Fixing Fuselage Square Alignment. A Twsit Fuselage or Simply Misalignment?

[Kafin Noe’man]

I have a profile plane that I think the fuse is a little bit twisted or simply a misalignment problem.

I’ll try to use a simple illustration to explain what I’m having now (please see the attached image below).

Black is the wing jig
Red is the wing
Orange is the fuselage
Blue is the triangle ruler

The wing is straight and level, as well as the alignment of the wing is square to the fuselage if we see it from the top view.

Problem is the fuselage is not perfectly square to the wing nor the working surface (as illustrated), but the weird thing is there are some parts along the fuselage that is perfectly square if we check it.

How bad this could be? Because if I check in various positions throughout the length of the fuselage, the triangle still touches most part of the fuselage at least 3/4 part of it.

So, what can I do here now? I’m looking forward to hearing more about it.


Best,
Kafin

[Ken Culbertson]

I will probably get roasted for this answer but here goes.  If the stab is perfectly alligned with the wing and the fuselage is square with the wing which you stated then I would do nothing.  Of all the things that need to be perfectly alligned, the vertical of the fuselage is last on the list, but that is just me and I could be wrong.  Personally, I would just sand it oval until it looked square.

Ken

[Mike Griffin]

Kafin,

I tend to agree with Ken on this.  There might be a slight "cup" in the fuselage at some point but I really do not this this is anything to stress about. 

Mike

[jerry v]

Kafin,
My Brodak P-40 profile ARF is a good example . The fuselage has a bow 1/4 inch. If put a straight edge to the outer “flat” side, touching the tail area, then there will be the 1/4 inch gap at the nose - the nose bent toward the circle center looking from the top. There was some twist in the fuselage too, but not to be concerned. I did not straitened the fuselage, I just shrinked the Monocote covering. The fuselage already went through the stress relief during the building in China, during the shipping over the sea, during the storage))  When I started the assembly P-40 I used big blocks on the fuselage sides in the nose and the tail area to be sort of perpendicular to the wing being level on the glass table top. I decided to make equal distance from the each wing tip to the tail end of the fuselage, ignoring the nose bowed . The nose was compensated with the washers under the engine logs at the front bolts. Also there is adjustable rudder to deal with the “bow “ compensation. My goal was to have a parallel alignment between the hinge lines of the wing and the stabilizer looking from the top and looking from the back. The crooked fuselage is just a solid piece holding the flying surfaces. My P-40 flies well with crooked fuselage, no bad tendencies . I can add some conspiracy theory : chambered fuselage creates  extra lift during the wingover compare to the flat fuselage!))

Jerry

[Brett Buck]

So, what can I do here now? I’m looking forward to hearing more about it.

   If all the flying surfaces are in proper alignment in nominal conditions, it's fine, leave it alone. To first approximation all the fuselage is there for is to keep all the important parts in the right places. 

     Brett

   

[Ken Culbertson]

I can add some conspiracy theory : chambered fuselage creates  extra lift during the wingover compare to the flat fuselage!))

Laugh if you will but that has been done intentionally on at least one plane I know of.  Inboard fuselage side flat and all of the curve in the outboard with a rudder done the same way.  ended up like a "Clark 'Y'".  Looks a bit weird and if I remember right, it had no real benefit probably due to propwash.

Ken

[Kafin Noe’man]

Apologies for my late response, I've been busy with works for the past couple of weeks.

Thank you for all of your responses.
It's good to hear/know that it's not something to over stress about.

It's now finished and ready to have its maiden flight.

[Colin McRae]

I purchased a Brodak P40 ARF a couple of years ago. I had heard of the possibility of a fuselage (and wing) warp in the P40 ARF kit. I got Brodak on the phone and specifically requested that before shipment of my kit, they open the box and verify the fuse and wing had no factory warps. Brodak has been good to work with and they did as I requested. My kit showed up fine (thankfully).

[Dave Harmon]

My P-40 arf came with a badly bent fuselage.
I took pix of it and contacted Brodak.
John looked at these pix and asked me to try to straighten it with heat, weight etc.
I tried...then reported back to him....he requested I return it...so I did.

Brodak sent another fuselage but this one was shipped in an unprotected box and was broken in half by the shipper.
I took more pix....this time they said just keep it...so I did.
Then they shipped another fuselage and it arrived safely and was straight.
It has been flying for some time now.

Can't complain about Brodak but they could take just a few more minutes on the front end to inspect these arfs....they would save considerable shipping cost and hassle for the customer if they insured what they were shipping was useable.

It's a really good flying airplane.

[Colin McRae]

My opinion is that Brodak's service has been excellent. I continue to support them. They are pretty much the last CL vendor around.

BTW, in the future Brodak is no longer going to offer ARF's and ARC's. Once their current stock is out, that will be it. They told me that if they were to order new ARF's from their China fabricator, that they would have to sell them for like $400-$500 to makes a reasonable profit. And no one will pay that. My P40 ARF kit 2 years ago was $180.

But Brodak will still offer kits for these models that they make up here in the US.