EF

I'm an experienced scale model flier (single and twin engine) and want to try some off-water flying, though I live in an area where I will probably have to tackle it by myself...

Is there a definite preference beween the usual double float configuration or the central single float/flying boat with wing tip floats configuration?

I was thinking of building a GP Cub with suitable GP floats, would this be a wise approach for a first timer to water, and is there significant preference to one of the three sizes this model is available in?

jrf

My Feedback: (551)

Single float setups are difficult to handle on the water because the tip floats must be held out of the water at all times except dead slow taxiing, and even then, you need a very effective water rudder to taxi straight ahead. Double float setups are far more forgiving on the water.

Scale Cubs often have yaw problems coming off the water. If you use the sub-fin you should have no problem. As to size, bigger always flies better.

Jim

jaka

Hi!
I don't think there is much difference to what type of airplane you choose.
For instance the Kyosho PBY Catalina that I have is very easy to take off and fly off water and doesn't need a waterruder at all and turns best at low to half throttle. My PBY is powered by two OS LA .15 engines and I run 15% all synthetic oil and 5% nitro.
I also think flying boats is more exiting to build and fly than a conventional airplanes with twin floats.
The GP CUB is perhaps not the best waterplane to start with, but as you are experienced ...go ahead. The bigger the better

Regards!
Jan K
Sweden

EF

Well I must admit the Catalina is far more attractive in my opinion than the float equipped Cub.
I am currently flying a scratchbuilt Mosquitto and find it wonderful, but thought I have to build a sort of water-trainer...but maybe I'm wrong.
Don't you find the assymetry caused by tip floats touching the water at landing or takeoff speeds a problem? don't they induce a sudden significant yaw?

jrf

My Feedback: (551)

I guess I should modify my earlier post a little. If both tip floats are in the water while taxiing, then of course there is no asymmetry and taxiing is easier. Getting the hull (center float) up on a plane is easier too. But then, that isn't scale, is it?

Jim

jaka

Hi!
They haven't been any problem to me as they don't touch the water, well not both at the same time anyway. The tip floats are a bit short so when the hull sits in the water the wing just rests on one float...not both, but as soon I give full power the Catalina starts balancing on just the hull and the tip floats don't touch the water so there is no jaw problem.

Regards!
Jan K
Sweden

Newc

You also may wish to take a good look at the Balsa USA Northstar for water flying. Not scale of anything, but a very popular kit for water flying. I've built 4 and really like them for their performance. If you are going to be building your own floats - which isn't difficult - I suggest that you see if you can find (perhaps a search of these boards will yield some hits) the articles written by Chuck Cunningham.

JimCasey

My Feedback: (1)

If you are comfortable flying scale planes, then a scale cub should be a good transition to water flying. Lots of Cub photos on the Brown's seaplane base website. Slapping floats on your favorite airplane is always a pragmatic approach.

If you want to fly a scale flying boat, there are a few nice scale kits/arfs out there. Probably would personally prefer an albatross or even better, a Canadair CL215 over a PBY. I suggest that you first build a less detailed standoff scale model to get your feet wet (pun unavoidable) before building a fully detailed Top-Gun 1/4 scale Martin Mars....

Contrary to intuitive logic, yaw from tip floats is less when the floats are set a bit lower than if you hoist them up more. Bottom of the tip float should be about as high as the top pf the step. That way the plane is not "out of shape" when the tip float touches (lightly) then it does not cause much disturbance.

britbrat

My preference is for flying boats. They handle rough water notably better than twin float types.

EF

Thanks for everybody's inputs.
I have decided to now look for a reasonable sized plan or kit for a Catalina (no ARFs for me thank you )
I figured since I already fly a scale twin, why not fly one off water, and the Cat can also be flown from a regular runway if I fit a removable gear, best of both worlds

MinnFlyer

My Feedback: (4)

With all due respect jrf, I have to strongly disagree with your statement.

It has been my experience that single-hull "Flying Boats" are MUCH easier to handle than a standard plane with floats.

