first float plan
 

I am building a set of GP 60 size floats and am now debating which plane I want to install them on. The 2 pissiblites are a PT60 with OS60SFN or a 4* with OS91 Surpass. I really prefer flying the 4* on wheels and think it would be the better choice for floats, but wonder about the low wing. Anyone have thoughts or first hand experience?

RE: first float plan
 

The GP 60 size floats are designed for the GP 60 size cub kit, which is a giant scale airplane. They are rated for 8-15 pound airplanes with wingspans in the 90" area and the floats, with struts and spreaders, will weigh about 4 pounds when finished. They are way too big for either one of your choices.

I have a set on my 11 pound 4* 1.20 and they are even a little big for that airplane.

Jim

RE: first float plan
 

The recommended length that a float should measure is aproximately 75% of the overall length of the aircraft.A little longer won't really matter as long as your not killing it with a ton of extra weight also .The wingspan of the model is not really part of the formula when trying to figure out float dimensions for an aircraft.If that was the case,you wouldn't have clipped wing Cub's flying off water with floats.A larger wing generates more lift at slower speeds thus making it quicker and easier to get off the water.However,the larger wingspan model also weighs more than its short winged cousin causing the floats to submerge more and raising the water line further up on the sides of the float.The hardest part of float flying,is getting the floats to rise and plane on top of the water.This allows the plane to pick up enough speed so that finally the aircrafts wing can begin to generate enough lift to fly it off of the water.Without speed ,you aren't generating much wing lift.With the floats riding higher up out of the water,less power and effort is required to get the floats to plane,which means you are going to obtain your lift off speed much faster also.A float plane with good floatation is very important also when it comes to success in float flying.It's not just a matter of float size and length.Once you have both models(standard wing,short wing) up on step and planeing,the standard wing will lift off at a slower speed than the clipped wing version due to its increased wing area.The clipped wing aircraft needs to plane on top of the water much faster in order for it to generate similiar wing lift of the full sized version.This means longer take off runs.Good float floatation and a model with a lighter wing loading will reduce the distance of the take off run.What you want to figure out is what your wing loading will be with the added floats on your plane.The higher the wing loading,the harder and trickier it will be to get it off the water and to fly it.A well designed float makes this task a heck of a lot easier.Happy flying!;)

RE: first float plan
 

OK. My floats are nearly finished. Are they really too big to attach to my 4*60?

I thought good floatation, light wing loading and power (91 4stroke) would be OK. I believe the 4*60 is about 7 pounds without floats. Adding 4 pounds of floats should put them right in range. Am I wrong?

I have to admit now that the floats are about done they are large, but....

RE: first float plan
 

That 8-15 pound range is for the airplane without the floats.

Like anything else you add to an airplane, you want to use the lightest floats that are big enough to do the job. Floats also create drag and some lift in strange directions. The smaller the float, the less the drag and off center lift.

The correct size floats will add about 2 pounds. Your 4* flies very well at 7 pounds. It will still fly pretty well at 9 pounds. Do you really want to see how it will fly at 11 pounds?

Jim

BTW, your choice of float plane is excellent for the reasons you stated, plus a low wing will be more resistant to crosswinds than a high wing would. Your problem is that at 11 pounds, you no longer have a light wing loading.

RE: first float plan
 

KKachler,don't worry.You are on the right track.The Great Planes floats will work just fine on the Sig Four Star 60.Those floats are designed specifically for 60 size aircraft and quite frankly,you'd be hard pressed to find another 60 size aircraft of comparable dimensions that has such a light wing loading as the Four Star 60.Its design is simple,straight forward and most of all,very light weight.With your four stroke .91 on board,it will fly with those floats very well indeed.Once you see her pop off the water for the first time,you'll be wondering why you ever had doubts in the first place.;):)

RE: first float plan
 

Well Turbobeaver,

I'm glad you rethought your first repsonse and hope you are right. I came to the same conclusopm amd decoded that I definitely was going to fly the combination, but your first reply was cause for apprehension. Noticed an add for the Falcon Cardinal on floats - 9.5 lbs and 680 sq in wing. I figure the 4 Star/GP 60 floats with 920 sq in wing should fly evein if it comes out heavy at 12 pounds. The 4 Star is mounted on floats, but waiting purchase of music wire for corss bracing. GP cross braces were too shrot for my installation. Anyway, I guess it should be good practice for a future warbird.

