Liberty's high speed RC OutRigger boat build thread

[LibertyMKiii]

I figured I would start a dedicated thread for this build and share with my Arrma family/friends here because we have the best forum in the world.

For those less informed about RC boats there are about 4 different hull types. Each as it's strengths you can read more about that in the general RC boating thread .
Per my usual I wanted to build something custom from composites, CAD design, and way too fast (if there is such a thing.)

Out riggers some times called just riggers, shrimp boats, or classified as Hydros and they are the fastest design by far.

The current world record is held by the JAGs team at 206 mph. Video of that boat record run here.

The idea is absolute minimal drag in both the water and the air. The boat is actually flying just above the water using ground effect airplane principles. You can see the design nearly replicates the shape of an airplane.

At any rate I have some amazing ponds close to home versus having no great roads over 1000ft for RC car speed runs, so I started dabbling in boats! (I will still finish my 200+ mph car build this winter)

I am on my 5th version of the design and it looks something like this:

Over the past weekend I began printing the front parts which are called sponsons in two parts. They are 400mm long.
The entire boat is 48" long for some perspective on how big it will be.

In this picture they are both on an aluminum rod I found in the garage. In final form I will be using carbon fiber tubes...
The sponsons will "skinned" in fiberglass to simplify the process versus making molds and making the parts from carbon fiber.

I expect I will revise the design after testing and learning, so there is no point in making the final molds and final draft version just yet.

Should be a fun/interesting process. Starting out I will be working my way up to a goal of 130+MPH. Depending on how that goes I might shoot for the moon

Currently my Creality CR-10 S Pro is printing 1/3 of the main center hull. That 1/3 of the hull is a 40 hour print (3D printers are a life saver and time saver in this world of home made custom designs!!!)

Stay tuned for more!

 

[Malice]

I had a hunch this was coming when you started talking about boats!

 

[AIan]

Shhhweeeet

 

[KvConivore]

I'll be keeping an eye on this..

 

[Doom!]

Well, I guess I'll watch this thread, not much else to do.

Looking forward to seeing what the final product looks like, vs what your initial concept looked like.

 

[LibertyMKiii]

Already started designing adjustable wings on the rear and vertical stabilizer that will guide the air around the rudder hardware.
The interesting thing about these boats is how they start at one angle of attack and then when they get up to speed only the prop is in the water on the back end which changes the angle of attack/aerodynamics. I could see where some airplane flight controller gyro could be utilized to adapt the ground effect based on speed/throttle input.

Another picture of a well thought out high speed rigger. Here you can see what I mean by the boat having wings and looking like a plane! This one was claiming 120+ speeds. Pulled this picture from a for sale add on OfferUp months ago.

 

[Camaroboy383]

I'm not sure if you have a dead set aoa on the sponsons.. but it is a good idea to have some aoa adjustability...

Also I'm sure you know, but refrain from having the bottom of the hull and sponsons "shiny" ... Once all surfaces are true/flat sand the surfaces with fine sand paper 800-1000 will do.. This will reduce the chances of a Bernoulli effect on the surfaces in contact with the water....

 

[LibertyMKiii]

I'm not sure if you have a dead set aoa on the sponsons.. but it is a good idea to have some aoa adjustability...

Also I'm sure you know, but refrain from having the bottom of the hull and sponsons "shiny" ... Once all surfaces are true/flat sand the surfaces with fine sand paper 800-1000 will do.. This will reduce the chances of a Bernoulli effect on the surfaces in contact with the water....

I appreciate the tips!
I will keep that in mind

I do plan on making the front "arms" of the sponson mounts adjustable at the main hull for AOA adjustments. The other thing is I will be adding ride pads on the bottom of them to adjust the angle that actually makes contact with the water.

 

[Camaroboy383]

I appreciate the tips!
I will keep that in mind

I do plan on making the front "arms" of the sponson mounts adjustable at the main hull for AOA adjustments. The other thing is I will be adding ride pads on the bottom of them to adjust the angle that actually makes contact with the water.

I look forward to seeing some saw passes..

 

[Sargent_Horse]

That offerup boat has the support between riggers shaped more like a tear drop. Probably harder to do, but maybe worth it over round rods?

 

[LibertyMKiii]

That offerup boat has the support between riggers shaped more like a tear drop. Probably harder to do, but maybe worth it over round rods?

Absolutely!
Aerodynamics becomes a whole separate topic that could be talked about for hours...

