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Old Sep 27, 2014, 10:38 AM
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United States, MN, Albert Lea
Joined Feb 2012
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Pondhopper - Seaplane outerzone foamie conversion - with plans

I've been having a lot of fun using Sketchup to convert some of the Outerzone website plans over to Dollar Tree Foam. I've been looking for a fairly simple pusher seaplane and came across this Ken Willard design:

Pondhopper

I converted the PDF plan to a BMP file and loaded it into Sketchup. I've got the prototype drawn up and started building the wing.

The original is a 56" span but I've shrunk it down to 40". Construction will be DTF with mostly paper off, covered with colored packing tape. Wing will be a modified Armin type with some dihedral for stability. I've come up with a fairly simple method for a balsa/carbon composite spar with dihedral built in. Wing will be removable and held on with rubber bands.

As designed it should fit up to a 7" prop. I've got a couple different bell-type outrunner motors from Headsup Hobby to try, haven't picked which one to try yet. 3S battery, 1300-1800 mah.

Planning to do a build log and I've already got started on the wing. Any comments or suggestions are welcome. I'll be tweaking some things and working a few details out as I go. If everything works out and she flies I'll post some plans if anyone is interested.

Steve


10/13/2014 - Plans added

This project seems to be coming together pretty well so I will try to upload the plans in PDF format. A bit about how I do the plans - I tile them out within Sketchup using a 7.5" x 10" dashed line border and then print using CutePDF. When you print the PDF this border should match those measurements as a way of confirming the proper size. The sheets should fit nicely on standard US 8 1/2 x 11" paper.

Instead of tiling and taping into one big sheet I like to break the parts into groups of 2 or 3 pages. I cut templates and then cut the parts as I work along the build so I find the smaller groupings of parts a little easier to manage.

I've added a screen capture with an overview of the parts layout so you'll know how the PDF sheets tape together. Hopefully this makes sense. Later on when I have time I can try to rearrange things into a single sheet if people prefer. For now though if anyone wants to build one of these this should get you started.


10/15/14 Added an untiled version of the plan which prints onto a 20" x 30" sheet. Where parts have duplicates such as the 2 fuse sides I only included one on the layout.
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Last edited by Heddon125; Oct 15, 2014 at 11:40 PM. Reason: added plans
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Old Sep 27, 2014, 12:11 PM
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United States, CA, Sacramento
Joined Feb 2010
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Nice! looking forward to seeing this come together.
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Old Sep 27, 2014, 07:30 PM
skumgummi dave
Gresham, OR.
Joined Mar 2004
1,879 Posts
Good looking seaplane. Looking forward to seeing your simple method for a balsa/carbon composite spar with dihedral built in.

Dave-
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Old Sep 28, 2014, 02:20 AM
If it flies, I can crash it.
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Cleveland, Ohio, United States
Joined Nov 2003
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Looks good.
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Old Sep 28, 2014, 07:03 AM
Marty Petri Sr.
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Thailand, Uttaradit, Bo Thong
Joined Jun 2007
768 Posts
Happy to see another Sketchup user hard at work. Looking forward to your progress.

Marty
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Old Sep 29, 2014, 09:19 AM
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United States, MN, Albert Lea
Joined Feb 2012
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For the wing I've used the a minor variation on the experimental airlines/Armin wing. The basic technique is well documented in the foamboard scratchbuild university thread sticky.

My variations:

- Instead of sanding the mating bevel on the bottom inside TE surface I sand it on the top. The surfaces that will become the ailerons extend from the bottom surface instead of the top. It makes it easier to fold the wing over.

- I pull the paper off the foamboard and recover the top and bottom with colored packing tape.

- I use 3m 77 to stick things together instead of hot melt glue.

- I cut the ailerons off and reattach later using 3m Blenderm tape. Easier to bevel them for the hinge joint that way.

-I use a straightedge and the edge of a sanding sponge to sand a groove at the desired LE fold.

Measurements for the wing layup are below.

For the spar, I used a 3/8" square x 36" balsa stick. I built a simple jig with 2 pieces of lumber about 2" x 20" x 1/2" think (exact dimensions don't matter). The ends of these pieces are beveled and hinged end to end with a tape style hinge and covered in packing tape then waxed. You can set this on a flat surface and raise 1 end to the desired dihedral angle.

I picked up a spool remnant of 12k carbon tow from CST. $3 gets you about .1 lb of tow which is about 180 feet, enough for plenty of spars. Cut the balsa stick in the middle, sand the desired dihedral bevel in the ends.

