Yet another Atlas test...

[Navherc130]

Just got back from the lake. Pretty much dead calm. Lowered the strut 3mm or so per Craigp. 5s setup yeilded 52 mph. But 170 on the motor and 20% on Batts remaining. Batts temps 125. ESC 105. That was with m645. 10 minutes later ran 4s again with x648. 43 mph. Motor 133. Batts 33% remaining at 120. ESC was 99. Cornered ok but may take some inward angle out of the turnf fin. You could hear what sounded like "digging in" when in the turns. I was full throttle the whole time and ran much longer straights, then ripped her through the turns. She just seemed happier on 5s. I suppose the big questions are:
A. What would a larger 3 blade on 4s likely yield...
B. Would this current 5s setup run the x648 with no significant penalty given the current setup?

[CraigP]

It seems the data is backwards for the two props... I would just be guessing, which you do a lot when working it out. My big question is what was the motor speed? A data logger is critical (for me) to work things out. Also, motor temps sky rocket as soon as you pull the boat it. So it should be data logged while running... sorry I couldn't help you more!

[rol243]

also how long are you running in the water and what mah and c size is the battery pack ?? also hydros do like a curled turn fin and the fin should be at c.o.g. balance point, if you straighten out the fin abit you might find the hull will slide alittle in the turns which is how these hydro flip over.

[Navherc130]

Actually it is apples vs orange I think. 5s + m645=52. 4s + x648=43mph. Data logger not really in the cards a this point. Guess I'll try the 1 minute run trick. I may get a cnc 3 blade 452 just to experiment on 4s. I can always use that prop on the gp400 I have yet to complete. The 9 mph difference looks alot larger in sight, then reported via cheapo gps.

[Navherc130]

5000 may 65c turnigy packs, 2 minute runs. Packs are kinda old. 2 yrs.

[CraigP]

I missed the 5s 4s change... I think a boat that size needs 5s. It looks at least 36", please let me know if that assumption is wrong. I try not to change so many things in a small period of time. I made 6 runs getting just my strut depth/angle set right. I then worked on my rudder and turn fin angles. That was 5 runs... I was running in the mid-40's. Then I propped up and hit 56mph. I run 8s on a 36" hydro. What is your motor specs? Maybe start there and let's do some calculating and try to predict where things may fall out.

[Navherc130]

Thanks for your input craigp. The GPS is an old timex Ironman watch, so the speeds are likely close but probably a little inaccurate. So, since there are technically no stupid questions, you went from mid 40s to 56 on propping up? From what to what? My motor is a T600 red turnigy 1400kv. She is about 35" long and just about 8 pounds loaded. I agree on the 5s, but again this is a scale boat and took forever to build...3 yrs off and on. I would hate to crash it, so....6s is out. My cg is about 2 inches behind sponson. Black tic in photo.IMG_20170821_204901.jpgIMG_20170821_204953.jpg

[Navherc130]

Oops on pics....

[CraigP]

Well Nav, let's talk about that. I assume you are not racing the boat, I don't either. So I set mine up with 8s to run much lower current than half the battery volts would run. The motor takes a watt value, V X A=W. Hang in here with me. Let's just take an example, a 3600W motor. You can make those watts with lower voltage BUT much higher amps. Or you can make the watts with twice the voltage and half the amps! So, a 4s system would have 14.8V and would require 243amps. Now, an 8s would have 29.6V and would require 121 amps to make those watts. Now, what do you think is going to run more cool, have less stress on batteries and ESC? You don't HAVE to increase power with increase in voltage! So, taking this to the next step, assume for a moment that between the two setups, the prop shaft speed is exactly the same, say 33,000rpm. That SAME prop does not know the difference between the two setups. The trick is to match kv to battery voltage, then you have a much more reliable system, and a more enjoyable boating experience... to answer your question about my prop change, it was a 38 X 55 Grim to a M445. At that point, my amps DID go up, but I predicted the increase and designed it to still be within the power limits.

[CraigP]

I'm sorry but I don't know turning motors at all. Do you have the motor's dimensions? I'll look it up and give you a recommendation if you wish. This is a lot of work, so let me know if this concept sounds logical to you. BTW, my brother and I raced with Bill Muncy. He was the famous Atlas driver. We were both in Acapulco when Bill flipped and was killed. I was the mechanic, my brother the driver, we were in the O'Berto boat. My brother Scott was racing in Bill's heat. He stopped his boat and swam out to Bill. He was floating on his back, and already gone...

This boat has meaning to me... I'm still saddened with the memory of that fateful day, a long time ago...

[rol243]

c.o.g. balance point is good as so the turn fin looks good as well, leave it alone and work on the motor / battery issues and correct prop size.

[CraigP]

You have a 6s motor, 1400X22.2=31080rpm, unloaded. I think you're spinning the prop too slow, forcing you to use a larger prop and eat up power. You would do better with a 1700kv motor on 6s turning 37740rpm. Now loaded, you're at about 31,000rpm and now you can spin a smaller prop, like an M445.

I changed my motor to leopard 4082 1250kv from a 1050 and kept the same prop and hit 63mph. So you have to decide if you wNt to run higher or lower amps. so I went from 1050X29.6=31080. After upping the motor I'm at
29.6X1250=37000rpm. And I'm spinning a small prop. When my prop jumps out of the water then digs again, I'm not seeing huge current spikes that can damage ESC's and batts. You run this big props you mentioned, and you will have huge spikes. Prop hops can't be avoided, they have to be taken into account.

[MarkF]

A bigger boat like this should be spinning a bigger prop. A 445 isn't a good prop for this size boat. I hope you're also using 2 packs in parallel for 10,000 mah. This will also help with your speed. I don't like 6 series props and think you should be running an ABC 2015, 2016 or 2214 and 2215 prop. You still have to check temps with every prop change. 3 blade props just make you corner faster and are used mostly on monos. A hydro should run a 2 blade but the right design. The props you have now are old design and will work but you just need to check temps if you want to experiment with the ones you got. If you want speed, I suggest you try the ones I suggested. Brian Buaas at [email protected] is a good source for finished ABC props and is who I get my props from. He is also very knowledgeable about hydros and I would ask him what props to try with your set up.

Mark

[CraigP]

Hmmm, must be missing something.. my hydro is 35" and 10lb and it's running mid-60's with the M445 and pulling and average of 110 amps. I guess my message isn't getting thru. Good luck with the boat and I hope she always keeps the name up!

[Navherc130]

Not sure if I can get parallel 5s in the nose, Mark. It is the mlboatworks kit cut from Newton plans. Narrow tub I think was made for nitro motor. How thick is 2 5s laying on their sides? Either way, parallel 4s or 5s, I need to cut out the front brace I made.