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Amphibian RV-3

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SPEEDBIRD001S

I'm New Here
Hy to you all pilots!!
I'm new to the "Air Force", but I have to say that this forum is fantastic!
Anyway, several years ago I built an RV-3 B from the original kit, and I'm still flying it with joy every time that I could; after seeing online the picture of an RV-7 with floats a strange idea came to me...
So, I know that it's a strange idea and there are many factors to consider, but is technically possible to mount floats (with retractable gear) on an RV-3? I saw that there are different manufacturers that can provide floats, and I think (correct me if I'm wrong) that the 200 hp from my current engine could do their job contrasting the extra wheight and drag, so I'm curious to know what the most experts could say about my idea.
Thanks for reading and nice flying to all !
 
Often, floats are detrimental to stability, so floatplanes that are based on land-planes often end up with extra stabilizer area e.g. ventral fins, dorsal fins / vertical stabilizer LE root extensions, mini vertical stabilizers at the tips of the horizontals, etc. So, you should be ready to do something like that.

And the slower the airplane is, the better. I'd think about adding vortex generators, maybe extended and/or drooped wingtips, and maybe even drooping ailerons, depending on your comfort messing with the control system.
 
Thanks for the precious informations... I'm pretty sure that some aero modifications are mandatory for this type of conversion.
 
SPEEDBIRD001S said:
Hy to you all pilots!!
I'm new to the "Air Force", but I have to say that this forum is fantastic!
Anyway, several years ago I built an RV-3 B from the original kit, and I'm still flying it with joy every time that I could; after seeing online the picture of an RV-7 with floats a strange idea came to me...
So, I know that it's a strange idea and there are many factors to consider, but is technically possible to mount floats (with retractable gear) on an RV-3? I saw that there are different manufacturers that can provide floats, and I think (correct me if I'm wrong) that the 200 hp from my current engine could do their job contrasting the extra wheight and drag, so I'm curious to know what the most experts could say about my idea.
Thanks for reading and nice flying to all !
Click to expand...
There are many parameters to consider, not the least of which is the structure. You will need to fabricate and install mounts for the floats, which will certainly stress the current structure and add weight. You need to consider the useful load of the airframe after adding in the extra weight of the floats, hardware, and additional structure. It would not be wise to just increase the gross weight to accommodate the floats; there are many threads on increasing gross weight available to read. You will also need to address stability and control with the significant added weight and drag.

While it certainly may be possible, as you can see, there are many considerations to be made, and a definite chance of making a delightful aircraft…not so delightful.
 
Also, since the speed range of an RV-3, especially with that much power, is higher than floats are usually designed for, the strut mounting system will need to be examined for the higher aero loads. Along with that, the front struts could possibly be attached to the motor/main gear mount, but there are no fuselage hard points for the read struts, except for the rear spar bulkhead. My gut feel for this (based on being a retired aerospace structures guy and building an RV-3B now) is that it would be considerably easier to build a purpose-designed airplane than modify your -3.

But if you do it, please post photos! We'd love to see and discuss the changes and progress you make.

Dave
Now hooking up the engine to my RV-3B
 
One other thing to consider (along with the many points up above) is engine cooling. If you truly have a 200 HP motor up front, it is goign to require considerable cooling air, and with the drag of floats slowing the airplane down, you might not get enough air at anything close to full power. Extended slow flight on teh back side of the power curve heats RV engines pretty fast. Just another thing to consider.
 
Thanks for all the replies... for the front struts I think that I could modify the current gear attack point to mount a dumper (sort of). As you said the real question are the rear struts. Another point (assuming solved all the others with a good imagination 😬) is about installing the retractable gear system and also all the connections for the water controls (rudder).

I'm an engineer too and every time I think to this project new problems arrive...
Thanks again for all the replies; I didn't expect such interest in this topic as I'm a very new member! Thanks!
 
