I just finished glassing and detailing (rivets and panel lines) a pair of GP .60 floats, which are 42 inches long. My initial thoughts were to mount these floats on my .60 J3 Piper Cub. However, with the detail and scale appearance of these floats it almost seems sad to mount these floats on a plane that is not scale. Therefore, I have started building a Balsa USA 1/4 scale cub equipped with a Zenoah G26. However, using the 75% rule with the Balasa USA kit would imply the use of a 51" float. The float that Balsa USA suggests for its 1/4 scale cub has a 44" length. Any thoughts regarding the use of my 41" floats on the larger airplane? I believe the buoyancy of the float is ample for the size of the new plane; however, my apprehension is regarding the bobbing effect, particularly in rough water - any thoughts?


Jed

I just read an article on this very subject about a month ago. I am looking for it now. If I can find I will post the building floats part of it. It has a math formula for figuring out if your floats are adequate....

I'm looking I'm looking....

If the water is rough, it probably means that its windy. THe wind will be your problem more than the waves.

This article is probably the one you saw and "misplaced".
http://users.rcn.com/llfc/floats/

Thanks im_a_rcav8r, I think the formula you are speaking of is 75% of the fuselage length. I have read several articles on this and they all say the same thing. However, I am curious if anyone has any experience with a slightly shorter float (i.e., 60%) and what the effect has been. Further, if the 75% rule is a common law for float length then how can Balsa sell its 1/4 scale EVO float system for a Cub with a 68" length if the floats are only 44" long (64%)?


Jed

I can tell you from over 20 years of float flying experience, both full size and models, that float length is not as critical as most make it out to be.
70-80% is a good rule of thumb to keep you out of any trouble. (Or the least amount of trouble anyway)
I have flown many airplanes with floats that would be considered much to short. Some as small as 50%. They do tend to bob more in the waves, and are a bit more critical on take off and landing, but overall, if the plane sits level and does not have any tendencies to submerge part of itself, the floats are fine.
The difference between a 41" float and a 44" or 50" float on a plane your size would be barely noticeable.

Peter

www.climatemodels.com

I have been flying floats since the early 70's and have tried several differant float to airframe ratios. While you can get away with floats that are in the 60% range, the key is how long the floats are from the step to the bow. If, when the step is mounted such that the model balance is right on the step and the bow of the floats is at least 1 inch in front of the prop, the model will probably fly ok although the model will be be difficult in rough water and the floats will probably need to have spray rails to the front inside of each float in order to operate. If the floats are any shorter than this length their is not enough floatation foreward of the CG. and the model will dig in on any take-off attempt and can trip on landing. I think that the float application you are planning is a little small and I would be looking at larger floats in the 44 to 46 inch range.