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! This kit is pretty nice built stock, but came out before t' new E9 motor was available. Ahoy! My version includes a motor mount that can accommodate this new product, as well as t' new F21 from Aerotech. Begad! It also includes an ejection baffle, shiver me timbers, 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. Aye aye! Avast! T' balsa is a tiny bit softer than I'd prefer for somethin' this size, matey, and t' die cruncher could stand a little sharpening, ya bilge rat, too. Aye aye! More on this later. Ahoy! 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. T' 'chute, matey, motor mount parts and shock cord come together in a plastic bag. Avast, me proud beauty! Avast! A very nice bright red decal sheet is also included. As always with Estes kits, shiver me timbers, shiver me timbers, a well written and illustrated set o' instructions make t' kit complete. Begad! Begad! 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. 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. T' new fins are o' 1/8 basswood, matey, me hearties, and go through t' airframe and attach t' t' motor mount. 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. So a set was cut, ya bilge rat, complete with a tab t' pass through t' wall and with a notch in t' root edge t' accommodate t' motor hook retainin' tube. 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. Ya scallywag! 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. Well, blow me down! Arrr! A 95mm motor will now fit perfectly. Aye aye! 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. Aye aye! It was bent back on itself instead, and hooks on t' retainer tube. Arrr! A spacer will be required when usin' normal D size motors. Ahoy! 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. Avast! This arrangement can be used t' make an ejection baffle with just two additional parts and very little weight gain. First, me bucko, matey, t' third centerin' rin' was glued onto t' tube 5" from t' top. Begad! Then a plug be glued into t' top o' t' motor tube; this plug is simply a stack o' balsa disks glued together. Begad! A BT-50 size balsa block would also have worked. Blimey! T' block was soaked with CA t' help protect it from t' hot ejection charge. Next, ya bilge rat, a group o' holes was cut in t' tube betwixt t' plug and t' centerin' ring. Arrr! Ahoy! I'll normally cut t' holes in three rows evenly spaced around t' tube, me bucko, each row havin' three or four 1/4 inch holes. Next, a 5" piece o' BT-60 was cut from stock and a similar set o' holes was cut in it. Aye aye! T' edges o' t' holes were touched with thin CA on both parts. Blimey! Ahoy! T' BT-60 was glued t' t' last o' t' rings. Ahoy! 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. I wrapped one end t' Keelhaul®©™ shock cord around t' top o' t' BT-60 and glued it thar where t' two parts meet. 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 be tied off there. Avast! 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. Aye aye! T' motor tube be then glued into t' bottom o' t' rocket, me bucko, t' joiner rin' added t' that, and t' top part o' t' baffle be 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. I had a bit o' trouble with t' two halves nay matchin' perfectly at t' joint. Begad! T' top half is a tiny bit larger in circumference than t' lower half producin' a sort o' hump in one spot. Avast, me proud beauty! Blimey! I spent a good deal o' time workin' on this t' minimize t' potential hump back appearance it might cause. Aye aye! Finally, matey, t' fins were glued in. Avast, me proud beauty! I used yellow glue for everythin' on this kit, except for t' fin fillets wherein I used epoxy. Arrr! Epoxy produces perfectly smooth fillets but it adds a lot o' weight so it's important t' avoid gettin' carried away.

