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Apr 02, 2013, 02:53 PM
Letís eschew obfuscation.
scott swanson's Avatar
Thread OP
Build Log

SlowBoat foamy seaplane with plans & video

Here are plans, construction article, and videos of a foamy seaplane I designed last year and have put numerous flights on since. I have been very pleased with both the flying and water handling characteristics, and the guys who have seen it fly at the Electric ‘Nall and HHAEF have said good things about it. The model is adept at slow flight, has some 3D capabilities, and can be flown in quite restricted areas. A favorite trick is to fly slow figure 8's while dragging a wingtip in the water. It will take off in about 1 plane length from either water or grass. Though the thrust ratio is considerably more than 1:1, the high thrust line does not produce any noticeable throttle-induced pitch changes. It’s built of 6mm Depron.

The design is reflective of the Taylor Coot and the Seabee, with some construction ideas borrowed from the Polaris. There is also a strong resemblance to the Mermaid in this forum, but I was unaware of either the prototype or the model Mermaid until a few days ago.

The specs are:

Wing Span: 39 in.
Wing Area: 383 sq. in.
Flying Weight: 15 oz.
Motor: Himax HC2812-0850, 150W
Battery: Thunder Power 1350mA 3S LiPo
Prop: APC 10 x 4.7 SF
Servos: 4 Futaba S3114
Speed Control: Castle Thunderbird 18
BEC: Dimension Engineering ParkBEC 1.25A
Receiver: Orange RX 8 chan (Futaba FASST compatible)

See the files below for free plans and a construction article.

Here are a couple of excellent videos by Austinaeronautics2 of a plane he built from the plans.
Edit 11/14/13: The third video was made by the same videographer of me flying at the 2013 eWeek at Triple Tree Aerodrome.
Edit 11/1/14: I made the fourth video with an on-board camera. See post #915 for more info.

SlowBoat at the Lake video:
SlowBoat at the lake (3 min 33 sec)

Showboating the SlowBoat video:
Showboating the SlowBoat (5 min 8 sec)

Extreme R/C float flying video:
Extreme R/C float flying (2 min 8 sec)

Playing in the backyard with a camera on a SlowBoat:
SlowBoat in Backyard (2 min 30 sec)

Edit 7/4/13 & 10/4/13:
Part dimensions are given in the plans and construction article, and I cut my foam directly from the measurements. If you would prefer to work from a full size drawing, I suggest you print the cut pattern page of the drawing at 5X size. Either take this to Staples or let your printer software tile it (my printer does this if I select "500%" and "Poster" in the print options). After you have taped it together, spot check the dimensions against the original plans and make sure they match; it will be a lot easier to fix in paper than in foam. Some guys make templates of poster board and trace onto the foam.

Edit 1/18/16:
Birdofplay posted Hoosier Cutout Service's cutting files as 1:1 PDF's in Post #1445, complete with the tab in slot feature. Thanks, Bob

Edit 10/4/13 & 1/19/14:
Now you can skip the foam cutting step altogether and let Hoosier Cutout Service do the hard part. Go to for more info.

Edit 11/14/13 & 1/13/15:
I built another SlowBoat using what I learned from the first one and from the posts here. My updates (including updates on CG and right thrust angle) and a few construction photos are given in Post#303

Edit 1/19/14:
The files now reside here at RCGroups.

Edit 6/1/17:
To see more build photos and a different way of doing some things, check out Pecanpatch's build log at

Last edited by scott swanson; Jun 01, 2017 at 04:55 PM. Reason: point to birdofplay's files
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Apr 02, 2013, 03:23 PM
Crazy Foamie Builder
JettaManDan's Avatar
very cool...may have to build one!
Apr 02, 2013, 03:41 PM
skumgummi dave
Very nice! Good flier...

Apr 02, 2013, 07:56 PM
Registered User
That is a very nice flying plane. I really think I need to build one soon. Thanks for sharing.
Apr 03, 2013, 07:46 PM
Letís eschew obfuscation.
scott swanson's Avatar
Thread OP
Dan, Dave, and Russ,

Thanks for the kind words, guys! Keep me in the loop if you build one.

Hey, I've just doubled my number of posts in RCGroups. How many of you can do that with one post?

Apr 03, 2013, 08:25 PM
Steve 0's Avatar
either my PC is goofy or I'm reading this right. You joined RCG 4 years ago and this is your FIRST post with a follow up second in the same thread Amazing enough in and of itself.

That said- your slowboat is certainly a well behaved plane on land, sea and air. maybe SEAL 1 would be a nickname for it.

Great series of touch and goes.

Apr 04, 2013, 03:03 PM
gatorb8's Avatar
Nice job!
Apr 04, 2013, 03:51 PM
Registered User
Nice plane. Thanks for sharing.
Apr 04, 2013, 07:54 PM
Registered User
Got the parts cut out. I will start on building in a couple of days. Thanks for the great plans and build guide Scott.
Apr 06, 2013, 07:50 PM
Letís eschew obfuscation.
scott swanson's Avatar
Thread OP

I'm excited to have someone else build my design. It looks like you have already done the hard part.

A few questions:
1) What type of foam are you using?
2) It looks like the ailerons are still attached to the wings. Is this some super building technique I am unaware of, or just procrastination on your part?
3) Do you have to use a special T-square to get accurate layout using the round table edge?

Apr 07, 2013, 01:59 AM
This helicopter smells funny
scottyvisco's Avatar
Hi Scott I saw your video of the slowboat and thought that will be great at my local lake, I have redrawn it up in sketchup for my cnc router and have started cutting it out ,I had to cut the fuselage in half to fit it on the router though cheers Scott.
Apr 07, 2013, 08:47 PM
Registered User
Scott...I use a speed square and yardstick mostly for layout. I am using fanfold foam on my build. I didn't cut the ailerons off yet. just finished the cut out and wanted to get a pic befor I had to get back in from the shop. Hopefully I will get more work on it tomorrow. It looks like it will go together fairly quick. Thanks for the good design.
Apr 10, 2013, 07:04 PM
Registered User
flashsolutions's Avatar
Was looking for something different to build. Saw your slowboat and decided it was just the ticket.

I am out of the good stuff, so I am building this one from FFF using two sheets.

I too have a CNC machine, so I worked it up in Sketchup and cut it out. Attached is my Sketchup File for those who have CNC machines.

I added a panel for the servos (not in sketchup yet) and started the build a couple days ago. It is coming along nicely.

Here are pics so far. Will update progress when there is more to show.
Last edited by flashsolutions; Apr 10, 2013 at 07:09 PM. Reason: add sketchup file
Apr 11, 2013, 05:05 PM
Registered User
Got it done. It is windy now so no maiden yet. Mine came out at 14.7oz. I am running an E-Max 2822-1200 motor with a 9x3.8 apc prop and a 20amp HK esc. It balances with a 1000ma 3s lipo in the nose.
Apr 11, 2013, 08:20 PM
Registered User
The wind finally laid down right at dusk so I gave it a maiden in the low light. It flies GREAT!!! I didn't get to do much because it was hard to see but I did get a few loops and rolls in. It took off at just under half throttle and just slowly cruised around at 1/4 throttle. Unlimited vertical at just under 3/4 throttle. I can't wait to get another flight in. I will get a video on the next flight. Thanks for the awesome plane design Scott.

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