I am going to fly it on a large Adirondack lake during my vacation next week, August 14th. The mountain lakes are dead calm until about 11 AM, so I'm thinking it should be a good venue for a first attempt. Our local club sits adjacent to a drag strip. Two years ago the dragstrip owner enxtended the strip runout and built a pond in the process. Nice pond, but reeds every where and kind of down in a saucer.

RE: first float plan
 

KKachler,there was no rethinking on my part as per my first post.Both the first post and second post are in unison with the same theories and principals.There is nothing new here that you are doing as it has been done many times by others(many in my own club even) so not to worry.Your level of flying proficiency will be more of a deciding factor here than anything else.If you are flying at the intermediate level at least(or better),you won't have any unpleasant surprises thrown at you with this combination.If your expecting it to fly like a trainer on land,that's not going to happen.Any time you install floats on any type of plane,irregardless of its original wing loading,you are going to add extra weight and drag to the originally designed model and you must be prepared and experienced enough to know how to handle models that have higher wing loadings and drag related issues and fly them within these limitations.They will ALL stall sooner both at high and low speeds and also require higher R.P.M's from the engine to achieve comparable flying speeds.This is related to the increased drag and weight of the float installation.If you don't have a complete comprehension as to what these limitations are and how to handle them,they will always come back to bite you in the butt.If you ever get a chance to design flaps into your float plane,do it.It makes all the difference in the world for both take offs and landings.Take offs are quicker and landings are much slower and more controlled(less chance of low speed stalls due to the increased wing lift).Happy flying!;)

RE: first float plan
 

I'm flying a 4* 60 on my own design floats.

RE: first float plan
 

Interesting float design JRF. Particularly the installation. If you have a chance it would be interesting to see a close up photo showing the detail of the installation. What was the total aircraft weight?

Being new to float planes and having installed what are probably over-sized floats on my 4*, do you have any thoughts whether changes to control throws should be considered. I was thinking of increasing throws maybe 25%.

RE: first float plan
 

Thanks for the reply and comments on my floats. To try and answer your questions I'll begin with wieght. The 4* 60 is an ARF kit that had a slight miss hap and was recovered with Sig Coverall and then painted. The forward silver half of fuse was painted with thinned epoxy, sanded, and then covered with Flite-metal aluminum. It Came out around 7 lbs. The floats are only about 3/4 lbs. So the all up weight is very light.

You can see from the closeup photos that mounting is very simple. Just make sure to use an extra screw on the King Post to keep it from rotating around the axle. The King Post being the bar sticking striaght up that the spring and lanyard are attached to.
The floats are 13" long and 4 1/2" wide. The step is 1/4" deep and located straight under the axle and back two thirds from the nose of the float. Floats are made from balsa and ply. Ply bulk heads, Keel, and float bottoms. Sides and tops are done with balsa. Then glassed with 1 oz. glass cloth. The rear float is very similar but reduced in size and has no step. Hope this helps.


These floats work great and tippy toe accross the water on touch and goes.

RE: first float plan
 

Realized I missed one of your questions. I didn't increase my control throws at all. On your plane, if you use the GP floats, you may want to add rudder throw and maybe a sub rudder fin. My rudder is not very effective on this bird flying off wheels, or my float cinfiguration. With the GP floats all that extra side area may need some help.

Happy landings

RE: first float plan
 

Hey, another set of "tail dragger" floats. I see yours have a step. I cut mine off at the step, using only the forward portion. They seem to work pretty well. The plane picks its tail up quickly. Admittedly, it is a fun fly plane that is very light, even with the floats, and with a TT .46, it gets off right now.

I have yet to see any downside from these floats. I imagine on a full scale, you'd want the fuselage to sit level to see on the water and for passenger entry, etc.

RE: first float plan
 

A couple more photos, they were big.

Looks like we are getting a hurricane down in my neck of the woods. I am in Ft Walton Beach, Florida, area and Bonnie is supposed to make landfall just east of us. The Panama City guys probably won't be doing anything but cleaning up this weekend. Been there.

RE: first float plan
 

Well - The 4* flew on the GP60 floats. As predicted the combination was heavy and needed to fly very fast all the time. Made 3 flights while on vacation. All were successful. Longer than expected take-off runs were necessary, but uneventful. Landings were also successful, but lost power after touchdown on the first 2. On the 3rd landing I got the hang of applying power just prior to touchdown.

Any thoughts on flaperons on the 4*. I am thinking about experimenting with the set up on wheels first. What I am looking for is greater lift at slower speeds.

RE: first float plan
 

No, just make it lighter.