Tow boogie general design

[Etiennebzh]

Hi everyone,

Regarding the interest of dual motor tow boogie, I create a new topic to gather knowledge, pictures, measurements about general design outside electronics.
Thanks @ludwig_bre from Bremote to allow us differential steering. It opens a new era of easy build because servo steering gear is not the easiest to achieve.
I think we need to gather minds to help forum members to avoid 10 iterations before enjoying a good session with this beautiful toy.

I would like to deal with:

Board, hull shape
Weigh distribution
Tow point position
Pod length and position
Direction of propeller rotation
Underwater appendix
Sailings behaviour

A very good movie to explain my goal in term of sailing behaviour by @strongarm

Tow Boogie - Wanaka 2022

For the moment, what officially exists:
Displacement hull 75 kg by Takuma with 2 deep waterjets
Inflatable Zerotow by @Strongarm : 1.30m 29 kg
Some of the forum members like @jenz @Jesserosco @rttn @Jatem @kkolli @Valhalla @okp have already good builds. Sorry if I forget somebody

To start, I would say that more the rig is heavy, more we’ll have a chance to have a comfortable behaviour in the chop and to keep the prop in the water. 75kg is too much IMO for logistics, but starting around 25/30 kg is the good range for launching alone without trolley and battery consumption

Deep pods like 20cm are good to allow the propellers to keep the thrust even on the chop

Wide boards are better to handle the roll when the rider goes on the sides of the wake (20 inch is not enough by personal experience)

Long boards are good for speed, glide and battery consumption

Short boards are easier to steer but bounce on the chop or make submarine

Long tow bar is good for steering, easier will be the steering by increasing the lever between traction point and propeller pivot point.

Low tow point (around water surface) avoids tow boogie nose up by reducing the torque between rope and propeller

Fins avoid tail drifting when the rider foils on the sides

Don’t hesitate to give your experience, researches, pros, cons.

[Larsb]

Good initiative! I’m building a tow for this summer and have the same questions.

I already have a plug that’s 120x75cm, for minimum planing drag the proportions w/l should be around 0.41 so 120x50 would be better, but possibly too narrow for the tow stability if you already have this experience?

[Etiennebzh]

For the moment 137cm (4’6) 50cm (20 inch) only works fine going straight but I definitely can’t steer it with my load or with differential motor speed, it flips, but it could come from another reason.

I’m tempted to say that my motor are too outside. I’ll try to go a bit more inside.

One other solution I’ve imagined is to put surf handplanes on both sides to create a trimaran, to have shape efficiency and stability.

I bought a 48 inch bodyboard by 24’ wide on the web to try something else later.

[Larsb]

I think i’ll make my first tow bottom with a plywood sheet reinforcement to be able to change mounting for stuff freely

[Strongarm]

This was the Boogie from the video in Wanaka. I don’t have this one any more so I can’t take measurements but it seemed to work quite well and was stable.

The half noodle underneath helps with tracking, and meant that you didn’t need fins.

[nekitesurfing]

Great idea to creat this thread. I’m at the research stay while I get the funds together for the battery.

Can electronics be asked in your thread or would you rather keep that separate? I just have a couple of queries on the size.

[Etiennebzh]

Did you install a steering gear on this one ?
Because it seems so manoeuvrable and you can really use it like a nimble slingshot !!!
Where was the tow point please ? Just at the back ?

[Etiennebzh]

I would prefer another topic if you don’t mind to be a bit more tidied than Foil Assist topic. I invite you to launch the Tow Boogie Electronics topic

[rttn]

Great topic. In addition to bodyboards, we made several boogies based on the shapes of standard foilboards and not one of them worked. The first ones were of large volume and we did not have batteries of such weight to load them enough; they drove unstably and constantly yawed. Then we reduced the volume and also failed, the board rode in a straight line, but fell on the sides during turns. Two boards and another failure. And finally everything worked out. We glued two pieces of foam plastic to the sides of the last board, now it goes in a straight line and turns.

