WM Cub on Floats...Back from the Lake  
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WM Cub on Floats...Back from the Lake - 8/7/2003 11:36:27 PM   
shv2sail


 

Posts: 111
Joined: 8/21/2002
From: Odenton, MD, USA
Status: offline 		Thought I'd post an update on my Cub on floats project, and post a pic.

After a spending a week on a perfect flying lake in central NY, the cub has still not made her first successful flight off water. I ran into a couple of issues. One was that I had a hard time getting the CG even or forward. The first few flight attempts were with a little aft CG, and without flying this plane (ever) and not being more than a novice rc pilot, I had a hard time with control and rolled in each time on takeoff - not good.

After repairing damage to the floats/mounts, I gave it another shot, but couldn't keep it from veering off to the side when on setp. Come to find out that post-repairs, one of the floats was angled outboard and caused the turning when at speed/on step.

After additional repairs and 'some' adjustment to the CG - same results as first attempts - CG still too far aft. SO, I piled on the lead in the nose until it balanced where I wanted. BUT, now it appeared that with the lead in the nose, the all up weight was more than the floats could handle (they were cutting it close length-wise as it was) and sitting in the water the floats would sink by the stern. I had to be taxiing forward to keep it afloat! With the addition of shearing a spur gear (the cub is electric powered) on every-other prop strike, it was overall a very frustrating experience.

It does look cool on floats, though!

I'm looking at revising the power system for more overall oopmh, moving radio gear around for better balance, and procuring some floats that are actually long enough/bouyant enough to support it correctly.

Live and learn, I suppose....

Steve

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WM Cub on Floats...Back from the Lake - 8/8/2003 1:49:14 AM   
FLYBOY



Posts: 8687
Joined: 1/7/2002
From: Missoula, MT, USA
Status: offline 		The floats look fine. I had to put lead up front on mine, but I put it right at the leading edge of the float. Made it so I didn't have to add as much by putting it in the nose of the plane.

Also, don't fly on crystal smooth water. Harder to get off. If it is heavy due to the battery and stuff, that may add to the problem of it not floating properly. Sounds like you said you were getting spray on the prop ruining gears? Maybe a piece on the inside of the float sticking down in the water to direct the spray. I have seen that too.

_____________________________

Fly it till the wings come off.

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       Post #: 2

WM Cub on Floats...Back from the Lake - 8/8/2003 2:04:57 AM   
JohnBuckner



Posts: 3824
Joined: 12/23/2001
From: Kingman, AZ, USA
Status: offline 		Hard to tell but those floats look far to forward and very likely the problem. The CG should be exactly where it indicates on the plans or manual, not just close but exactly and hanging level when supported at that point. Usually on a float installation if forward weight must be used they are installed on the bows of the floats thus requiring less weight.

OK now assuming we have balanced the airplane and know where that CG is the step of the float should be either even with that point or no more than a quarter inch behind it.

John

_____________________________

"Keep your controllines tight"

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WM Cub on Floats...Back from the Lake - 8/8/2003 12:30:15 PM   
4*60


 

Posts: 1265
Joined: 3/10/2002
From: Blind Bay, BC, CANADA
Status: offline 		The weight should go into the floats so that not only you use a minimum but also the CG will be good for wheels once you remove the floats. If you weight the airframe, you need to adjust the weight when you return to wheels.

The floats appear slightly ahead of the prop. We recommend at least 2 inches ahead to reduce prop spray, but I am not sure about electric. I have seen successful flights(many) with the rear of the floats submerged while moving slowly. The model was able to get on step and take off well. I think the floats may be a little shallow for the weight you have, but if you have enough power you should get off. Once you are on step, it is almost a given that you can get off the water.

It appears to me you may not know that the cub is not the easiest to get off the water. Also you may not be aware that up elevator is used initially to get on step(you succeeded at that) and then get that elevator neutral or whatever it takes to keep the cub moving on step. The slightest of up elevator should encourage it to take off, or it will take off without that "touch" possibly. Too much up continued after "on step" leads to trying to lift off to slow, drives the rear of the floats into the water, therefore erratic behaviour on the water and if liftoff occurs, often a turn to one side or the other and a dump into the water (stall/spin whatever due to inadequate flying speed).

Just my .02.......fairly new float flyer. with many flights and only one engine out on wet landing. (that'll change now, won't it)

(in reply to shv2sail)
       Post #: 4

WM Cub on Floats...Back from the Lake - 8/8/2003 7:01:56 PM   
shv2sail


 

Posts: 111
Joined: 8/21/2002
From: Odenton, MD, USA
Status: offline 		The floats looked too far forward to me as well, but the step is just SLIGHLY aft of the plane's recommended CG, so I think they're correct (they extend less than 2" infront of the prop as well).

