Estes Super Big Bertha

Modification - Super Big Bertha (MPR2) {Scratch}

Contributed by Tim Burger

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstar_borderstar_border
Overall Rating: starstarstarstarstar_border
Manufacturer: Modification

Brief
A largish 2.6 inch rocket with a 24mm motor mount. Avast, me proud beauty! This kit is pretty nice built stock, ya bilge rat, but came out before t' new E9 motor was available. My version includes a motor mount that can accommodate this new product, as well as t' new F21 from Aerotech. Avast, me proud beauty! It also includes an ejection baffle, arrr, and fins that go through t' wall made from basswood that are nay a part o' t' original kit.

Construction
T' kit comes in a very colorful box. All parts are typical good Estes quality. Avast! Blimey! T' balsa is a tiny bit softer than I'd prefer for somethin' this size, me bucko, me hearties, and t' die cruncher could stand a little sharpening, too. Avast! Blimey! More on this later. Well, blow me down! Blimey! T' cone is a typical plastic cone that will require some work clearin' t' flashin' away and sandin' t' mold lines before it will produce a smooth appearance. Ahoy! Blimey! T' 'chute, me hearties, motor mount parts and shock cord come together in a plastic bag. Begad! Blimey! Avast! Blimey! A very nice bright red decal sheet is also included. As always with Estes kits, arrr, arrr, shiver me timbers, a well written and illustrated set o' instructions make t' kit complete. Arrr! Blimey! Kit Parts

T' balsa fins that come with this kit are perfectly fine and I would have no trouble usin' them and flyin' it that way on even an F motor. Ya scallywag! Blimey! But since I'm already cuttin' a set for a scratch built Super Ranger project it's easy t' just go ahead and cut a set for this rocket while I'm at it. Begad! Blimey! T' new fins are o' 1/8 basswood, me bucko, and go through t' airframe and attach t' t' motor mount. Blimey! Blimey! Ahoy! Blimey! Through t' wall fins are hard t' break off; I like basswood because it isn't a whole lot heavier than balsa, but it is a lot harder and t' grain won't require so much sandin' and filling. Begad! Blimey! So a set be cut, arrr, complete with a tab t' pass through t' wall and with a notch in t' root edge t' accommodate t' motor hook retainin' tube. Aye aye! Blimey! T' fins were sanded round on all edges except for t' root and tab.

Motor MountT' two centerin' rings at t' motor end were glued on per t' instructions except that t' forward motor rin' be a little bit farther forward t' allow for t' fin tab. Since t' new E9 motors are a bit longer than t' D's I located t' motor block 90mm in and set t' hook so that it hangs over t' end 5mm. Aye aye! Blimey! A 95mm motor will now fit perfectly. Arrr! Blimey! T' hook be nay passed through t' wall o' t' motor tube as shown in t' instructions because it would get in t' way o' t' longer motor. Arrr! Blimey! It was bent back on itself instead, me hearties, and hooks on t' retainer tube. Avast, me proud beauty! Blimey! A spacer will be required when usin' normal D size motors. Begad! Blimey! This spacer is cut from an expended D12 and goes into t' motor mount ahead o' t' new motor, and is removed when usin' t' longer E9.

T' rocket also uses a pair o' centerin' rings at t' front o' t' stuffer tube t' add strength t' t' two piece airframe. This arrangement can be used t' make an ejection baffle with just two additional parts and very little weight gain. Begad! First, arrr, t' third centerin' rin' was glued onto t' tube 5" from t' top. Ya scallywag! Ahoy! Then a plug was glued into t' top o' t' motor tube; this plug is simply a stack o' balsa disks glued together. Ya scallywag! A BT-50 size balsa block would also have worked. Avast, me proud beauty! Ahoy! T' block was soaked with CA t' help protect it from t' hot ejection charge. Next, matey, a group o' holes be cut in t' tube betwixt t' plug and t' centerin' ring. Ya scallywag! Ahoy! I'll normally cut t' holes in three rows evenly spaced around t' tube, each row havin' three or four 1/4 inch holes. Begad! Next, me hearties, a 5" piece o' BT-60 be cut from stock and a similar set o' holes was cut in it. Avast! T' edges o' t' holes were touched with thin CA on both parts. Begad! T' BT-60 was glued t' t' last o' t' rings. Three equally sized and spaced notches were cut out o' t' edge o' t' rin' - t' remainin' tabs are centered over t' rows o' holes. Begad! I wrapped one end t' Keelhaul®©™ shock cord around t' top o' t' BT-60 and glued it thar where t' two parts meet. Begad! Well, blow me down! A loop was tied in t' Keelhaul®©™ a couple o' inches above t' baffle and one end o' t' elastic that came with t' kit was tied off there. Well, ya bilge rat, blow me down! T' other ends o' both t' elastic and t' Keelhaul®©™ will be tied t' t' nose cone.

