The LOOSE GOOSE Custom Build

[Neveryachtz]

This thread will detail my summer project. I am a mechanical engineering student at Sacramento State. Life long boater, new to r/c hobbies. I helped build a r/c plane for a competition through the campus aerospace club over this past year. I had a lot of fun and learned way more than I expected. So I figured I'd try my luck next with a boat.

The plan is to design a custom stepped hull using CAD. Have the hull machined into a foam mold by a local company. Lay up the hull with either fiberglass, carbon, or a combination of both. Then install the parts, test, run, test, run, drink beer, etc.

This thread is not only for the reader's entertainment watching me stumble through a boat build, but also to help me do things correctly the first time.

I WILL BE ASKING A LOT OF QUESTIONS.

Another hobby of mine is using Solidworks, so the boat, and every part, will be fully modeled using that program.

Thanks everyone for tuning in, I hope I can share a little bit of the fun with everyone here at OSE.

[Neveryachtz]

BOAT SPECS:

HULL
LOA: 45" (1/12 scale, assuming full size boat is 45')
Overall Beam: 11"
Chine Beam: 10"
Transom Deadrise: 28 degrees
Maximum Deadrise: 43 degrees

POWER
Motor: 2x Leopard 4082-1600
ESC: 2x Hobby Wing SeaKing 180
Battery: 4x 3s Lipo 5000mAh
Servo: HS-5646WP

That's all I have finalized right now. More parts will be filling that list soon.

[Neveryachtz]

I've been researching stepped hulls for months now. There's a lot of interesting threads on thehulltruth.com that have kept me up until 3am debating the do's and don'ts. Supposedly, any boat under 30' won't see much of an improvement from a stepped hull. Not to mention a 4' r/c boat. But that's not stopping me, I'm trying to take what I've learned and scale it down. It's more for principle and education than performance.

Here she is...

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[Neveryachtz]

I really want to stress CONSTRUCTIVE CRITICISM.

If at any point, someone has an idea or notices something off, please let me know. Starting with the hull, and going through every stage of the build.

[Neveryachtz]

First Questions

#1: 25C or 45C batteries?

I need 4 of them. It's a difference of $100 total. Worth it or not? The Leopards say they run 2000W with 3500W burst. At 22.2 Volts that's 90-158 amps. The batteries say they should be discharged at 70% constant rate, so 88 amps for 25C, 158 amps for 45C. I'm not going to be at full throttle the whole time obviously.

Will the 25C suffice, or should I be safe and go 45C?



#2: Rudder options!

I haven't bought the rudder yet. I'm going with a single blade, stuck way out back behind the props. My internet searching has left me with the Speed Master 6 1/4" x 4" backspacing, or the MTC Rudder III 115.

The Speed Master looks kinda plain, and the MTC seems way overbuilt for the hull size. Other rudder options are welcomed too.

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[larryrose11]

Welcome!!
I appreciate your enthusiasm.
Im also an engineer, and have done some design on boats.
Let me start with a word of caution:
Water is quite thick.
Subtle design changes can have a large impact on how the final boat handles and runs.
Catamaran hulls can handle better than monos in general, because they are similar to two deep vee hulls side by side.
RC boats like to flip over, so stability is important. You can compare the Genesis vs Cheetah to demonstrate this. The Cheetah is quite wide. Genesis must slow way down in the turns to prevent flipping
You may be better off starting with a known RC boat hull design, and modifying it.
Choose something common, as the RC boat community favors proven designs, and you would get more feedback.
Something like making a 3d scan of a common hull, and then importing it into Solid Works. You could change the top, and the overall size, but leave the proportions the of the water contact area the same.

A plug can then be made (CNC) and given a surface finish. From there, you can either or vacuum bagging a positive shell as some maker do, or make a mold from the finished plug to achieve a grade A finish, right out of the mold, as is more common.
Should be interesting.

[Fluid]

Welcome to OSE. I've built many stepped hulls, and in spite of what you may have "read" stepped hulls can be a big advantage in R/C boats. In Europe stepped hulls as small as 500mm are raced, and the advantage in their NAVIGA-style racing is that less power is required to run the boat. This means you can achieve the same speed with a stepped hull using lower power or get longer run times - or you obtain higher speeds with the same power. With FE we can over-power a mono enough to negate most of the speed advantage of steps, but step's real advantage in monos is the lower power requirement for the same speed. Just remember that due to the scaling effects of water, the steps must be deeper than on a full sized boat. Good luck with your build.

You will probably be better off with 45C cells. While 25C cells may work okay, they may do this if overstressed:

DSC00028.jpgJim's Nano Fire 3.jpgJim's Nano FIre 2.jpg







.

[NativePaul]

Steps definitely work at model sizes, unstepped bpats are not at all competitive in Naviga racing over here, and we have classed down to Mini Mono for boats smaller than 450mm (under 18"), the steps are very large in comparison to the ones you have drawn there, a single step is the most common by far but there are a few twin step race boats.

