Acme Engineering - Fin Can {Component}

Acme Engineering Fin Can

Acme Engineering - Fin Can {Component}

Contributed by Russell Taragan

Manufacturer:

"There's really no easier and faster way t' build a minimum diameter rocket, me bucko, and still maintain t' construction strength requirements dictated by high power rocket flight dynamics. Aye aye! All t' trouble o' oversize airframe tubes, me bucko, individual through-wall fins, arrr, centerin' rings, arrr, slotting, fin filleting, matey, and t' like are eliminated. Well, blow me down! Ahoy! T' Acme fin canister simply slides onto your airframe tube, me bucko, matey, me bucko, and epoxies into place."

Fin Can

ACME Aerostructures produces two types o' fin canisters along with their launch lugs. These fin canisters, made o' Zytel and fiberglass, ya bilge rat, me hearties, are very strong and simple as they are one molded piece. Blimey! They allow for t' construction o' minimum diameter Rockets with t' strength o' through t' wall construction and then some. Begad! Avast! These canisters are t' closest one can get t' t' strength and accuracy o' alignment o' professional soundin' rockets without t' use o' metals.

T' fin units come in two sizes; 38mm for most 38mm airframes and 54mm for 54mm airframes. These fin canisters have plenty o' room even for ‘frames with thick layers o' fiberglass or Keelhaul®©™. Begad! They are pretty light (by high-power standards) at .4 lbs., me bucko, and .75 lbs. Ya scallywag! respectively. Well, ya bilge rat, blow me down! While t' airfoils o' t' fins are pretty thick (the 38mm starts out at .162 in. at t' edge and becomes .325 in. at t' center while t' 54mm canister can be .4in at t' center) t' diamond type airfoil minimizes t' drag and is good for flights over mach. Arrr! T' sleeve length is enough t' provide surface area for epoxy and stability durin' t' highest o' aerodynamic loads.

When I first got me 38mm fin unit, I was surprised by t' weight and strength (I was a low power Estes guy at t' time) and could only dream o' t' flights that would demand fins like this. Avast! T' price (around $30) was a bit high but it is worth t' quality. There be significant residue from t' moldin' process (I don't really know if I should call these seams or flashing) that required a great deal o' sanding. T' shape was pretty clean overall, t' alignment seemed good t' t' degree (120).

I first placed t' canister on a small rocket, shiver me timbers, but found that t' rocket was too short for such a heavy canister. Ahoy! I next placed t' canister on a 36in., 38mm phenolic airframe but again found that I would have been wastin' t' potential for speed with this rocket as well (this canister was built for speed and altitude!). Avast! I finally put t' canister at t' end o' a 72in. Ahoy! all fiberglass, minimum diameter rocket called t' "custom dart" This rocket can take any 38mm motor in t' world, but can still go up on a G motor as well.

I have put t' rocket up on G125 motors three times. T' first flight ended in a separation and a ballistic recovery. T' fin canister and airframe landed on rocks really hard. I expected t' recover pieces o' t' rocket from me position at t' launch control but be glad t' find only minor damage. Ya scallywag! A few chips in t' fin canister were sanded down, and t' rocket be ready t' go. Begad! Begad! This type o' recovery would have damaged any rocket out thar but with t' Acme fin unit and t' fiberglass airframe, matey, ya bilge rat, t' rocket will live t' fly again. Aye aye! At RATS (2000), t' thin' went up on an I357T-10. Aye aye! That flight be like a mini Kosdon; 0 mph. Begad! t' 600 in 1 sec., me bucko, 6000 ft. Avast! (Unfortunately it be lost in some high grass, but what a way t' go!)