Follow me on this...

With a single-hull design, 95% of the weight is on the hull. What little weight is on the one tip resting on the water is counter-balanced by the opposite wing - so the weight is minimal. Once you pick up speed, that wing will easily lift out of the water, and once it does, it doesn't matter if the plane is not perfectly level. In fact, if one tip touches, it will just skip off the water like skipping a stone.

Whereas, with a dual pontoon design, all of the weight is on two pontoons. As you pick up speed, you must be VERY careful to keep the wings perfectly level or one pontoon (Let's say due to torque that it's the left one) will create significantly more drag than the other. This will cause the plane to pull to the left. If you don't get the wings level (and sometimes you can't tell that they're NOT level) and apply right rudder to correct, this will cause the plane to tilt even more to the left, and very often results in something seaplane fliers have seen way too often... The left float digs into the water causing an abrupt end to the flight often accompanied by significant damage to either the floats, the plane, or both.

jrf

My Feedback: (551)

Mike, I don't know what to say. In 20 years of flying two float airplanes 12 months a year (I'm talking many, many hundreds of flights), I've never touched the ailerons on a take-off run. And since I quit using Gee Bee floats, I've never had a water loop with a two float airplane. If the floats are set up properly, they are self leveling. Is it possible that what you are experiencing is pilot induced?

With the seaplanes however, if one tip float is in the water, the drag yaws the airplane to that side. I have had water loops on take off with a seaplane when one tip float touched a wave. I admit that my experience with seaplanes is limited to those with scale appearing tip floats like the ones on the Mariner. I will have to accept your analysis of the behavior of ski type tip floats like those on the Sea Master.

Jim

MinnFlyer

My Feedback: (4)

I guess that it's quite possible that the ground loops are pilot induced, but I have had them happen to me, and I dare say that I am far from an amateur when it comes to seaplanes. I personally have only had one pontoon plane (Anniversary Cub) and never had any problems with it, but I have ground looped other people's float planes (Including CGM Cubs) so it could be they were set up improperly.

All I know is, I have flown many different seaplanes - both mine and other peoples - and I've only had problems with the ones on pontoons. Never with a flying hull.

Right there that tells me that the hulls are easier in that they are designed for water from the get-go as opposed to someone having to properly "Set-up" a set of floats.

I mean... I know how to set up floats, but how many other people do?

Newc

EF - I have spent a bunch of time looking for a Catalina kit as you mention, because I also am not into the ARFs, no matter whether or not the Kyosho one is OK.

I found G&P Sales as about the only kit manufacturer, though you could get plans from Fred Novak at Vintage RC (ads in most RC magazines, including RC Report) and have the kit cut by Precision Kit Cutters.

I have been in contact with Bill Price of G&P Sales (http://www.rcairplane.net), and was going to have him send me a kit for his 104" PBY-5A Catalina. After viewing the tape Bill sent me of the building and flying of this, and seeing at the end of the tape the water handling characteristics of the PBN Nomad versus the Catalina, I told Bill to send me a PBN Nomad kit, which he is putting together right now. The only downside of the Nomad is that the full scale Nomads weren't built as amphibians - they were only built as flying boats - so there’s no gear for flying off land. Not a problem for me, since I live on a lake, but a concern if you want to fly off land as well, as you indicate.

Check out the G&P Sales planes.

Newc

EF

Yes, I have found this site yesterday and am thinking of the 81" PBY.
I already made contact to try and find out the shipping cost to my part of the world.
Since I also have a fantastic runway to fly land planes off, and since this aircraft was also in service in my country's airforce, I prefer this aircraft.
The Novac plan is also an option, probably the 72" one for 30 fourstrokes but we'll see, I may go for the bigger one.

JimCasey

My Feedback: (1)

JRF and I have been known to disagree but I'll come down squarely on his side in this discussion.

Floatplanes tend to run straight on takeoff. The only one I can ever remember having a problem was an AstroHog with John Sullivan floats, and I think it was just setup wrong...Advance throttle... go fast...waterloop.

