Designing a Hydrofoil Boat

I am designing an electric hydrofoil boat, and need help with a few key details.

The hull of the boat will be roughly 13-15 feet long and 4 feet wide, made mainly of polyurethane foam with an aluminum skeleton, reinforced with a fiberglass and carbon fiber coating. Ideally the hydrofoil would be able to be detached. The boat will be using 2 separate hydrofoils, both of them fully submerged and with built in control surfaces. A hopeful weight of less than 450 Lbs for the boat, and roughly 5 people (900 Lbs)

The things I am yet to figure out are as follows:

Size and how to design the lifting surfaces

how long the mast should be

what to make the mast out of

how strong I need the hull to be

how fast is a good target speed

where should the CG be compared to the hydrofoils

what SAS software/hardware should I use (currently looking at dRehmFlight, yes I know its not made for manned vehicles)

how much power should the motors have (in watts or horsepower)

edit: I'm working on some less messy sketches right now, the mast of a hydrofoil refers to the vertical shaft that connects the hydrofoil to the hull. The number of people is flexible depending on how extreme the power would have to be. the average weight of the people I would be on the water with are roughly 140 Lbs. Power is from motors, not wind.

 

As much as I dislike recommending his book,
it's one of the best "Guides" and that's all it is,
a guide to figuring all that out.
So, it's Ray Valenga or some such thing.
Write us a thesis and report back.
Then we'll tear the crap out of all your hard work,
you'll get upset, eventually you'll thank us for all our sound advice.

Welcome to the Forum, do-up your seatbelt.

EDIT: Oh, and look up "design spiral" and "statement of requirements" (SOR).
And search this Forum for past threads, it's all been done before.
Hydrofoils tend to be load sensitive, you may find five passenger capacity will compromise performance.
ray vellinga hydrofoils - Google Search https://www.google.com/search?q=ray+vellinga+hydrofoils&oq=ray+velinga&gs_lcrp=EgZjaHJvbWUqCAgCEAAYDRgeMgYIABBFGDkyCAgBEAAYDRgeMggIAhAAGA0YHjIKCAMQABgFGA0YHjIKCAQQABiABBiiBDIKCAUQABiABBiiBDIKCAYQABiABBiiBNIBCTEwNjYzajBqN6gCALACAA&sourceid=chrome&ie=UTF-8

 

5 people in a 13 to 15 foot boat is a crowd. You are going to need some serious foil lift and plenty of horsepower in order to support the 450 + 900 pound load.

Do you have preliminary drawings or structural details? Post the drawings if you have them.

 

Since the enquiry mentions mast size,I'm guessing that the hope is to generate that horsepower from the wind.Which may be a bit difficult.We don't know much about the boating experience of the enquirer and I hope a spell of learning the limitations of experience or lack of it in all facets of building and using a small,fast boat will lead to a good outcome.

 

I think what you really need is someone to design the boat for you (not just a few small details), based on your SOR.
Maybe with that little change in approach to the problem you could find more help.
Good luck.

 

Well, that pretty much Nailed it.......!

 

Hi Nail, electric means batteries and controllers and motors = weight. 5 people = weight, well I hope they're children or very under nourished people. A mast means air drag at speed, and weight, and complexity. Do you want a power boat hydrofoil, or a sailing foil ? I doubt you can have both for the weight you mention. Please clarify and give us all the details you have, and show us your working of sums. And photos, drawings, rough sketches and examples of what you want. I'm slightly doubtful.

 

I am going with a hydrofoil powered with an electric motor. from my research I had concluded that the mast of a hydrofoil was the shaft that connected the foil to the hull. I have preliminary sketches pending moderator review that I will add to my original post once cleared. the number of people is somewhat flexible, and the average weight of each person is roughly 140 Lbs

 

this is my preliminary sketch. I plan to make a 1/5 scale model before the full version as well. this would help me to get some of the kinks worked out and finalize the hull design before going too big.

