Curved lines are pleasing to the eye

[G-man]

I think curved lines look great on airplanes, and
it looks to me like Artur Blejzyk feels the same way.

Here is a project that combines classic elliptical wing tips
with a wonderfully round-shaped fuselage from Blejzyk Models.

Back in the early 1990s friends and I flew the Hobby Horn SENSOAR.
These photos are my son flying the glider around 1992 when he was 13 or 14.

 

[G-man]

This past winter, I got to thinking about the beautiful tip shapes and I dug out
the drawings (dated 1982) and started building this open bay design balsa glider.

Meantime, I built the Blejzyk FIRST, to get some training gliders ready for action
this spring and I was mightily impressed with the Artur Blejzyk fuselage appearance,
engineering, and production quality.

Turns out, Aloft will sell Blejzyk fuselages alone. Thank you, Wayne.

 

[G-man]

I finished covering the wings today and cobbled together the airframe for photos.
I have yet to decide how to mount the wing - could be rubber bands like the
original SENSOAR, or possibly a nylon bolts mount as in the Blejzyk design.

I did utilize the Blejzyk-designed bolt-on tailfeathers method.
The wings separate in the center for ease of storage and transportation.

More later when I get the control components installed.
And when we get it flying and see the sun shining through the wings.

 

[Konrad]

I'm sorry, I missed the size of your model.

Are you using the large diameter fuselage, like that found on the First? Or the narrower diameter fuselage like that found on the Mefisto?

With the ability to buy fuselages from Wayne, I like the Mefisto as my replacement fuselage for the 1.5 to 2 meter ships as they are a bit longer.

Not that you asked but for me it is bolt on wings all the way.

All the best,
Konrad

 

[G-man]

Konrad,
It's a 2-meter / 78-inch span.
The large diameter FIRST fuselage. It is five inches / 13 cm longer than the drawing on the SENSOAR plans.
Bolt on is smooth and secure, but I'm also thinking about beginners flying it, and the possibility of catching a wing tip on landing.
The rubber band mount can assist in self-preservation of the airframe. Fat, draggy, flat-bottom airfoil also. This is a slow-boat floater wing.
When my head hits the pillow, I think about this plane drifting skyward in a thermal.
// Dave

 

[Konrad]

It is my experiance that the rubber bands for beginners doesn't really work all that well. Seems like a 1930's solution from the days of free flight and before "Plastics", to quote the Graduate. They cut into the TE and destroy the wing from the aft end. I like to use #6 and and #4 nylon bolts that are torqued tight. The tighter the torque the sooner they shear. History has shown this to be a better set up for me and my students.

 

[Wayne]

Dave, that really looks great! You have a great eye as that fuse really works well with those wings. You could put some white accents on the wing and really tie the 2 together. Give a nice vintage feel to the colors too.

 

[G-man]

Mr Konrad,

I decided to go with bolt-on wing, for the reasons you mentioned.
The 1/4-20 nylon bolts insert from the bottom. I have not yet decided
how to strengthen the fuselage to bear the pressure of the bolts.
I'm leaning to plywood cross-pieces inside the fuselage, one for each bolt.

Would I be too effusive to mention again how much I love the Blejzek fuselage?
Beautiful shape, innovative engineering, quality molding. All to a very high standard.
It's lots easier to work on a fuselage with the front parts installed later in the process.

// Dave

 

[Konrad]

"Would I be too effusive to mention again how much I love the Blejzek fuselage?"
Not at all, your thread has gotten me back to working on my Mefisto.

Now that is thinking outside the box! I'd think #10 or even #8 bolts would be enough and still shear in the cartwheel. I'd use tubes braced to the fuselage at the top and bottom. I assume there will fiber wraped around the threaded inserts and center line rib.

BTW: It's not Mr., my first name is Konrad.

All the best,
Konrad

 

[G-man]

"I assume there will fiber wraped around the threaded inserts and center line rib."

Another one of your good ideas.

 

[Konrad]

Thanks.
Ah, but what fiber to use?

 

[Wayne]

I thought you where going to put a little plywood plate near the top fo the fuselage to bolt down too. Then drill a big enough hole in the bottom of the fuselage to slip the screw and screwdriver into.

 

[G-man]

Yeah, and with any luck those holes will generate a cool sound.
The coolest sound in silent flight.

 

[Konrad]

So you are going to go with the short bolts and guide tube (whistle) rather than the stand off mount (long nylon bolts)?

 

[G-man]

We got some air under the wings of the SENSOAR, now with Blejzyk FIRST fuselage.
It flys just like I remember from 28 years ago. Looks much better now, of course.
Many thanks to Steve Wattenberg for photography.

 

[Konrad]

How does this compare to the "stock" First (thermal)?

Blejzyk FIRST 2-meter Polyhedral Build

My introduction to Blejzyk kits is the 2-meter polyhedral FIRST. What a joy to build because the engineering is superb and the quality of the wing components and tail surface parts is so high. The fuselage is in a class by itself - a wonderful example of the molder's art. My FIRST build took...

forum.alofthobbies.com

All the best,
Konrad

 

[G-man]

Hi Konrad,

Original FIRST build time: 14.25 hours (pre-sheeted wings, solid pre-cut tail parts)
SENSOAR wing build time: 40.25 hours (push sticks together, heat-shrink covering)
(Includes my home-brew engineering for split-wing design modification, and nylon bolt wing mount.)
(I copied the original FIRST design for removable tail parts - bolts inserted from the bottom.)

Original FIRST all-up weight: 30.9 ounces, 876 grams
SENSOAR wing all-up weight: 27.3 ounces, 774 grams
I think a rubber band wing mount on the SENSOAR would have been a couple ounces lighter.

For a flight performance comparison, I'd have to fly them both on the same day.
I find building with sticks a pleasant pastime, and I like seeing the sun shine through the translucent covering.
The slight undercamber airfoil on the OEM FIRST gives impressive flight performance.
I have yet to core a thermal with either airframe.

 

[Konrad]

Wow, 26 hours difference!
100 gram difference. I like that when looking for lift, but don't like that once in lift.

A couple of onces lighter with rubberbands? How heavy are the bolts and center rib?

Not enough time on ether ship to make an honest assesment. I like that answer.

 

[Wayne]

Looks great! Surprised it is that close in weight, and I totally agree with the translucent covering.

I think I need to send you a retirement gift.

 

[G-man]

OK, maybe more like 1.5 ounce weight penalty for my plywood-and-brass wing hold-down part.
Not shown on the scale are two pieces of 5-ounce fiberglass cloth, the length of the wing chord, to stiffen the fuselage to receive the pair of 1/4-20 wing mount bolts.
The wing hold-down would have worked fine with thinner plywood and smaller diameter bolts, as you mentioned.