Apogee Components SR-72 Darkbird

Apogee Components - SR-72 Darkbird {Kit}

Contributed by Alan Rognlie

Manufacturer: Apogee Components
Apogee - SR-72 Darkwing
(Contributed - by Alan Rognlie) 

[Rocket Pic]T' SR-72 is an ejectin' power-pod boost glider, matey, much like one o' Astron Mike's Marauders or t' Estes SR-X, ya bilge rat, shiver me timbers, with an overall length near twelve inches and wingspan o' about 7-1/2 inches. Blimey! Well, blow me down! It is designed t' be used with 13mm mini-motors. Arrr! Avast! When t' power-pod is ejected, matey, it releases t' elevons for glide. Avast, me proud beauty! Ya scallywag! Tim (van Milligan) packed it in with an order I had placed t' week before for body tubes, arrr, me bucko, arrr, centerin' rings and nose cones, arrr, me hearties, and included a letter sayin' it was t' first production kit out t' door. Ahoy! It had been on back-order waitin' for 18mm nose cones from Tim's supplier. Since t' nose cones were still nay in sight, me hearties, Tim has produced t' kit with a vacu-formed nose cone and a coupon good for a replacement injection-molded (he's still waiting) or balsa (in stock) nose cone. Ya scallywag! T' vacu-formed nose cone and base look very good, me hearties, and the only question about it (accordin' t' Tim) is how well it'll hold up t' the inevitable crashes any boost glider is subject to. Avast, me proud beauty! T' kit includes two sheets of nicely diet balsa, various body tubes (18mm and 13mm) and centerin' rings, some clay nose weight, arrr, several small (dental) rubber bands, some template sheets and a good construction manual. Begad! T' photo o' t' elevon hook placement didn't reproduce very well (too dark t' see much detail), but t' rest o' the instructions read well and have good illustrations. Ya scallywag! I be mildly disappointed that t' balsa was diet rather than laser cut like his MicroVAX, but t' cuts *are* clean and t' pieces almost fall out o' t' carrier. T' elevon adjustment looks like it may be a bit o' work t' get t' initial setting, but it should hold well once set. Well, blow me down!

Construction

28 March, 1998 Finally, matey, a chance t' start workin' on t' Darkwing! Today, ya bilge rat, me hearties, I marked t' body tubes, glued together t' pieces for t' wings and wingtips, loaded clay into t' nose cone and glued it together and assembled the power pod (except for attachin' t' streamer). Ahoy! Avast, matey, me proud beauty! Blimey! I only used one o' t' two pieces o' clay provided in t' kit. If it glides acceptably with only t' one piece o' clay, I'll adjust t' boost CG by wrappin' some chrome tape around the nose o' t' power pod. Blimey! I'm usin' Elmer's ProBond Carpenter's glue for most assembly, with some specialty glues as required dependin' on materials. Aye aye! Blimey! For the nose cone, I used some Tenex-7 liquid glue (in moderation!) t' attach the vacu-formed base and tip. Begad! I only used a drop, shiver me timbers, ya bilge rat, ya bilge rat, countin' on capillary forces to pull it into t' joint, since I wasn't sure how strongly it would attack the styrene. Ya scallywag! Arrr! Blimey! It turned out very well.

29 March, 1998 Rounded edges o' wings and wingtips. Attached the wings t' t' main body tube and applied t' first glue fillet t' t' body/wing joints. Begad! Blimey! I expect t' apply two or three thin fillets t' provide strength and prevent t' sinkholes common t' carpenter's glue fillets. I also attached the engine inlet cones t' t' outboard tubes. Tim recommends cyanoacrylate (CA) for this step, and I've got t' agree with him. I tried tube plastic cement (Testor's), but it turned out t' be too aggressive and deformed t' bases of the inlet cones. Begad! Begad! Blimey! It might have worked better if I had laid a bead o' cement in the body tube, matey, ya bilge rat, allowed it t' dry and then used thin liquid cement t' join the inlet cone t' t' cement bead. Arrr! Well, me hearties, blow me down! Blimey! I was able t' get them installed passably by usin' a sharpened dowel t' center and support t' tips on t' outboard tubes while t' glue dried, matey, but CA is likely t' work MUCH better (and faster). Begad! Blimey! Once the inlet cones have fully set, ya bilge rat, I'll be punchin' holes in t' outboard tubes so they can be attached usin' glue 'rivets' for a stronger bond with t' wings, wingtips and rudders. Arrr! Blimey!

