To shave or not to shave

On profile fuselage is is recommendable to shave the rear portion down to a point? If so, where do you start removeing material and do you take it off of both sides or only one? Once completed, do you need to reinforce the fuse with some type of covering material?

Or is it just better to leave the fuse alone and only round or taper the rear edge?

Thanks,

Leave it full width.. Any material you take off will make it that much more flexable and profiles tend have a flex problem anyway.

>Leave it full width.. Any material you take off will make it
>that much more flexable and profiles tend have a flex
>problem anyway.

True enough. But of more importance than leaving fuselage full width or tapering it is stiffness of the piece of wood selected. It's not unusual to see otherwise well-constructed profile fuselages allow the tail to flop around. In general, not a good thing.

Use of 1/64" ply doublers, either in spot applications, or (my preference) skinning the entire fuselage from front to rear, is a good option.

Applying Silkspan will help keep the fuse stiff.

LAST EDITED ON Aug-20-04 AT 03:59 PM (CDT)
 
Go to the Pampa web site. Great Documentation on how to build a better profile. If you you are not already a pampa member, you may want to join.
Great info.

Here is a snipit from one of the docs.
"Starting at the wing hinge line on the left side, mark the fuselage
top, bottom, and aft edges of the area of material to be removed
for a straight taper to rudder thickness or 1/8", as appropriate
(Figure 1).
Leave the fuselage right side perfectly straight. The
resulting "crooked" fuselage is not noticeable on the finished
model, while providing a few construction and even aerodynamic
advantages.
The first benefit is that the fuselage can be laid on its flat right side
for tapering and other shaping work. With all taper on the left side,
no left/right symmetry matching is required. Already life is easier."

I think it also says something about putting "Glass" on the fuse to make it stronger. Check out the site and docs.
http://www.control-line.org

Thanks
Paul

I am a retread, - I did C/L in my youth and did not know what I was doing then other then having fun. And not much has changed.

>Go to the Pampa web site. Great Documentation on how to
>build a better profile. If you you are not already a pampa
>member, you may want to join.
>Great info.
>
>Here is a snipit from one of the docs.
>"Starting at the wing hinge line on the left side, mark the
>fuselage
>top, bottom, and aft edges of the area of material to be
>removed
>for a straight taper to rudder thickness or 1/8", as
>appropriate
>(Figure 1).
>Leave the fuselage right side perfectly straight.
>The
>resulting "crooked" fuselage is not noticeable on the
>finished
>model, while providing a few construction and even
>aerodynamic
>advantages.
>The first benefit is that the fuselage can be laid on its
>flat right side
>for tapering and other shaping work. With all taper on the
>left side,
>no left/right symmetry matching is required. Already life is
>easier."
>
>I think it also says something about putting "Glass" on the
>fuse to make it stronger. Check out the site and docs.
>http://www.control-line.org

Larry's on line article is an excellent reference point for building profile fuselage ships. Remember, though, that Larry builds up his profile fuse, e.g. it is not just a slab of 1/2" balsa.

On another note, I was absolutely amazed what medium silkspan and polycrylic did for profile fuse stiffness.

V/r

Bob Kruger

LAST EDITED ON Aug-20-04 AT 08:20 PM (CDT)
 
THE SKY IS FALLING, THE SKY IS FALLING

Finch,
Most profile flex takes place at the trailing edge of the wing. If the fuse is not stiff just behind the trailing edge of the wing it will be magnified from there back. I taper mine from about 6 or 7 inches from the rear of the fuse forward before covering. This does not affect the rigidity of the fuse one way or the other. Picture shows a 1/4 inch rudder as it blends into a 1/2 inch fuse. Still a little blending to do. I draw a center line and some guide lines on the bottom of the fuse to help remove material evenly.

Hmm.. Got what I asked for great answers covering both sides of the question and both well supported with sound building logic. One of the main points I am concerned about is blending the rear fuse into to vertical stabilizer. Much like the pictures that GLBahrman posted. In this instance would it be good to start the taper just forward of the tail feathers and leave the full fuse width back to that point, say one or two inches? What risk does this leave for the tail feathers to be completely plucked on an inverted landing? Also I would assume that removing material from the rear of the fuse would dictate that a balance of weight be saved on the front end, else one risks the addition of weight back to the tail in lead.

Man! If building was easy everyone would be an expert..

Just one more consideration - -

Unless the Tail Moment is lengthened significantly on most profiles, (ala the "Fancherized" Twister) tail weight must be added. Why not just leave the fuselage full-width?

My porky Tutor weighs 38 oz., and with an old Max .35S requires almost 2 oz. of lead under the stabilizer to balance. And I've shortened the nose by 1½", too. Had I left the rear of the fuselage full width, I might have needed only 1 oz. of tail weight, and the rear fuse would have been much more rigid. The d!@# thing still flies much better than I can . . .

Sigh . . .

LAST EDITED ON Aug-20-04 AT 10:26 PM (CDT)
 
The real way to do this and to help with the balance. Do not wait until you are done. Add the motor and move forward and aft and add components as you build to adjust the balance where you want it to be so you don't have to add lead.