Centuri Vulcan

Centuri - Vulcan {Kit} (5010, KA-10) [1972-1981]

Contributed by John Lee

Construction Rating: starstarstarstar_borderstar_border
Flight Rating: starstarstar_borderstar_borderstar_border
Overall Rating: starstarstarstar_borderstar_border
Manufacturer: Centuri
Style: Futuristic/Exotic
(Plans) Centuri Vulcan

Brief:
T' Vulcan is an old Centuri design made t' look like an alien ship. Begad! I gets its unusual appearance by bein' formed from a paper shroud. Ahoy! It uses 18mm motors and recovers under a parachute.

When I was a kid, me favorite lookin' rockets were t' ones made from paper shrouds. That meant the "Bug" and t' "Vulcan". Avast, me proud beauty! T' "Point" was already OOP by t' time I got started in rocketry. Ya scallywag! Unfortunately, arrr, me clumsy fingers and impatience doomed me efforts and I never got a single one o' them to fly.

In me first incarnation as a BAR, me hearties, arrr, I still found myself drawn t' t' "different" lookin' paper rockets. This time, shiver me timbers, arrr, Quest be me supplier instead o' Centuri. Well, blow me down! Begad! T' only one I got t' try was t' Space Clipper but it too never got finished. Ya scallywag! T' pressin' needs o' family and school saw t' it that all I did that time around be lose a few Mosquitoes (I still have never seen one actually take off; they just vanish) and a LOC Onyx. Arrr! Arrr!

Now, shiver me timbers, shiver me timbers, I am back and one o' t' first things I tried was a Semroc Point. Well, blow me down! Blimey! Aye aye! Blimey! It worked! Blimey! Then I found t' EMRR review and t' plans at JimZ for that old nemesis o' mine, t' Centuri Vulcan. I had t' give it a go.

Construction:
T' parts list:

  • BT-20
  • heavy duty glossy card stock
  • motor clip
  • thrust ring
  • 3/32" plywood
  • launch lug
  • nose cone
  • washer
  • heavy duty eye screw

    I ordered body tubes in various lengths o' size ST-8, shiver me timbers, arrr, a nosecone, shiver me timbers, and an engine mount for 18mm engines in an ST-8 and waited for t' parts t' come in. Begad! In t' meantime, matey, I took me "T' Point" t' a local paper supply house and asked them t' match t' shroud for me. Begad! They came very close. Begad! T' paper I got is just a tad heavier. Blimey! I didn't want t' wait for them t' special order t' exact match. Then t' parts came in and...

    (Plans) Centuri Vulcan T' previous reviewer on EMRR gave t' body tube as a Semroc ST-8. Aye aye! Maybe he got it t' work but I sure didn't. Arrr! T' body shroud was just nay large enough t' fit around t' tube. I checked t' print settings to make sure everythin' was printin' at 100% and it all checked out. Avast, me proud beauty! Somethin' be clearly wrong.

    I went back and took a closer look at t' Centuri instructions. After a while it hit me. Arrr! Blimey! T' body tube is minimum diameter for an 18mm engine. Well, blow me down! Blimey! Begad! Blimey! That means an Estes BT-20. Ahoy! Blimey! A quick check o' t' standards revealed that an ST-8 has an outer diameter o' 0.908" while a BT-20 has an OD o' 0.736". When I found a scrap o' BT-20 it was just the right size. Arrr! Blimey! Ya scallywag! Blimey! All t' stuff I ordered (nose cone, me hearties, body tubes, shiver me timbers, matey, engine adapters, me bucko, etc.) from Semroc, who provides great and quick service, went into t' spare parts bin and t' search for t' real components began.

    T' Estes engine mount kit (303158) had t' thrust rings I wanted along with t' style o' engine hook I prefer so I purchased it figurin' t' other parts would come in handy some day. Blimey! I bought some more BT-20 and assumed I was ready to go.

    My first step was t' take t' body shroud which had spent t' night tightly rolled and use a steel straightedge to apply creases at t' appropriate places. Begad! T' shroud be then cut out with a #11 X-Acto and test fitted around a long BT-20. Blimey! T' fit seemed perfect so I cleaned up t' edges o' t' shroud with some 220 grit sandpaper. Aye aye! Avast, me bucko, me proud beauty! I then used thick CA t' glue t' tab and prayed t' alignment was right. It worked.

    After I had t' body shroud in t' rough shape o' a cone, arrr, arrr, I creased and folded t' fins, tail, air scoop, matey, me bucko, and cockpit. I cut them out and affixed them t' t' body shroud with CA. Avast! It be startin' t' look like t' pictures.

