Sharing some info and pictures of my tethered hydroplanes

[Ricky Neal]

Hi, I'm new to the forum and have already found some incredible information. A few members asked about the tethered hydroplanes that I run so I thought it would be best to share what it is as its a bit of a niche section of our hobby and hopefully some of you may find the information interesting.

First of all, I am by far one of the most junior members of the UK tether hydro community, I have been running for only about 4 years but my boats are competitive and I was hoping to take some British or even international records before Covid hit - Next year I guess!

I will start by explaining what tethered hydros are and then the classes and then I will show some of the boats and engines that I have.

Tethered hydros are hydroplanes that are not RC, in fact, there is no control of the model once it's launched. They are connected to a pole in the model of the lake with some bridles, much like tethered cars. The engines have a venturi rather than a throttle and they are started with an old fashioned string.

These boats have props with a lot of pitch so to help them get going they are launched with a bungee cord.

The idea is to go as fast as possible so the pole in the centre of the lake has a rotary encoder that is connected to a readout on the bank, the competitor signals when to start counting and then the speed is recorded by calculating the speed in which the models completes a number of laps. After a number of heats, the fastest competitor wins for each class.

The classes of tethered hydro's
There a number of different classes but to keep it simple I will focus on the main classes.

A1 - This is 3.5cc (.21cu) surface piercing prop, 3 point hydro's - Fuel is 20% castor oil, 80% methanol
A2 - This is 7.5cc (.46cu) surface piercing prop, 3 point hydro's - Fuel is 20% castor oil, 80% methanol
A3 - This is 10cc (.61cu) surface piercing prop, 3 point hydro's - Fuel is 20% castor oil, 80% methanol
B1 - This is 2.5cc (.15cu) Airscrew (an aeroplane propeller) - Fuel is 20% castor oil, 80% methanol - These are like F2A control line speed but on water, calling them a hydro is a bit of a stretch at times

There are other classes for homemade engines, Electric versions and even flash steam engines but the main competition classes are the ones mentioned above.

International speed records for the classes above are as follows:

A1 - 132.75 mph
A2 - 135.92 mph
A3 - 144.23 mph
B1 - 176.58 mph

Believe it or not, we have steam-powered hydros that have gone 129 mph!

There are no kits available for this type of model so everything is made from scratch, in some classes this includes the engine.

Here are some pictures of some of my boats



This is my A1 hydro with a Soluev .21 engine and a selling pipe with all the adjustable length parts and different stingers. Also my A3 boat with a Picco speed .60 engine (this is the same engine used in the fastest tethered cars that can doo 200+MPH) and also a Novarossi .61 speed engine that I have converted to have the exhaust and crank output on the same end so it can fit in the boat (this is a 1 off engine that I have developed and I would be happy to share more info on that if anyone is interested?) you can also see my Picco speed 60 pipe.





Above is a B1 class boat, this is almost entirely carbon fibre

See below some pictures of the props we use







My A3 boat was constructed in a way that I do not think anyone has done in tethered hydro's before, I designed it in cad and had is CNC machine on a router. The below pictures show how I collected them after machining.







Here are some more pictures from the construction of the A3 boat



I have hit the picture limit so I will add some more sepeeratly

 

[Ricky Neal]

More pictures of the A3 construction











I have loads of more pictures and would be happy to share any information so if you have any questions please feel free to ask.

Also, see this link for a more depth look at a B1 hydro



Kind Regards

Ricky

 

[Mario Johnston]

These are wild! I knew almost nothing about how these worked til now.
Thanks!

 

[brad nichols]

Nice job! Pretty wild!

Brad

 

[LohringMiller]

Very interesting. The big difference in speeds between the water propellers and the air prop shows the huge drag of things in water. Also, you don't have rudders or other things in the water that explain the difference in speeds over RC SAW speeds.

Lohring Miller

 

[Ricky Neal]

Very interesting. The big difference in speeds between the water propellers and the air prop shows the huge drag of things in water. Also, you don't have rudders or other things in the water that explain the difference in speeds over RC SAW speeds.

Lohring Miller

Agreed, completely different drag characteristics, these hydro’s also weigh a lot less. My A3 is less than 2kg ready to race and the A1 is less than 1kg ready to race.

The B1 is just 440 grams.

 

[ALLAN YUEN]

I wonder that Where is dealer for Picco marine engine?

 

[Ricky Neal]

I wonder that Where is dealer for Picco marine engine?

I dont think Picco make marine engines anymore. The Picco engine above is designed for tether cars

 

[dwilfong]

I dont think Picco make marine engines anymore. The Picco engine above is designed for tether cars

Is that eng still available new from PICO?

 

[Ricky Neal]

Is that eng still available new from PICO?

one pictured is the latest version of that engine and i have 2 more but of an earlier version.

Picco do not really actively produce this engine for sale but as Gautiaro Picco was so heavily involved in the tether car scene they still produce these engines for tether car racers but they seem to only be available through certain members of the tether car scene and there is a fair amount of demand so getting one can be very difficult.

The pipe is also very nice and comes with a number of adaptors to adjust the pipe length in 1mm increments

 

[dwilfong]

one pictured is the latest version of that engine and i have 2 more but of an earlier version.

Picco do not really actively produce this engine for sale but as Gautiaro Picco was so heavily involved in the tether car scene they still produce these engines for tether car racers but they seem to only be available through certain members of the tether car scene and there is a fair amount of demand so getting one can be very difficult.

