dansuf

My Feedback: (3)

I am trying to put floats on my new Kadet LT40 arf, the CG ranges from 3.5" to 4.25", and the drop in the floats should be at CG or not more than 1/2" aft of the CG. Which no. should I use?
If someone has done this project earlier, I will appreciate very much for your guidance.
Thanks,
Jamal

PeterC

Use the CG that you like flying the plane at on wheels and use that position for reference. A 1/2" either way isn't going to hurt anything. Most critical is that the planes wing should be slightly positive to the top of the floats. The top of the floats is a datum for most floats. Be sure your struts are rigid as you don't want the floats flopping around on take-off.
Welcome to the fraternity,
Peter

dansuf

My Feedback: (3)

Thanks Peter,
Do you have any pictures, if so could you post them or email them to me, thanks. I forget to mention that I am using GP .60 size arf floats for my plane.
Did you make new mounting plates/brackets to mount the floats? Or how did you mount the floats on this plane?
I am putting OS .50 SX in mine, what do you think about the engine size?
Thanks again and keep in touch,
Jamal

jrf

My Feedback: (551)

According to Tower, GP doesn't make a 60 size ARF float. They do make a 40 size ARF float set that is 40" long and weighs 4 1/4 pounds!

I think I'd be looking for a set of 32-36" floats that weigh about half that much for an LT40. Anything but Gee Bee floats.

Jim

Danh4

My Feedback: (5)

Jamal,

I put my LT-40 on floats last year so I could fly it off snow in the winter. I got my floats from www.foamfloats.com and you can visit that site and see the installation article with photos that I wrote.

Dan

PeterC

My feeling is that GP overestimate the size and weight of the planes their floats are intended for. I have a pair of the built up GP floats (40 size) and I think they will work fine on a 60 sized aircraft. I am going to use the 60 size GP floats on my 8' Unionville Beaver.
Check out the Falcon Trading Co floats. They might be closer to what you need.
Amen to jrf on Gee Bee floats.
Sorry I don't have any pictures of your type of installation but there were some posts a short while ago about a similar situation. Check back a month or so.
Peter

seaplane

This is how I set my wife's LT-40 up. I bent the 5/32" wires myself. I should have attached the cross brace high on the front wire and low on the rear wire. But it works.....Seaplane

seaplane

Here's another pic of the underside of the fuselage. I cut 2 slots similar to the main gear slot, then epoxied in 2 hard wood blocks inside the fuse centered over the slots. I use nylon straps to hold the wires in the slots.....Seaplane

All Thumbs

I agree with PeterC on the CG choice. Use the one that you normally fly your plane with. I built a set of GP 40 size floats (which are 34.5" long by the way) and added them to my Hobbico Superstar. Here's what the instruction manual recommends:

For 60-size Floats: Move the CG 1/2" ahead of the manufacturers recommended CG.

For 40-size Floats: Move the CG 3/8" ahead of the manufacturers recommended CG.

For 20-size Floats: Move the CG 9/32" ahead of the manufacturers recommended CG.

That's actually pretty vague if you think about it, because you're given a range of CG with your airplane. If you like, modify your CG range to 3 1/8" to 3 7/8". I moved mine a bit forward of my normal flying just to be safe and it works fine. In fact I'm sure that leaving it where it was would have been just as fine. Does your current CG fall in that range somewhere? Just use it. The important thing is to locate the step of the float 1/2" rearward from whatever CG you finally decide on (I made a quick plumb bob out of fishing line and a sinker...held it on the wing saddle 1/2" back from my desired CG...put a level on top of the floats, and then slid the fuse around on the gear until the plumb bob pointed at the step...to find my fuselage attachment points). I assume that when you said the "drop in the floats" that you were referring to the "step". Also, remember to have a slight positive incidence from the bottom of your wing to the top of the floats as recommended above.

Hope this helps with your CG question...I'm a newbie at this too so I gave you quotes right out of the instruction manual. In any case, my plane operates great in the water so I'm satisfied they had it right.

jrf

My Feedback: (551)

The following was taken from the Tower Hobbies website, under Great Planes 40 size floats, PREASSEMBLED (ARF)

SPECS: Float Length: 40"
Model Weight Class: 5.0-9.5 lb (2270-4310g)
Model Size Class: .40-.60
Approximate Weight of Assembled Floats: 1900g

COMMENTS: The box says they are 34.5" long but they are really 40".

These floats are fiberglass, not wood. 1900 grams = approx. 4.2 pounds. Your LT-40 probably weighs 6 to 7 pounds. With those floats on it you're looking at over 10 pounds. You probably won't like the way it flies at 10+ pounds.

The Falcon Trading floats (33 1/4" long) weigh less than 2 pounds with struts, and a decent set of foam core floats would probably be even lighter.

Jim

All Thumbs

Just to be clear...what I was referring to was the Great Planes kit, not the preassembled. I certainly can't recommend the kit unless you've got the time to enjoy building them just for building's sake. I'm currently between working contracts so had the time to build, and had a lot of fun with it. But....by the time you buy some music wire and monokote, and a few other assorted items you'll be close in price...so no real money savings and I spent two weeks getting them all together.

I don't have a real good scale (I'm going to correct that soon), but the cheap one I have shows my trainer at about 7 lbs with my new floats. The plane was about 5.5 lbs before...so the floats are about 1.5 lbs complete with struts and cables (these figures are rough but certainly well within a half pound and the actual difference I measured has to be even more accurate). Other threads on RCU have shown that at 1.5 lbs I'm probably a little heavier than most finished kits. I'm wondering if the 4+ lbs is even accurately reported by Great Planes on the preassembled? Dang those would be heavy.