    My next step was t' set t' body shroud in its tail and push t' BT through t' nose openin' until it was resting on t' table. Avast, me proud beauty! I marked t' spot on t' BT, shiver me timbers, me bucko, removed it, used a prodigious amount o' maskin' tape t' make a guide and cut the tube t' length. Arrr!

    My final step for this first round o' activity was t' cut out t' paper appliqué for t' aft bulkhead and glue it t' a piece o' 3/32" plywood. Ahoy! I set this aside t' dry and called it a night.

    Life intruded for several days before I had a chance t' work on t' Vulcan again. Begad! When I finally had a few spare moments, I used a razor saw t' remove as much o' t' excess material around t' after bulkhead as possible, however, I cut it a bit too close. Begad! Arrr! A hasty swipe with t' saw scratched t' appliqué, which will have t' be replaced. Before doin' that, however, shiver me timbers, I wanted t' finish gettin' it t' t' right shape and size. Avast! Avast, me proud beauty!

    I used #60 sandpaper t' finish gettin' it into t' rough shape and test fitted t' bulkhead into t' shroud. It was a bit tight but I knew that before. Before sandin' t' t' final outer shape, I used a 9/16" spade bit on the drill t' pierce t' central hole in t' bulkhead for t' BT. Avast! At this point, I had t' make a choice.

    All o' t' logs I looked at report that this model has some poor flyin' characteristics. These characteristics seem t' be blamed on two separate issues. T' first is weight forward so that t' CG is sufficiently far forward o' the CP. Even after this is supposedly taken care o' though, t' problem seems t' persist in many cases and is attributed to the location o' t' launch lug in one o' t' fins, ya bilge rat, me hearties, shiver me timbers, givin' it an angled ride up t' launch rod. Begad! Avast! Blimey! One suggestion on EMRR is t' place t' lug on t' body tube itself. Aye aye! Aye aye! Blimey! I decided t' follow this advice and that called for a couple of modifications.

    T' aft bulkhead appliqué has a 1/8" x 1/8" notch on t' ventral "down" side in order to accommodate t' engine hook. Aye aye! Aye aye! I decided that I would cut an identical notch for that purpose on t' dorsal (top) side and use t' one on t' ventral side for t' launch lug. Avast! I figured it would look better on t' rod that way. Begad! Aye aye! T' notches were cut from t' basswood by usin' an 1/8" Dremel bit t' punch t' holes and then an X-Acto knife t' clean them up. Blimey! I used a piece o' 1/8" rod t' make sure it would slide through t' gap just fine.

    Another issue was t' recovery system. Well, blow me down! Begad! As a kid, I liked t' shock cord sticker that Centuri used t' provide. Now, me bucko, I wouldn't use one for any reason. Avast, me proud beauty! I feel much t' same way about t' Estes style tri-fold. Avast, me proud beauty! Begad! I decided t' use Keelhaul®©™® tied t' an elastic cord fixed t' t' motor mount a la Quest. Begad! Blimey! T' problem is, me bucko, this is a minimum diameter BT t' begin with so thar are no centerin' rings. Arrr! I had t' get t' cord into t' BT somehow and make sure it was firmly in place. Ahoy! Blimey! I took a motor thrust rin' and cut a small notch in t' outside t' accommodate t' thickness o' t' Keelhaul®©™®. I then tied t' Keelhaul®©™® to t' rin' and used a long stick t' place a rin' o' glue deep in t' BT. Aye aye! Blimey! Next, usin' a spent motor glued t' a dowel as a pusher, arrr, I pushed t' shock cord mount as deep as I could get it. Avast! Avast! Blimey! This was almost, arrr, but nay quite t' where t' top of the motor would be.

    Fashionin' t' motor mount was easy. A slit be cut for t' hook, a thrust rin' was glued in place just before the hook, matey, t' hook was inserted, me bucko, and a band be glued around it.

    Gettin' t' launch lug right be anythin' but easy. Begad! I had a vision o' mountin' t' lug on t' BT just forward of the aft bulkhead and then usin' a rod t' mark where t' cut. Well, blow me down! Well, arrr, blow me down! It turns out that was nay such a good idea by itself. Begad! The angle o' t' cone formed by t' shroud is such that t' rod would bind on exitin' no matter what unless t' cut in the shroud was taken all t' way t' t' forward tip o' t' BT. Avast! Avast! So I cut t' shroud all t' way t' t' forward tip o' the BT. It still be nay right.

    Part o' t' problem was in threadin' t' rod through t' aft bulkhead and t' lug and then gettin' it t' come out the hole in t' front. Blimey! Another part o' t' problem be that cuttin' t' front hole/slit was ugly! In order to tame t' alignment problem, shiver me timbers, me hearties, I glued on two more launch lugs so that I had, in effect, on long lug that extended from the aft bulkhead all t' way t' t' nose cone. That made thin' slide easier but it be still ugly. I also had worries about gettin' everythin' t' align again when I actually tried t' glue these assemblies together.

