Saturday, December 18, 2010

Review: First Flight Hobbies Under Dawg (Beta)

The First Flight Hobbies Under Dawg is a large (58" x 2.22" - 5.6oz) , 4FNC, 2-stager.  It features a BT-70 body that transitions to BT-60, an appealing set of booster/sustainer fins and a small set of fins on the upper body.  This adds up to a sharp-looking, impressive modroc that flies on 24mm motors.  Mine was a beta-test build so the final components could vary slightly.  Click through the page break for my full review.

Parts
The main rocket consists of 2 BT-60's and one BT-70 tube.  A nice quality balsa transition and long balsa nose cone are provided.  You cut the fins from balsa stock using supplied templates.  The motor mount is pretty standard.  It utilizes laser cut ply rings and a motor hook.  Recovery is handled by two 15" 'chutes, one for the upper body from the transition up and the other for the lower body.  These are Hartle Engineering Chute Skinz.  A Kevlar leader is attached to the motor mount and two elastic cords are provided, one for each section.  There are also two short pieces of Kevlar that you attach to the ends of the elastic to provide a attachment point for the provided swivels.  Lets see, that leaves a 3/16" lug and a screw eye.

The booster is also BT-70.  A mount similar to that in the sustainer is provided as well as a BT-70 coupler.

Construction

The instructions are complete and have a fair number of diagrams.  They are oriented towards experienced builders but should be sufficient for the novice if they read them thoroughly before starting.  An experienced builder will undoubtedly skip around.  For instance, I filled the balsa before any gluing occurred.

The balsa transition's lower shoulder is a little on the short side, but should work fine.  The transition has a hardwood dowel in it's base so the screw eye should be well secured.  I really like this feature of the First Flight line.

The booster uses a minimal length gap staging.  That is, the booster and sustainer motors are not taped together.  The 'motor block' on the booster includes two rings and short piece of BT-20 to help guide the gasses to the upper stage.  As with other gap stagers, you have to remember to drill the recommended vents.  This is emphasized in the instructions but is still probably the most likely forgotten step. The booster includes its own motor hook so you won't be littering the field with spit casings.

You cut the fins from the balsa stock yourself.  Wrap-style fin marking guides are included for both tube diameters.  I first installed the sustainer fins and then used them to align the booster fins.  I clamped the latter in place with a plastic ruler and some light clamps while the glue was setting.  Even if you don't have them on straight, using this method will at least insure that the two sets will be perfectly aligned.

Finishing

I filled my balsa with dry-rub Fill-n-Finish and then primed thw whole thing with Painter's Touch 2X.  This also became the base coat for the majority of the model (along with a clear coat of Future Shine).  The green trim is Rustoleum fluorescent and multi-colored upper fins were painted with Testors brush-on.
The kit comes with a simple decal with the rocket's name.  The decal tended to curl so I immediately coated the edge with clear fingernail polish (an idea from my beautiful and understanding wife) and followed up with a couple of  coats of Future Shine. This curling should be corrected in the production kits.  I added a The Rocketry Forum sticker (which Nick threw into the shipping box), an MDRA sticker, and some bands of silver vinyl to complete the build.


Flight

Prep includes adding wadding (I used two balls of dog barf wrapped in some Quest wadding) and packing the two 'chutes.  The instructions say to put the lower body's 'chute in first, followed by the upper section's. I often put them in the opposite order but followed the instructions on the first three flights.  On the fourth flight, I installed the upper 'chute first.  Since both motor mounts have hooks, you just slip the motors in and go.



The recommended motors are the C11-3 and D12-5 for single stage flights and the D12-0/C11-3 and D12-0/D12-5 for staged flights.  My RockSim model agrees with these recommendations and I have flown this kit on all of them, as well as D12-0/C11-5 combo (the -3 is better as noted).   This is a big modroc and the two stage flights tend to weathercock.  On one two stage flight, the sustainer corrected itself and proceeded straight up but on another it ended up way downrange. The only other issue was on the single stage D12-5 flight where the lower body's 'chute didn't deploy.  Luckily, the booster did a steep glide into the grass and suffered no damage. Packing the upper section's 'chute before the lower should help insure that both deploy.  Some people say this increases the risk of the two 'chutes tangling, but I've had good luck with this order.

Conclusion
I think this rocket looks cool and I love its size.  The component quality is good and the instructions are sufficient.  However, you really need to read through them in advance and make sure you understand them.  The main issue I had was the decal curling.  This will be remedied in the production kits, but I recommend you give it a clear coat as soon as possible after installation.  The big kit flies well but tends to weather cock when flown in the 2-stage configuration.  Thus, you should wait for calm winds.  If you do, you will get impressive flights with short walks.

I want to thank Nick for the opportunity to test this kit.  I think it will become one of my favorites.