BUILD a RAM AIR PARAFOIL CHUTE for R/C By

BUILD A RAM AIR PARAFOIL CHUTE FOR R/C by

Wally Gitchel

Modifications with permission of Wally Gitchel

Robert Deadmond

John Sedovic

7 cells, 24”, chord, 49” span, 8 sq. ft. area, for a #2 R/C Jumper

#1CONSTRUCT A RIB TEMPLATE. Materials needed are I sheet of art board 22” x 28” yard stick, protractor, 12”, ruler, pencils, T pins or brads, a standard length of 1/16” piano wire and a suitable board about 6” x 28" that will hold the pins or brads firmly.

#2Cut a piece of art board 8” x 28”. Draw a datum line on center full

length of the piece of the art board.

#32” from the left end of the datum mark a point and number it 0 just

below the datum.

#4¼”, to the right of 0 mark another point and number it 00 just below the datum.

#5With the yardstick and starting from point 00 measure and point

off on the datum the following dimensions. 1”, 2”, 3”, 4 ½”, 6”, 7 ¾”, 9 ½”, 11 ½”, 13 ½”, 15 ½”, 18", 20”, 22”, 24”.

#6With the protractor omit point 00 and draw vertical lines above and 90 degrees to the datum from the points established in step #5. Make these lines about 3” long. Draw a vertical line from point 0 similar.

#7On these vertical lines, measure up from the datum and point off the following dimensions in numerical sequence left to right.

Point 0 is ¼” (past 00 ) then 1 3/8”, 1 ¾”, 2", 2 ¼”, 2 7/16”, 2 ½”, 2 ½”, 2 3/8”, 2 3/16”, 1 15/16”, 1 9/16”, 1 1/8”, ¾”, and ¼”.

#8Lay the protractor with its base line an the datum and its center

over point 00. Point off 45 degrees downward from the datum, slanting to the right of point 00. Draw a line through and beyond these points about an inch or so. This line should intersect at the ¼” point above the datum at 0.

#9Extend line 24 about an inch downward and make a point on it ¼”

below the datum. On the 45 degree line, mark a point 3 ¾” downward from 00. Draw a line from this point to the point ¼” below the datum on 24. Along this line mark off 4 equal spaces.

These are canopy line attach points. A total of five front to rear.

#10On the datum, make a point 5” to the right of 00, another point10 ½” but ½”, above the datum, another point 16” but ½” above the datum. Draw 1 ½” circles on these center points.

#11Place the layout on the pin board and set pins or brads firmly in the points established on the verticals above the datum.

#12Press the 1/16” piano wire up against the pins and draw a curve

connecting all points. Make minor adjustments as necessary.

#13Carefully cut out the rib template and circles. NOTE The seam

stitch lines are ¼” inside the top and bottom cut line.

#14CONSTRUCT THE BOTTOM CAMBER CELL TEMPLATE. Cut a piece of art board 7 ½” x 21 ¾” into a 90 degree rectangle. Draw lines ¼”,

from and parallel to the cut line top and bottom. (stitch lines) Draw a line on center full length of the template. (stitch line) Draw a line ¼” from and parallel to this line. (seam edge line)

#15 LAYING OUT AND CUTTING THE PARTS. A hot knife is required to cut the parts and prevent fraying. Convert a 23 or 25 watt

soldering iron. The tip is soft copper. Hammer it flat and file it to the shape of a small pointed spade. The blade need not be knife sharp as heat does the cutting. A sheet of tempered masonite 1/8” x 3' x 5', or similar, for lay out and cutting surface. A 5’ straight edge (Aluminum extrusion from hardware), a T square, a yard stick, a measure all and pencils or ball point pens.

#16The cloth is ultralow or low porosity 1 or 1.1 oz. rip stop Nylon parachute cloth ( the real thing ) Available in several colors from ParaGearEquipment Co. 3839 West Oakton St., Skokie, IL, 600763438. Their $2.00 catalog is a wealth of information pertaining to full size. Cloth yardage is a builder choice depending on color selection (One of the tip ribs and its adjoining bottom panel should be a different color, gold, yellow orange etc. visible from the ground to tell which way the chute might be traveling).

Smooth out the wrinkles and creases with a WARM IRON before working.

