T' main disadvantage o' shroud wraps is that they are limited t' conical shapes. Well, blow me down! A couple o' years ago, arrr, I ran across a report from US Rockets based on t' work o' Korey Kline that had a technique called t' "Ace Fugue Shroud Method." Whereas this technique is nay specifically designed t' create curved shrouds, it is capable o' creatin' them! T' report is nay t' easiest bit o' readin' that I’ve ever done, matey, so I thought I’d give you me version. This isn’t t' easiest technique t' figure out and it requires a good bit o' arithmetic t' pull off. T' basic idea o' t' method is, instead o' addin' an extra paper wrap t' t' transition, t' cut sections out o' t' larger size body tube and compress and bond t' remainin' sections o' tube into t' transition.

First off, you need t' figure out t' size o' your body tubes. Blimey! Here is a link t' a handy tube reference chart:

http://www.ninfinger.org/~sven/rockets/body_tubes.html

Also, ya bilge rat, havin' some CAD software is awfully handy t' have. Here are a couple o' links where you can get trial versions:

http://www.turbocad.com/

http://usa.autodesk.com/adsk/servlet/mform?siteID=123112&id=8337786

It takes a bit t' get used t' usin' t' software, but once you get t' hang o' it, it becomes nearly invaluable!

Now that you have a couple o' t' basic tools, ya bilge rat, let’s go on t' t' process. Arrr! For our example, me bucko, we will make a fairly simple BT-60 t' BT-20 3" long shroud. Avast, me proud beauty! As you can see in t' first diagram (see diagram 1), shiver me timbers, I have laid out t' basic shape o' t' shroud, showin' t' front and back diameters. Additionally, I have divided t' cone lengthwise into four sections. Ya scallywag! T' more sections that are used, t' more complex t' computations required, arrr, but t' more accurate t' curves. Havin' CAD software is extremely useful here in that it can give you extremely accurate measurements. T' software I use defaults t' four decimal places!

Once you have your diameters calculated, you need t' determine t' circumference. This is calculated by multiplyin' t' diameters by pi (3.1415). T' second diagram (see diagram 2), shows t' diameters from our example relative t' each other. Ahoy! T' next step is t' decide how many sections you want t' divide your tube into. Again, ya bilge rat, t' more sections, matey, t' smoother t' possible shroud, matey, but t' more difficult it is t' work with. Ahoy! For this example, I will be workin' with a fairly low count for simplicity. Four works fairly well, me hearties, but I have worked with as many as eight.

Diagram 1	Diagram 2

To determine t' shape o' t' individual sections, you have t' divide t' circumferences we calculated earlier by t' number o' sections. Well, blow me down! These sections (quarters in this case) are then aligned along a central line. Begad! As you can see in t' third diagram (see diagram 3), by joinin' t' ends o' t' lines, me bucko, a curve is created. Arrr! After you have created t' first panel, arrr, simply copy it as many times as you decided t' make panels (in this case a total o' four panels). See t' fourth diagram (see diagram 4), me bucko, t' see our completed template. I usually allow a half an inch or so o' an extra tab at t' large end o' t' tube for ease o' markin' t' tube. So, just t' summarize t' concept again, what you are doin' here is cuttin' t' larger tube into equal sections that are t' same diameter as t' smaller tube.

Diagram 3	Diagram 4

Okay, now it’s time t' print out your pattern and walk away from t' computer and get out t' t' workbench. Arrr! Blimey! Wrap t' template around t' tube (see photo 1). Arrr! Be careful t' get it as squarely taped in place as possible. Carefully trace t' pattern onto t' tube and remove t' pattern. Next, as precisely as possible, cut off t' extra sections betwixt t' tapered panels o' t' shroud. Whereas you can use your trusty ol’ x-acto here, as long as you are workin' on fairly thin wall tubing, shiver me timbers, it’s easier t' use scissors. Ya scallywag! I know that sounds weird, but it seems t' be t' case t' me as long as t' cuts are bein' made along t' length o' t' tube instead o' around it (see photo 2).

Photo 1	Photo 2

Photo 3

Now that we have t' triangular pieces cut from our large tube, take t' smaller tube that you want t' transition down t' and put a centerin' rin' on t' end that will be inside t' larger tube and glue this assembly inside just past t' end o' t' cuts (see photo 3). Ya scallywag! After t' glue has set, you want t' make a small cut in t' large tube just past t' centerin' ring, on t' transition side. Avast! This allows for a little flex in t' tube as you form it into t' smaller tube. Arrr! Gently bend t' larger tube into t' smaller one. Blimey! You may need t' add a little extra curve t' t' outer tube t' get it t' properly match up. Begad! Dependin' on t' length o' your transition and t' thickness o' t' tube, shiver me timbers, you may get some slight crimps. Begad! T' only way I have found t' avoid these is t' use a much higher number o' sections and workin' with thinner tubing. Ahoy! It’s okay if you get little crimps, ya bilge rat, they can always be sanded out later.

I then use CA(superglue) t' smartly bond t' ends o' t' transition t' t' smaller diameter tube, matey, workin' on opposite sides at t' same time (see photo 4). Blimey! Be careful here with t' CA glue as it bonds skin even more readily than rocket parts! After t' first sections have set, continue with t' others until they have all been formed inwards (see photo 5). I like t' bond t' seams closed with CA. Nay only does this cure quickly, but it also makes t' tubin' much more sandable… Which brings us t' t' last step in any rocketry project… Sand, fill, repeat. Ahoy! I find that with a coat or two o' Elmer’s Fill-‘N-Finish, I can usually achieve a fairly smooth curve and surface on t' transition (see photo 6).

Photo 4	Photo 5	Photo 6

Hopefully you will find this process a little less dauntin' than I did t' first time I tried it. You can achieve great lookin' transitions with a lot o' strength in a wide variety o' shapes usin' this technique. Well, blow me down! Good luck!