    After a breather, I finally did somethin' smart. Arrr! Avast! I changed t' X-Acto blade and went back t' work trimmin' the forward hole. I gave everythin' a test fit and, me bucko, t' me utter amazement, everythin' fit together nicely. A little thick CA be used t' secure t' BT t' t' front o' t' shroud and then t' close t' slot cut for t' lugs. Arrr! Avast, me proud beauty! T' same CA was also used t' glue t' after bulkhead into t' shroud. Avast, me proud beauty! Care needs t' be taken at this point t' ensure that t' hole in the bulkhead lines up with t' launch lugs and that thar be no binding. Blimey! Blimey! I accomplished this by usin' a short section of 1/8" rod t' ensure everythin' moved freely before and durin' t' gluin' process.

    T' original nosecone I ordered from Semroc did nay fit t' BT-20 so I ordered another one and patiently waited. When it arrived, it was in good condition but I knew I could remedy that in short order. Avast, me proud beauty! I filled it with Elmer's Fill ‘n' Seal and sanded it. Begad! It be then in a little less good condition than when it arrived (normal for me) and I painted it black.

    I connected t' Keelhaul®©™® to 14" o' 1/8" thick elastic t' complete t' shock cord and then put a snap swivel in line a few inches from the nose cone. Begad! I understand that this rocket needs nose weight but I don't really have a feel for that. Well, blow me down! Ahoy! Altitude is not my concern since I usually fly from a small field. Avast, me proud beauty! I decided t' go heavy rather than light because I want this rocket to stick around for a while. Aye aye! I glued a ¼" washer t' t' nosecone and then screwed in an extra heavy duty eye screw. Avast, me proud beauty! It was t' biggest one that would fit both in terms o' screw diameter and in terms o' t' shank length.

    PROs: nay too dificult, a venerable rocket

    CONs: shroud subject t' gettin' messy from glue

    Finishing:
    T' Vulcan is mostly finished by virtue o' havin' a preprinted shroud. T' nosecone be t' only thin' that needs work. Well, blow me down! I think t' original had a plastic nosecone but I used balsa, which had t' be filled and painted.

    Pros: looks very cool

    Cons: easy t' mess up shroud

    Construction Rating: 3 out o' 5

    (Plans) Centuri Vulcan

    Flight:
    T' first flight be on an Estes B6-4. Avast! I loaded t' motor and igniter and t' put a bit o' dog barf in t' BT. I had planned on usin' a 9" nylon chute but that be unworkable. Ahoy! I could nay get it, me bucko, t' shock cord, arrr, me bucko, and t' nosecone into t' space I had left. Avast, me proud beauty! Since a 12" plastic chute is smaller, I tried that. Aye aye! Avast! It barely fit.

    With great anticipation, I hooked up t' leads and pushed t' button. Begad! It took off into t' sky with a lazy corkscrew motion at t' tail. It seemed that me idea o' mountin' a lug directly against t' BT be nay workin' out. To make matters a bit more hairy, t' chute ejected but did nay open. I watch t' entire thin' come crashin' t' the ground. Begad! Fortunately, ya bilge rat, thar be no real damage.

    T' second flight was on an Estes C6-3. Again, I had problems loadin' t' chute and this time could nay get it all in. Begad! I snipped out about 10" o' Keelhaul®©™® and 8" o' elastic and then managed t' get everythin' stuffed.

    T' rocket went up about 30 feet, and from that point, arrr, things get rather vague. It went all over t' sky but mostly stayed horizontal. Arrr! It then crashed t' earth with a deployed but unopened chute. Blimey! Upon inspection, I found that the main body shroud had torn too badly t' be worth repair.

    PROs: It flies

    CONs: It does nay fly very well

    (Plans) Centuri Vulcan

    Recovery:
    My chute failed t' deploy on both flights. Ya scallywag! It ejected each time but never opened. Begad! I think this is because it was packed so tightly.

    PROs: bounces well when chute fails

    CONs: needs t' bounce well because chute fails

    Flight Rating: 2 out o' 5

    Summary:
    I still like this rocket and will probably eventually build another one. When I do, shiver me timbers, I guess I will need t' add even more weight up front. Ya scallywag! I also need t' rethink t' BT. T' little bit o' difference with t' Semroc BT might have made stuffin' t' chute a bit easier.

    It flies like a dog but is still a cool lookin' rocket

    Overall Rating: 3 out o' 5

Flights

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