3394 - Design Ideas

08-08-2008, 06:01 AM

Jim Small | 3394 - Design Ideas

Hi All,

Jim Small has some ideas that he would like to share with the membership. I will include his email with his thoughts. His email has two images which I will include in this and the next post.

Thank you Jim for getting the discussion started. Regards, John

From Jim Small

email: Dr.JimSmall@comcast.net

Subject: Extended Wing - Discussion


There are two performance features of the Seawind that I would like to change. (1) We have a fairly limited useable load. (2) The landing speed is rather high for a seaplane. (I am thinking about rough water.) An extended wing would help both issues. The Seawind wing is straight, not tapered. It would not be too difficult to add a straight extension between the present wingtip and the sponson.

Attached are two cartoons which show the concept. The idea is to extend the wing by just the length of the ailerons. Some of the projected performance numbers are compared to a Cessna 182RG, which I am currently highly privileged to fly on occasion. It looks like a wing extension could allow us to takeoff and land with 15% lower speeds and 33% lower kinetic energy. If we assume (conservatively) that the additional structure weighs 200 lbs, the useful load still would increase by about 800 lbs over the Standard Seawind. The glide performance and fuel economy would probably also improve.

Note: The longer wing will not require taller sponsons. When the Seawind sits on calm water with one sponson touching, the hull tilt is about 3 degrees, same as the wing dihedral. The lower wing is substantially parallel to the water surface. An extended wing can use the standard sponson.

Any comments or other insight? - Jim, Tucson, AZ

08-17-2008, 06:12 AM

Doug Fir | 3401

Jim, Good to see you are considering ways to improve the airplane. Before someone holds up "Da Book" let me make an observation that there is no product or system on this planet that couldn't benefit from some improvement in efficiency. For our plane, less wing loading is a good thing for the reasons you mentioned but such an alteration would entail reviewing the stress paths on the wing spar, the rear wing attach points and other control surface effectiveness. One design point that gives Seawind it's 'Gee Whiz' look is the wing tip sponson. I like the look however, reason and prior art dating back to the 1930s have shown that wing pontoons are better placed farther inboard. The reason is simple physics. IE. When a large force (water), is applied on the extreme end of a long lever - (the wing), it reacts directly with the large flywheel (the prop) that is producing gyroscopic forces. Simply said cartwheel time if the plane is near flying speeds. It will never happen to me? I certainly hope not. Dean Rickerson living down in Alaska, in my opinion had the guts to do it right and he has been noticeably missing from our discussions. To bad because he has the talent, time and experience in numerous flying boats to know what he is doing. Foldable pontoons was his answer. Slick, beautiful, functional and placed right in the location needed. Draggy? Probably a bit on water landing approaches, but so what? They fold up quickly when not desired and the bottom of the wing becomes clean. Eliminating the wing tip sponsons allows that area of the wing to be better utilized for lift in flight. This translates to higher flight levels if you are interested in those altitudes. Yes we lose some ground effect of the Sponson Horner type wing tips but perhaps that can be compensated for by the use of bat tips which are less draggy at high speeds. Dean`s wing was extended straight out a wee bit further then the original wing span - I believe the figure was 2 foot 2" per side. Someone please correct me if I am wrong on this measurement. This won`t bring the wing loading down to that of a C-182 but there are several points to remember. The SeaWind was orginally slated at 3200 lbs gross. Then 3400, and now 3600lbs. And yes we have another guy with true grit up in Aussie flying at over 4300 lbs. gross. Some C-182s set-up for across Pacific flights can sometimes be 30% over gross and 25% over gross is common with world rounders. Beside lengthening the wing, the only other approach is to search for ways to lighten the plane up. Jim please send me your MIT email address again. Cheers Doug

12-03-2008, 06:59 PM

Mike | Hummmmmmmm....I wonder

In re-posting I was wondering what would be needed for the folding section. I beleive the corsair had this type of arangement. Would this work as well if the alierons were left where they are?

03-09-2009, 06:07 PM

Dean | extended wings

jim, I extended mine by 2 1/4 feet each side and retracted the sponsons, outward and up into the extended tips. my stall speeds are close to 60 mph without a harsh break without power. With power i can get it close to 50, but the nose angle is too high to get into the water smoothly.

03-30-2009, 01:30 PM

Jim Small


Those are very interesting comments. I am currently thinking about extending the wings about 3 ft on each side. Did you also increase the flap span? - Jim

04-01-2009, 07:23 PM

Jim Small

Mike, I had some ideas about a manual folding arrangement that could be done after engine shutdown. A 10-ft extension is a pretty large change in design. At the moment, I am thinking about adding 3-ft to each tip without folding.

04-01-2009, 07:26 PM

Jim Small

Mike, One more thought. For each increase in wingspan by 1-ft, you get about 100 lbs increase in gross weight for the same max wing loading.

04-01-2009, 07:35 PM


600 lbs isn't shabby. Six more feet, humm, I don't know if it will fit in the hanger. At that point might just have enough fuel for around the world without stopping.

Anyway, really good ideas. I am interested in what Dean did with folding the sponsons up into the wings.

I have also thought about some type of retractable hydro-foils

04-04-2009, 02:53 PM

Jim Small

I would like to try hydrofoils after I get flying. I think they could give much better rough water performance. But first, I have to fly. That is probably two years away for me. Jim

04-04-2009, 02:57 PM


I had given some thought to folding hydrofoils on the wheels. Just a thought.

PS - How bout a bow thruster using the hyd pump. to move the bow around......

06-05-2011, 11:02 PM

Rusty | Removable Wing Tips.

One of the earliest kit builders, Paul Array, had the cartwheel problem--perhaps there was no tank equalizer. He mounted flat plates flush with the planing surfaces of the bottom starting at the widest point and extending straight back to the rear. It stops the tendency to suck down due to the taper, planing instead.

I once heard from Craig Easter, I think, that Dean Rickerson did the folding tip floats in order to avoid the little icebergs floating around in some of the lakes. It must be hard to watch your clearances three places at once at 70 mph.

Anybody thinking about tip floats as aux. fuel tanks? Never get out of a spin, but might get from California to Oshkosh nonstop?

Has anyone some thoughts on how attach removable sponsons, I.E, how well? I'm thinking AN3 flat head screws on 3in. centers to anchor nuts around the joint with two AN4 bolts to anchor nuts on the rear and main spars. Finding them with a looong extension on the main spar might be a problem. I have to do this, as I am building in a 20ft by 40ft recycled chicken shed in my back yard that has an 8ft x 8ft bump in the middle of one side to accommodate the nose. The doors opposite the right wing won't clear the aileron, much less permanently installed sponson. Left wing's O.K.--took a Sawzall to the wall. If I knew how to post pictures, I'd show ya'll how us po' rednecks have to do it.