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FSII Dihedral

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jbhart(at)onlyinternet.ne
Guest

Posted: Sun Nov 19, 2006 6:34 am Post subject: FSII Dihedral

At 07:11 AM 11/19/06 -0500, you wrote:

 	  Quote: 	
		  



It flies hands off, you can drive it around with rudder only, and it seems 

to handle very well. Flown it like that for a year, no negatives. I put my 

MKIII in the garage yesterday, it is getting longer wing struts and we'll 

see how it does.


	


Richard,



It seems like it would require additional rudder to side or forward slip.  

This could be a factor for cross wind landings.  Have you noticed any 

difference?  What is the actual dihedral in degrees?  Has it influenced 

roll rate?



Jack B. Hart FF004

Winchester, IN

David.Lehman

Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA

Posted: Sun Nov 19, 2006 6:41 am Post subject: FSII Dihedral

Oops...  Aren't Kolbs supposed to have dihedral?...  Mine does, although I've never measured how many degrees...

  

 DVD

  

 do not archive



 

 On 11/19/06, Jack B. Hart <jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)> wrote: [quote]--> Kolb-List message posted by: "Jack B. Hart" < jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)>



At 07:11 AM 11/19/06 -0500, you wrote:

 	  Quote: 	
		  --> Kolb-List message posted by: "Richard Pike" <richard(at)bcchapel.org (richard(at)bcchapel.org)>

 

It flies hands off, you can drive it around with rudder only, and it seems

to handle very well. Flown it like that for a year, no negatives. I put my

MKIII in the garage yesterday, it is getting longer wing struts and we'll 

see how it does.


	


Richard,



It seems like it would require additional rudder to side or forward slip.

This could be a factor for cross wind landings.  Have you noticed any

difference?  What is the actual dihedral in degrees?  Has it influenced 

roll rate?



Jack B. Hart FF004

Winchester, IN



[b]

_________________
ô¿ô

"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."

--- George Bernard Shaw

Bill Vincent

Joined: 30 Jan 2006
Posts: 84

Posted: Sun Nov 19, 2006 7:54 am Post subject: FSII Dihedral

Hi Gang

 My FS II flies perfect with just a little bit of  dihedral. I used to own a TO-Bird, which had a lot of dihedral, I could fly it  "hands off" but I paid for it with a lot of adverse Yaw, meaning if I give it  left rudder the nose would go right.

 Bill Vincent

 FS II

 Upper Peninsula of Michigan

 Do Not Archive

 [quote]   ---

_________________
Bill Vincent
Firestar II
Upper Peninsula of Michigan

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Sun Nov 19, 2006 11:38 am Post subject: FSII Dihedral

---

_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

planecrazzzy
Guest

Posted: Sun Nov 19, 2006 3:21 pm Post subject: Re: FSII Dihedral

Hi Dave,

             They say that there's No Dihedral in the wing....But in the builders manual it sez how to go about setting the wings and measuring the lift strut length....and it sez you'll get an inch or so of Dihedral....



  "I" snuck just a little more....and I've seen others that took "ALOT" more.

 My next plane ( Tailwind ) has no dihedral either.... I wonder if I'll sneak a little in there.... I don't know yet....

.

.

.             

Gotta Fly...

Mike & "Jaz" in MN

.

.

.



[/quote]



 	  David.Lehman wrote: 	
		  Oops...  Aren't Kolbs supposed to have dihedral?...  Mine does, although I've never measured how many degrees...

  

 DVD

  

 do not archive



 





[b]

AirworthinessInspection 023.jpg

Description:

Although from this picture I can't really see the dihedral that I added

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60.64 KB

Viewed:

429 Time(s)

David.Lehman

Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA

Posted: Sun Nov 19, 2006 5:28 pm Post subject: FSII Dihedral

Hi Mike...

  

 Mine's not real noticable, in fact, I didn't realize it was there until I tried to install a "connecting" tube between the two leading edge tubes and found that the tubes pointed down...