#17Lay the top canopy cloth on the cutting table smoothly with the

selvage edge at the top. (All parts are cut lengthwise and parallel to the selvage) weight or tape it down so it won't shift easily. Draw a rectangle, 90 degrees all around, 26” x 49 ½”. With a straight edge and hot knife, cut the rectangle but do not remove it.

The melting action causes the edges to stick slightly to the table surface and it will be easier to draw the lines in the next step. Carefully, remove the scrap.

#18 IMPORTANT (ALL STITCH LINES SHOULD BE DRAWN BROKEN TO DISTINGUISH FROM EDGE LINES).

#19 At both ends of the panel, draw STITCH LINES ¼”, from and parallel to the cut edge (for tip ribs). Avoid accumulation of tolerances.

Measure and mark seven equal spaces between left and right stitch lines top and bottom of the panel. Draw broken vertical lines between these

Points, mark the center of each space (3 ½”) top and bottom and draw a broken line between these points.

These are stitch lines for the inner ribs.

They are ¼”, to the right and parallel to the stitch lines, draw solid lines. These are seam edge guide lines for installing the ribs. Remove the finished layout from the table and lay it aside.

#20Lay the cloth selected for the bottom camber cell panels on the table. Using the cell template from step #14, cut the required cell panels. Leave them stuck to the table and transfer lines and dimension from the template to the cloth. Draw broken lines for stitch lines and solid lines for seam edge guide lines. A total of seven panels required. Remove the material from the table.

#21Lay the cloth selected for the ribs on the table. Using the rib template from page #1 cut 13 ribs including the cross port holes. Cut the 2 tip ribs but do not cut out the cross port holes. Draw the canopy line locations as per the rib template. Make these lines about an inch long.

#22Cut 40 lines 56” long (Planer board tow line or catfish line from tackle shop or other as you choose) The lines are extra long to avoid confusion. There will be waste during rigging. Coil each line into two or three finger coils and rubber band each coil. This is to prevent them from stringing all over the place as you work on the chute.

#23Attach the canopy lines to 6 inner ribs locating them as marked in step #21. Use Gel C/A glue sparingly, tack them in place on the rib then machine sew vertically. Repeat on the two tip ribs. Leave the lines bundled until rigging.

#24Working one rib at a time is recommended. Too many ribs tacked on

may come loose while sewing, In that case you will start over. Spot tack a number one inner rib (No lines) to the canopy. Apply tiny spots of C/A gel to the canopy between the edge line and the seam line. Space them about 1/8” to ¼” apart at the leading edge for a distance of about I”. Apply the leading edge of the rib aligning the cut edge of the rib to the seam edge line on the canopy. Repeat another inch or so. Notice that the rib so attached begins to raise the leading edge of the canopy. Proceeding to the trailing edge in this manner will cause the canopy to take on the airfoil curve. You may increase the tack spacing some as work to the trailing edge. DO NOT FORCE OR STRETCH THE FABRIC AS YOU WORK. Sew the rib in place with ¼” seam. A zipper foot on the machine should do the job. Install the second inner rib (WITH LINES) in like manner. Install a third inner rib (WITHOUT LINES) Install the fourth inner rib (WITH LINES). Following this sequence install the remaining inner ribs a total of 13.

#25With the canopy top side up, tack and sew the tip ribs (WITH LINES) onto the topside of the canopy aligning the cut edge of the rib to the cut edge of the canopy. The seam will be on the inside of the chute when the tip is turned down.

#26Select an end cell panel and lay it flat on the table. Note the position of the stitch line and seam edge line. Turn the canopy, tip under bringing the bottom cut edge of the first inner rib (NO LINES) into alignment with the seam edge line and over the seam stitch line on the panel. Rotate the panel if necessary to match these lines. C/A gel tack the rib in place keeping all in alignment and sew in place. Repeat the process on the remaining cell panels attaching the inner ribs (WITHOUT LINES) to the centers of each cell panel.

#27Working one rib at a time tack and sew the edge seams, sandwich style, of the ribs with lines and the cell panels keeping all edges in alignment. Tack and sew the tip ribs to its panel in like manner.

#28Lay the canopy bottom side up on the table with the trailing edge toward you. The excess material on the trailing edge may be cut off carefully with a straight edge and hot knife then zig zag stitch to close the edge full length or trim it to an appropriate width and turn a hem to close full length.