2 April, shiver me timbers, shiver me timbers, 1998 Added right 'engine pod'. Begad! Blimey! Added second fillet t' top wing/body joints and attached right 'engine pod'. Well, blow me down! Blimey!

3 April, me bucko, 1998 Added left 'engine pod'. Begad! Ya scallywag! Put second fillet on bottom wing/body joints and attached left 'engine pod'. Begad! Also attached lower rudder extensions t' bottoms o' t' engine pods. 

5 April, 1998 Added wingtips I cut out t' wingtip dihedral template and laminated it t' t' cardboard backin' for a pad o' paper. Blimey! Ya scallywag! After trimming the laminated template, I reinforced t' edges with thin CA per t' kit instructions. Begad! T' template made it very easy t' add t' wingtips at t' proper dihedral angle. Ya scallywag!

7 April, ya bilge rat, 1998 added rudders Again usin' t' kit-supplied template I attached t' rudders (double-glued and with glue rivets) t' t' engine pods. Avast! Blimey!

10 April, 1998 added elevon hinges and fillets. I attached t' elevon hinges t' t' win' usin' thin CA. Blimey! I did this by positionin' t' hinge material on t' wing, addin' a drop o' CA t' one o' t' corners and pressin' with a small piece o' waxed paper until t' CA set. Avast, me proud beauty! Begad! Then I added sufficient CA to adhere t' remainder o' t' front half o' t' hinge t' t' wing, ya bilge rat, again pressing it in place with waxed paper until t' CA set. Avast, me proud beauty! I then added glue fillets t' the wingtips and rudders. Ahoy!

11 April, me bucko, 1998 added elevons. Aye aye! Blimey! T' help ensure I didn't glue the elevons t' t' wing, I cut a narrow (about 1/16" wide) piece o' waxed paper and placed it betwixt t' win' and t' elevon. Begad! Blimey! I used a piece o' masking tape on t' back o' t' hinge line t' hold t' pieces while I attached the hinge material t' t' elevon with thin CA. Arrr! Blimey! It *might* be easier t' do t' hinge attachment before attachin' t' wings t' t' body tube - I may have t' try this if it ever comes time for a rebuild. I also added t' elevon stops t' one of the wings. Aye aye! Blimey! I was pleasantly surprised t' find t' elevon angle came out very close t' t' recommended initial setting. Avast! Blimey! I be expectin' t' have t' use gap-fillin' CA t' build up t' stop and sand down for adjustments, but it looks like I'll only need t' use thin CA t' strengthen t' contactin' surfaces o' the stops. Aye aye! Blimey! Avast! Blimey!

15 April, arrr, 1998 Finished taxes, installed other elevon stop. Ya scallywag! The elevon stops are *tiny* pieces o' balsa. Begad! Well, ya bilge rat, blow me down! With me fat fingers <G>, me bucko, it was a challenge t' get them positioned properly. Ya scallywag! Ya scallywag! I think next time I'll have t' get some tweezers t' make handlin' these small pieces easier. Well, blow me down! After t' fillets for the elevon stops dried, ya bilge rat, me hearties, arrr, I installed t' orthodontic rubber bands t' see how close I was t' t' proper initial elevon setting. At this point it looks pretty good. Well, blow me down! We'll see how it goes on test glides.

16 April, 1998 installed launch lugs I lined up t' launch lugs against t' wing/body joint - I just prefer t' have them snugged up there rather than hangin' entirely out in t' breeze. T' streamer has been taped to the power-pod. Avast! Well, blow me down! I'm also addin' some chrome tape t' t' front o' t' power-pod to help assure a safe CG/CP relationship for boost. I did this because I'm *NOT* usin' all t' clay supplied for t' nose cone (lighter gliders (tend to) glide longer <G>). Begad! All that remains before paintin' is test glides, gluin' t' nose cone in place and t' first launch. Well, blow me down! Aye aye!