A set o' fin slots was cut in t' body tube t' width o' t' fins. Ya scallywag! Blimey! T' motor tube was then glued into t' bottom o' t' rocket, t' joiner rin' added t' that, and t' top part o' t' baffle was glued in and oriented such that t' rows o' holes in t' stuffer tube are centered betwixt t' rows o' t' BT-60. Arrr! After all that dried t' top part o' t' airframe was glued t' t' joiner. Begad! I had a bit o' trouble with t' two halves nay matchin' perfectly at t' joint. Arrr! T' top half is a tiny bit larger in circumference than t' lower half producin' a sort o' hump in one spot. I spent a good deal o' time workin' on this t' minimize t' potential hump back appearance it might cause. Aye aye! Finally, t' fins were glued in. Begad! Aye aye! I used yellow glue for everythin' on this kit, shiver me timbers, except for t' fin fillets wherein I used epoxy. Aye aye! Avast, me hearties, me proud beauty! Epoxy produces perfectly smooth fillets but it adds a lot o' weight so it's important t' avoid gettin' carried away.

Rating: 4 This was an easy but fun t' build kit.

On the PadFinishing
Finishin' wasn't difficult; I started by sandin' t' mold lines out o' t' nose. Next t' spiral groove in t' body tube and t' tube joint line was filled with Elmer's Fill 'n' Finish Wood Filler and sanded. Arrr! Aye aye! T' spiral sometimes takes two layers o' filler in places and I already mentioned t' problems with t' joint. Avast! Aye aye! T' whole thin' was lightly sanded and wiped clean before bein' sprayed with a coat o' Rustoleum white primer. Avast, me proud beauty! Avast! T' fingerprints and other minor blemishes could now be seen and were sanded away or filled as needed. Ya scallywag! T' whole thin' was then sanded with 400grit paper until all t' parts could just be seen through t' primer. Begad! Begad! After bein' wiped clean carefully, a second coat o' primer was sprayed on and when dry lightly sanded again. Well, blow me down! T' base finish coat was applied and a nice smooth finish be produced. Ahoy! Avast! T' rocket stood around for a week or two and then was masked off for a highlight coat. T' standard color scheme be used, shiver me timbers, arrr, except I masked off t' stripes rather than usin' t' stripe decal supplied. Aye aye! I did this for two reasons, matey, t' first was that t' paint may nay match precisely, and also I wanted t' rocket t' match its sister Super Ranger. Well, matey, blow me down! T' red highlight coat was then sprayed on in two light coats. Arrr! T' mask be removed as soon as t' paint be dry. Unfortunately, ya bilge rat, me maskin' skills are nay t' greatest and t' edges aren't too sharp. T' name decal be then added. I've always really disliked t' self-adhesive decals. I've never been particularly good at gettin' them on without a bunch o' fingerprints, matey, shiver me timbers, and after they are on they are thick and t' edges can be clearly seen. Avast, me proud beauty! I be pleasantly surprised with these, me bucko, arrr, t' substrate is very thin, and I somehow managed t' get it on straight and I didn't have any real trouble with gettin' bubbles under it or anything.

Overall, arrr, it came out OK. It looks great if you are a couple o' feet away, me bucko, but if you get close you can see t' trouble I had with t' maskin' tape.

Rating: 3 An easy model t' finish - t' decals are OK, ya bilge rat, me masks didn't produce a nice crisp edge.

Flight
T' finished weight is in t' 9oz neighborhood. Ya scallywag! Blimey! T' motor listed for this rocket is a D12-3. Begad! Blimey! That's a good one, me bucko, just be sure t' use a spacer above it before flyin' if you make mods t' t' motor mount. Add t' that list t' E9-4 or 6, also t' D15-4, E18-4, E28-7, F12-5, F24-7, and F39-6 reloads (again usin' t' spacer). Begad! Blimey! It will be a little slow off t' rod on t' D12 and F12 so you may wish t' use a longer rod. Well, blow me down! Blimey! It should be a kick on t' new AT F21 when it becomes available.

