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LT-40 on Floats-No go!

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LT-40 on Floats-No go!

Old 05-03-2005, 01:05 AM
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Soloflyer!!!
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Default LT-40 on Floats-No go!

I have recently put Foam Homebuilt floats on my LT-40. However after testing them they didn't perform as well as I would of liked. I took off twice- but only due to a strong wind. However I tested them again when it was calm and it didn't take off. The floats are around 2 pounds and are 43inches long. The step is 3/4" high and is just under the center of Gravity. When full throttle is applied the plane doesn't get up onto the step but slags back and the tail of the floats were nearly submerged. The plane wouldn't take off. Does anybody have any hints and improvements I could make?
Thank you -here is a picture of the plane
[img][/img]
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Old 05-03-2005, 02:36 AM
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Default RE: LT-40 on Floats-No go!

Have you flown floats before? If not....you keep the stick back initially and when you get a little speed up you relax the elevator a bit forward. Then it will get up on plane and you can coax it into the air with a very slight back pressure.
Old 05-03-2005, 05:44 AM
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Default RE: LT-40 on Floats-No go!

Could you provide a photo out of the water and from the side? If we could see this side view it would help.....Seaplane
Old 05-03-2005, 08:33 AM
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exeter_acres
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Default RE: LT-40 on Floats-No go!

which engine are you using?

Seaplane, what is a normal weight for your floats??
I have no knowledge (but you knew that when you guys trained me!) but 2 pounds sounds heavy..... or is that normal?
Old 05-03-2005, 09:10 AM
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johnboyrc
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Default RE: LT-40 on Floats-No go!

Are your floats level with the wing, or do you have a small angle with the front of the wing up (so the front of the floats nose down a hair). A friend of mine had no problem with the plane and floats being level with each other, but another guy with a different plane and floats needed a slight angle between the two.
Old 05-03-2005, 10:04 AM
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Default RE: LT-40 on Floats-No go!

Here's my LT40 on foam floats. It is a great sea plane with the .75 I have on it. A friend has one with a .60 that does well also. I have not flown an LT40 on floats with a .40 but I think it would be marginal. I have an Avistar on floats that had a .40 on it and I changed to a .46. Good plane but doesn't get off the water as well as the LT40.

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Old 05-03-2005, 01:37 PM
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Default RE: LT-40 on Floats-No go!

Does the bottom of your float behind the step look like the top or bottom drawing I provided?
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Old 05-03-2005, 07:22 PM
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JimCasey
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Default RE: LT-40 on Floats-No go!

If you are holding back stick..don't. If you are letting the elevator go neutral, try pushing a little down, at least until the plane rotates over onto the forebody of the float. If that works, you can shift the floats a little to the rear (recheck balance) If your water rudders don't kick up, trim some off of the bottoms of them.
Old 05-03-2005, 10:51 PM
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Wayne22
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Default RE: LT-40 on Floats-No go!

Again, if you posted a side view of your plane on floats, we could help you. You can get away with 36 inch floats easily...the fact that the back end is digging in seems to confirm that your floats are too long and this may be part of the problem.

The LT40 is a decent plane and has flown with all kinds of float configurations, so there is a solution for you....we just need more info from you.
Old 05-04-2005, 01:16 AM
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Default RE: LT-40 on Floats-No go!

We had a couple of LT40's on floats at our float fly this last weekend... and a couple of LT25 ..... all flew quite well. (Nony, you missed a good time...I think Dan would have enjoyed himself).

I'm not sure how much "float" experience you have, but floats are a bit of a different animal....I flew off the water for the first time this weekend and I'm glad I had some experienced help to check out my setup and "wisper" a few words of guidance to me.
Old 05-04-2005, 03:18 AM
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Soloflyer!!!
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Default RE: LT-40 on Floats-No go!

I have an O.S 40LA up front on the LT-40. I am woundering weather it will have satisfactory power for the plane to take off water. My Floats have 1 rudder which is ok in no wind. But it doesn't retract. It extends about an inch below the bottom of the floats and I am woundering if it is causing quite a bit of drag. I think I will shorten it. Regarding the question posted by "Seaplane" with the diagram. The floats match the bottom diagram with the angled rear end of the floats. I am unable to post a picture of the plane in the water but I will do next time I go flying. It looks similar to the image below when at full speed.
I am still puzzeled about the floats but I will continue to try different thinks which it is all about.
I will accept any comments or hints about what I can do, Thankyou for all the coments so far.
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Old 05-04-2005, 05:26 AM
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Default RE: LT-40 on Floats-No go!

