Scratch built sponson/rigger micro - RC Groups
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Jan 20, 2016, 11:45 PM
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Brake Weight's Avatar
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Scratch built sponson/rigger micro


I wanted a small boat and got bored. So I did some light research and decided to build a micro Predator Outrigger. I downloaded the .pdf and took that to my local UPS store. I had them print off a few copies onto card stock paper in the 12x18" size. This makes for a decently small boat. I cut out all the pieces and then laid that onto some 3/32" balsa. This was the smallest size I could get due to my hobby shop being closed for 2 weeks. He's back open and I have some 1/64" ply for Version 2.0.

I know this boat will be heavy and probably won't work without a ridiculous amount of work...or not at all. But it'll be a learning experience and that's what matters.
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Jan 20, 2016, 11:57 PM
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Brake Weight's Avatar

Scratch built sponson/rigger micro


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I bought a carbon arrow as the blueprints calls for but not thinking of the scaled down size of mine. So I scoured the house and found a little thing from some old mini blinds. It was as light as the arrow and slightly smaller OD. So I used that. I have some small carbon fiber rods coming for the next attempt.
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Instead of making two small hatches, I cut one large one. I have attached a lip on the forward and aft of the hatch. I have a round dowel ball I will use as a handle to bow the hatch slightly so that it fits in as tight as possible. I'll try to decorate the ball like a helmet. Then all I'll need is a little bit of clear scotch tape and it should be sealed up.
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I carved a nose out of pine tonight and it's in the process of drying. Tomorrow I'll sand it all down smooth and attempt the lacquer and tissue paper covering.
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All my hardware is coming from GearBest and Banggood. I ordered way too much and will use what fits best. Im having difficulty figuring out a flex shaft setup. This is another reason as to why I didn't put a motor plate and I made one big hatch. I'll glue in a motor plate when I determine where it needs to be. Using the ply next time I won't be able to make the hatch as big, but I'll know what spacing I'll need.


Any thoughts, comments, heckles? I'm open to most all as this is my first boat. I haven't a clue as to the weight.

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Jan 21, 2016, 03:18 PM
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Brake Weight's Avatar
Lacquer and tissue paper is a no go. I thinned some 2 part epoxy and painted that on. It'll need sanding and a second coat before I paint. It does float and no leaks from the hull.

Holding up a 540. So it may work after all.
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Jan 24, 2016, 07:13 PM
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Brake Weight's Avatar

Scratch built sponson/rigger micro


The epoxy I used was a 5 minute epoxy and didn't want to thin out very well before setting up. I was able to get it lumpily applied and sanded down smooth. Although I had to let it cute for over a day. While sanding it before fully cured some of the large epoxy runs wanted to peel up. I got it feathered in as best I could and it looks...not the greatest. But it'll do for a first timer. I had to use some filler on one of the sponsons as one cut of the wood didn't want to cooperate for me.



Jan 24, 2016, 07:21 PM
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Brake Weight's Avatar
Jan 25, 2016, 03:56 AM
Boaters are nice people.
Hi Brake weight,

Can you shoe horn one of the watercooled motors in from this series?:
http://www.hobbyking.com/hobbyking/s...00kv_300w.html

These outrunners have gobs of torque for their size.

Something that caught my eye; the trailing edges of yout sponsons don't look sharp, such a ragged edge will cause drag, affecting the running attitude.

Regards, Jan.
Jan 25, 2016, 10:51 AM
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Brake Weight's Avatar
I don't think I'd be able to get that motor into the hull. I only have an 18mm opening, but it's 17cm long. I could squeeze in a motor with a can or water jacket into it that's bigger than 18mm, but then there's the amount of space inside. Directly behind the riggers I have a space of 25x25mm. So motor space is severely limited in every aspect.

This boat is my first boat ever and is purely a test boat for me. A test in building and a test in powering. It doesn't weigh much due to it's size, and the amount it can carry is also limited. I've looked online for something that may work for a motor and ended up with at least 40 tabs open on my browser. When I finished eliminating them because of size or weight I ended up with this one: http://www.banggood.com/AX-19g-1806N...p-1023681.html
I'll try to make/retrofit some sort of blades to push air through it as it spins. I have a small non cooled brushless ESC that I can put some small aluminum tubing around and heatshrink down tight to cool it somewhat.

Basically, I just want to see this get up out of the water as it's supposed to and go in a straight line.
Last edited by Brake Weight; Jan 25, 2016 at 10:56 AM.
Jan 25, 2016, 11:45 AM
Boaters are nice people.
Hi BW,

As it'll fit, give it a go; these outrunners run relatively cool, so you should get away without a cooling fan.
The ESC should be able to handle the motor without cooling if it's rated 10-15A.

