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. Arrr! Begad! This kit is pretty nice built stock, ya bilge rat, me hearties, but came out before t' new E9 motor was available. Avast! Begad! My version includes a motor mount that can accommodate this new product, matey, as well as t' new F21 from Aerotech. Arrr! It also includes an ejection baffle, 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. Well, blow me down! All parts are typical good Estes quality. Ahoy! T' balsa is a tiny bit softer than I'd prefer for somethin' this size, and t' die cruncher could stand a little sharpening, too. More on this later. 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. Well, blow me down! Begad! T' 'chute, motor mount parts and shock cord come together in a plastic bag. Ahoy! A very nice bright red decal sheet is also included. Well, blow me down! As always with Estes kits, a well written and illustrated set o' instructions make t' kit complete. Aye aye! 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. Begad! Blimey! Begad! 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. T' new fins are o' 1/8 basswood, and go through t' airframe and attach t' t' motor mount. Ahoy! Blimey! Well, blow me down! 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. Aye aye! Blimey! So a set was cut, shiver me timbers, complete with a tab t' pass through t' wall and with a notch in t' root edge t' accommodate t' motor hook retainin' tube. Ya scallywag! Blimey! Ya scallywag! 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' was 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. A 95mm motor will now fit perfectly. Ya scallywag! Begad! 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. Avast! It was bent back on itself instead, and hooks on t' retainer tube. Blimey! A spacer will be required when usin' normal D size motors. Aye aye! This spacer is cut from an expended D12 and goes into t' motor mount ahead o' t' new motor, matey, 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. Begad! Blimey! This arrangement can be used t' make an ejection baffle with just two additional parts and very little weight gain. Avast, me proud beauty! Blimey! Blimey! Blimey! First, t' third centerin' rin' was glued onto t' tube 5" from t' top. Avast! Blimey! Then a plug was glued into t' top o' t' motor tube; this plug is simply a stack o' balsa disks glued together. A BT-50 size balsa block would also have worked. Ahoy! Blimey! T' block was soaked with CA t' help protect it from t' hot ejection charge. Blimey! Blimey! Next, me hearties, a group o' holes was cut in t' tube betwixt t' plug and t' centerin' ring. I'll normally cut t' holes in three rows evenly spaced around t' tube, shiver me timbers, each row havin' three or four 1/4 inch holes. Well, blow me down! Blimey! Arrr! Blimey! Next, a 5" piece o' BT-60 was cut from stock and a similar set o' holes was cut in it. T' edges o' t' holes were touched with thin CA on both parts. Arrr! Blimey! T' BT-60 was glued t' t' last o' t' rings. Arrr! Blimey! 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. Ya scallywag! Blimey! I wrapped one end t' Keelhaul®©™ shock cord around t' top o' t' BT-60 and glued it thar where t' two parts meet. Aye aye! Blimey! A loop be 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. Ahoy! Blimey! 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. Avast! Avast, me proud beauty! Blimey! T' motor tube be then glued into t' bottom o' t' rocket, t' joiner rin' added t' that, ya bilge rat, 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. After all that dried t' top part o' t' airframe be 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. Begad! I spent a good deal o' time workin' on this t' minimize t' potential hump back appearance it might cause. Finally, me bucko, matey, t' fins were glued in. I used yellow glue for everythin' on this kit, except for t' fin fillets wherein I used epoxy. Avast! 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. Well, blow me down! 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. Avast, shiver me timbers, me proud beauty! T' spiral sometimes takes two layers o' filler in places and I already mentioned t' problems with t' joint. T' whole thin' was lightly sanded and wiped clean before bein' sprayed with a coat o' Rustoleum white primer. Begad! 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. Arrr! After bein' wiped clean carefully, arrr, a second coat o' primer be sprayed on and when dry lightly sanded again. Well, blow me down! Blimey! T' base finish coat was applied and a nice smooth finish was produced. Avast! T' rocket stood around for a week or two and then be masked off for a highlight coat. Begad! Blimey! T' standard color scheme was used, me bucko, except I masked off t' stripes rather than usin' t' stripe decal supplied. I did this for two reasons, t' first was that t' paint may nay match precisely, shiver me timbers, and also I wanted t' rocket t' match its sister Super Ranger. Ya scallywag! T' red highlight coat be then sprayed on in two light coats. Ahoy! T' mask be removed as soon as t' paint was dry. Ya scallywag! Unfortunately, me maskin' skills are nay t' greatest and t' edges aren't too sharp. T' name decal was then added. I've always really disliked t' self-adhesive decals. Blimey! 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. I was pleasantly surprised with these, ya bilge rat, t' substrate is very thin, matey, arrr, 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, me bucko, it came out OK. It looks great if you are a couple o' feet away, shiver me timbers, ya bilge rat, 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, me masks didn't produce a nice crisp edge.

