EDF Boat Build

[kookie_guy]

I have a couple 64mm EDF's laying around, so figured I'd build an EDF boat. The EDF's are pretty decent, at 4s there's about 1000g of thrust each.

The hull is going to be out of rigid insulation foam. 20" long, 10" wide.
Motors - 2x 3500kv outrunners spinning a 64mm EDF fan each
ESC - 2x 45A hobbyking ESC's (non water cooled)
Battery - 2x Rhino 4900mAh 2S 20C (running in series for 4s)

Here's the initial concept design. Everything is 100% to scale. Still have to add the steering mechanism, which will be like an airboat, so this can glide on land.

[bwells]

What is the correct COG on airboats? I think I remember 20-40% but not sure. What is the COG you plan on?

[kookie_guy]

What is the correct COG on airboats? I think I remember 20-40% but not sure. What is the COG you plan on?

I really have no idea. I will basically control it with battery placement. I have lots of room for movement.

[bwells]

That was my thinking as well. I found that I need to move the batts all the way to the transom in order to get a 25% COG. I was expecting the opposite so I'm now cutting a rear bulkhead (crossmember) to get to that 25%. I wish I had checked that before construction. 2 EDF's will be interesting. I keep an eye out on this one.

[Boaterguy]

Will be following this.

[kookie_guy]

Will be changing the steering. Initially was going to do a fin to direct airflow, but because the motor has the cone on the back, it would look weird. So I'm going for broke, and making the fans steerable. Thrust vectoring baby, lol.

[Boaterguy]

Good luck, just hope you have strong enough revolving mounts, so your edf's don't cone right off while running (I have exp with this)

[kookie_guy]

Good luck, just hope you have strong enough revolving mounts, so your edf's don't cone right off while running (I have exp with this)

Gonna design and machine a custom mount system. I have full access to a machine shop at work, so I can get creative. My plan is to have the shrouds mounted to a bracket. That bracket will then be on a post. The post will go down into the actual hard mount, and will run through ball bearings to make it smooth.

[bwells]

How do you plan on fastening all the equipment to the foam? Are you using the rigid stuff for insulation on a roof or the blue stuff?

[kookie_guy]

How do you plan on fastening all the equipment to the foam? Are you using the rigid stuff for insulation on a roof or the blue stuff?

Using the pink foam stuff used to insulate walls.

http://www.homedepot.ca/webapp/wcs/s...k=P_PartNumber

Not sure about fastening yet. Will probably just use construction adhesive.

[Boaterguy]

what I did is built an arc, on the floor of the boat, and a post on the edf, to provide two points of contact, but the post must be able to slide within the arc, and the arc must directly follow the path of rotation of the servo, attached is a picture.

[sundog]

I have an inexpensive EDF boat that uses motor mixing for steering - one motor will go faster than the other to steer. In an effort to improve the holeshot and steering, I am in the process of installing a small waterjet drive that should fix both problems. We'll see. Here's a stock photo - mine is red.

[kookie_guy]

Finally made some more progress on the design.

Here's the overall shot....


Here are a few detailed shots of the rear mount/steering setup for the EDF fans. They will be linked together, driven by 1 servo. Mount posts go through 2 needle bearings each for low friction turning. I have the bracket already made from plastic, nice and light.

[bwells]

Nice drawings! How thick of a boat are you planning on as the servo is 2"? Good job on the idea and keep up the good work!!!

[kookie_guy]

Nice drawings! How thick of a boat are you planning on as the servo is 2"? Good job on the idea and keep up the good work!!!

thanks for the kind words. That's the great thing about solidworks, you get beautiful scale drawings, and you can see if everything fits and work before ever cutting any material.

Right now the hull thickness is 0.75" pretty well all around. But that's still flexible as I have not cut any foam. I will also be putting slider rails on the bottom, made from low friction plastic to save the bottom from scrapes if I run it on a hard surface. The servo (without the mounting tabs) is just over 1.5" long. I'll probably have the EDF pivot brackets cut on the CNC some time this week, so I'll post pics of some actual hard parts soon.