Rating: 4 This be 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 be filled with Elmer's Fill 'n' Finish Wood Filler and sanded. Avast, me proud beauty! Ya scallywag! T' spiral sometimes takes two layers o' filler in places and I already mentioned t' problems with t' joint. Well, blow me down! T' whole thin' be lightly sanded and wiped clean before bein' sprayed with a coat o' Rustoleum white primer. Aye aye! T' fingerprints and other minor blemishes could now be seen and were sanded away or filled as needed. Blimey! T' whole thin' be then sanded with 400grit paper until all t' parts could just be seen through t' primer. After bein' wiped clean carefully, a second coat o' primer was sprayed on and when dry lightly sanded again. Ahoy! T' base finish coat was applied and a nice smooth finish was produced. T' rocket stood around for a week or two and then was masked off for a highlight coat. Avast, me proud beauty! Begad! T' standard color scheme be used, except I masked off t' stripes rather than usin' t' stripe decal supplied. Arrr! I did this for two reasons, t' first be that t' paint may nay match precisely, matey, and also I wanted t' rocket t' match its sister Super Ranger. Begad! Ya scallywag! T' red highlight coat was then sprayed on in two light coats. T' mask was removed as soon as t' paint was dry. Begad! Unfortunately, me maskin' skills are nay t' greatest and t' edges aren't too sharp. Well, blow me down! T' name decal was then added. Ya scallywag! I've always really disliked t' self-adhesive decals. Avast, me proud beauty! Begad! I've never been particularly good at gettin' them on without a bunch o' fingerprints, and after they are on they are thick and t' edges can be clearly seen. Aye aye! Ahoy! I was pleasantly surprised with these, matey, matey, t' substrate is very thin, shiver me timbers, 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, it came out OK. Ya scallywag! It looks great if you are a couple o' feet away, me hearties, 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, arrr, me masks didn't produce a nice crisp edge.

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

It was flown t' first time at t' club polar bear launch on January 12, shiver me timbers, 2002. Aye aye! T' flight was OK, shiver me timbers, despite high winds. Well, ya bilge rat, blow me down! T' motor was a D12-3 and it left t' rod with an impressive amount o' speed and smoke. Begad! Ahoy! It did weathervane some, and ejection was just after apogee with t' nose cone down. Begad! Because o' t' wind, shiver me timbers, shiver me timbers, I used an 18" 'chute rather than t' supplied 24" one. Ya scallywag! I misjudged t' angle o' t' wind and it drifted over t' hard top parkin' lot. Well, blow me down! With a smallish 'chute t' rate o' fall be pretty fast and it hit hard. Begad! One o' t' fins shattered along t' grain and it lost a half inch square chip out o' t' bottom, but t' fin did nay break off. T' wind also dragged it across t' lot so it has a fair amount o' hanger rash under t' nose cone. Ahoy! T' fin was easily repaired by runnin' CA down t' cracks and gluin' in a plug t' replace t' missin' chip. 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. It would be perfectly fine built stock. 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, arrr, t' t' point o' makin' even t' shock cord easily replaceable. Aye aye! T' relatively new Super Big Bertha seemed t' be experiencin' deployment problems. Ya scallywag! Blimey! Begad! Blimey! After two embarrassments in a row it was time t' investigate. Begad! Blimey! Shinin' a light down t' motor tube revealed quite a mess. T' motor tube itself was all twisted, apparently durin' construction, and was badly burned. Avast, me proud beauty! Blimey! Avast, arrr, me proud beauty! Blimey! 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, me bucko, me bucko, and nay wantin' t' waste fins and nose cone a rebuild was undertaken (undertaker, please drive slow).. Since t' motor mount is sort o' t' core o' t' model, me hearties, and since it is locked in with t' fins, ya bilge rat, 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. Avast! Also, t' top section o' t' airframe is severely damaged anyway. Arrr! So a complete overhaul be t' best and worst I can do. Ahoy! Begad! 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). Ya scallywag! Now t' airframe be cut away t' reveal t' badly twisted and charred motor tube. Aha! T' motor tube be damaged durin' construction; it had probably seized when bein' inserted and was damaged by too much force. Aye aye! Well, me bucko, blow me down! OK, now that we have that out o' t' way, t' fins were removed from t' tattered remains o' t' motor tube. Ya scallywag! So now I have a nose cone, shock-cord, and a set o' basswood fins. Blimey! Avast, arrr, me proud beauty! So I need t' add some centerin' rings, a motor tube, an airframe tube, shiver me timbers, and launch lugs! T' airframe came from Totally Tubular as did t' motor tube. Arrr! 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! Rail buttons sound like a good idea, me bucko, 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. Avast! Blimey! 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. Aye aye! Blimey! Arrr! Blimey! T' glue and remnants o' t' tubin' still clingin' t' t' fins sanded off until they were more or less smooth. Avast! Blimey! Arrr! Blimey! T' rail buttons were already on hand, havin' purchased extras from Magnum with me last order. I also just happened t' have an Aero-Pack retainer.