22 April, matey, 1998 glide trimmin' I brought t' SR-72 t' show off at the April meetin' o' WOOSH. Begad! Blimey! While waitin' for everyone else t' show up, matey, I trimmed the glide o' t' model. Avast! Blimey! Tim provided two squares o' clay for balance, but I had only installed one t' start with. T' first few glides were pretty nose heavy (good thin' thar be some soft grass t' land in) and I wound up removing almost half o' t' clay I had initially loaded in before I got a decent glide. When I got home after t' meeting, I glued in t' nose cone and re-attached the sub-rudder that broke off when it landed on t' street on one o' t' test glides. It looks like all that's left is t' get out and fly this bird! Blimey!

Other Reviews
  • Apogee Components SR-72 Darkbird By Patrick Wright

    Brief: Rear engine type mini-motor powered boost glider. Designed to imitate the appearance of the SR-71 spyplane. Construction: According to a note in the kit, Apogee had a supply problem with the nose cones. So as to not delay delivery any further Apogee vacuformed their own nose cones as a substitute. The note went on to say that the vacuformed nose cone probably wasn’t ...

Flights

Comments:

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T.B. (July 1, 2000)
This is a nice, fun kit. While the construction might pose a problem or two for the beginner, it is straight forward and I thought the instructions were well written. The quality of the component met my expectations and were perfectly adequate for the type of model. The molded elevon lock is a extra I am not used to seeing on a small kit. The only place where I varied from the plans was in the CG placement for the glider. I ended up with the CG even with the front of the nacelle tubes (not the cones). As built, my model did not require any weight to be added to the nose, I trimmed it by adding to the glue fillets. For boost I added clay behind the centering rings at the front of the power pod. The boost CG (loaded and ready to go) is 1/2 inch ahead of the glider GC position. I also left off the folded paper canopy simply because I was too lazy to want to do the filling and sanding. I finished the model with one light coat of spray Poly-crylic water based coating as a sealer and a coat of Krylon semi-gloss black. Boost was arrow straight on the recommended engine sizes. On an A10-3 I was able to get 42 second flights on a calm but humid day. Very nice. The model would benefit from longer delays as it is still going up at ejection and the added push of the ejection makes is perform a tight loop before it settles down to a even glide. Pros: good quality kit and an easy build. Great flyer! Cons: the centering rings are a tight fit by the time the large wing is attached. I believe the shrinkage of the white glue fillets distorts the tube a little. Sanding of the rings is required for the pod to slide well inside the tube. DO test glide and trim prior to boosting the model. A cut down bottle brush works very well for cleaning out the gunk left from ejection and insuring the pod doesn't stick on the next flight. I disagree with opinion about tossing the glider hard for a test flight. The glider is only going fast at boost and at the boost to glide transition. It then settles down to it's glide speed. The ideal test glide should be close to the gliders natural glide speed with a even level push. Over energetic throwing generally ends up with spearing the model into the ground or in inducing a stall.
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D.F. (December 7, 2001)
I built this according to the instructions including the clay in nose with C.G. as stated in the plans. The maiden flight resulted in a nose dive for the sod. I cut off the nose cone, dug out all the clay, reattached the nose cone with the C.G. now where T.B. had his even with the nacelle intakes (not the tip of the cones) and the rocket glided well. I will now test glide any kit gliders I make and not take the kit maker at their word like I did with this one. The joint of the repaired nose cone is weak and it fell off and was lost after the third flight. Now I have a noseless darkwing until I replace the nose some how.
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J.A.G. (June 25, 2002)
Order on friday arrived on monday. One kit backordered but two emails to communicate what was up before I even received the other kit. This is what customer service is all about. I will be back for more but right now a "Dark Bird" awaits my attention

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