Flap lower skin to fuselage overlap adjustment

[flydjd]

Hi all and seasons greetings.

I have searched this subject and see that some builders have had to bend the lower flap skin up or joggle it down according to their rigging requirements.

In my case the skins are being bent down by the fuselage, left side more than right. In fact the leading edges are rubbing against the fuselage bottom skin. (All wing incidence settings double checked OK since drilling rear spar attach.)

I know that others have joggled the flap skins using hand seamers and I think that this will be the answer for me as I don't want to just cut this skin off completely and leave the flap rod hole uncovered.

My Q is this (eventually) :-

Has anyone trimmed these skins with an S shaped cut to clear the interference but maintain the cover of the flap rod hole.
If so what are the aerodynamic considerations ?

QB Wings and fuselage.

 

[pierre smith]

Yes......

....we did cut some off our -6A, David. We had to remove almost all the flap skin because there was no way they could be left on. Van said that it's not a big issue. Our flap hole is uncovered but you only see that if you lie down under the airplane anyway ...plus we still run over 200 MPH.

Regards,

 

[flydjd]

Thanks Pierre,

I am still undecided......what about the draught into the push rod holes...is that noticeable at 200mph ? I'm guessing it is fairly insignificant.

 

[L.Adamson]

I cut the skin off, and made a seperate piece with the joggle on a sheetmetal brake. It's riveted on with flush "squeeze" rivets.

L.Adamson --- RV6A

 

[flydjd]

Well, I have tried a "joggle" on the L flap but there is still interference which prevents the last 1/16th upwards movement to get the alignment with the aileron.... so its out with the Dremel !

 

[GAHco]

I helped fix my buddy's

I helped fix my buddy's,

His fuselage was a little more than 1/4" lower than where the flap bottom was.

We removed it and bent it down at about 25 to 30 degrees right next to the inboard rib, then at the correct angle and distance to make it look good we bent it to be parallel with the belly skin when fully retracted. We actually barely over bent it to slightly press against the belly skin.

I have been working with aluminum a long time and I was still very happy that it looked so good on the first try.

I might be able to get a picture, but I don't know just when the next time I will see him and his plane. If I do I will re-post.

 

[flydjd]

My solution

Tom, thanks for the response...was his a 7 ? ... because the 7 has a very slight curve along the fuselage and I wasn't happy with my attempt at the initial bend so close to the flap rib and I was still seeing a flex pressure on the flap hinge when the flaps were retracted......anyway for me it's a "done deed" now as I have trimmed both lower flap skins ....
now I just need some sort of rubber or other flexible material to put on the inside of the pushrod holes to prevent the draught...

Lessons learnt for anyone following - I spent a looong time fiddling with setting up my incidence and sweep and followed the Vans http://www.vansaircraft.com/pdf/Wing_ Incidence.pdf instructions ...BUT because I diligently set sweep at zero I was unable to test retract the flaps fully due to the upper flap skin interference against the fuselage and I didn't want to trim those skins before drilling the rear spar attach holes...CATCH 22 !

 

[flion]

One of my flaps was flush with the bottom of the skin, the other needed to come above it by about 1/8". I trimmed it with a 1/8 gap, scuffed the edge, put release tape on the fuselage, and laid up a joggle using 3" glass tape. I reinforced the edge bond on the inside with flox. Trimmed to match the other flap, they both don't quite cover the pushrod exit hole but at least they look even and neat.

 

[GAHco]

It was a 7

Tom, thanks for the response...was his a 7 ? ... because the 7 has a very slight curve along the fuselage and I wasn't happy with my attempt at the initial bend so close to the flap rib and I was still seeing a flex pressure on the flap hinge when the flaps were retracted......anyway for me it's a "done deed" now as I have trimmed both lower flap skins ....
now I just need some sort of rubber or other flexible material to put on the inside of the pushrod holes to prevent the draught...

Lessons learnt for anyone following - I spent a looong time fiddling with setting up my incidence and sweep and followed the Vans http://www.vansaircraft.com/pdf/Wing_ Incidence.pdf instructions ...BUT because I diligently set sweep at zero I was unable to test retract the flaps fully due to the upper flap skin interference against the fuselage and I didn't want to trim those skins before drilling the rear spar attach holes...CATCH 22 !

It was a 7.

I too will make some sort of rubber lips to keep the flap rod area from being another drafty area on my 6 when I get that far.

I will also put those aileron rod booties on, that sounds like a must.

Best wishes.

 

[flydjd]

Flap pushrod "boots"

Tom,

Thanks for the replies....having now trimmed the flap skins I am actually very happy with the results...top speed isn't an issue for me...I also wonder how many others have trimmed their bottom flap skins off...maybe a poll is needed !

Also having seen the Classic Aero aileron rod boots maybe there is a market for a flap rod boot as well - miniature version..