I laid the bottom first. Set 2 layers of the tow on the bottom of the spar with epoxy, then set that bottom down on the jig which is laid flat at first. Then raise the jig to the desired dihedral and block it up in place. Then paint epoxy on the top of the spar and lay the top layers of tow. I put 3 layers on the top of the spar but since the spar needs to be strongest on top center I only extended the top layer of tow to cover about 1/3 of the span on each side. I added a short piece of tow on the front & back to cover the dihedral joint.

Finished spar weighs 16 grams.

Hope that description makes sense. I didn't take pics of the sparmaking process but plan on building more and I can add that in a separate post.
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Old Sep 29, 2014, 12:17 PM
skumgummi dave
Gresham, OR.
Joined Mar 2004
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Cool spar info! Thanks.

Dave-
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Old Sep 29, 2014, 04:04 PM
A Day @ a Time - Matt. 6:25-34
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North AL, USA
Joined Nov 2009
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Nice, even though I don't have a pond, with sufficient power she should do grass nicely...
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Old Sep 30, 2014, 04:16 PM
Slipping the Surly Bonds
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Attica, MI
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Good looking!

Ken
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Old Sep 30, 2014, 09:32 PM
flyin' fool
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Vancouver Island, Canada
Joined Jul 2003
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Ken Willard..............a pioneer and legend in simple great flying models.

Worth a read to know the history of model aviation..................................... https://www.modelaircraft.org/files/WillardKen.pdf
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Old Sep 30, 2014, 09:46 PM
flyin' fool
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Vancouver Island, Canada
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I float fly every Monday all year round and need one of these. It's a perfect size at 40 inches and have a stash of MPF needing a home. Hurry with the plan Steve.
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Old Oct 01, 2014, 05:56 AM
Slipping the Surly Bonds
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Attica, MI
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I really love these flying boat type seaplanes. Will build one of these for sure to add to my SeaBB 42 and Mermaid fleet.

Ken
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Old Oct 01, 2014, 01:35 PM
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United States, MN, Albert Lea
Joined Feb 2012
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Goldguy - Thanks for the link to the Ken Willard bio - I see his name on a lot of old plans all the time but didn't know much about him beyond that. Hope my efforts can do justice by him.

I'm up to my neck in a couple other house projects that take priority so this build is going to be a bit slower than I'd like. I'm trying to figure out what I'm going to say to the wife when I emerge from the basement with a brand new plane while the other projects aren't done yet.

The lake usually doesn't freeze until mid to late November so there's time yet...going to get the wingtip floats done and the motor pylon next. I think this one should be good on snow too so there's always that.

Steve
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Old Oct 03, 2014, 01:06 PM
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United States, MN, Albert Lea
Joined Feb 2012
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Got the floats done...deviated from the plan in that rather than solid blocks like on the plan I built them laminated.

Used 3m 77 to glue them together. I love that stuff to laminate parts - except for the gummy overspray. Mask off the areas you don't want gummed up with a bit of masking tape. I haven't had any problems melting the foam as long as you hold the can back about 12 inches. Medium spray to both parts and stick together.

I added a wider strip of foam on the bottom so it's more like a ski than a float. I think it should work though. Covered the bottom with a piece of blue packing tape. A light spritz of 3m 77 helps it stick.
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Old Oct 03, 2014, 01:35 PM
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United States, MN, Albert Lea
Joined Feb 2012
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OK next step is the motor pylon. My idea is a ply/foam sandwich with a channel for wires to the ESC which would velcro to the underside of the wing. Ply tabs will be buried through top & bottom wing surfaces and then epoxied in. I was thinking I would be able to easily swap out different motors to test but the connectors will be buried. I can make extensions but don't have spare stuff on hand, although could cannibalize connectors from another ESC and motor.

I have the emax CF2805 1300kv from Headsup. Their prop data shows 15 oz thrust, 8 amps with a 3s pack and 7x4 prop.

I also have a heavier emax CF2812 1700kv. This gives 23 oz thrust.

I have no idea what this plane is going to weigh, hopefully not much more than 16 oz. but that's just a guess. Wing surface area is going to be about 290 sq inches.

I'm hoping for a nice tame flyer and maybe use as a trainer for my nephew - thinking the lighter motor will be adequate? Want to make sure it will rise off water though. Anyone have thoughts?
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