Make the next mini rigger with a wider tub to make life easier for yourself.

Keep us posted!

Regards, Jan.
Jan 25, 2016, 06:50 PM
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Brake Weight's Avatar
I've got a couple of brushed 180 motors that'll fit if I turn them sideways. None of my running gear has made it from China and I got an email saying some of the pieces on my order are out of stock. So it looks like it'll be another 3-4 weeks waiting on that.

I'll try to cobble together something out of some aluminum angle I have and a bicycle spoke. I can tap some threads onto the rod and pick up whatever prop the hobby shop here has. They have only three to choose from and they're all Horizon replacement props.
Jan 26, 2016, 02:51 PM
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Brake Weight's Avatar

Scratch built sponson/rigger micro


I found a prop, may not work, but it screws onto a pushrod and that'll be my shaft. prb282024


And I found a BL outrunner @ 3900kV, that according to measurements will fit. I'll find out when I get home.
EFLH1516

Picked up some .055" piano wire and some 3/32" brass tubing for version 2.0. I'll use the .055 for a pushrod also.
Last edited by Brake Weight; Jan 26, 2016 at 02:57 PM.
Jan 26, 2016, 05:11 PM
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Brake Weight's Avatar
Jan 26, 2016, 06:03 PM
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Brake Weight's Avatar
I got all the electronics stuffed into it. The motor is almost too big to fit in the hull. I actually split the wood getting it in/out.

I'm trying to keep some weight up front and have enough room to manipulate the motor angle. It'll be a straight shaft using the pushrod and I'll try to fab up a coupling using some aluminum round stock. I'll chuck it into my drill press and mill a hole through it. Then hopefully press fit it on the motor and shaft.

Since this won't have a flex shaft and I'm deviating from the Predator plans, should I put the shaft/prop at the lowest angle possible? And how far back should the prop be? It would be simplest for me to just put it through the back of the hull and not the bottom since I didn't find anything to sleeve it with at the hobby shop. I still have to fab up a rudder, too.



I'll sticky tape the Rx to the top of the hull. The servo will be glued to the bottom of the hull with the long horn pointing up and the .055 wire running down the top corner of the hull to the aft. I'll use the 3/32" brass tuning to sleeve the wire though the hull and hopefully act as a water barrier and friction reducer. The batteries used will be sticky taped to the top of the servo. The motor will be mounted to a loosely glued piece of 3/32" balsa. It's so big I could probably hold it in with some double sided tape. The ESC will be towards the back and stickied to the side of the hull. If I put the shaft straight out the back and as low as I can I could use some teflon to act as a bushing and hopefully seal out water. I have an O-ring kit with several that fit it also. I've even considered making an old school leather bushing soaked in oil.


Any thoughts on the shaft and placement?
Jan 28, 2016, 01:48 AM
Just Plane Nutts
AirDOGGe's Avatar
Do you think a 2.3mm diameter flex shaft running in an aluminum stuffing tube and fitted with a plastic or aluminum CNC'd prop would be a small enough and light enough drive assembly for this project?

http://www.hobbyking.com/hobbyking/s...aran_Boat.html
Last edited by AirDOGGe; Jan 28, 2016 at 01:57 AM.
Jan 28, 2016, 07:03 AM
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Brake Weight's Avatar
It may work. I'll order one of those, too. I just put the straight shaft in last night.

I tried to make a coupler for it out of 1/4" aluminum rod stock. Every time I'd start my hole the bit would walk off center slightly. I'd cut about 20mm off the rod stock and chuck that in my drill press. I don't have anything to hold a bit to look up upwards so I held it with some locking pliers. Each time the bit would make contact it'd walk off. I have access to a big lathe at work and I'm going to try to spin up a bunch of them with a small ID. This way I can put an exact size on them at home. Also drill a hole through them and tap it to m3 threads and then it'd clamp down like a prop saver on each shaft.

All bits bits were back ordered from Gearbest so I placed an order at Banggood, too. I've got a flex shaft, strut, and rudder combo on eBay I'm looking at getting, too. Hopefully I can put a piano wire in this little boat and my next one will run the flex shaft and proper bits.
Jan 28, 2016, 07:16 AM
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Brake Weight's Avatar

Scratch built sponson/rigger micro


I tried to make this coupler out of the little nut off of a bicycle spoke. The motor shaft is splined and I pressed that side on against my work bench. The prop side shaft is a pushrod and hard steel. I lightly filed it down to press fit and glue into place. I put a drop of glue in it then pressed/wedged it in as far as I could then went to bed. Some point before the glue cured, or maybe the glue itself, it became dislodged and is slightly off center.






I'm starting to think this boat will never run. I'm planning out the next one in my head now and it'll be a lot better and simpler.


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