Pulsar 4 meter salvage build.

[Dan Tandberg]

Brian Kloft crashed this beautiful 4-meter Pulsar several years ago in Florida.  I don't exactly remember the story, but it seems like he crashed into a swamp and hit a Burmese python and then got the center section chomped by a large 'gator.  Something like that . 

The center panels are completely destroyed and in the Florida landfill.  And the pod has a few big cracks. He decided that he couldn't face making or locating a replacement center section so he made me take it for an attempt at salvage.  It has been in my shop for over a year, so here goes.

[Dan Tandberg]

All he model pieces shown are without damage, except for the cracked pod and the missing center panels.  It includes a pretty expensive Neu motor and a nice big fat ESC, plus a bunch of servos. I tried to give him some money, but he wouldn't hear of it.

[Dan Tandberg]

Here is the beginning layout for the center panels.  I am planning two inches between 1/8" balsa ribs, no cap strips.  The rib profile templates were traced from the wing tip roots.  

[Dan Tandberg]

Here I am planing down the flaps so they closely match the rib profile. Lots of work to get these right, but well worth the time.

[Dan Tandberg]

And now I am gluing hardwood stock to the front edge of the two flaps for added stiffness.  This will help keep them straight and warp free.  Notice the plywood rib profile templates are close at hand for frequent checking.

[Carris Mike]

Nice gliders. 

The AG 24-26 airfoils work really well.

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[Dan Tandberg]

Laminating the rear trailing edge spar. 

Dan Tandberg, MD

Professor Emeritus

UNM School of Medicine

[Dan Tandberg]

Yes, Mike.  I am using the traced outline of the wing outer panels for this project.

[Dan Tandberg]

The Pulsar series profiles are propriatary "modified" AG series, so careful tracing seemed like a good approach.

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The RC model Pulsar sailplanes primarily use modified versions of the Mark Drela AG airfoil series, specifically the AG 25 modified and AG 26 modified airfoils. [1, 2, 3]

These airfoils, designed by Dr. Mark Drela of Charles River RC, are known for their high performance in thermal duration gliders, particularly in models with wingspans of 3 meters and larger. They are optimized for generating high lift at low Reynolds numbers, which is typical for light, slow-flying RC sailplanes searching for thermals. [1, 4, 5, 6, 7]

Different models within the Pulsar line use slightly varied versions:

• The Pulsar 4E uses the AG 26 modified airfoil.
• The Pulsar Pro 4.0 E, Pulsar PRO 3600 E, and Pulsar 2E models use the AG 25 modified airfoil. [1, 3, 8, 9, 10]

These airfoils contribute to the models' very light structure and ability to hold their shape, allowing for excellent low-speed thermalling capabilities and efficient flight performance. [2, 11]

AI responses may include mistakes.

[1] https://www.rcgroups.com/forums/showthread.php?1700913-Esprit-Model-Pulsar-4E-ARF-Electric-Sailplane-Mini-Review-With-156-75-Wingspan

[2] https://www.youtube.com/watch?v=mtYIQ9OBdZ8

[3] https://www.hyperflight.co.uk/getfile.asp?code=PULSAR-PRO-3600&code2=2

[4] https://www.rcgroups.com/forums/showthread.php?4444471-Selection-of-an-airfoil-with-high-lift

[5] https://forum.flitetest.com/index.php?threads/what-airfoil-should-i-use.56876/

[6] https://www.youtube.com/watch?v=ecY-g1ZrNqU

[7] https://www.sv-jme.eu/?ns_articles_pdf=/ns_articles/files/ojs30/601/6555eef629d55.pdf&id=7001

[8] https://www.soaringusa.com/Pulsar-Pro-4000-Compact.html

[9] https://www.soaringusa.com/Pulsar-Pro-3600-E-FH-.html

[10] https://www.rcgroups.com/forums/showthread.php?3064712-Pulsar-2E-Pulsar-Ultra-Lite-Electric-ARF-Sailplane

[11] https://www.facebook.com/groups/ultramicrorcplanes/posts/2812178798956752/

[Dan Tandberg]

Shown above are actually a pair of rear trailing edge spars.

[Carris Mike]

I think the modified part might be the under cambered trailing edge that is difficult to build if not molded or cnc cut. The Aether had the same series  "modified" airfoil and was very heavy,  yet flew very well. 

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[Dan Tandberg]

Hand planing and finish sanding for an exact match of the Pulsar airfoil.

[Dan Tandberg]

Here are the rib templates and a lot of blanks. I've decided to make the ribs out of laminated 16 in stock and use three laminates. The blanks will be bolted between two templates and then carved sanded and filed to the exact profile. 