My completed 40 size kit floats are exactly 34.5" long...measured. They must have carried over that value as a typo to their new float's box label. I'll bet they split the difference in the kit sizes to make it work for both 40 and 60 size planes and made them a generic 40". But as PeterC said above, I'm certain even the ones I have will easily float a 60 size plane. Keep in mind that your floats should be about 75% of your plane's length. If you haven't bought floats yet, jrf's recommendations are good ones (but I do love the floats I have...but you need the time, normally I don't and I'm just a happy ARF guy ).

hy flyr

My Feedback: (27)

Just a note on G.P. arf floats. I ordered a pair and was a little dissapointed in them. The wire gear was very nicely done but the floats themselves were poorly made. The seams weren't glued well and were coming apart and the fiberglass was pitted and done sloppy.
I sent them back and ordered the 60 size kit.

All Thumbs

Hy flyr, I don't think you'll be disappointed in the kit. They actually go together pretty quickly. Most of the time I spent was with the finishing. The monokote process is a little involved, but I took my sweet time and the result is great. I'm new in the float game and haven't seen too many yet, but I'm happy with what I've got.

By the way, can you confirm that the preassembled floats weigh over four lbs as reported by Tower?

seaplane

My foam core balsa sheeted 34" floats weigh 9 oz. each with nylon mounting blocks attached. My 42" floats weigh 14 oz. each. The Great Planes built up floats weigh more, but I've forgotten exactly how much.........Seaplane

hy flyr

My Feedback: (27)

Hello all thumbs,
I have built GP size 40 floats before(2 sets) and your right about going together pretty easy. I'm almost done with my 60 size floats and they aren't much different. The only things I don't like about them is the deck is 2 pieces and the sides are three pieces that need to be glued first. I know they make balsa sheeting wide enough and long enough to do them in 1 piece. Probably cheaper for them.
How did your monocote hold out on them? I 'glassed mine and was fairly pleased. As far as weight, my 40 size weighed about 3lbs, lots of epoxy and paint!! The arf 60 size could have gone 4lbs but I didn't weigh them. I'm guessing my 60 size kit floats might go about that much also. One other thing. they should have instructions on the heighth of the rudder so it's out of the water when plane gets on step.

All Thumbs

It's too early for me to give a real good report on this. All I can tell you is that they seem great so far. At first I was unsure about it, but after I did them, and after about 40 flights I think they're going to last a long time.

I followed their directions pretty much to the letter, but before I did, I put on three pretty heavy coats of clear LustreKote. I did a lot of sanding and had a fairly smooth surface prior to monokoting. I think they might have been ready to float as they were. I used a real hot trim iron and really seared them to the wood. Heck, even the paint was getting re-sticky due to the heat (305 degrees). For the trim pieces there was no concern about discoloration...know what I mean? For the rest I ran my big iron a little hotter than usual and went over every seam with the trim iron again as I added all of the overlapping pieces (the melting paint made me go through two socks). I don't think this stuff is ever coming off!

Unfortunately I can't give you the definitive report for a few years, you know? I have a good feeling about them, but that doesn't do you much good. They did come out light though. I'm embarrassed to say that I've been weighing my planes with a bathroom scale (thus, all my disclaimers). But my trainer was suppossed to weigh 5.5 lbs and that's what it showed. With the floats, it shows 7 lbs. Pretty crude, I know...I mentioned I'm going to fix that, I just haven't found the right scale yet and it didn't seem that critical until I joined this forum . But that's consistent with what I've read elsewhere. The floats are light and I'm very happy I decided to go with monokote. They turned out much better than the idea first sounded to me. They "feel" tough, and I'd do it again. Sorry I can't give a better report.

I can give a flight report though...the lighter floats make the plane fly sweet. I only have a 46FX on it but I'm happily looping, hammerheading...all the normal stuff. I sit high in the water and takeoff quick and land smooth. Pretty fun. I'd recheck some other threads maybe, or start a new one to see how the older monokote jobs are doing because I think it's going to be worth it.

PeterC

In regards to hyflyr's comment that the rudder comes out of the water when on step; I would take that as a good characteristic. I have had rudders dragging in the water on take off and it sure makes the plane squirrily. Note that full scale seaplane pilots retract their floats before takeoff. The air rudder has plenty of authority at speed.
Peter[8D]

PeterC

Typo, typo. (or brain fade) They retract their water rudder before take off.
Peter

jrf

My Feedback: (551)

All Thumbs:

Scale accuracy aside, your method will give you the weight of the floats, minus the landing gear you took off. The gear can weigh as much as 12 oz. depending on the wheels used.

Your method is the correct one to figure out how much weight you are actually adding to the airplane, but it is misleading when trying to compare the weight of various float setups.

If your airplane is now 1 1/2 pounds heavier, I'd guess that the floats, by themselves, weight 2 pounds plus.

Jim

All Thumbs

Good points jrf...I DID neglect to consider the weight of the gear that was removed...and I promise to publish no more weights until I get a sufficiently accurate scale! Good thing I provided enough info for you to deduce what I was doing . When I do weigh it, it will include the floats, water rudder, my built up struts, and the control cable. I still have my old land gear for it and I'll have to weigh that too. Soon enough I'll get myself out of the "weighing" dark ages. No guarantees I'll get that before this thread goes out of focus though.

dansuf

My Feedback: (3)

Thanks a lot guys with your professional suggestions and tips. I have not been able to finish my project yet, got distracted else where. I am hoping to finish it pretty soon.
"Drop in floats" means the step in the floats, very well corrected indeed. I have to mount the wire frame in reverse direction on the floats to achieve the +ve incidence for the wing (LE is higher than TE). What my understanding is that these floats are generally designed for a CUB. However, I think these floats would work perfectly.
Thanks again everyone guys.
Jamal