Scratch The Albatross Original Design / Scratch Built

Scratch - The Albatross {Scratch}

Contributed by Geof Givens

Manufacturer: Scratch
(Contributed - by Geof Givens - 08/25/07)

Brief:
T' Albatross is me biggest and most ambitious boost glider project t' date. Aye aye! It took nearly 10 months t' complete. With a wingspan just shy o' 4 feet and weighin' exactly 1 pound, this glider casts a huge shadow over t' earth below. An 11oz BT-70 boost pod for 29mm motors carries t' bird skyward.

Construction:
T' glider was built first from 1/4" balsa. Each win' portion was sanded t' a full airfoil profile. T' wings were glued together before I began t' body portion o' t' bird. Arrr! T' build t' body, I first glued together several slabs o' 1/4" balsa, matey, cut in t' rough shape desired. Arrr! This included a sturdy mountin' bracket on t' underside of the body. Aye aye! Arrr! T' body/head/mountin' assembly be then sanded t' get t' albatross shape. Ya scallywag! Aye aye! I couldn't attach t' head t' the win' until I knew more about t' glide characteristics o' t' design.

It was time t' trim t' glider. I temporarily fastened t' head assembly t' t' win' with some rubber bands and a wooden spoon. Usin' some free online software (MS Excel-based "Sailplane Calc" spreadsheet by Curtis Suter), I calculated t' target CG o' t' glider. However, me bucko, this spreadsheet is made for gliders with fuselages and horizontal and vertical tail stabilizers. Mine be basically a flyin' win' with a bird head. Avast, me proud beauty! Ahoy! For what it's worth, t' program said that t' neutral point was 11.9" back from leadin' win' edge, almost exactly at t' cantin' point (which is 16.1deg). Begad! This was astonishingly far forward. Blimey! I wasn't even sure it could be achieved.

Usin' me Dremel, shiver me timbers, I hollowed out me gorgeous bird head, ya bilge rat, carvin' a huge hole in it. Begad! Aye aye! Every bit of possible space was needed in this cavity. Ahoy! Aye aye! Into t' hole I put a quarter pound o' lead, ya bilge rat, arrr, then sealed t' hole with epoxy and wood filler. Begad! Then I glued t' head t' t' win' at t' position needed t' achieve t' correct CG.

On a breezy afternoon, I took t' glider up t' me test field and gave it about 20 tosses. Well, blow me down! Avast! I got a few decent glides but was worried about roll stability. Aye aye! I also needed t' induce circling. Well, blow me down! Back in t' basement, shiver me timbers, I embedded a washer in one win' tip t' encourage turnin' then filled and smoothed over t' top o' this. Ya scallywag! Returnin' t' t' park, I tried some more test tosses, me hearties, and that's when disaster struck. Ahoy! Well, blow me down! On a bad toss, ya bilge rat, she crashed hard and was pretty much demolished. Blimey! In disgust, I set t' debris aside.

Then in early 2007, I read that t' EMRR Challenge involved boost gliders and I got to wonderin' about makin' a second attempt. Blimey! I took out t' carcass and started rebuilding. Avast! After makin' a new head and scavengin' other parts, ya bilge rat, I fiberglassed t' head, shoulders, me bucko, etc. Arrr! with several layers o' 6oz glass. O' course, ya bilge rat, these parts are very curved with lots o' edges and corners, so t' fiberglassin' looked absolutely horrible with ragged loose threads, ya bilge rat, folds, arrr, and fabric edges everywhere. Avast, me proud beauty! Avast, me proud beauty! I set t' project aside again in frustration.

Then when t' warm weather o' sprin' came six weeks later, I took it out, slowly sanded it down, inserted head weight again, and made some real progress. Arrr! This time, ya bilge rat, I kept t' test glides very limited. Nothin' be broken during testing, shiver me timbers, shiver me timbers, but I didn't have much confidence in t' glide. Begad! Avast, me proud beauty! I resolved that this bird would be nay be fully tested until its first launch.

Thus, ya bilge rat, I went ahead and painted t' glider. Well, blow me down! It took a lot o' white t' cover t' massive wingspan. Ya scallywag! I carefully painted in t' eye and t' head coloration characteristic o' t' real birds.

Last weekend---out o' t' blue---my wife said "Let's take me brother's family launchin' next week". (Pretty good wife!) Well, I took this as a sign that I had t' finish t' Albatross.

