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[mbm999]

Hi all,

My (nearly) finished Aeronaut Diva had its maiden voyage and whilst i'm really pleased that everything works and there are no leaks -  thanks to all who contributed to my novice questions during the build.

However, it runs slower than i expected (leisurely i would say) so i'm after some suggestions to improve the speed.
I'm a little surprised that the bathing platform sits in the water (causing drag?) or maybe the boat is too heavy (or both)?

I'm quite nervous about using lipos (never used them before and they seem a bit overly sensitive and quite expensive) but maybe i have to bite the bullet and get a 3S?
or would you try changing the prop first (i may be able to squeeze a 35mm in) - 2 blade/3 blade?

Some boat stats below.

Appreciate any suggestions/thoughts,
Thanks
Mark

30mm M4 3 Blade Propeller
Tornado Thumper 2836/08 1120KV, 270W
Tornado NiMh 3800mAh 7.2v
Mtronics Hydra 30 ESC

Total Boat weight (inc Battery) is 1362g
Battery weight is 361g

[tica]

First thing IMO you should change to LiPo and try with a 3S 2200mA low weight and lots of amps on hand.
Else check my build thread with the Classic (almost the same as the Diva)

https://www.modelboatmayhem.co.uk/forum/index.php/topic,57838.0.html

[canabus]

Hi mbm,999
I checkout you setup and the motor will handle up to 4S Lipo batteries but the ESC with only go to 12 volts(3S Lipo).

I check the weight of my 3S 2650mah 30C in at 250 grams.
A drop of 110 grams!!!

Increasing the voltage for 7.2 to 11.1 Volt will change the unloaded rpm from 8064 to 12432!!!
A 50% increase in rpm !!!
The power output of the motor is measured on the maximum voltage.
The prop should be OK.

For Lipo batteries a good balance charger with a safety bag and a battery voltage alarm for checking the total voltage and each cell voltage.
Canabus

[dougal99]

First of all try a plastic 2 bladed racing prop. If still not good enough move on to lipos.

[radiojoe]

Hi I scratch built a copy of a Diva similar size, running on a  1100 KV out runner, 2S lipo and 35mm Xtype prop if it were any faster it would take off


I understand what you mean about the lipo batteries I was the same, I'd heard of them catching fire , exploding etc. the fact is they are perfectly safe if treated right, yes they do take more looking after ie. if not being used for a while putting them in storage charge is important, if stored for a long time fully charged they can puff up, but if looked after they are excellent batteries power to weight ratio. a balanced charger is recommend, these usually have set charges ie.  normal charge, fast charge, storage charge etc.


Joe.

[mbm999]

Hi all,
Thanks for the input which seems to suggest i've not missed anything obvious with regards the "fix".
Have to admit i was trying to avoid using lipos but i suspect this is the issue - i'll probably get a 3S?
When i bought a charger last year for the niMh i splashed out for an Overlander RC6-VSR 80W (just in case i needed to use lipos!) - hopefully that should be ok.
I'll probably buy a few of the suggested props too - i guess they may prove useful in the future.

@Joe - I'd read a few threads that suggested the boat was almost too quick (using lipos) so i thought this set up would be fast enough (I'm not sure it's even on the plane).

The current set up uses Tamiya plugs which i've now read are not the best - I thought about using EC3 which means i'll have to change the ESC plug too. Is that a good choice?

Also, when tightening the grub screw on the U/J to motor, do you use any thread lock?

Thanks,
Mark

[radiojoe]

Hi Mark My Diva is running on a 2s lipo and with an Xtype plastic prop, I wouldn't say it was too fast, certainly on the plane and you have to use the throttle sensibly when turning, a 3s lipo in mine Diva would be well over powered.


It's wise to use tread lock on all running gear threads.


Joe.

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[radiojoe]

Re the Tamiya plug not the best but unless your having problems with them I'd leave them, course if you change to lipo you'll have to change to what ever plug the lipo battery has I've not seen a lipo with a Tamiya plug yet, I use XT60 s just my choice.


Joe.

[RST]

Is it worth asking what a "realistic speed" you expect  is?  Most videos I see these days are most certainly in the "colin macrae" drivers approach, yu can hear aeration trying to turn at full speed also.  After your post, I looked up a Diva on youtube looking perfect on a speed 400 motor albeit voltage wasn't mentioned -I guessed was 7.2v Ni-Mh but maybe not.  Is there any option for you to try an 8.4v Ni-Mh pack first -otherwise I'd agree changing prop might help; too big or pitched and it will drag down performance on any motor.  A smaller prop might help -any pictures you can post?
...I'm nervus about Li-Po's also.  With my sailing habits and extended unattended periods inbetween, I just couldn't convert to them so far with so much more care required compared to Ni-Mh.  But that's just me.

Rich

[unbuiltnautilus]

As above comments, change the prop. Three blade 30mm will be a very shallow pitch affair. at 7.2/7.4v that motor will be happy with a bigger prop. Personally I would fit the 35mm 's' pitch 2 blade prop rather than the 'x' pitch one, but that is based on fairly extensive testing on a 37" Perkasa. I found that the amps ramped up noticeably with any of the 'x' pitch props. I ended up with a fairly big (45mm) prop at a fairly low (8.4v) battery supply, and have a sparkling performance. Your only problem will be space for bigger diameter props.

[mbm999]

Hi,
Thanks again for the comments.
My sailing habits are pretty erratic too, something always crops up that stops me going.
i think my nimh may not be in the best shape either so i'm happy to change it but now stumped between a 2S and 3S - don't want to buy both!
I have no access to an 8.4 nimh but i would guess that's even heavier.

