Scratch Re-Build Centuri Chuter-2 Night-launcher with LED Payload section.

[Paul Howard]

This is a scratch rebuild of the fuselage/body of my originally scratch-built Centuri Chuter-2 converted to an LED illuminated night flier. What happened you ask? The rubber estes-type shock cord snapped and the fuselage went un-found in a nearby grass field whilst the payload/nose floated down nice and slow with the parachute. Ugghhh. At least I don't need to rebuild the nose/payload section. The first scratch built Chuter-2 had the "authentic" fin shape, but this time I'm going with squared off tips for aerodynamic improvement and a little bigger area per fin for better stability - though the first one was a really good straight flyer, and it also had slightly canted airfoiled fins for slight spin.

So, here's what I have going so far, and yes, I'm an airfoil geek from my long-ago altitude rocket comps as a kid and current RC Glider building.

Yes, I am inducing slight spin intentionally with a modified asymmetrical flat-bottom with raised "Phillips Entry" leading edge airfoil if you know your aircraft airfoil types - vaguely a very flattened modified "Clark Y" airfoil. The Curved side is the "leeward" side of air passage to better keep the air attached for closer-to-laminar flow (it's never perfect) and produces "lift in a radial fashion around the long axis for slight spin.


Hardwood Leading and Trailing Edges for durability and better airfoil shaping. Nice "character" balsa that will get a shellac finish. Since where the fins will mount to the engine mount, there are differences in the attachment points (because of the layers of white paper over the middle of the retainer hook) so each fin, slot, and portion of the motor mount is labelled "A", "B", "C" and "D" to keep everything straight. Fins "A" & "B" have to accommodate the white paper hold-down layers over the retainer hook, fins "C" & "D" have a nice flat continuous surface to mount onto the motor-mount tube.

I used a spent D12-3 inserted in the body tube for support whilst making the cuts for the slots for the fins - this helps a LOT.

The White Paper Wrap with Blue Masking Tape is my scratch made fin & launch lug marking guide.

I put White Paper wraps around the top (3 layers for anti-zipper and dent protection) and bottom (2 layers just for dents/dings) of the tube.

The Ejection Baffle is from Apogee but I used all 4 half-circles that came with it instead of the 3 it's designed for - that took a little work with a file but it's better protection. Also, the "Blast Side" is coated with epoxy for durability. Kevlar Shock cord attached to top of baffle. Note the Extra Ring on the Top of the Motor Mount - That makes it easier to get chunks of motor debris shaken back out of the rocket rather than catching on or in the lip of the motor mount (if it didn't have that ring). You can't see it but where the Eyelet Screw is inserted there is a scrap plywood "Doubler" behind what you can see inside the baffle for extra anchoring of the eyelet screw.

The Aft Ring on the Motor Mount has slots between fins for pressure relief from the pressures from a hot motor inside and the quick loss of external pressure outside as the rocket climbs. Also, the Motor Mount has 2 layers of extra White Paper wrapped around it for better strength.

Yellow Aliphatic Resin Wood Glue primarily used everywhere other than in Ejection baffle "Blast Zone". Thin wicking Cyanoacrylate applied to Inside of Top of tube for durability, easier sliding of balsa plug of payload section, and some "zipper protection" added to the paper wraps on the outside as well as the end of the Motor Mount for more durability of that edge.

Last picture is my fins and motor mount with pre-gluing with Yellow glue waiting for the glue to dry.

Stay Tuned.

 

[Paul Howard]

Fins Mounted!!! If you look at the back-lit early morning pictures you can see the light come through the trailing portion of the fin which is how I like to make the trailing edges on airfoils of small rocket fins and most of my Rocket Gliders, RC Gliders and FF Gliders. I only do this when the fin & body design has the motor striking the ground first on recovery, I tend to leave swept fins with "points" hitting the ground first (think Estes Alpha) rounded/blunt at the tips where they will contact the ground first upon landing but airfoiled elsewhere. Yeah, I'm really "that" much of an airfoil geek. I also rebuild the special slalom skateboard racing trucks I ride and race on and lathe-cut my wheels myself since slalom podiums are often measured in 10ths to 100ths of a second (see my icon picture from a Giant Slalom event).

