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Float Rigging

PostPosted: Wed Jun 13, 2018 12:38 pm
by mr157ifhz
A few questions on float rigging. I've a Rans S7s with Rotax 912s, to go on Full-Lotus 1450 floats. Pretty much have only settled on a couple things - Float angle to fuselage, and step distance from CG.
There are two things that I am undecided on:
Float stance - I am leaning towards a more narrow spacing center to center - say, 66" vs 72". Have read (was on this forum somewhere..AV8er?) that closer spacing will give better t/o performance than wider from the action of the bow waves ......is this just theory or did someone actually try a narrower stance vs wider?
Rigging Height - I'm thinking lower would be better. As long as good prop clearance from the water, a lower height, say 20~22", from the top of the floats to the fuselage would work better than 24 or higher (Murphy Rebels on floats seem to be almost 3ft!) Less pendulum effect, closer to water so more ground effect, lower CG increasing stability somewhat to offset the stability lost by going narrower on the stance, shorter rigging would = lighter weight too. Oh, and maybe no step needed to climb aboard.
Thoughts?
-Matt

Re: Float Rigging

PostPosted: Fri Jun 15, 2018 2:28 pm
by mr157ifhz
Pretty much have the info I need now after reading about float installation trials and tribulations on this and various other forums. Going to go 66" c to c, 22" Height and a 3* throat angle - will start there and see how its goes.

Re: Float Rigging

PostPosted: Wed Oct 31, 2018 2:51 am
by Retter
Sounds like you are heading in the right direction for the float rigging. A buddy of mine will be working on the Rotax 912s project right after we finished installing the new tires and rotiform wheels on his current truck project. Would appreciate any more info from your project.

Re: Float Rigging

PostPosted: Fri Jan 18, 2019 12:52 pm
by mr157ifhz
Also Going to have the step quite further aft than typical - This is because of the design of the FL1450s. Unlike most floats, the step is well aft of halfway, where most others are. If I mount the step in a conventional position, it would move the CG quite a bit foreword. The fellow I bought the floats from has lots of float experience and is willing to think outside the box. He had suggested forgetting where the step was, and instead hang the floats so that the overall CG of the plane empty on floats is the same as it would be on wheels.
I just read an article where a fellow with a Glasair Sportsman on floats did just that. He moved the floats back on the airframe several inches (when compared with other Sportsman installs) Glasair had been recommending shollower throat angles for higher cruise speeds, 2.5 degrees or so, at the expense of takeoff performance. This fellow increased the throat angle to nearly 4 degrees, resulting in much better takeoff characteristics (35knt t/o vs 45) and was surprised to see his cruise was also up 5% over his old setup.