The parameters of the boogie that I determined for myself were weight up to 20 kilograms, length up to 1 m 20 cm. I assumed that the rider could enter the water with a boogie and board without outside help.

[Strongarm]

No steering. Tow point about 10cm to the back of the board. It took about 5 iterations to get it working good, so many second hand body boards from marketplace to get the weight distribution correct.

[Etiennebzh]

Very interesting @rttn , it would possibly mean that my board has not enough volume (30 liters).

Btw, as far as I know, you’re the only one of the forum with a proper dual motor tow boogie, because @Jesserosco uses more a shape of a surfboard.
Could you give us some input on your actual setup ? Does it work good ?

[rttn]

What data exactly is needed? Physical parameters or electronics?

[Etiennebzh]

What’s a size of your boogie ?

Where did you positioned your Pods ?

Where is your tow point ?

Can you steer it only with your weight when you’re foiling ? Does it handle a slingshot ? I ask because I’ve a doubt with Dual motor now ? Maybe one motor makes a better pivot point than Dual…

Are you satisfied with the behaviour of your Dual motor compared to a mono motor ?

[rttn]

I’ll respond on Monday after I take measurements.

[Jesserosco]

My dual motors slingshot really well and turn great. It is probably just the extra size on the boards. I can’t stress enough about limiting throttle especially when slingshotting. Bring the motors closer together and see if that helps as well.

Positioning and weight is crucial and any little change makes a huge difference in my experience.

[bbe]

Great idea to start a thread focusing on tow boogie dimensions etc only. Lots of good info in various build threads, but I was missing a common thread where all the tow pioneers could share actual measurements and experiences with their (final) choices.

I plan to make a dual motor 6384 based on @Jesserosco ideas. I’m gonna put two (leftover) 120x59x7cm XPS sheets together, add a hole for the battery in the front and some nose rocker, then use plywood sheets in a sandwich with the bottom XPS for the motor mounts (cut 55cm Gong mast in two), and then fiberglass the board. With this design, the motors position will not be movable, hence position must be fairly spot on from the start. I will make room for adjustments of battery pos to get good balance. These are my initial questions:

What would be a good spacing of the two motors for a 59cm width board (or ratio for any given width 50-70cm), and what are the tradeoffs of going narrow vs wide, in terms of steering and torque balance? Again some range in cm would be nice.

How far from stern to prop is ideal? Given only 120cm boardlength it is important to not go too far forward to have some adjustment range with battery position, but still far enough to avoid “rear position issues”.

Would going longer than 120cm be better (Zerotow is 130cm)? And is 59cm wide enough?

[Jesserosco]

I will try and get some measurements on my setup tomorrow and post them.

[Strongarm]

Hey Jesse - What happens if you don’t limit the throttle when whipping on to a wave?? Does the boogie flip?

[Jesserosco]

On mine it doesn’t flip unless you pull really hard outside the boogie and keep the throttle hammered. I just ease up on the throttle and steer it with the BREmote and it works perfectly. I don’t have to let up on throttle at all when I’m just maneuvering around using the BREmote steering cause I stay behind the board and not to the sides. Mine are very stable. The one time I threw everything on an actual boogie board it was super unstable and flipped really easy. I’m going to try an actual boogie again at some point just for fun, but I’m happy with my setups. The weight distribution is very important. If someone tries to use my tow board on a larger volume board it’s very hard cause it submarines really bad, but for me at 190lbs on a 27L board it works perfect without submarining ever.

I’ve gotten pretty dialed in and don’t generally have to whip into waves. I can do a controlled turn onto the wave, but it’s come with a lot of time using it.

[Etiennebzh]

Here is the distance between the 156mm diameter propellers on my 20’ wide board.

I plan to decrease this distance to see if my boogie stops flipping

Longitudinal pod position. I’m satisfied with this one because my boogie as a good trim unloaded and during ride also.