This is an old aerospace text book reference, but a great one. They compared an airfoil to a rod/metal wire. The drag was the same but as you can see the size difference is drastic. Streamlined shapes are always best for airflow!

This is a flow visualization of different shapes, again the streamlined shapes are clearly much better

The relation of the airflow between the ground plane and the acceleration of that airflow will be important as this will act like a wing with more camber. When close to the ground an asymmetrical airfoil can be used and still create lift. Too much "squish" between the airfoil and the ground plane and you will have a significant increase in drag. The cord length is relative to this scenario. My parts will be in the range of centimeters so the drag should be very negligible.

My design actually will include the carbon fiber tube as the main internal part, and I will form a streamlined airfoil shape over it. This isn't the clearest picture of the shape, but might help illustrate what I have planned.

 

[jkflow]

Another idea, and it's actually on the picture in #6, do not simply use carbon tubes but shaped versions. I was considering them back in the Quad days.
They would have to be aligned, though, or they will provide lift.

By all means start dialing it in with standard hardware and make incremental changes from there on out.

 

[Sargent_Horse]

Absolutely!
Aerodynamics becomes a whole separate topic that could be talked about for hours...

This is an old aerospace text book reference, but a great one. They compared an airfoil to a rod/metal wire. The drag was the same but as you can see the size difference is drastic. Streamlined shapes are always best for airflow!

View attachment 164303

This is a flow visualization of different shapes, again the streamlined shapes are clearly much better

View attachment 164304

The relation of the airflow between the ground plane and the acceleration of that airflow will be important as this will act like a wing with more camber. When close to the ground an asymmetrical airfoil can be used and still create lift. Too much "squish" between the airfoil and the ground plane and you will have a significant increase in drag. The cord length is relative to this scenario. My parts will be in the range of centimeters so the drag should be very negligible.

View attachment 164309


My design actually will include the carbon fiber tube as the main internal part, and I will form a streamlined airfoil shape over it. This isn't the clearest picture of the shape, but might help illustrate what I have planned.

View attachment 164305

I just finished my fluid dynamics class, don't go off making my head hurt again!

I did not see the airfoil design on your CAD's, but I probably didn't look close enough. Are you planning to finish the boat before winter?

 

[LibertyMKiii]

I just finished my fluid dynamics class, don't go off making my head hurt again!

I did not see the airfoil design on your CAD's, but I probably didn't look close enough. Are you planning to finish the boat before winter?

In some of the pictures I shared the airfoil shape was not present. It is a component in the CAD drawing that I can turn on/off and was doing some adjustments to the sponsons where I had that airfoil shape turned off at the time.

I am hoping about 2 months. October, November, and December are great months here in Texas with mild weather.

 

[LibertyMKiii]

Revised drawing showing what my vision for this boat would look like complete.
The rear vertical holds the antenna, directs air around the rudder parts, and acts like a rudder itself.

The rear wing endplates help avoid "wing tip effect" and the related higher pressure zone washing over to the low pressure zone. I'll make those removable parts incase they hinder performance.

You can see in the drawing the main hull segments as they will come off the 3D printer. The front 1/3 will be finished tonight and I am excited to see it when I get home from work!

 

[LibertyMKiii]

Starting to take shape and look like something!

 

[LibertyMKiii]

2nd piece of the center hull finished today. It was a 42 hr print. You gotta love 3D printers for stuff like this!!!

My order from Amazon of True Composites resin and chopped strand mat fiberglass came in yesterday. I didn't realize I got the one with 10 yards of fiberglass. Looks like I will have plenty of leftovers!

 

[jkflow]

I see more prototypes in the future, you've got the fiber!

 

[LibertyMKiii]

I see more prototypes in the future, you've got the fiber!

I'm already planning a V2 design
It would be interesting to sell boats... I feel like the RC boating community is willing to pay reasonable prices for quality parts versus the RC car community. (with the exception of a few people)

Plus so many of the designs (especially riggers) are ancient wood designs.

One example I was selling my carbon fiber RC bodies for $350-450 and got a lot of push back on that. Martin Pearce in the UK spend $2,500 on his carbon fiber body made by someone over there in Europe. RC boat guys routinely spend $1000 + on high end boat hulls. I suppose because there is no market for composite RC bodies people can only reference Protoform and Delta Plastiks as comparables when its not comparable at all.

 

[jkflow]

Boat community definitely seems to be stale. If you want to make it a business, you probably need to design for the racing categories and be somewhat compliant.