Soloflyer,

Jack up that 40LA and replace it with a 60 or at least a hot 46FX.

My Avistar with the 40 would get on the step and as soon as I applied up elevator for take off the rear of the floats dug in and the water rudders drove a stake in the water and slowed the plane enough it wouldn't take off. In calm water it wouldn't take off but I could nurse it off in choppy water. A Tower 46 solved the problem.

The 40 LA is a fine engine, I have several. But, IMO, you are not going to like your LT40 as a float plane until you get more power on it. If you have to buy an engine, take a look at the GMS 47 or 76. I have the 47 and it is a sweet engine and powerful.
Old 05-04-2005, 04:32 PM
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Default RE: LT-40 on Floats-No go!

From your description and the drawing it looks like you are holding up elevator as you try to take off. That would explain your problem.

The proper floatplane takeoff proceedure is like taking off a tail dragger from a hard surface runway, except that you usually don't need right rudder with a floatplane.

Taxi out, throttle back and let the airplane weathervane into the wind. Add full up and full throttle, then almost immediately ease the elevator back to neutral. The airplane will come up on top of the water and start to accellerate. When it has reached flying speed, add up elevator to break free of the water. If you hold in up elevator or add it back in too soon, the rear of the floats will drop into the water and prevent the airplane from reaching flying speed.



Jim
Old 05-04-2005, 11:18 PM
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Default RE: LT-40 on Floats-No go!

We had a couple of LT40's on floats at our float fly this last weekend... and a couple of LT25 ..... all flew quite well. (Nony, you missed a good time...I think Dan would have enjoyed himself).
Yes, I'm sure I did!! Many planes there????
Old 05-04-2005, 11:32 PM
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Default RE: LT-40 on Floats-No go!

Not as many pilots as we had expected. About 15-20 aircraft, pretty decent weather... little windy later in the day.
Old 05-05-2005, 12:19 AM
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Default RE: LT-40 on Floats-No go!

many times I have flown underpowered planes (or overloaded real ones) and could not get off the water using conventional take off. Say you are in a heavy loaded Beaver, you can get off WAY quicker if you roll a float out. Get up some speed then use say right aileron to roll one float out while holding in left rudder to keep the plane straight (with the right aileron you may not even have to get on the rudder as P factor is helping you out here). After you roll the one float out the plane will really accelerate (with half of the drag out of the water now) and you can pull a little up to pop it off. Once you master this technique you will find yourself have alot of fun doing cool takeoffs that most people cant do or know how to do...
Old 05-05-2005, 01:26 AM
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Default RE: LT-40 on Floats-No go!

Listen to jrf ..JimCasey...myself.....neutral rudder once you are moving....then a little up once you are full speed. The 40LA may be a little light on power but you should get off. I would also consider smaller floats in the future.
Old 05-05-2005, 09:09 AM
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Default RE: LT-40 on Floats-No go!

The advise I gave is not just for show.... I have flown several RC planes that did not have the power to break the water unless you hit a boat of jet ski wake... The ONLY way to get them off the water was to roll it out. Sometimes, even if it is up on step and you slowly ease in the up all it will do is dig in the heels and slow you down...Everyone has given good and truthful information that works in most cases, however, sometimes a different technique may be the difference between an airplane and a airboat !!!!
Old 05-05-2005, 05:06 PM
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Default RE: LT-40 on Floats-No go!

i need some help, i have a sig somthin' extra on floats, and i was able to pull it out of the water on a OS 46 LA. the poblem is that it didnt fly very well, and i could only get it about 3 feet off the water. any ideas?
Old 05-05-2005, 07:29 PM
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Default RE: LT-40 on Floats-No go!

We need a little more info. What floats do you have? Have you flown the plane on wheels? If so, how did it perform? I've included a pic of my SE on my 30" foam core floats. I really thought it acted almost the same as on wheels. In fact, it performed inverted better than on wheels, due to the added lift from the floats. Mine is powered by a 45 and it can almost hover with the floats on.....Seaplane
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Old 05-06-2005, 10:44 PM
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Soloflyer!!!
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Default RE: LT-40 on Floats-No go!

