Venteral fin... or fins

[akflyer 1427]

I need to build some fins for my plane.  The EDO floats are alot deeper and the side area really shows up on a windy day with the nose hunting and pecking around.  These are rudder intensive planes anyways, and the additional float area really makes it a work out at times.  Instead of the large fin under the fuse like the factory had, I was thinking about making two fins to bolt top and bottom of the stab using the tail brace bolts.  What so you guys think about using those points to mount a fin say 12" tall the width of the elevator top and bottom on each side ?  You think the two little bolts would hold them along with the tail braces? 

 

I am thinking there will not be too much force on those bolts so it shouldn't be an issue.  Worst case, I can cut a couple holes in the fabric and weld in some new bosses to bolt through a little bit outboard of the tail braces.

 

Any ideas or thoughts?

 

[EDMO 1078]

Amateur Opinion from one who tends to overbuild - I would weld in mounts. Just don't have a lot of faith in 3/16 bolts - but that depends on where and at what angle the leverage, and possible flutter, would come from - the struts form a triangle mount, and that is a lot stronger than a single attachment. Would like to see some photos of the tested and proven outcome - interesting thoughts - you probably watched the 747 that carries the space shuttle, or an old Bellanca tri-tail?

Good Luck with your experiment - Hope it works good for you.

EDMO

P.S. Afterthought - Below the HS, you could attach a small strut from the fin to your HS strut, and have that same angle brace for your fins. Just a thought.

Edited 18 Jul 2013 by Ed In Missouri

[akflyer 1427]

Good Idea!  Gives me something to think about!

 

Thanks Ed

 

The pic shows what I am thinking about doing wit the black outline on the tail.  One on each side should be good.  I have seen them on Citabrias and Beavers and several other aircraft. 

 

 

[EDMO 1078]

Suggestion: How about just one braced on the bottom for a start, maybe a little larger there than you had planned - see how much it helps before worrying about top? This is unknown territory.

EDMO

Believe I read somewhere about fins not being really effective unles the height is at least 1/2 of horizontal chord? HS chord? Including elevator chord? I don't know! For a complete - top and bottom fin, height should equal chord.

Adding this: I would have to find my original fin to measure it, but guessing about 9 inches high and 18 inches long. Maybe that will help in determining size?

Could you brace the top one to your wing-fold brackets?

ED

Edited 18 Jul 2013 by Ed In Missouri

[Av8r3400 1179]

Thought #1 -- how does the h-stab attach to your plane? Is there enough beef there to handle the forces you want to put there?

#2 -- in a x-wind situation, will these fins do anything? Look at the silhouette of the plane. Answer: not much.

#3 -- adding a ventral fin to the trailer tongue mounts is how Wilson designed it to work. Why reinvent the wheel?

[EDMO 1078]

Thought #1 -- how does the h-stab attach to your plane? Is there enough beef there to handle the forces you want to put there?

#2 -- in a x-wind situation, will these fins do anything? Look at the silhouette of the plane. Answer: not much.

#3 -- adding a ventral fin to the trailer tongue mounts is how Wilson designed it to work. Why reinvent the wheel?

Well, with the exception of #2 - where I think the Slipstream will overcome x-wind effects, and that is what the fins are for, I tend to agree with you.

Now Leni, we need your reasoning for the addition of this cute modification! And why are you not "going with the crowd"?

This is the best use of this site - A meeting place for minds and ideas and problem solving - Well, with a smattering of joking too!

EDMO

EDMO

Is there an echo? Heat index is over 100F here - too hot to do anything else on plane.

Edited 19 Jul 2013 by Ed In Missouri

[Av8r3400 1179]

I work outside for a living.  I don't care what the heat index is.  It is just to f'n hot to do much of anything...

 

 

You got a job for me up there on the 'slope?  I can deal with misquotes but this southern heat is killing me.

[akflyer 1427]

  why did michelin invent the run flat tires... or a better mud and snow tire? 

 

The tail gets real low when the plane rocks back to get on step.  Anything hanging below the rudder hits the water and casues drag, extending the time it takes to get up on step.  I am all about shorter take off runs, and still getting the job done.  increased surface area works.  that has been proven in alot of float installs on various airplanes.  Some beavers have the ventral fins  under the tail like the one Dean designed for this plane.  Others have the ones that I am looking at building.  Different stroked for different folks I guess.  I think the twin fins on the horizontal stab look better. 

 

The reason for them is not to make handeling better in a cross wind, but to counteract the additional side area from the float profile forward of the CG. 

 

The big fin under the plane, in addition to hiting the water, makes a great something to get ripped off on the docks, trees on the shorline etc

 

Kinda like why use grove gear instead of the stock bungee gear... your sold on the fact that its a superiour gear... I am not gonna rgue that one with you, because it is a much better gear than the stock narrow gear

 

[akflyer 1427]

I work outside for a living.  I don't care what the heat index is.  It is just to f'n hot to do much of anything...

 

 

You got a job for me up there on the 'slope?  I can deal with misquotes but this southern heat is killing me.

 

Larry, you would get too spoiled only working 6 months a year That would give you way too much time to fly, and WAY too much time to day dream while your stuck up here.

 

 PM me your quals and what kinda job your looking for!

 

[EDMO 1078]

  why did michelin invent the run flat tires... or a better mud and snow tire? 