Can't see a way round it, i'm going to have to experiment a bit with props - there is no way anything bigger than 35mm will fit (and i'm not sure even that will).

When you say pictures - do you mean of the boat running or statically - I haven't done a video in the water but am planning too (if i can get back to the water soon!).

Must buy some thread lock too!

Thanks,
Mark

[mbm999]

Hi,
Thought i would update the thread with what i have done so far.

Bought a 35mm 2 blade and 35mm 3 blade. I've also ordered a 2s lipo which hasn't arrived yet.

I ran it today with the 2 blade and the difference was marked (cost £1.35) such that i'm now happy with the performance!
So, i guess i don't need the lipo really but will be interesting to try it.

I'll also try the 3 blade just to see what effect that has.

If anyone is interested i'll post the results?

Cheers,
Mark

[canabus]

Hi mbm999

Would be interested in the performance as a new club member has one to build.

Canabus

[clockworks]

I finished my Diva a couple of months ago.
I'm using:


Cheap 2830 1400kv brushless motor from eBay
HobbyKing Marine 30A ESC
2s 5000mAH Turnigy LiPo
35mm brass 3 blade prop (Raboesch I think)


No additional ballast. I haven't fitted the rear platform.
I replaced the kit propshaft with a better quality unit.


The boat handles very well, decent turn of speed on full throttle. Comes up on the plane nicely.


I originally used a 1000kv motor, and that seemed to push it along at a reasonable scale speed, but I don't like running at full throttle all the time.
The faster motor means  I can cruise at low throttle, and get the bow right out of the water at full throttle.


I'm very impressed with how well the boat runs, considering the very low price. Straightforward build too.

[mbm999]

I've now tried a 35mm 3 blade plastic and a 35mm 2 blade plastic.
Both improve performance but the 2 blade seems to just have the edge in speed, so that is my chosen prop - i'm happy for now 
I've received the 2s lipo but have yet to swap the connector on the ESC as i've decided my approx 35 year old 15W soldering iron probably isn't really up to the job (so i'm on the hunt for a new one - maybe a soldering station - always wanted one of those!).

@clockworks - great summary, thanks, i agree that a 1400kv(ish) would probably be just about right to save being on full throttle most of the time.

I think the Diva was a great first choice to build and really looks the part, hard to know what to do next!

[clockworks]

Maybe try a SLEC Huntsman?


I'm just finishing mine off (the 24" version). It's a bit more of a challenge than the Diva (a bit more sanding and shaping), but not too bad. It's the first "non-Aeronaut" wooden kit that I've built. I'd say that the instructions are even better than those that came with the Diva, it's just the hull shape (balsa blocks for the bow) and the amount of fittings that make it harder to build.


Lovely looking boat though, so worth the effort

[mbm999]

Ran the Diva on a 2S 2200mA lipo and runs slightly better again, the 3S would have been overkill i think. Maybe i'll "borrow" one and see 

@clockworks - Decided on a SLEC Swordsman (and bought it), think the balsa blocks will be my biggest challenge as i don't do symmetrical (or straight)!

[clockworks]

Ran the Diva on a 2S 2200mA lipo and runs slightly better again, the 3S would have been overkill i think. Maybe i'll "borrow" one and see 

@clockworks - Decided on a SLEC Swordsman (and bought it), think the balsa blocks will be my biggest challenge as i don't do symmetrical (or straight)!

I thought the same about the balsa blocks on my Huntsman kit, but in practice it really wasn't an issue. I carved them roughly to shape following the lines of bulkhead/skins and "shelf", then used sandpaper wrapped around a suitable tube to get the concave shape. Vey little filler needed, and looks fine to me after laying the glass cloth, primer and paint.


I did have a problem with the running gear though - terrible vibration at certain RPM. Turned out to be a slightly bent propshaft, now replaced with a straight one.  Goes very nicely on the water.


I'm now building the 34" Huntress. The hull has been glassed and primed, just waiting for my Permagrit block to arrive so that I can trim it to fit the deck rubbing strips.
It looks huge compared to the Diva and Huntress!

[mbm999]

Thanks for the fedback.

Glad to hear you found it ok to do, fingers crossed i do too.

It was a toss up between the Huntress and the Swordsman for me and I decided that it was just too big to fit in the house (I've just about got away with the Diva being on the dining room table - not sure for how much longer tho)!

I'd be interested in some pics of your Huntress tho as the Diva does look small on the water.

The propshaft in my Diva kit (2mm) was so bent it wouldn't even turn tho i'm not sure i would have been able to diagnose the issue if it was only slightly bent - something to bear in mind for the future.

[clockworks]

I'll see about getting some pics of all 3 lined up together.


Took me a while to figure out what was going on with the vibration. The Huntsman was really quiet at very low speed, and also when flat out. Between the two extremes, it sounded like the motor or something was trying to shake itself apart - like a playing card rubbing on bicycle spokes, but very fast.
I tried swapping the motor, motor mount and coupling.
I also swapped the ESC, incase it was a problem with one phase (brushless).


Eventually I pulled the shaft out, and rolled it on a sheet of glass (an old shelf from a cabinet), and the shaft was very slightly bowed. Only about half a millimetre, so barely noticeable. Enough to set up vibrations because it was out of balance, but not enough to physically rub in the tube.


From now on I'll be checking shafts and tubes before I use them