Ironflight said:
One other thing to consider (along with the many points up above) is engine cooling. If you truly have a 200 HP motor up front, it is goign to require considerable cooling air, and with the drag of floats slowing the airplane down, you might not get enough air at anything close to full power. Extended slow flight on teh back side of the power curve heats RV engines pretty fast. Just another thing to consider.
Click to expand...
Correct observation about the cooling; because of that I have already modified the cooling system when I rebuilt the engine some years ago.
 
Hi Speedbird, I'd be interested in hearing what modifications if any, you made to your 3B to shoehorn in a 200hp engine?
 
When I rebuilt the engine (Lycoming O 320) I mounted a belt driven supercharger; I had to do some hard work to fit it, mounting new custom engine cover with extra hot air exhaust, obviously all the belt system from zero; I was forced also to install an electronic ignition system and many other modifications to make it airworthy.
When taking off you have to apply throttle very smoothly (like in every plane, especially taildragger); in flight I never use 100% power mainly for fuel economy and maintenance reasons, but with te supercharger you have your power constant up to 10000ft (with my belt ratio). I have also to say that this conversion costed me more than the kit itself!
 
SPEEDBIRD001S said:
When I rebuilt the engine (Lycoming O 320) I mounted a belt driven supercharger; I had to do some hard work to fit it, mounting new custom engine cover with extra hot air exhaust, obviously all the belt system from zero; I was forced also to install an electronic ignition system and many other modifications to make it airworthy.
When taking off you have to apply throttle very smoothly (like in every plane, especially taildragger); in flight I never use 100% power mainly for fuel economy and maintenance reasons, but with te supercharger you have your power constant up to 10000ft (with my belt ratio). I have also to say that this conversion costed me more than the kit itself!
Click to expand...
You can dream up most anything--making it work is another story.
 
SPEEDBIRD001S said:
When I rebuilt the engine (Lycoming O 320) I mounted a belt driven supercharger; I had to do some hard work to fit it, mounting new custom engine cover with extra hot air exhaust, obviously all the belt system from zero; I was forced also to install an electronic ignition system and many other modifications to make it airworthy.
When taking off you have to apply throttle very smoothly (like in every plane, especially taildragger); in flight I never use 100% power mainly for fuel economy and maintenance reasons, but with te supercharger you have your power constant up to 10000ft (with my belt ratio). I have also to say that this conversion costed me more than the kit itself!
Click to expand...
PICS!!!
 
Ironflight said:
One other thing to consider (along with the many points up above) is engine cooling. If you truly have a 200 HP motor up front, it is goign to require considerable cooling air, and with the drag of floats slowing the airplane down, you might not get enough air at anything close to full power. Extended slow flight on teh back side of the power curve heats RV engines pretty fast. Just another thing to consider.
Click to expand...
If you think about the angle of the very well-designed RV cowling inlets with normal gear, the airflow is usually adequate at departure power and eventual speeds to keep CHTs in the normal range. Change that sight picture to an RV on floats and the angle the cowling would take on with a full power water departure before the floats get on the 'step': high, nose-up configuration with decreased airflow through the cowling inlets as, at that angle, most of the air is going OVER the cowling inlets. And for how long? Yes, it might not take too long to get up but might be long enough to cause issues....... :unsure: Interesting challenges to consider.

My answer: it would be really COOL:cool: to see but would be a major PITA to accomplish and, in the meantime, your airplane is grounded.🤷‍♂️
 
Thanks again for the answers...
At the moment the project is suspended mainly because I don't have the time to do such a big step and the friend that helped me building the RV 3 isn't really enthusiast about this modification because is almost sure that it ruins the airplane.
There is another factor: in my region there are very strict rules about amphibian planes... and there is also the financial side of the adventure...
The more I think about the project the more I think that the best thing to do is to do noting😬
 
If you haven't seen them, you might get some ideas how to mount floats by looking at the RV-6A and RV-7A that have been put on floats in the past. Eustace Bowhay in BC did the -6A conversion, I don't know if he was involved in the -7A or not. There were discussion about both conversions here on VAF in the past, you might find them with a search.
 
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