  

 DVD

  

 do not archive



 

 On 11/19/06, planecrazzzy <planecrazzzy(at)yahoo.com (planecrazzzy(at)yahoo.com)> wrote: [quote]--> Kolb-List message posted by: "planecrazzzy" <planecrazzzy(at)yahoo.com  (planecrazzzy(at)yahoo.com)>



Hi Dave,

            They say that there's No Dihedral in the wing....But in the builders manual it sez how to go about setting the wings and measuring the lift strut length....and it sez you'll get an inch or so of Dihedral.... 



"I" snuck just a little more....and I've seen others that took "ALOT" more.

My next plane ( Tailwind ) has no dihedral either.... I wonder if I'll sneak a little in there.... I don't know yet.... 

.

.

.

Gotta Fly...

Mike & "Jaz" in MN

.

.

.

[quote="David.Lehman"]Oops...  Aren't Kolbs supposed to have dihedral?...  Mine does, although I've never measured how many degrees... 



DVD



do not archive

[b]

_________________
ô¿ô

"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."

--- George Bernard Shaw

vincenic1(at)earthlink.ne
Guest

Posted: Sun Nov 19, 2006 7:55 pm Post subject: FSII Dihedral

Previous message:



 	  Quote: 	
		  > It seems like it would require additional rudder to side or forward 

> slip.

> This could be a factor for cross wind landings.  Have you noticed any

> difference?  What is the actual dihedral in degrees?  Has it influenced

> roll rate?

>

> Jack B. Hart FF004

> Winchester, IN



I wrote a couple of notes about the flight characteristics with 
	


increased dihedral.  The notes are partially copied below from the 

archive for those who might be interested.



Vince Nicely

Firestar II



do not archive



Part of Note 1 - Aug 98



*My Firestar II is mostly a rudder airplane, but it was not always that way.

Let me explain.  When first setup as nearly as I could follow the Kolb

builders manual, my airplane gave an unusual rudder response compared to my

GA experience.  Specifically, on application of rudder, it would slow, pitch

nose up and  eventually could ususally be made to stall if rudder was held

full over.  Furthermore, if the airplane was in a bit of a bank, the rudder

alone would not lift the wing or cause the airplane to unbank, but caused

the other responses noted above.



I decided to add more dihedral because that seemed like it had a chance to

make the responses more conventional compared to GA planes which I wanted.

Three degrees (3.6 degrees actually, VAN 11/06) of dihedral makes my Firestar II able to fly all day without

touching the stick.  Slight rudder inputs provide all the roll control that

is needed.  It can be brought out of a fairly steep (say 20-30 degree) bank

with rudder alone.  It has just about neutral spiral stability, i.e., when

put in a bank it will approximately hold or slightly lower the bank angle

without control inputs.



When my plane is stalled, the rudder is very effective at lifting a wing (or

in the other direction for putting it into a spin).  I have not tried the

ailerons near stall, so can't comment until I fly it again.  However, I

might not want to start using the ailerons because if it became a habit I

think that can complicate

the stall situation in many GA aircraft which I fly some times.  Also, I

understand that in some aerobatic aircraft, at least, flat or knife-edge

spins are initiated by how the ailerons are held at spin entry.



At any rate, it would appear from my experience the details of setup can

make some difference in how they fly.



Vince*



Note 2 in Answer to Some Questions -



*>Vince:  Very interesting.  I only have experience with wings rigged to

 	  Quote: 	
		  Homer's standards.  By increasing dihedral, have you decreased performance?

 How much increase in inches to get 3 degree increase in dihedral measured

at the outboard rib?



john h

A very reasonable question. Sorry I didn't think to include that information
	


the first time.



I raised the outer tip of the wing 10" above the inboard edge.  This turns

out to be about 3.5 degrees I think.  By the way, on my Firestar II that

means the lift struts needed to be 2-1/4" longer than the standard setup.

Because my plane is folded in storage, I can't easily measure at the

outboard rib at this time, but it will be about 9" or a little more.