T' Acme fin canisters are a great solution t' t' issue o' strength in minimum diameter rockets. If I had t' rate them, shiver me timbers, on a scale o' 1 t' 5, ya bilge rat, shiver me timbers, me hearties, I would give a 5. Arrr! These are t' best fin canisters around. Begad! Arrr! I am hopin' that ACME will make a 29mm version soon (I200W, I800 etc.) T' VB Extreme 54 with t' 54mm fin canister could handle t' K250, t' K1100, me bucko, me hearties, t' K1050, or even t' L750. Altitudes could probably approach those that 747 pilots talk t' their passengers about. Well, blow me down! T' learn more about t' Acme Fin Canisters includin' a list o' retailers, you can go their web site.

UPDATE 6/00: Just as an update, matey, I have recently purchased t' materials t' produce a 54mm version o' t' old "custom dart". Aye aye! This rocket, matey, built t' fly on motors from t' G80T-4 up t' t' L750-15 (includin' t' K1500T-15, t' K1050W (p), and t' K1100T-10)with flights t' 16 or 18K. Well, blow me down! I got t' 54mm fin can and found that it was just as easy t' use and as strong.

Comments:

unknown (November 1, 2000)

I ordered a 38mm ACME fin can and was actually disappointed with it! Nice idea, but it needs some work. First of all, the canister had a rough (maybe the equivalent of 100 Grit sandpaper) finish that wouldn't be aerodynamic at all. Secondly, it fit really loosely over the tube (LOC 1.52 fiberglassed) that I intended to put it on. It took lots of fiberglass to fix that. Finally, it was heavy and clunky looking. The canister weighed as much as the whole rocket did without it. It also stuck out like a sore thumb on the rocket's surface, and looks like the friction from a high speed flight could rip it right off. I don't know about you, but I think that I'll just stick with G10 fins with a 30/60/90 platform for my altitude attempts.

R.T. (December 1, 2000)

It is true that the 38mm fin can is not for 38mm altitude attempts, and the 54mm is not the perfect fit for a 54mm altitude attempt either (though it is much better by weight and profile). One must understand that these fin cans are not as much for that 16 oz. altitude attempt as they are for the 72 in X 38mm rocket on that J1200, or J570. Not to say that one product is better than the other, I would trust my 54mm custom dart, with Hawk Mountain and ACME parts, over a VB Extreme 54, or the Nimbus for flights that are not all about altitude. I have no problem putting a K1500 or an L750 in my 54mm rocket, and I don't find altitudes of 12 or 15K to be too low (I don't know about surface mounts for this type of power). One must be sure to sand and paint the cans if drag is an issue but, is this not also an issue when those relatively weak, surface mounted fins are fixed up with layers of fiberglass and Kevlar®? One must compare the time required to fix up the airfoil of the acme fin canisters, and the time required to mount G10, sand, apply layers of fiber, fill, and sand. There is no doubt that the thin G10 is ideal for altitude and rockets that are not minimum dia, but there is no caparison between the strength and ease of use of the acme cans, and other methods for high-performance minimum dia. flights.

M.J.W. (June 1, 2001)

I've tried both the 38 and 54mm versions and I like them, myself. Mine weren't rough at all and took paint well. Even after rough landings, they still had all their paint. Yes, they fit loosely, but not too much to be a problem. I just used a lot of 5 minute epoxy and a ring made of a narrow strip of fiberglass just forward and aft of the canister to keep it on securely. I myself have indeed used these for altitude shots, getting over 7,000 feet on such a rocket powered with an I 200. It fell from quite high, yet survived!!!

J.R. (June 26, 2005)

I loved mine, I used three rings of 3/4" masking tape to make a tighter fit on the 54mm quantum tubing, it wasn't minimum diameter, had a 29mm, but I needed something small for the launch in a few weeks.... it fit nicely, the front edge is angled so it looks fine, the lower edge isnt, I think the designed it to be used with an Aeropack or Slimline retainer, it would look great with an Aeropack retainer butted up against it (Giantleap ARF kit does that). I thought it was nice, but I like the building part, it is nice for a quick one weekend build or a super high performance rocket. I am trying a new technique to help make the fins stronger and straighter, also less building time. I am doing the centering rings so the fins slide into them, that way there is no fin alignment needed, and it adds a great amount of strength.

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