nose down - or flyong at speed and staying flat is definatly related to hull drag vs motor depth… if you shorten the masts you’ll get less nose lift…
Ive found the majic distance from a flat square tail pushing is at least 550mm of flat arear behind the props - batteries infront of mid point helps too -
Ive tested adding movable ballast right forward - it doesnt work as the added weight also increases the hull drag… its self defeating…
you can also tilt or shim the masts/motors aiming slightly downward…
I had air running down on one of my first bodyboard builds, left a white bubble trail behind the Boogie, at the time didn’t think too much of it.
My first inflatable version used the same fixed mast would suck the shell in tight after about 10 minutes of use due to the same Venturi effect, then the bubbles would stop.
This would have affected the efficiency a bit, but I don’t think it would cause the large roll effects that you are seeing.
Are you using counter rotating props?
Yeah counter rotating props, Ive tried both ways - ‘outward spin’ and inward spin, similar behavious.
The Cavitation is only at over about 17 KMPH - and its instantanious at that speed, the split on which side goes first is random and unmeasurable… As soon as one side cavitates, it loses its ‘grip’ and will basically over spin /over power and lose all pull, this allows the opposing prop to win the torque twist battle…
Of course I could go wider with the hull, or slow down 
But no… hahahahahahahh
Im going to go hard on a perfect uninterupted water flow… Its time …
My Hull moulds are finally finished after around 2 months of really painstaikingly slow progress, polishing, sanding and perfecting the hull plug…
With the Molds complete for the hull, the team have descided a Carbon Fibre lid was the go for maximum stiffness for the top seal. The space to add battery cases / tech is immense - You can fit anything you like inside with 450 x 1500 x 200mm of internal space (rolled on the dec from 140mm up) -
We tried a Big plastic box that was 300mm x 140mm x 930mm and it drops in nicely…
Some other random sizes tested listed on the carboard pics below for easy drop in.
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Well I hope it is only that, but looking at your setup, -
that is about 6000% more refined than mine, so probably not.
I think my design was also particularly bad, with an open 30mm tube going from top to bottom and then inside the mast to the motor
Creating a direct tunnel for the air to go from top to the prop.
Have you considered placing a camera under water to see what is happening?
Saw this in a YouTube video, where he would do this to see how the different propeller designs would perform.
RC test flights videos shows this, he was purposely injecting bubbles to see the flow and vortices around a propeller.
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Yes, that is the one.
I thought that was pretty clever.
I was considering to put a GoPro to the side underwater to see what was happening.
But the problem disappeared with the seals around the cables, so I never got to it.
Finally got to test TOW Boogie and it went well.
My mate had a go and was up on foil with a few goes.
But eventually one motor started stuttering I think the ceramic bearings might of clapped out not quite sure yet but shouldn’t be too hard to figure out.
Has anyone had this issue before loose wire joint or bearings?
Not sure but are props for tow boogie supposed to rotate outwards or inwards? Chat gtp say outwards is better for stability is that right?
Thanks in advanced.
not sure either, mine are set to spin inwards (looking at the motors left is CW right is CCW). will do a test to see how it handles spinning outwards
I’ve just swapped mine over. I’m sure I had them going outwards before and it felt more stable and turned better and less to none torque roll
Hello,
Propellers spinning direction, I’ve always used outwards motion. Better for moving air bubbles outside than sending to the other propeller and better for stability.
About this air bubbles, I would say it is the last main issue I experience. Comparing dinghy tow to my best friend Zerotow, it is night and day. He is able to take off with headwind and when Zerotow bounces in the chop, the Manta propeller never ventilates.
Whereas when the dinghy tow starts to do little jumps in the chop or when I try to start with headwind, I see a lot of air bubbles coming from the back and I often loose line tension . It’s annoying to be honnest !!!
It’s very hard to determinate the cause of this air bubbles. Too short masts ? Air coming from forward because of the hull shape ? Bad propeller design ? Too short distance between mast and blades ?
Something obvious between our respective propellers, design is very different. Manta propeller is lower aspect ratio and has more surface than mine.
It may handle more load on the blades than mine which may saturate at high load.
Any ideas or same experience ?
For what it is worth, my first attempt at the tow boogie had a fixed 3 blade propeller. It looks like the same as yours. I had lots of ventilation. I then changed them to a 3 blade folding prop printed in aluminium via craftcloud that are close the the genuine foil drive ones and I got far less ventilation. Run time was also greatly improved.
Dinghy tow looks fairly short no? Compared to zerotow that’s about 130cm long. That and shorter mast and the hull shape I can imagine when dinghy jumps on chop makes it worse
Saif Seas: A remote rescue craft, with some iterations on their website. Underpowered, but relevant.
RTM (roto moulded), more on the price than anything (€500) , but it looks like it could be adapted.
Adding to this thread as something I keep coming back to as quite interesting, as my primary issue with boogie was cavitation.
Something to look at is surfacing piercing propellers, where the propeller is always ventilated. I don’t necessarily believe it is the correct answer, but it is quite interesting.
It is relevant in two places:
-
Offshore powerboat racing
-
Solar circumnavigation
What is peculiar to me is that these are the two extreme opposite ends of the spectrum, with different power curves, different energy sources, and different speed ranges, and yet both ended up with this related design.
Last mentioned here
Definitely a big difference in stability in running outwards and steers better tried with a 40l board with me at 95kg and easily pulled me out. I will buy the Armstrong tow rope though this one I have has no stretch and pulls arms out of sockets. Tried the new MK2 MA890 and absolutely love it smooth and carves great. Need to work on my technique with sinking board I couldn’t sink board. What technique are you guys using?
As for ventilation Im not noticing it. But ion the big choppy day it was launching off the waves into wind breaching props a bit but not a big issue
Is there anywhere I can buy these Ali blades from? But they may not suit these 6579motors