Dan Tandberg, MD

Professor Emeritus

UNM School of Medicine

[Dan Tandberg]

1/16th inch stock in three laminates for 3/16th ribs.

[Dan Tandberg]

Here I am gluing up some 0.014" carbon cloth to the 3/4" x 1/8" spruce spar caps.  Lots of heavy lead-filled baby food jars and overnight epoxy assures a really good bond for those  substandard  landings.

[Rocky Stone]

"substandard landings"??  Now you're talking MY language!

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[Dan Tandberg]

Here the screw clearance holes have been drilled into "loaves" of rib blanks.  The four templates are used to align the drill.  A drill press, guides, tape, jigs, etc are used to keep the drill holes exactly parallel to the rib bottoms.  For the carving and sanding steps, a pair of templates will be bolted to the sides of the loaves.  The oval wire slots behind the spar cutouts (arrow) are just made by drilling three holes.

[Dan Tandberg]

Here I am removing excess stock from the bolted up loaf of rib blanks using a scroll saw.  A hand coping saw works fine too. This part is a lot easier if you use flathead countersunk screw heads.  

[Dan Tandberg]

The loaf of ribs after sanding.  The sanding block makes a different sound when you get down to the plywood templates on the ends, so It is easy to avoid removing too much material.  The spar cap slots are easy to clean out with a razor saw, a sharp chisel, and a piece of spar cap scrap with 80 sandpaper glued on to it.

[Dan Tandberg]

Finally, all the ribs are done!

[Rocky Stone]

These ribs are done too. 

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[Dan Tandberg]

   

Yours look better! 

[Dan Tandberg]

Carbon/spruce spar caps separated and cleaned up.

[Dan Tandberg]

Lots of nice big laminated shear webs!   Time to start gluing tomorrow.

[Dan Tandberg]

Everything has been dry fitted and sanded.  Now for some careful aliphatic glue and pins!

[Dan Tandberg]

Starting the glue up of square joiner boxes. These will be wrapped with carbon and epoxy. 

[Dan Tandberg]

Now the tricky part.  Lightly coat the carbon wing joiners with  paste wax this will keep the 30 minute epoxy from sticking to the joiner box halves during gluing. Rubber bands are used to hold the two "L" shapes snugly in place while the epoxy dries.  The tips are blocked up so there is no misalignment strain on the box during set up.  Shift the joiners slightly (2-3mm) every 10 minutes to make sure there is no sticking. Here is what it looks like after the glue has completely set up and the box as been removed.  The boxes will be cut to length after wrapping.

[Dan Tandberg]

Here is the box, wrapped with 3mm carbon tape, 30-minute epoxy, and set up to cure. After everything is dry clean out any glue from the inside with a sanding stick. The fit will be perfect.

[Dan Tandberg]

By the way, thanks much to Rocky for the carbon tow.  He has a mile of this and is very generous!

And finally, the top spar cap get glued down tightly.

[Rocky Stone]

Correction... I "used to" have a mile of it. I saved a little bit for myself and gave the main spool to Dan. He'll put it to good use.  :)

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[Carris Mike]

Nice work Dan.

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[Dan Tandberg]

Here the spar ends have been wrapped with strong thread and CA.  Buzz Averill taught me that I-beam spar delamination begins at the ends; thus you really only need to wrap the ends.  

[Dan Tandberg]

After cutting the joiner box stock into two pieces, clean up any glue or debris.  The box should slide easily onto the carbon joiner.

Next, the joiner box will be glued in place.

[Dan Tandberg]

30 minute epoxy and chopped fiberglass are used to glue the jointer box to the spar. Wetted carbon cloth is underneath the whole assembly. It is important to block up the wingtip to the exact dihedral angle during this procedure. Clamps and weights are used to hold everything flat and square. 

[Dan Tandberg]

Epoxy cured.  Now is a good time to start the left-hand center panel. 

[Dan Tandberg]

Carbon tow and epoxy wrap around joiner box and spar.

[Terry Tombaugh]

That looks really nice. I am gradually recovering from the exhaustion of looking at the 3 ply laminated ribs !  🤯

On Sat, Jan 10, 2026 at 11:54 AM Dan Tandberg <tandb...@gmail.com> wrote:

Carbon tow and epoxy wrap around joiner box and spar.

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Terry

[Brian Kloft]

Dan - looking good! I look forward to seeing it fly again!

Brian 

[Dan Tandberg]

Super light, super easy, super strong trailing edge "rib slots."

[Dan Tandberg]

The second panel always goes together a lot quicker.

[Dan Tandberg]

Gluing in ribs in front of joiner box.