very "slight" keel (pics to come). Someone told me it was a :California Racing boat. IDK.

Mike.

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