The pipe is also very nice and comes with a number of adaptors to adjust the pipe length in 1mm increments

View attachment 285825

Yes that is a very nice pipe that was my next question where do you get the pipe.
Would love to see the eng broke down.

 

[Ricky Neal]

Yes that is a very nice pipe that was my next question where do you get the pipe.
Would love to see the eng broke down.

That is a Picco supplied pipe, specifically for that engine.

i also have this unusual pipe that i bought from someone in Russia

 

[dwilfong]

That is a Picco supplied pipe, specifically for that engine.

i also have this unusual pipe that i bought from someone in Russia

View attachment 285826

That pipe would suck the guts out of a eng and slam them back in hard......LOL

 

[Terry Keeley]

Very interesting, thanks for sharing!

Just wondering what plugs you use to light the 80/20? I know Jack O'Donnell had some super hot plugs for his 10cc tether cars.

Also, is the horizontal wing adjustable?

Very cool way to build the hulls BTW...

 

[Blair Warren]

Very cool way to build the hulls BTW...

I can see the wheels turning in Terry's head......

Awesome stuff, thanks for sharing!!

 

[Ricky Neal]

Very interesting, thanks for sharing!

Just wondering what plugs you use to light the 80/20? I know Jack O'Donnell had some super hot plugs for his 10cc tether cars.

Also, is the horizontal wing adjustable?

Very cool way to build the hulls BTW...

I am happy to share, sadly the fact that this part of the hobby is dying so the more light I can bring to it the better.

Plugs wise, there are various options but the likes of Novarossi and Picco make some great turbo plugs for these engines, Picco P5 plugs work great but most of the hot plugs work well. Jack O'Donnell's plugs are great though.

The wing is not adjustable but I have made various different sizes and shapes that are interchangeable - The goal of this wing is not to produce downforce but to aid stability, Ideally, we want to reduce drag as far as we can so no wing would be best but due to the pitch we run on the props and the lightweight nature of the models, the boat tends to be very unstable until is reaches something close to full speed. The back end of the boat will bounce out of the water losing speed without the wing.

Building the hulls this way not only made it a lot easier and quicker but also much more dimensionally accurate. The one pictured was made of balsa wood with a marine ply skin, you can see that the outer ply skin was machined through at the front and from about halfway down the sides leaving only balsa. This was intentional so that I could make it as light as possible while adding strength (Ply) only where I needed it - The middle of the boat where the engine mounts.

I would argue that this may be the lightest A3 tethered hydro ever built due to this design but it is very delicate. As you can see, inside the engine section is skinned with carbon cloth and the entire outside is glassed with lightweight glass fibre cloth to add strength but its very easy to pierce the surface if you drop something on it (That's exactly what happened the first time I run it)

The next one I machine from solid wood I am thinking of making from Poplar or basswood, this will be a bit heavier but a lot more resilient. I have also been looking at moulding one from solid carbon but the complicated mould is slowing me down at the moment.

For reference, the A3 hull weighs just 228g This is after the internal pipe section has had 2 coats of high-temperature epoxy and the total weight of the hull all built up with sponsons all hardware and wing is less than 800g. It's about roughly 35" long

 

[Wasted wages]

couple of questions.....
why doesn't the UK allow the use of nitro ?
Is it cost?

and, do the boats/plane ever take flight and crash? The boats don't look like they would survive a tumble at those speeds!

What is required for your safety and spectators?

Those models really haul the mail !!!!
Very interesting portion of our hobby!

 

[Ricky Neal]

couple of questions.....
why doesn't the UK allow the use of nitro ?
Is it cost?

and, do the boats/plane ever take flight and crash? The boats don't look like they would survive a tumble at those speeds!

What is required for your safety and spectators?

Those models really haul the mail !!!!
Very interesting portion of our hobby!

Re Fuel - its nothing to do with costs, it's just one of the class controls, In fact, most speed-related models, be it F2A control line speed or tether cars, they all run the same fuel. I am under the impression but have never tested and confirmed this but I have been told that higher nitro fuels yield more torque but due to a slower burn rate has less max RPM potential. That could well be an old wives tale though.

Crashing does happen from time to time, mostly caused by choppy water and the hydro becoming unstable and dunking in or they can crash as a result of a poor launch, they are pretty hard to get away sometimes.

Most of the time the model is fine but it does really depend on speed and how the accident happens

As for safety, we have various rules and procedures, the main concerns are keeping the course clear (that's easily managed as we only run one boat at a time)

The other main concerns is the strength and quality of the bridle cables and how they are affixed to the model, Firstly, the method of securing the bridles to the model is well established and scrutinised by the club to make sure they meet the required standards.

The main line's from the pole to the boat are owned and managed by the club and is replaced every year as well as inspected every time we use them. These lines are varying thickness depending on the class of hydro going around. (the material and size has been established through some very rigorous testing)

Then the final cables attached to the model are replaced every season, the model builder is responsible for making these and again the construction method is established and the club inspects them every season to ensure safety.

I think we probably have the strictest safety rules relating to the bridle cables and lines, I have never seen any bridles break in the UK but I have seen this happen elsewhere where they seem to not be as stringent on the standards of the bridles.

As for spectators, it's no more dangerous than normal RC boats really as we only ever run one at a time so crashes and accidents are pretty rare.

 

[ALLAN YUEN]

How much of limit tank ounce? And how long run to empty ?

 

[Ricky Neal]

How much of limit tank ounce? And how long run to empty ?

There is no limit to the size of the tank but we only have to complete 8 timed laps per run. You will need additional fuel for starting and some warm-up laps, they typically run for about 2-3 minutes generally