Flight
T' finished weight is in t' 9oz neighborhood. Blimey! T' motor listed for this rocket is a D12-3. Begad! That's a good one, just be sure t' use a spacer above it before flyin' if you make mods t' t' motor mount. Ya scallywag! Add t' that list t' E9-4 or 6, also t' D15-4, me bucko, E18-4, shiver me timbers, E28-7, ya bilge rat, F12-5, me bucko, F24-7, matey, and F39-6 reloads (again usin' t' spacer). Arrr! It will be a little slow off t' rod on t' D12 and F12 so you may wish t' use a longer rod. Ahoy! 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, arrr, 2002. Well, blow me down! T' flight be OK, matey, despite high winds. Ahoy! T' motor was a D12-3 and it left t' rod with an impressive amount o' speed and smoke. It did weathervane some, ya bilge rat, and ejection be just after apogee with t' nose cone down. Ya scallywag! Begad! Because o' t' wind, I used an 18" 'chute rather than t' supplied 24" one. Well, blow me down! Well, shiver me timbers, blow me down! I misjudged t' angle o' t' wind and it drifted over t' hard top parkin' lot. Well, blow me down! Avast! With a smallish 'chute t' rate o' fall was pretty fast and it hit hard. Begad! Avast! 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. Ahoy! T' wind also dragged it across t' lot so it has a fair amount o' hanger rash under t' nose cone. Begad! T' fin be easily repaired by runnin' CA down t' cracks and gluin' in a plug t' replace t' missin' chip. Avast! Avast, me proud beauty! 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. Avast! Blimey! It would be perfectly fine built stock. Avast, me proud beauty! Blimey! My additions simply make a good rocket that much better. Ya scallywag! Blimey! Begad! Blimey! 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. Ya scallywag! Begad! T' relatively new Super Big Bertha seemed t' be experiencin' deployment problems. Ya scallywag! After two embarrassments in a row it was time t' investigate. Begad! Aye aye! Shinin' a light down t' motor tube revealed quite a mess. T' motor tube itself was all twisted, shiver me timbers, apparently durin' construction, and was badly burned. Begad! 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, shiver me timbers, and nay wantin' t' waste fins and nose cone a rebuild be undertaken (undertaker, please drive slow).. Well, blow me down! Ya scallywag! Since t' motor mount is sort o' t' core o' t' model, shiver me timbers, and since it is locked in with t' fins, arrr, and also since it is integral t' t' baffle, me bucko, it would be nearly impossible t' get it out o' t' airframe and replace it with another. Begad! Also, ya bilge rat, ya bilge rat, t' top section o' t' airframe is severely damaged anyway. Avast! So a complete overhaul be t' best and worst I can do. Well, blow me down! 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! Now t' airframe was cut away t' reveal t' badly twisted and charred motor tube. Well, blow me down! Aha! T' motor tube was damaged durin' construction; it had probably seized when bein' inserted and be damaged by too much force. OK, now that we have that out o' t' way, ya bilge rat, arrr, arrr, t' fins were removed from t' tattered remains o' t' motor tube. Begad! Ya scallywag! So now I have a nose cone, shock-cord, and a set o' basswood fins. Well, ya bilge rat, blow me down! So I need t' add some centerin' rings, a motor tube, an airframe tube, me bucko, and launch lugs! T' airframe came from Totally Tubular as did t' motor tube. Avast! Since I’m rebuilding, matey, ya bilge rat, 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, ya bilge rat, 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. Arrr! 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. Ahoy! T' rough edges were sanded and test fit with t' tubing. Ahoy! Avast! T' glue and remnants o' t' tubin' still clingin' t' t' fins sanded off until they were more or less smooth. T' rail buttons were already on hand, havin' purchased extras from Magnum with me last order. Arrr! 