Float installation 2870 Edo

[huntaero]

Fitted 2870 floats to my Bearhawk used the older style 249-2870 with the swivel attachments, all the struts had corrosion under the clamp on steps so I purchased new struts blanks from Southern aero in Georgia Products (southernaero.net) PN LS-4. Attached are a couple pics of my set up and the ventral fin I fabricated and attached to the tailwheel mount and fwd mount of 4130 sheet welded across the bottom tube at the fwd end, with a tie down handle to maneuver the aircraft on a beach. I used the Edo rule and went 40% of the widest part of the float which is 12.04 inches aft of the center C of G to the step or 28.5 inches aft of datum. The 2 fwd struts remain the same length and my step was within ¼ of the 40%. I set my angle from the top of the floats to bottom of the wing at 3.5 degrees and if not enough I can shorten the aft strut by ¾ in without much work, and get about 0.7 more degrees to put it at 4.2. Fabricated my fwd strut attach fittings from 2024 alum. I fabricated new rear attach fittings from 4130 and used the original cross brace wires on the aft but needed shorter ones for the front which my buddy had for a set of 2425 floats. Fabricated my sling also to pickup on the fwd spar attach bolt and the L and R upper eng mount bolts.

[zkelley2]

I never really thought about making the attach blocks from steel. That'd be a lot easier than aluminum.

Do you have drawings you'd be willing to share on the attach blocks?

[huntaero]

I could draw them up if you want for the fwd or aft fitting

[zkelley2]

Ya that would be great. Did you make the blocks and drill the holes in place to get the angles right?

[huntaero]

Actually I made the rear attach fitting with a tube welded on the inside to give me a dimension of 1in then installed it in the end of the strut, then made the strap that bolts to the fuselage bushings (previously installed welded in 3 places to match the fabric so they would be flush and 90 degrees to the fabric). Then I mocked up the floats as you can see in the pics using the spreader bars, 2X6 boards, all the original attach points and the original struts then I matched up the bracket with the strap and welded it in place. It would have been difficult to get the right angle otherwise. On the bottom I had to weld another bushing in the bracket to get it to match up with the one in the fuselage when the bracket extends out to attach to the cross brace flying wire.

[Steve W]

I kinda don’t get the 40% Edo rule. If I get the basis of what your doing, then you are saying your center of mass of the floats is 12.04” ahead of the step? Then the center of mass of the floats is centered on the forward/aft index of the plane? I always understood the center of mass of the float was to be located at the most used c of g for flight. Not caring where the step was. I think these are both the same end result. I’m a bit dyslectic and the 40% doesn’t jump out at me as to where it’s being used.

[huntaero]

Ya i know the 40 % rule seems a little strange but my friend just installed CAP 3000 on his Rebel and his empty Weight C of G only moved half inch, he did all the calculations with the buoyancy and C of G on the floats and all were about the same. Rob from Alaska used this formula on his Bearhawk also and his seems to fly very well.

[schu]

This is a pretty clever way of doing this. Thanks for sharing. If didn't already make float mounts, I would have for sure done it that way. Much cleaner when the floats aren't on the airplane.

[zkelley2]

This is a pretty clever way of doing this. Thanks for sharing. If didn't already make float mounts, I would have for sure done it that way. Much cleaner when the floats aren't on the airplane.

Agreed. I wish I'd have seen that idea a year ago.

[whee]

Agreed. I wish I'd have seen that idea a year ago.

Bob designed bolt on rear float fittings like 20 years ago. They are shown in an old newsletter.

[zkelley2]

Bob designed bolt on rear float fittings like 20 years ago. They are shown in an old newsletter.

Are you talking about the bushings that are in the rear of the fuselage? That huntaero used to bolt into? I've not seen an actual bolt on fitting going back through the beartracks.

[huntaero]

The rear fittings are 1/4 inch bolts x 3. You can weld the bushings in then make your bracket later and use the spreader bars and float fittings to mate the floats to the aircraft thats when you will get the right angle at the aft brackets also you have to offset the flying wires so they dont rub were they cross. Added some pics and descriptions to make it a little esier to follow. Have fun

[huntaero]

Ventral fin fabrication and attachment structure