I have seen plenty of flying boats and/or monohulls with tip-float related instability.
Tip floats have to be large enough so that they will not be submerged by whatever effects tend to dunk them. And that means not only volume but a hefty planing area, too. Push one wingtip to the water surface and if the wings don't pop back to level instantly, you need bigger tip floats. They have to have proper incidence, which is slightly greater (and certainly not LESS) than the hull incidence. ANd they seem to work better when they are mounted low enough that both are displacing water when the plane is at taxi speed. My guideline is the bottom of the float at the height of the top of the step. My first floatplane was a TF Kittiwake monofloat, and I gave up float-flying for several years because of how hard thet thing was to get airborne. It waterlooped the first three or four times I tried, and I always had to do major repairs after a waterloop. My second floatplane was a big Lazy Bee on (2) BJ foam floats, and It was as easy to fly as the KW was difficult.

I experimented with tip hydrofoils instead of tip floats on one of my flying boats. They worked well for takeoffs and landings, but the plane was a B*TCH to taxi because of the lack of floatation at idle speed. If you think a float in the water makes the plane yaw, an entire wingtip in the water is nearly insurmountable. And wingtips are not shaped so they come unstuck easily from the water's surface.

Mounting tip floats inboard at about 2/3 span seems to be occasionally popular. Advantage: They can generate less leverage to yank the plane off line if they hit a wave. Theoretically the plane will be more responsive in roll with the masses closer to the CG. Disadvantage: They can generate less leverage to bring the wings back to level is the plane gets upset by a wave or crosswind. So you'll need larger floats for the same corrective effect.

Where Floatplanes do have a big disadvantage is in the wind. My Telemaster has standard dihedral and the floats are mounted a bit narrower than 1/4 span, and it is difficult to get it turned around in a breeze when taxiing. It's not hard to get it flipped over on its back, tho'. Single-float takeoffs and landings are just part of the hot-doggong it does easily, and there is little drama unless I get it tilted enough to drag a wingtip. With a Flying boat and proper tip floats, the wind is much less likely to get under a wingtip and cause problems.

jrf

My Feedback: (551)

Thanks Jim, for your support. I must add that low-wing float planes usually have the wing at about the same height above the water as a flying boat and therefore have about the same resistance to wind problems on the water.

Jim

Turbobeaver

Jim and JRF,I have to totally agree with the analysis that you have given on the comparisons between twin float flying and mono hulled type flying boat designs.In all my years of water based flying,this has proven to hold true for me as well.

When the water gets on the rough side,I typically lean toward flying twin float type aircraft as it gives me more stability on the takeoff run and landing if the water is fairly choppy.Generally speaking,I find they are more foregiving all around and can handle rough water much better.With the engine and electronics much higher out of the water,there is less chance of getting swamped and having your flying day prematurely cut short.With that said,I personally prefer flying mono hulled flying boats myself because of the challenge and typically I like the aesthetics factor much better.They can be a hand full though if one of the sponsons makes momentary contact during a high speed takeoff run or if your landing a little too hot.Typically what happens is the sponson making contact with the water generates drag on that side causing the model to pull hard in that direction.The sponson becomes a pivotting point.The further out the sponson is from the hulls center line,the greater this pulling effect will be when it does happen(relative to speed/inertia).The design element is crucial here and not all mono hulled sea planes are created alike.Some are more prone to this effect than others based on their hull/sponson design and the relative heigths and locations of both.Those high speed piroettes are sure something to behold though when they do occur,aren't they?!

r_kopka

Most sources I read say to mount the tip floats so that they are clearly outside the water when taxiing and if the wing is leveled. I fly small flying boats (Aventura, Catalina) and the only problem with the tips is at very low speeds. As soon as I have some (low) forward speed the wing levels and the tips are outside the water. Then takeoff is easy.
I much prefer flying boats especially if there is some wind and waves. With a floatplane I always fear it gets flipped if it's not really calm, and it happens every now and then.

RK