Heinkel 31 Float Plane
 

This is from Ed Westwood's plans, published in RCM, Feb 95. The 31 was the last of a series of low wing floaters designed by Ernst Heinkel in the '20s and 30s. Ed says it's easy to fly and quite aerobatic, which is why I chose to build it after having the plans for at least two years. (Didn't have all the requisite skills until recently.)

He used a geared Cobalt 035, but says you can also use a .10, so I've got it set up for my LA. If it needs more punch, a Magnum .15 fits on the same holes.

Had to use a wing jig for the wing and all tail surfaces, due to mostly symmetrical airfoils. I built wing, stab and fin in one piece, and then sawed the ailerons, elevator and rudder off. Never did that before. Kinda fun. Fuse is mostly sticks, and very tedious, but interesting to build.

Fuse is not quite completely framed up, but that and the floats should be finished next week.

Should have her done in time to test fly as the ice retreats from Lake Cadillac.

RE: Heinkel 31 Float Plane
 

It looks very similar to the Danish HM II, which was a Heinkel He.8 seaplane designed for the Danes. This one is plan pl-729 from 6/78. 63 inch span. A buddy and I were thinking of scaling it up to .90/1.20 size with some foam core floats.

Both planes appear to have good moments, nice long fuselage, so they would more than likely be very aerobatic, even with floats. Here's the photo from the RCM plan page. The Danish planes were painted red, as in the photo, silver and camouflage.

RE: Heinkel 31 Float Plane
 

Ed:

I'm glad you responded, as I had forgotten about Westwood's reference to the HE-II in his instruction sheet. The the 31 and the II are part of the same series. I'm still searching around for information on the series, but there doesn't seem to be much available.

I'd be willing to bet, even though I haven't flown mine yet, that any version of this bird would be a good flyer. If you guys scale one up, I'd like to get a copy of the plans, etc.

In any event, I think I might get the HE II plans after my 31 is finished. I live about 3 miles from a good size lake that has plenty of room for flying.

Regards,

Bob Hunt
Cadillac, MI
AMA 748101

RE: Heinkel 31 Float Plane
 

Here she is, all done and after the first flight. She's wicked fast, a real Schneider Cup contender.

The plans show the float steps behind the CG, which is how I built it, and of course it wouldn't get up on plane. Moved em about 3/4" forward and that took care of that. Then the OS 10 had about enough power to turn it into a very weird looking power boat. Out came the 10, in went the Magnum 15, and wow, does it go. Very glad I made it orange, cause it gets far away in a hurry. Water handling and the touchdown were really smooth. Next takeoff should be, too, now that I have the trims.

Can't wait to slow it down and play with it a little. Great fun flyer, as it fits in the back of my Malibu without taking it apart. It takes about 10 seconds to install 2 oz of fuel, and away we go. The Mag 15 is one of the easiest starting engines I've ever owned.

RE: Heinkel 31 Float Plane
 

Now that the Heinkel is debugged and named ("Seedrache") I'm going to start on a Herr Aqua Star.

I just got done looking at all the posts on that one, and have a few thoughts:

1. The plans show the CG right over the step on the hull. Everything I've experienced to date with ROW says this is trouble. It causes difficulty getting on plane, and more difficulty in rotating for takeoff. I'm going to relocate the step former 1/4" forward.

2. It's a deep V hull. I'm a power boater, have been for 20+ years. I have a 26' foot Wellcraft cruiser, and it has a deep V hull. It takes a LOT of power to get it up on plane, and without trim tabs to hold the bow down, it won't stay on plane at a comfortable cruising speed. The floats on the little Heinkel have nice, FLAT bottoms, and even when it was underpowered, it jumped right up on plane. I'm going to modify the Aqua Star so that the hull has a flat bottom. Shouldn't be that difficult.

3. I will add the chine rails as suggested in the mod sheet, and start out with the engine at 0 degrees thrust.

RE: Heinkel 31 Float Plane
 

Photos of our nearly finished Danish HM II (Heinkel He-8) float plane from RCM plans.

Power: Thunder Tiger .46 Pro. A muffler extension was needed to clear the fuselage & wing.

The plane is finished in red-orange as they were painted for the 6-year, Greenland photo-mapping endeavor. The bottom is silver gray. Fire red Ultracote covering and paint was used.

The floats are scale, squared off on front, flat bottom forward of the step, wide V rear of the step. The floats are built up from balsa, covered with fiberglass cloth and polyurethane and finished with fire red (top) and silver (bottom) Ultracote paint. The struts are close to scale. The inner sections are wire, silver soldered and covered with balsa. The outer struts from the floats to the outboard section of the wing are not load bearing and are made from streamlined tubing painted silver.

We had planned on pilots and a dummy radial engine, but have found that our usual source, Williams Brothers, have retired and closed up. My buddy, who built the plane, says he will get on making dummy cylinders in the future.

Next weekend, if the winds are nice, we'll test.

WW II & Korean war Marine aviator, Carl "Flaps" Laffert in the photo is the builder.

RE: Heinkel 31 Float Plane
 

More photos

RE: Heinkel 31 Float Plane
 

Even more photos

RE: Heinkel 31 Float Plane
 

That is one pretty airplane.

I heard, somewhere on this forum, that Williams Bros sold all their dies and stuff to another outfit that intends to have it all back in production soon. It might have been in the scale area.

Bob Hunt

PS The Heinkel is turning out to be a real hoot. With the Magnum 15, it has a really good rate of climb so can be flown from very small lakes (ponds, really) that are surrounded by trees. It's also responsive enough to thread the approaches between several trees.

RE: Heinkel 31 Float Plane
 

Here are some photos of the Danish HM II (Heinkel He-8) on test flight day. Flew just fine. Water handling is excellent.

Could use more power. It flies scalish, more like a sport plane, but without a lot of vertical. I think all the scale struts add a lot of drag so I need a bigger engine to compensate. Right now we have a TT .46Pro in it, but I have an older OS .61SF that I can use. I am going to leave it just like it is until after we go to the Winchester, TN, float meet on June 4th.

RE: Heinkel 31 Float Plane
 

Ed:

That is one nice looking bird.

After all the messing about I had to do to get one flying boat right (see my thread on the Herr Aqua Star), I think I'm sold on low wing float planes. I might try one like yours next time.

Bob

Believe the He-8 (Danish HM-II) and the He-31 were same basic airframe. Primary diff in the engines: He-8 with the Brit Armstrong Siddeley Jaguar 14-cylinder twin-row radial, and the later, one-off, He-31 with its US Packard 3A-2500 12 cylinder liquid-cooled mill. Attached are additional scans of dejlig Karen Riddell and the HM-II. An early model was built from the RCM plans by professional builder-pilot Dick Hansen and was campaigned quite successfully in the NW seaplane meets. Articles were published in 4 countries/3 languages.
http://www.rcuniverse.com/forum/atta...mentid=1968586http://www.rcuniverse.com/forum/atta...mentid=1968587