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, ya bilge rat, me bucko, and t' others spaced properly t' match t' fin tabs. Eight 1/4-inch holes were cut betwixt t' top two rings t' form a baffle. Next, shiver me timbers, 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. Ya scallywag! Avast! 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. Avast! 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. Ya scallywag! Ya scallywag! T' lower half was marked up for fins, ya bilge rat, and t' slots were cut. Arrr! T' parts were again test fit, me bucko, and findin' them satisfactory t' motor tube and coupler were epoxied into t' lower airframe. 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, and I noted that t' airframe tube grabbed one o' t' fins a little and was indented at t' root edge. Blimey! Avast! 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! Begad! T' rail buttons were placed carefully such that t' screw is driven into t' wood rings. Ya scallywag! T' holes were carefully predrilled. Avast, shiver me timbers, me proud beauty! 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. Avast! Avast, me proud beauty! It be also pretty “fuzzy”. Begad! T' correct this, I coated t' whole thin' down t' t' lower airframe with thin CA. Blimey! It was sanded as soon as t' CA cured until smooth. Aye aye! I continued workin' on it until t' upper section fit snuggly, ya bilge rat, but nay tightly and would slide smoothly. Avast! 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 be then sanded heavily. Ya scallywag! T' blemishes that were revealed were filled and another layer o' primer be put on. Begad! That was sanded with 400 grit paper and t' dust tacked off. Arrr! A layer o' Rustoleum Satin White was added and allowed t' cure for several days. Begad! T' highlight was then taped off with blue maskin' tape and sprayed. Begad! Well, blow me down! I must have been standin' on me head when I masked off t' rings, arrr, since t' pattern is upside down! A logo be created usin' t' computer, shiver me timbers, cut into maskin' tape by hand, me hearties, then transferred t' t' model and sprayed usin' Rustoleum Flat Black. Arrr! Avast! Since this “new” model is sportin' a 29mm mount I decided t' call it Magnum Big Bertha; that’s reflected in t' new logo. Avast, me proud beauty! A gloss coat o' clear was planned, arrr, me bucko, but never done.

Flying:
T' weight is kind o' hefty: 12oz. Aye aye! T' original version was about 9oz. Well, blow me down! 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. 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.. 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, me proud beauty! Ahoy! It’s actually a tad over. Begad! T' me surprise, it be an excellent flight and went a good deal higher than I expected. Cool!

It be flown again at t' club launch usin' an E28-4 reload and a hemispherical nylon ’chute (hand made by me young lovely). Aye aye! Blimey! A very nice flight indeed, arrr, matey, ya bilge rat, 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. Aye aye! Blimey! Blimey! 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! Arrr! Blimey! It was a bit slow off t' rail and arced into t' wind a bit. T' delay could have been shorter, arrr, but it came out OK. More motor, be t' cry! Blimey! 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. Begad! It should fly well on F40-7 reloads, shiver me timbers, shiver me timbers, and 24mm F21-6 Econojets, too, nay t' mention a variety o' G’s.

This is a pretty fun model t' fly. Begad! Avast, me proud beauty! It’s good for relatively low power motors, matey, arrr, but can accommodate some mid-power motors, ya bilge rat, arrr, too. It could handle H motors, me bucko, too, matey, ’cept it would probably never be seen again!

Flights

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