 

It would appear what Nail is referring to as a "mast" (singular) is/are, actually, the struts for the hydrofoils.

Nail, I have one question for you at this point:
How old are you?

 

Yes, that Is what I was referring to what you called a strut, I believed was called a mast is strut the right term? I'm in the ladder half of high school, and am taking on this project as a way to soak up my extra time while using it in a worthwhile way, that's not doom scrolling or some other kind of instant dopamine brain-sucking thing, and something that I can learn many new skills that will help me with what I hope to do as a career.

 

Congratulations on your quest for knowledge Nail. I encourage you, as will others here.
I suggest that you concentrate on your physics and math courses. Both those are an important part of boat and ship design and many of the other disciplines in which you might become involved in your future.

Best of luck to you and please do not lose your ambition to learn and to create.

 

Hi Nail,
cool that you identified this Nick Rehm controller soft already, it probably means you are familiar with all these RC foiling vids like

RC seems like a much quicker and funnier road to something that works than iterating at full-size straight away, and like the only affordable and realistic one, the alternatives basically beeing years of (fulltime!) theoretical study and design work before building anything. Or paying someone to do the design job, which, beyond the expense, would be kinda boring. Or worse, building and throwing away the first 3 or 4 full-size boats that just don't work and can't be fixed.
If you get an RC model to fly reliably, and measure how much power it needs for takeoff and steady flight, you'll know more or less how your full-size craft will behave (scaling table from the Ray Vellinga book attached, but beware of the limits he is outlining) )

The hull seems fairly irrelevant to what you are aiming to do, it just needs to plane a few seconds during takeoff, like this for example:

All else will only be optimisation, to be able to take of with a bit less propulsive power, or in higher waves. There is no need to build a small planing boat hull, there are always plenty available for free in small adds etc. - you'd just need to pick a fairly light one, then make it even lighter, like by cutting out any unneccessary stuff. Surfboards or SUP's are also a good start, like Ray Vellinga plays with in his book, or beach catamarans. BUT you can definitely not have a round corner at the rear like you drew, because that will suck the rear edge of the planing surface into the water instead of generating lift.

For wings, you could use readily available foilboard or moth stuff, but there are also sections on this forum and on EPPLER 817 HYDROFOIL AIRFOIL (e817-il) http://airfoiltools.com/airfoil/details?airfoil=e817-il#polars (search for more on that site) that could be 3d printed.

RC plane design softs like XFLR5 can be used to get a rough idea how the 'infinite span' Lift/Drag values of the sections would translate into real 3-dimensional wings (it's not pretty)

Designing for reasonable stability is going to be the hard part. Ray's book talks about what can be done physically, electronic controls can also be an element, user input has its limits in a situation where you are never more than a second away from crashing into the water surface.

As others pointed out, batteries are heavy, so are people. So it's probably going to be quite feasible if you want it to run 5mn on some lake for fun. Just don't count on going anywhere with the kind of size (and what i imagine about the level of expense) you have in mind. (The optimization level of a Candela cost them millions for a reason, and the lightness and stiffness make them several times more expensive than a classic non-foiling runabout with comparable speed and carrying capacity. Even aiming for half Candela's efficiency in a DIY project would seem very ambitious.)

Good luck and have fun !

 

Thanks, this has really helped aim my research. I have ordered the book, and am waiting for it to arrive. I understand that I'm probably not going to get an extremely efficient and long runtime hydrofoil, but I'm going to shoot for the stars and see where I land. I'm going to be putting some time into learning a CAD software, to help solidify my plans, and work out more exact dimensions. the portion on the back, is for getting in and out of the water with ease while in the middle of a lake where I plan to use this. I am familiar with videos of other RC hobbyists as well, and pull some inspiration form them. I will continue to keep this thread updated as I progress.

 

Nail, did your "book" arrive?
What do you think?
Any questions, ideas, plans, comments...?