A 45" FE boat is pretty ambitious for a first FE project, have you considered scaling it down further? If it was 30" you could use a single motor, ESC, a 4s pack and easily halve the build cost and not have to worry about the price difference between 25c and 45c packs (I would go for 45C if it was me).

sorry about the big/odd size photos, it seems now picassa has turned into google+ it has removed the ability to create 800x600 photos for posting.

ToySport Syncron twinstep hull


Tenshock Mono1 twinstep hull


Not sure what this one is but it is a 1.5 step compromise


On to the single steps now this is the probably the most sucessfull mono in recent years the ETTI Exiga single step hull


The new up and coming contender the Raush Essenze winged single step hull

[grsboats]

Welcome !This is the best place to trade/learn about Fe models...I've been learning tons of important data and will follow this thread with interest as I work with all kind of molds and technics.45C or up is the way to go with Lipo batts with less worries....btw very nice mono's. Gill

[RaceMechaniX]

Neveryahtz,

Welcome to OSE. Since you mentioned you are at Sac State, a great resource is just coming up for you to attend: The electric Nationals are being held at Lake Minden just north of Sacramento running June 4th through the 9th. You can meet a lot of the local boaters and probably see one of the largest varieties of FE boats.

If you don't like either of those rudders systems you can always modify or machine one from scratch in the student machine shop. I'm assuming Sac State has one? BTW, I graduated from Davis and spent most of my time in the student shop working on "G-jobs" for my projects.

Tyler

[grsboats]

try this link..they have nice hardware for big boats ,Gill

http://www.arrowshark.com/

[Neveryachtz]

Glad to see so much feedback already. If only I was this good at making friends in grade school.

Before I even started this project, I went to RC Country Hobbies and talked to the boat guy there. He had the same impression, that I am in over my head with a big twin mono FE built from the ground up.

My inspiration for this build comes from the many memories I have on the water of Fountains, Formulas, Cigarettes and Donzis blasting by me with twin 575 Mercs roaring out the pipes. I could attempt a smaller hull with a single screw and cheaper parts, but that's not going to make me as happy in the end. This is more geared as a scale build than a race build. The finished product will resemble a Outerlimits/Mystic/Fountain more than a dedicated racing mono.

For example, here are 2 threads I have been keeping track of that are a big inspiration.
59-Outerlimits-SV43-Voltaic
54-Bonzi-Fountain-build

Thanks for the pictures and info on the r/c boats with stepped hulls. I didn't know they had such a significant impact on this scale. I will modify mine a bit. I actually started off with ones a lot larger, 0.4" deep, then thought they looked too big so I filled them into the current 0.2".

The hull got it's roots from the Traxxas Spartan. I took about 20 pictures from different angles of the one that belonged to the guy at RC Country. The transom deadrise, and the 3D sketch of the chine all the way up to the bow are as close to the Spartan as I could get without an actual 3D scan. From the number of modified Spartans on the web, I assumed that was a good platform to build off of. Modifications that I made were in the longer strakes, and the addition of steps.

I'd love to hear more specific concerns with the geometry. The hull is still a work in progress and nothing is really set in stone yet.

[Neveryachtz]

Neveryahtz,

Welcome to OSE. Since you mentioned you are at Sac State, a great resource is just coming up for you to attend: The electric Nationals are being held at Lake Minden just north of Sacramento running June 4th through the 9th. You can meet a lot of the local boaters and probably see one of the largest varieties of FE boats.

If you don't like either of those rudders systems you can always modify or machine one from scratch in the student machine shop. I'm assuming Sac State has one? BTW, I graduated from Davis and spent most of my time in the student shop working on "G-jobs" for my projects.

Tyler

Thanks, I will have to check that out. And yeah we have a huge machine shop. The guy that runs it is a bit of a harda$$ though, you can't just walk in the door and fire up the lathe. But it's worth looking into.

[Rocstar]

Glad to see so much feedback already. If only I was this good at making friends in grade school.

For example, here are 2 threads I have been keeping track of that are a big inspiration.
59-Outerlimits-SV43-Voltaic
54-Bonzi-Fountain-build

Your grade school friends weren't as cool as we are.
Awesome project, I'm in!

[Neveryachtz]

Loose Goose hull prototype #2.

The steps are bigger, now 4% of chine length at 0.4" deep. Also, the deadrise at the stern was decreased to 24 degrees for a more stable straight line ride pad. I worked the deadrise decrease into the steps, so the bow is still as sharp as it was in proto #1.

The hardware on the transom is in there tight. I will have to buy the T bracket for the rudder because the standard L bracket wouldn't fit. This is where laying the boat out in CAD really helps. I decided on the Speed Master rudder due to it's price, size, and simplicity.

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