You are right that I have given up a little performance.  At the time, I

made some estimates and as I recall it was a trivial amount.  The amount of

dihedral was not optimized, either.  Because I had to purchase parts to make

the new lift struts, I made them at the longest I could imagine would be

needed so they could be shortened if needed.  I liked the way it flew with

the 2-1/4" longer strut and did not experiment further.



As you can imagine, the wings are noticeably canted up.  Some have wondered

if this is a problem in a cross wind with getting the wind under the wing

and raising it.  I have set the plane sidewise to an 11 knot wind on an

airport ramp to see what happens.  Then by trying to lift the up-wind and

down-wind wing tip, I decided the wind at 11 knots puts little lift on the

up-sloped wing.



Regards,

Vince*

Dave Bigelow

Joined: 29 Jan 2006
Posts: 103
Location: Kamuela, Hawaii

Posted: Mon Nov 20, 2006 1:15 am Post subject: Re: FSII Dihedral

The FS II rigged with only a few inches of dihedral from the plans has spiral instability.  If you let go of the stick and get bumped into a little bit of bank, the bank will continue to increase until you provide a correction.  Some people confuse this with roll responsiveness, since it takes very little stick input to start a roll, however it takes a lot more input to stop or reverse the roll.  An aircraft with spiral instability that has powerful ailerons is not unsafe, but does require a constant hand on the stick to keep the wings level.  It's kind of like driving an automobile that does not have the front wheel camber, caster, and toe in set correctly.



I added dihedral to my FS II until I could fly it hands off, and if rudder was held in either direction, the aircraft would gradually start a bank in that direction.  It makes for a much more pleasant flying aircraft, and I notice no appreciable difference in performance.  If you add too much dihedral, it can reduce the roll rate.  Here's how it goes:



1.  Add dihedral - more roll stability; more adverse yaw when moving the ailerons; more yaw/roll coupling when you move the rudder.



2.  Remove dihedral - less roll stability; less adverse yaw when moving the ailerons; less yaw/roll coupling when moving the rudder.



Too much one way, and the aircraft gets twitchy and harder to fly.  Too much the other way, and it becomes a truck.  Look for the sweet spot in the middle somewhere.

_________________
Dave Bigelow
Kamuela, Hawaii
FS2, HKS 700E

leecannon(at)telus.net
Guest

Posted: Mon Nov 20, 2006 7:53 am Post subject: FSII Dihedral

I recently purchased a Twinstar which the builder added dihedral to.( 

about the same as the subject FS II)  He also added a full wrap aluminum 

leading edge skin. I called Homer Kolb and asked  his opinion on these 

changes and he didn't seem too alarmed. I believe he said something like, " 

Maybee he planned on doing some cross country flying"  (referring to the 

builder).  If you look at many planes from the past ( champ, cub, t craft, 

beaver ) they have a bunch of built in dihedral - it's a good thing . 

Actually, when I first looked at Kolbs I was surprized that there was no 

dihedral - I still don't really get it? Why don't Kolbs have dihedral?

cheers, Rob Cannon, Saltspring Island, B.C.

---

jbhart(at)onlyinternet.ne
Guest

Posted: Mon Nov 20, 2006 9:34 am Post subject: FSII Dihedral

At 01:15 AM 11/20/06 -0800, you wrote:

 	  Quote: 	
		  



1.  Add dihedral - more roll stability; more adverse yaw when moving the ailerons; more yaw/roll coupling when you move the rudder.



2.  Remove dihedral - less roll stability; less adverse yaw when moving the airlerons; less yaw/roll coupling when moving the rudder.



Too much one way, and the aircraft gets twitchy and harder to fly.  Too much the other way, and it becomes a truck.  Look for the sweet spot in the middle somewhere.




	


Dave,



My FireFly was the twitchy truck variety with the Kolb plan specified 

dihedral.  The reason it was a truck was because cause of excessive aileron 

chord that lead to high control forces in roll. One could not displace 

the ailerons at cruise.  This doomed one to kicking rudders to keep the 

wings level.  By changing the wing chord from fifteen inches to nine inches 

and changing the crank to push rod leverage points the truck became a 

twitchy sports car.