So, if I'm so Aero-minded, why mess things up with adding white paper reinforcement rings at the top and bottom of the body tube? -The boundary layer right next to and touching the tube starting at the junction of nose & body is rather messy and those extra paper ring layers probably aren't messing things up much more (think of rivet locations on early Russian Mig Jet aircraft placed in already aero-messy sections), but also, those actually might help by "turbulating" the closest layer and keeping the next layers smoother and tighter. Since I don't have a wind tunnel and smoke machine, I'll probably never know. But, I'm after durability and aero-cleanliness both so there's trade-offs.

CyanoAcrylate added to aft-end of motor mount for more ding/dent resistance.

Yellow Glue fillets being placed on the fins as I post this entry.

More to come!

 

[Paul Howard]

I decided to add Freeflight "stick-n-tissue" model type White Tissue Paper after I mounted the fins to stiffen them some and make them more durable - ideally I should have added it prior to mounting the fins. The better type of Tissue has a "grain" and will be stronger in tension in one axis throughout the sheet. This can be determined by a simple "pull-until-it-tears test" and you'll easily tell if it has a stronger axis - and in which direction. I like to put the Strong Axis Perpendicular to the Grain of the Balsa when I want to stop the balsa from being split along it's grain. However, you can arrange the strong axis however you want to reinforce the wood. I used White since it's more transparent when applied so it would still allow that cool streaky look of the balsa and hardwood leading and trailing edges.

De Lux Easy Coat brand water based resin was used this time for the tissue paper application, it's made for applying thin light fiberglass. I've used Zinzer brand Shellac (straight - not thinned) to apply tissue paper in the past as one would use old fashioned airplane Dope and the Shellac worked really well also (possibly better. The tissue was "trimmed" by sanding with sand paper and an emery board (like for fingernails).

I previously marked my body tube with my scratch made fin-n-lanch-lug guide, then used a straight scrap piece of metal rod to align the lugs once glued on.

The Shock cord is anchored with heavier Kevlar to the top of the Ejection Baffle, has an anti-zipper cushion of 3 layers of heat-shrink tubing with transition piece of masking tape (for now). The rest of the Kevlar is thinner/lighter material out to the payload/nose.

This is the first time I've ever used the "Bungee in the loop" method so I'll see how that works out. I'm doing this method since the whole reason I'm re-building a new body is the original was lost due to the rubber elastic shock cord snapping and the body was lost in a grass field. Hopefully this shock cord arrangement prevents that mishap.

The fins were finished with 4 coats of Shellac, masked off after giving it 48 hours to fully dry/harden/cure then painted the body with Apple Red Satin Rustoleum brand 4 coats (1 coat per hour per directions - the print was sooooo small that I needed reading glasses plus a magnifying lens, sheesh!!!!).

I may add some Sky Blue or Turquoise accents.

 

[Scott_650]

Neat build! If you’re looking for one of the Estes repro kits from a few years back as a companion to your build I have a couple in my backlog I’d gladly send you for the cost of the postage.

 

[Paul Howard]

Neat build! If you’re looking for one of the Estes repro kits from a few years back as a companion to your build I have a couple in my backlog I’d gladly send you for the cost of the postage.

Thanks, but I already had one and used the laser cut balsa remnant "negative" for cutting out the fins of the other one that I recently lost and I still have the old original Centuri kit instructions and paper template from back when we all had to cut out the template, draw the fin shape on the supplied balsa and cut fins out ourselves (like "Real Rocketeers", ha, ha). Glad you like it!

This version I opted for square fins for better tip aerodynamic cleanliness and a smidge bigger so I won't need nose-weight.

This one is also a Night-Flier with LED's in the payload section.
-Paul