I took the plane for another test flight or as it turned out a taxi. No flight occured. However I have taken a few pictures of it to see what you guys think it is doing and why it isn't getting up on the step. I have changed the rudder so it doesn't stick into the water as much to reduce drag and I have taken about 3-4 inches off the back.When the shots were taken I had netural controls and at full throttle. I have a feeling it may be due to lack of power but it still should perform better. I tryed the aileron roll out technic but the airlerons had no effect. I made the flots from Styro-Foam-Polystyrene from an article written by Chuck Cunningham; http://www.flyinglindy.homestead.com/skisandfloats.html
Here are the two photos of the plane at full speed;
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Old 05-06-2005, 11:49 PM
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Default RE: LT-40 on Floats-No go!

If that is at full power, then you need more ponies... Did you hold full up, full power, then as it comes up on step release the up... It looks like you are just plowing and not getting up on step. Sometimes, you have to play with the elevator to get it to pop up on top.
Old 05-07-2005, 06:08 AM
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Default RE: LT-40 on Floats-No go!

I said it once and will say it again. "The LA40 doesn't have enough power!" He doesn't have enough power to get on the step no matter how he works the elevator. There is no comparison to the drag of two floats in the water compared to the wheels on land. He is not marginal on power, he's on the backside of marginal. Been there, done that!
Old 05-07-2005, 06:10 AM
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Default RE: LT-40 on Floats-No go!

From the pics it looks like the back of the floats are still in the water. At takeoff speed, only the step should be in the water. All LT-40's I've flown needed a little down elevator trim to fly level. Try a little down elevator which would lift the rear of the floats up and hopefully speed the plane up. If this works, add a little down trim. Also, the water is smoothe which makes it more difficult to break loose. A little more chop would help. I'm not familiar with the LA's but I've heard they are not powerhouses. Hope some of this helps.....Seaplane
Old 05-07-2005, 10:01 AM
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Default RE: LT-40 on Floats-No go!

AN OS.40 LA has more power than that. Your photos look like you are getting no more than a fast idle taxi...maybe 4 clicks.

Is your throttle going all the way open? Or is it going MORE than all the way open? Max power is when the hole in the carb aligns with the hole in the barrel. There is a little screw in the back of the throttle body that needs to be installed, and on an LA it needs to be snug ( it is not the idle position screw on an LA).

Do you have the right prop? I would try an 11-4 to a 10-6. or a 9-6 3-blade for more clearance.

Find somebody who has been flying a while and get him to help you tweak the carb. I think you can lean it out and get more revs.
Lean it out (turn the screw clockwise) a click at a time until the revs peak. Then back it out slowly until the revs juuust start to drop the tiniest bit. The little hole in the front of the carb should be pretty close to exactly half-blocked with the idle air bleed screw. The engine should idle for a minute or 2 without changing revs, and then respond instantly when you increase throttle. If it slows down while it idles then spits fuel out the muffler, responding slowly when you add power, then you need to back out the idle bleed screw a bit. If the engine speeds up progressively when you let it idle then coughs when you add power, it's lean and you need to close the idle bleed screw a bit. 45-degrees (1/8 turn) is all you need to turn the screw at one time.

Or, take the baffle out of the muffler. You may have a bad baffle altho' I have never heard or seen that happen. Removing the baffle will decrease back pressure and increase power(and noise). You will again have to retune the carb.

Just for fun, check that the screws that hold the plastic backplate to the engine are all snug/present. It's plastic so don't tighten them gorilla tight, just squeeze them down somewhat firmly with a #0 phillips screwdriver. A leaking backplate gasket will cost you a LOT of power, and the engine may still idle OK because of suction in the crankcase at low power settings.

OS40LAs are not super powerful but they are adequate and reliable. You should get 10,000 rpm out of it, or somewhere close. I have one of the original 46LAs and it has zillions of hours on it and still runs like new.

One more thing: your step and the stern of the floats should have sharp edges. If you radiused them when you sanded the floats, it will contributeto /cause difficulty in getting un-stuck.

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