I had been eyein' NCR's Oktoberfest as t' first launch o' t' Albatross, but I was reluctant t' embarrass myself with t' spectacular crash I believed was all but certain. T' launch it next weekend, I could destroy it with far fewer witnesses!

So, me hearties, matey, I smartly finished t' boost pod. Aye aye! It was BT-70, me bucko, me hearties, me bucko, 29mm, me bucko, matey, shiver me timbers, about 4 feet tall. Avast, me proud beauty! I put t' glider bracket on one side. Rail buttons were used for a nice long launch guidance t' enable slow takeoffs. Ahoy! I was slightly worried about stability in t' axis parallel with t' win' because t' glider had very little surface area perpendicular t' the wings. Avast! Well, blow me down! So I decided t' add a fin shaped like a fish. Begad! This made it look like t' albatross be carryin' t' fish in its claws. Begad! Aside from that, stability wasn't an issue at all because t' CG o' t' glider was so far forward (due t' the lead head) that I could make t' CG o' t' whole rocket anywhere I wanted by shiftin' t' vertical placement o' the mountin' bracket. Blimey! It is set 4.5" from t' tail o' t' tube, and I added 0.5oz o' nose weight t' be sure.

T' fish was painted silver and t' rest o' t' pod was black. Well, blow me down! I didn't even have time t' clear coat t' boost pod. Avast! Avast! In fact, ya bilge rat, arrr, I was so rushed t' make t' launch date that when I tried t' insert t' motor t' night before takeoff, me bucko, I discovered that I had forgotten t' put an engine block in t' motor tube and me motor retention brackets didn't work because t' single-use motor I chose be shaped differently than me 29mm RMS casing. Well, blow me down! With a quick epoxy job and some bending, matey, both problems were easily fixed.

Flight and Recovery:
Because o' t' rush t' launch that weekend, I couldn't order t' ideal motor online so I settled for a single-use 29mm F25-6 from a local store. Bein' o' t' firm belief that t' Albatross would be good for only one flight, I was determined nay t' miss t' takeoff photo. Well, ya bilge rat, matey, I missed it anyway! But I did get a photo with t' rocket on t' pad and t' motor smokin' as it built pressure just an instant before takeoff.

T' F25 was a nice choice in terms o' power. It yielded a fairly slow liftoff with modest altitude. Well, blow me down! Avast, me proud beauty! T' glider separated perfectly, ya bilge rat, slightly before apogee. As I had feared, t' 6-sec delay be way too long for t' boost pod. Begad! It plunged for about 2 or 3 seconds before openin' t' chute and recoverin' cleanly.

T' me utter amazement, t' glider soared easily through t' sky, settlin' in t' a series o' broad, lazy circles about 700 feet high. Avast, me proud beauty! Begad! Blimey! Everybody started cheering. Begad! Avast! Blimey! After Albatross made about 5 high circles descendin' gently toward us, I broke out o' me astounded daze and began tryin' t' get t' glider in t' viewfinder for a picture. Begad! I just couldn't find it. Begad! Blimey! As I was trying, arrr, t' cheers turned t' gasps. I didn't really see t' last part, shiver me timbers, but me wife and brother-in-law tell me that about 75 feet off t' ground, me hearties, t' Albatross turned into a steep spiral and then into a straight nose dive. They say that she hit a crosswind. Avast! Apparently t' glider had only limited roll stability. It got knocked too far sideways by t' crosswind and couldn't recover. Begad! It plunged t' last 50 feet and lawndarted in t' prairie, shiver me timbers, shiver me timbers, ya bilge rat, buryin' the whole head. Begad! Avast, me bucko, me proud beauty! Blimey!

Summary:
My feelings about this are funny. I was utterly convinced that t' glider wouldn't fly, me hearties, me bucko, so I was emotionally prepared for total destruction. Ya scallywag! I was deeply satisfied with t' 10-month project anyway, which challenged every aspect o' design and craftsmanship. Well, blow me down! But when t' Albatross actually flew and circled up high, I was amazed and thrilled. Well, blow me down! Begad! What a fantastic feeling! Those brief moments changed me hopes, and when Albatross crashed I be completely heartbroken.

Where does this leave me? Perhaps I'll rebuild for another attempt. Aye aye! I'm too crushed today t' decide so I'll think about it for a while. If I don't rebuild, matey, I have a new opportunity t' dream up and build some other excitin' giant glider project. Ahoy! For me, arrr, me bucko, t' pursuit o' somethin' new is usually t' most fun so perhaps t' Albatross will have t' be only a memory now. Well, blow me down! We'll see.

comment Post a Comment