Removing all slack from the aileron control system and adding VG's the 

twitchiness has disappeared.  If one lets go of the stick it will slowly 

roll off to one side.  Stick pressure required to keep the wings level in 

rough air is very light.  It is nimble and quick and goes where it supposed 

to.  And best of all, I can fly it an hour in the middle of the day and have 

enough energy left to get right back in it and do it again.



Adding dihedral to compensate for aileron high dynamic loading will make the 

aircraft more stable in roll. But it will require more pilot effort to fly 

in the middle of the day or cross country than a plane with reasonable sized 

ailerons.



Jack B. Hart FF004

Winchester, IN

Dave Bigelow

Joined: 29 Jan 2006
Posts: 103
Location: Kamuela, Hawaii

Posted: Mon Nov 20, 2006 6:35 pm Post subject: Re: FSII Dihedral

Jack,



The heavy aileron control force problem you describe with the Firefly has little to do with dihedral.  The Firestar has responsive and easy to move ailerons.  Adding some dihedral adds little extra control force unless you go to extremes.



Almost any aircraft will slowly start a roll to one side or other if you stay off the controls long enough.  If it has spiral instability, it will continue to roll off to a high angle of bank.  If it has the proper amount of spiral stability, the bank will stabilize at 20 - 30 degrees.



Don't confuse light control forces with stability - not the same thing.

_________________
Dave Bigelow
Kamuela, Hawaii
FS2, HKS 700E

jbhart(at)onlyinternet.ne
Guest

Posted: Tue Nov 21, 2006 7:35 am Post subject: FSII Dihedral

At 06:35 PM 11/20/06 -0800, you wrote:

 	  Quote: 	
		  

The heavy aileron control force problem you describe with the Firefly has little to do with dihedral.  The Firestar has responsive and easy to move ailerons.  Adding some dihedral adds little extra control force unless you go to extremes.




	


Dave,



I agree.  As long as the in flight cg is below the wing the wing with a 

little dihedral will in, in most cases, right its self in roll.



I guess the point I was trying to make is that if you are going to increase 

dihedral compensate for heavy roll stick forces, there are other options.



First, you can accept it as it is.  If you want to fly with low energy 

input, this limits flying  to the quiet times.  If you want to fly during 

the mid-day times, you can bulk up your shoulder through strength training 

and attempt to keep the wings level.  If you do not want to end up with a 

sore shoulder, you can let it roll.  I have done this, but after an hour of 

kicking rudder pedals to help pick up the wing, I was close to up chucking.  

Even though I told my self that I would not apply side pressure to the 

stick, I could not refrain from trying to keep the wings level with the 

horizon.  This resulted in a sore right shoulder.



Second, you can add dihedral, and wing will right itself more quickly in 

rough air.  But roll stick forces will remain high.  On cross countries it 

will be a little bit more comfortable, but in my case I would arrive with 

sore shoulder.  On a FireFly this means you have to replace four struts.



Third, you can add spades with their additional weight.



Fourth, you can reduce aileron chord and modify the aileron linkages to 

reduce roll stick forces.  This lets you fly in the middle of the day with 

low pilot energy output.  This is extremely important to me because I am an 

"old guy" who rarely gets to the airport before 2 PM. Dropping a few inches 

off the aileron chord saves some weight on the FireFly.



Fifth, you can sell your aircraft and purchase or build something that is 

more fun to fly.



In my case, my choice was the fourth option.  After the addition of VG's and 

removing all slack from the roll control components, the FireFly is a pure 

delight to fly.  In rough air, I do not have to kick a rudder to pick up a 

wing.  I just apply a little side pressure to the stick and the FireFly 

plows straight ahead and the wing remains level.  It will bob up and down a 

little, but this is not bothersome if the seat belts are tight enough to 

keep your back on the seat.



Jack B. Hart FF004

Winchester, IN

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