T' centerin' rings were epoxied t' t' motor tube, ya bilge rat, matey, with t' many-holed one at t' very top, arrr, and t' others spaced properly t' match t' fin tabs. Begad! Eight 1/4-inch holes were cut betwixt t' top two rings t' form a baffle. Next, me hearties, 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 was epoxied into t' top. Finally, ya bilge rat, 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 was measured and cut t' size, then cut again at t' 11-inch line. Blimey! Blimey! T' motor tube was test fit into t' airframe with a coupler t' verify t' size. T' new version will eject at t' center t' form a (hopefully) zipperless design. T' lower half was marked up for fins, and t' slots were cut. T' parts were again test fit, me bucko, and findin' them satisfactory t' motor tube and coupler were epoxied into t' lower airframe. Well, blow me down! Blimey! 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, me bucko, and I noted that t' airframe tube grabbed one o' t' fins a little and was indented at t' root edge. Aye aye! Blimey! Arrr! Blimey! Nuts! Blimey! Wish I’d seen that while t' epoxy be still wet! Blimey! Oh well, me hearties, it turns out that it isn’t too noticeable once t' fillets cured. T' rail buttons were placed carefully such that t' screw is driven into t' wood rings. Ya scallywag! Blimey! T' holes were carefully predrilled. Blimey! Blimey! 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. Begad! It was truly snug on t' upper section which would cause deployment problems later. It was also pretty “fuzzy”. T' correct this, I coated t' whole thin' down t' t' lower airframe with thin CA. Aye aye! It be sanded as soon as t' CA cured until smooth. Aye aye! I continued workin' on it until t' upper section fit snuggly, but nay tightly and would slide smoothly. 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. Arrr! That was then sanded heavily. Begad! T' blemishes that were revealed were filled and another layer o' primer was put on. Aye aye! Blimey! That be sanded with 400 grit paper and t' dust tacked off. Well, blow me down! A layer o' Rustoleum Satin White be added and allowed t' cure for several days. Well, blow me down! T' highlight was then taped off with blue maskin' tape and sprayed. Begad! I must have been standin' on me head when I masked off t' rings, ya bilge rat, since t' pattern is upside down! A logo was created usin' t' computer, cut into maskin' tape by hand, matey, then transferred t' t' model and sprayed usin' Rustoleum Flat Black. Begad! Since this “new” model is sportin' a 29mm mount I decided t' call it Magnum Big Bertha; that’s reflected in t' new logo. Begad! A gloss coat o' clear was planned, ya bilge rat, but never done.

Flying:
T' weight is kind o' hefty: 12oz. Blimey! Blimey! T' original version be about 9oz. Ahoy! Blimey! Begad! 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. 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.. Well, blow me down! I figured it wouldn’t be too spectacular o' a flight since t' maximum liftin' weight o' t' D12-3 is 13oz. Avast! It’s actually a tad over. T' me surprise, ya bilge rat, it was an excellent flight and went a good deal higher than I expected. 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, me bucko, but t' shock cord roughed up t' edge o' t' upper section. This was smoothed out, and t' inside o' t' tube coated with thin CA for about an inch or so. Blimey! 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. Blimey! It was a bit slow off t' rail and arced into t' wind a bit. T' delay could have been shorter, but it came out OK. 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. Blimey! Blimey! It should fly well on F40-7 reloads, me bucko, and 24mm F21-6 Econojets, too, shiver me timbers, arrr, nay t' mention a variety o' G’s.

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

Flights

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