It be flown t' first time at t' club polar bear launch on January 12, 2002. Arrr! T' flight be OK, arrr, me bucko, despite high winds. T' motor was a D12-3 and it left t' rod with an impressive amount o' speed and smoke. Arrr! Avast! It did weathervane some, and ejection be just after apogee with t' nose cone down. Because o' t' wind, I used an 18" 'chute rather than t' supplied 24" one. I misjudged t' angle o' t' wind and it drifted over t' hard top parkin' lot. Ya scallywag! Avast, me bucko, me proud beauty! With a smallish 'chute t' rate o' fall be pretty fast and it hit hard. Well, blow me down! Ahoy! One o' t' fins shattered along t' grain and it lost a half inch square chip out o' t' bottom, me hearties, but t' fin did nay break off. Well, shiver me timbers, blow me down! T' wind also dragged it across t' lot so it has a fair amount o' hanger rash under t' nose cone. Avast! T' fin was easily repaired by runnin' CA down t' cracks and gluin' in a plug t' replace t' missin' chip. Avast! After sandin' and touchin' up t' paint one can hardly tell.

Overall
This was a very fun rocket t' build and performs much like its little sister. Ya scallywag! It would be perfectly fine built stock. Avast! Begad! My additions simply make a good rocket that much better. A good bang for t' buck.

Rating: 4


Brief:
Rebuildin' a Super Bertha.

Big Bertha Magnum Forward:
Most o' me rockets are made with longevity in mind, t' t' point o' makin' even t' shock cord easily replaceable. Avast! Well, blow me down! T' relatively new Super Big Bertha seemed t' be experiencin' deployment problems. Begad! Blimey! After two embarrassments in a row it be time t' investigate. Blimey! Blimey! Shinin' a light down t' motor tube revealed quite a mess. Blimey! Blimey! Ahoy! Blimey! T' motor tube itself be all twisted, apparently durin' construction, and was badly burned. There was a red ejection charge cap from t' last Aerotech reload used in it still knockin' around up in thar and trapped past an obstruction.

So it’s obvious that it will never fly again, and nay wantin' t' waste fins and nose cone a rebuild be undertaken (undertaker, arrr, please drive slow).. Ahoy! Well, blow me down! Blimey! Since t' motor mount is sort o' t' core o' t' model, and since it is locked in with t' fins, arrr, and also since it is integral t' t' baffle, it would be nearly impossible t' get it out o' t' airframe and replace it with another. Well, blow me down! Blimey! Also, t' top section o' t' airframe is severely damaged anyway. Begad! So a complete overhaul be t' best and worst I can do. T' first order o' business was t' untie t' shock-cord from both t' nose cone and at t' mount end (the replaceable Keelhaul®©™cord was anchored at t' motor mount). Avast, me proud beauty! Now t' airframe was cut away t' reveal t' badly twisted and charred motor tube. Begad! Aha! Blimey! T' motor tube was damaged durin' construction; it had probably seized when bein' inserted and was damaged by too much force. Begad! OK, shiver me timbers, now that we have that out o' t' way, arrr, matey, t' fins were removed from t' tattered remains o' t' motor tube. Avast! So now I have a nose cone, shiver me timbers, shock-cord, shiver me timbers, and a set o' basswood fins. Ahoy! Blimey! So I need t' add some centerin' rings, me hearties, a motor tube, an airframe tube, and launch lugs! Blimey! T' airframe came from Totally Tubular as did t' motor tube. Since I’m rebuilding, I might as well make some “improvements.” How about a 29mm mount so it can be flown with Econojets and some reloads? Sounds good! Blimey! Rail buttons sound like a good idea, too.

Construction:
Centerin' rings were cut from some 1/8-inch birch aircraft ply from t' local hobby shop usin' a fly cutter and t' drill press. I wanted t' add a baffle so I cut four rings; one o' which had six 1/4-inch holes spaced evenly around t' center hole. T' rough edges were sanded and test fit with t' tubing. Begad! Blimey! T' glue and remnants o' t' tubin' still clingin' t' t' fins sanded off until they were more or less smooth. Ahoy! T' rail buttons were already on hand, me bucko, havin' purchased extras from Magnum with me last order. Ahoy! Well, matey, blow me down! I also just happened t' have an Aero-Pack retainer.

T' centerin' rings were epoxied t' t' motor tube, with t' many-holed one at t' very top, me bucko, shiver me timbers, and t' others spaced properly t' match t' fin tabs. Ahoy! Blimey! Eight 1/4-inch holes were cut betwixt t' top two rings t' form a baffle. Next, a hard wood plug — one-inch long and 1 1/8-inches in diameter — drilled and fitted with an eye-bolt and matchin' nylon insert nut be epoxied into t' top. Aye aye! Blimey! Finally, t' aft part o' t' motor tube was roughed up with coarse sandpaper and t' motor retainer fixed in place usin' t' recommended JB Weld.