Didn't think about adding the weight to the floats and not the airframe. Of course, these are "sealed" fiberglass floats, so I'm not sure how I'd add the weight in a "nice" manner without drilling big holes or strapping lead to the tops.

The 'not knowing how hard to get a Cub off water' comment appears to be dead on Oh, well. I was aware of the 'up elevator' to get on step thing, though. And actually I had NO problems getting it on step. I think the REALLY big thing was the CG issue (and my inexperience with this plane (on water)).

Thanks for the comments...will hopefully get the chance to put some in practice soon!

Steve

(in reply to shv2sail)
       Post #: 5

WM Cub on Floats...Back from the Lake - 8/8/2003 9:01:43 PM   
JohnBuckner



Posts: 3824
Joined: 12/23/2001
From: Kingman, AZ, USA
Status: offline 		Great Steve with the float/CG relationship as you describe then that is not the problem and as you suspect takeoff technique is very important. The techique as described by 4*60 is appropriate and the way to go. One thing you can do is watch the heels of the floats if they contact the water when you try to rotate for takeoff then it is like putting the brakes on. In your posts you never said if you had the balance point in the proper position only that you kept adding weights, you just have to do whatever it takes to put it there before attempting flight. This is even more important on a small airplane because even slightly to far aft is going to cause problems.

So yes do whatever is necessary in moving onboard equipment to get it there and if weights are required with the glass floats and you don,t want to cut them a good method is to hammer lead very thin and lay them over the top pf the floats or form them around the bows to look like rubber bumpers as on full scales.

I do not think Cubs have any more trouble in water takeoffs than any other type but because they are so commonly used for float planes that sloppy float installation or poor CG positioning by new float flyers has contributed to that reputation.

Best of luck and enjoy

John

_____________________________

"Keep your controllines tight"

(in reply to shv2sail)
       Post #: 6

WM Cub on Floats...Back from the Lake - 8/9/2003 12:26:33 AM   
shv2sail


 

Posts: 111
Joined: 8/21/2002
From: Odenton, MD, USA
Status: offline 		Thanks, John. No, I never did get the CG to where I thought it should be...the best I got was SLIGHTLY aft - which is still not cutting it. May try the 'flat lead pseudo bumper' trick on the floats...pretty cool idea. Of course that is after I move radio gear/etc to bring the balance back forward.

Thanks again for everyone's $0.02!

Steve

(in reply to shv2sail)
       Post #: 7

Cub on floats - 8/11/2003 8:53:56 AM   
pabdoc



Posts: 81
Joined: 3/23/2002
From: Minnetonka, MN, USA
Status: offline 		Steve,
I just returned from a week at my lake in northern Minnesota, and managed a first (and only) successful flight. My cub is a Goldberg Anniversary Edition, on CG floats (36" , powered by a O.S. .52 FS. I found it to be a perfect flier, take-off run was straight, with a bit of right-rudder trim, then an easy lift off the glass-like water surface.

However, I was too impatient, and neglected to do a proper job of engine adjustments, and after only perhaps two minutes in the air, the engine quit (I may have throttled back a bit too much), and I was forced to bring her down "dead-stick." When I tried to re-start the engine with the plane still in the water, the starter cone fell into the water, and that was the end of my flying for the week! I could not hand-start the engine....something I must have lost the knack for doing.

I had a Royal .40 trainer on the same floats you have, and IMHO, they are too small for the CG cub. The larger CG floats will buoy the plane out of the water quite a bit more, making for much easier handling in the water, and shorter, drier take-off runs. Be sure to keep the step near the cg, "toe-in" the floats slightly, and the top of the floats should be parallel with the wing bottom.

Try the Goldberg floats, and I think you will be glad you did!

Paul

_____________________________

"The difference between men and boys is the price of their toys"

(in reply to shv2sail)
       Post #: 8

WM Cub on Floats...Back from the Lake - 8/11/2003 5:06:24 PM   
shv2sail


 

Posts: 111
Joined: 8/21/2002
From: Odenton, MD, USA
Status: offline 		I think you're right about the float size, Paul. If I follow the 75%-80% of overall length rule for recommended float length, I should have 36" floats. The ZeeDoo's I was attempting to use are about 32" long - thought I could get away with it, but with all the other factors, it probably wasn't the best of ideas.

Steve

(in reply to shv2sail)
       Post #: 9

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