 

The tail gets real low when the plane rocks back to get on step.  Anything hanging below the rudder hits the water and casues drag, extending the time it takes to get up on step.  I am all about shorter take off runs, and still getting the job done.  increased surface area works.  that has been proven in alot of float installs on various airplanes.  Some beavers have the ventral fins  under the tail like the one Dean designed for this plane.  Others have the ones that I am looking at building.  Different stroked for different folks I guess.  I think the twin fins on the horizontal stab look better. 

 

The reason for them is not to make handeling better in a cross wind, but to counteract the additional side area from the float profile forward of the CG. 

 

The big fin under the plane, in addition to hiting the water, makes a great something to get ripped off on the docks, trees on the shorline etc

 

Kinda like why use grove gear instead of the stock bungee gear... your sold on the fact that its a superiour gear... I am not gonna rgue that one with you, because it is a much better gear than the stock narrow gear

 

I am certainly the last one in the world who would tell you not to do your own thing, or try to come up with something better. I had already guessed your reason, but wanted you to say it.

For my 2 cents worth - I say "jump in and see if it floats" pun intended!

EDMO

PS You might think about a stronger HS attachment?

[akflyer 1427]

I am thinking larger struts and cutting out the existing bolt bosses and using 1/4 bolts.  What you are really talking about here is the shear strength and the 3/16" should be plenty, but for the few hours it would take, upsizing the bolts may not be a bad idea!

 

[EDMO 1078]

I think my design borrowed from Piper / Maule is about the strongest HS attachment you could get - Check out the Foxy Flapper Fotos in Kitfox IV.

EDMO

[EDMO 1078]

I think my design borrowed from Piper / Maule is about the strongest HS attachment you could get - Check out the Foxy Flapper Fotos in Kitfox IV.

EDMO

I WASNT WORRIED about the struts - I don't like the flimsy, weak main attach for the HS. You could probably stand on my HS and not break the attachment. Undoubtedly overbuilt, but you could do something lighter and still be stronger than the original.

ED

Edited 19 Jul 2013 by Ed In Missouri

[Av8r3400 1179]

Larry, you would get too spoiled only working 6 months a year That would give you way too much time to fly, and WAY too much time to day dream while your stuck up here.

 

 PM me your quals and what kinda job your looking for!

 

 

 

You'll be the second person to know when the wife divorces me...

[akflyer 1427]

You'll be the second person to know when the wife divorces me...

Fourth... I bet her lawyer and best friend will know first and second

 

[EDMO 1078]

I WASNT WORRIED about the struts - I don't like the flimsy, weak main attach for the HS. You could probably stand on my HS and not break the attachment. Undoubtedly overbuilt, but you could do something lighter and still be stronger than the original.

ED

Leni,

I watched a Cessna on floats taking off, and the V-fin dragged in the water - I see what you mean - very good video with belly camera at Lake Iliamna, or Clark.

EDMO

Edited 19 Jul 2013 by Ed In Missouri

[akflyer 1427]

Leni,

I watched a Cessna on floats taking off, and the V-fin dragged in the water - I see what you mean

EDMO

and with the current rigging I have, my rudder just clears the water as it is.  I don't really want to raise it up any more due to the pendulum affect of the floats on the plane. 

 

I think I will do a quick sheet metal fin and see how much I need to help out the hunt and peck issue.  I dont think it will add crap for a load on the mounts.  If you see the three small bolts that holds the tail on an otter you would not worry about the loads a couple fins would put on our tails

 

[EDMO 1078]

and with the current rigging I have, my rudder just clears the water as it is.  I don't really want to raise it up any more due to the pendulum affect of the floats on the plane. 

 

I think I will do a quick sheet metal fin and see how much I need to help out the hunt and peck issue.  I dont think it will add crap for a load on the mounts.  If you see the three small bolts that holds the tail on an otter you would not worry about the loads a couple fins would put on our tails

 

I dumbly and happily flew anything with wings and a tail for years - my machine work was usually on the heavy end - Then I went to AMT school, and my "education" about planes put some fear into me. Now, I have to go watch the videos of the contraptions that the aviation pioneers flew in order for me to bravely get into some of the more flimsy, light weight, flying things. I still like the Taylor / Piper proven designs - And, no, I never looked at the tail bolts of an Otter or Beaver, but I understand that they do not fall off.

Keep us posted - This is interesting to me, even if I don't swim!

They have caught sharks in the Mississippi River at Alton, Illinois, 1750 miles from the ocean!

EDMO

Edited 19 Jul 2013 by Ed In Missouri

[C5Engineer 1170]

Is something like this what you had envisioned Leni?

 

[akflyer 1427]

Yep, but dump the fin under the fuse and just use the ones on the HS. but put them top and bottom.

 

[1avidflyer 1983]

Leni, don't know if you are aware of where that pic came from, but it's for sale in Ketchikan. Has a 912 in it, wants something like $21 or $22,000 for it. It's on barnstormers. Jim

[daveee 0]

Here is an Avid with lower twin ventral fins. I have done the same but haven't tried them yet.

 

A test pilot friend of mine says you need rudder pedal pressure to steadily increase as you press either of them, other wise you haven't got enough ventral fin area.

[akflyer 1427]

Damn, those look like 1320 floats.  Do you have any info on that plane or owner?

 

[EDMO 1078]

Leni,

Look closely at the Avid V-fins - Notice the extra brace.

And, I'll bet that the other one is banned on TKF!

EDMO

Edited 23 Jul 2013 by Ed In Missouri

[daveee 0]

A better pic, no info to go with it.