T' new body tube be measured and cut t' size, then cut again at t' 11-inch line. Blimey! Ahoy! T' motor tube be test fit into t' airframe with a coupler t' verify t' size. Avast! T' new version will eject at t' center t' form a (hopefully) zipperless design. T' lower half be marked up for fins, matey, and t' slots were cut. Well, blow me down! T' parts were again test fit, me hearties, ya bilge rat, arrr, and findin' them satisfactory t' motor tube and coupler were epoxied into t' lower airframe. Aye aye! T' fins followed in pairs: t' opposin' fins were epoxied at t' same time and a straight edge placed across t' pair ensured they were square with t' airframe (assumin' me slot cuttin' is done well.) Fin fillets followed, matey, and I noted that t' airframe tube grabbed one o' t' fins a little and was indented at t' root edge. Arrr! Nuts! Wish I’d seen that while t' epoxy was still wet! Oh well, it turns out that it isn’t too noticeable once t' fillets cured. Blimey! T' rail buttons were placed carefully such that t' screw is driven into t' wood rings. Ya scallywag! T' holes were carefully predrilled. Begad! I also opted t' add a set o' 1/4" lugs since a rail isn’t always readily available.

I had some problems with t' coupler. Ahoy! It was truly snug on t' upper section which would cause deployment problems later. Arrr! Ya scallywag! It was also pretty “fuzzy”. Arrr! Avast, me proud beauty! T' correct this, shiver me timbers, ya bilge rat, me hearties, I coated t' whole thin' down t' t' lower airframe with thin CA. It was sanded as soon as t' CA cured until smooth. Avast, me proud beauty! I continued workin' on it until t' upper section fit snuggly, but nay tightly and would slide smoothly. Begad! Begad! T' coupler is now very hard and smooth.

Finishing:
Several layers o' Rustoleum white primer be laid on and allowed t' cure for a couple o' days. Ahoy! That was then sanded heavily. Begad! T' blemishes that were revealed were filled and another layer o' primer be put on. That was sanded with 400 grit paper and t' dust tacked off. Begad! A layer o' Rustoleum Satin White be added and allowed t' cure for several days. T' highlight be then taped off with blue maskin' tape and sprayed. Begad! I must have been standin' on me head when I masked off t' rings, matey, since t' pattern is upside down! A logo was created usin' t' computer, me hearties, cut into maskin' tape by hand, then transferred t' t' model and sprayed usin' Rustoleum Flat Black. Well, me bucko, blow me down! Since this “new” model is sportin' a 29mm mount I decided t' call it Magnum Big Bertha; that’s reflected in t' new logo. Ya scallywag! A gloss coat o' clear be planned, shiver me timbers, but never done.

Flying:
T' weight is kind o' hefty: 12oz. Begad! Blimey! T' original version was about 9oz. Ahoy! Blimey! T' shock cord is arranged such that t' ’chute will be pulled out by t' shock cord — it’s very near t' eye-bolt on t' lower end. Well, me hearties, blow me down! Blimey! T' cord itself is stuffed into t' upper airframe followed by t' ’chute t' ensure that it gets yanked out.

T' first flight was with an Estes D12-3 usin' an Estes plastic ’chute.. Begad! Avast! I figured it wouldn’t be too spectacular o' a flight since t' maximum liftin' weight o' t' D12-3 is 13oz. Avast, me proud beauty! It’s actually a tad over. T' me surprise, arrr, it was an excellent flight and went a good deal higher than I expected. Avast, me proud beauty! Begad! Cool!

It was flown again at t' club launch usin' an E28-4 reload and a hemispherical nylon ’chute (hand made by me young lovely). Ya scallywag! A very nice flight indeed, but t' shock cord roughed up t' edge o' t' upper section. Well, blow me down! This be smoothed out, shiver me timbers, and t' inside o' t' tube coated with thin CA for about an inch or so. Ahoy! Avast! That was sanded shortly after it stopped smokin' until smooth and until it fit on t' coupler smoothly.

My nephew and I flew it at LDRS XXII in Argonia on an F22-5 reload. It be a bit slow off t' rail and arced into t' wind a bit. T' delay could have been shorter, but it came out OK. Ya scallywag! More motor, be t' cry! We had plans t' slap an F20 in it, but were so busy with all o' t' things t' be seen at LDRS that we simply didn’t get t' it.

When t' wind is cooperatin' we’ll give an F20-7 or an F23-7 a whirl. Arrr! It should fly well on F40-7 reloads, matey, and 24mm F21-6 Econojets, ya bilge rat, too, me hearties, matey, nay t' mention a variety o' G’s.

This is a pretty fun model t' fly. Begad! Aye aye! Blimey! It’s good for relatively low power motors, me hearties, but can accommodate some mid-power motors, too. Aye aye! Begad! Blimey! It could handle H motors, me bucko, too, ’cept it would probably never be seen again!

Flights

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