#29 MAKE THE RISERS AND SPREADER: Select a pair of round shoe strings or similar about 24" long. Two fishing swivel snaps (remove the

Swivels). Pass the line through the small eye of the snap and pull them to equal length. Secure the loop with carpet thread and clove hitch. Lock the hitch with an overhand knot and a small drop of thin C/A to make it permanent. Make the spreader from a piece of lawn chair canvas, or similar, 2 ½” x 3 ½”. Install eyelets in each corner. Pass a pair of risers through the eye lets at each end. From the snaps, measure and mark a point 6” on each line. Secure 3/8” split rings at these points in the same

manner as was done at the snaps. Cut off the loose ends.

Pull the spreader down as far as it will go and tie it to the riser at each corner.

NOTE:

The spreader, in this case, is used to help prevent the lines from twisting and to hold the lines clear of the jumpers arms. On full size chutes it is called a slider and is for a different purpose.

#30RIGGING THE CHUTE:

Lay the canopy on the table flat with cells collapsed and lines bundled. Free a line only when ready to work on it. Mentally number the lines front to rear 1,2,3,4,5. On the tip rib facing you, free the #2 line. With a felt point marker

, mark a point on the line at 45”, from the edge of the rib. On the same line mark a point 30” from the edge of the rib. Repeat this procedure on all of the #2 lines. Run the four right hand lines through the right hand front ring on the riser. Aligning the 45”, mark to the ring, tie each loop securely with button carpet thread a clove hitch and overhand knot to lock. Do not glue them as you might have to make changes. Repeat the procedure on the four left hand lines running them through the front left hand ring on the riser. Sight along the 30” marks for alignment. If all is in order secure the tie offs at the riser ring with a small drop of thin C/A glue. (Too much glue will wick down the line and stiffen it). Snip off the loose ends close to the tie offs. These lines, at the ribs, are the pivot points for setting the negative angle of

Incidence.

#31SETTING THE ANGLE OF INCIDENCE:

The original chute was set at a negative 10 degree angle and seemed to run well. With a soft wood slat ¼” x 1” x 22” or a piece of yard stick and thumb tacks fasten the edge of the tip rib flush and in line with the top edge of the slat. Bring up the #3 line and run it through the rear ring at the riser at a length estimating the negative angle. Make a temporary tie at the ring. Place a protractor with center point over #2 rib attach point and its base in line with the top edge of the rib and slat. Holding #2 line vertical against the protractor adjust the length of #3 line to a 10 degree reading. The trailing edge will be lower than the leading edge. Make a secure tie off on the loop but do not glue. Let the loose end hang.

(FROMHERE ON MAKE ALL TIES SECURE, BUT DO NOT GLUE AS YOU MIGHT HAVE TO MAKE CHANGES) Bring up the #1 line and tie it to the 30”, mark on #2 being careful not to change the angle of incidence.

On line #3 mark a point 30”, from the edge of the rib. Bring up line #4 and tie it to the mark on #3 in like manner.

Repeat this procedure on all of the rest of the ribs. HERE IS A

TIP (GLUE THE PROTRACTOR TO THE SLAT AND A PAIR OF HELPING HANDS WOULDN'T HURT EITHER) Check that all lines hang true and in equal taught ness. Make adjustments as necessary.

#32 The three #5 lines at either end of the canopy are steering lines. Mark a point 30” from the rib on each line. The center line of each three go to the jumpers hands left and right. Install a split ring on the rear riser rings right and left. Run each of the center #5 lines up through these rings and tie them well up out of the way. Tie all three of these lines together at the respective 30”, mark. The two #5 lines at the trailing edge of the center cell are tied onto their appropriate split ring on the riser. Adjust their length so that their ribs hang straight and all lines in equal taught ness. Check all for symmetry. Make any necessary adjustments then make all ties permanent with a drop of C/A glue.

Clip off all loose ends close to the ties. DO NOT CUT THE STEERING

(MAIN)LINES AS YOU MAY HAVE TO READJUST THEM.

NOTE: USE SMALL AMOUNTS OF GLUE ON THE TIES. TOO MUCH GLUE WILL WICK DOWN THE LINE AND STIFFEN IT.

FOLDING AND PACKING THE CHUTE

1.Lay the jumper face down with feet toward you

2.Bring the chute, lines and risers toward you laying the risers and spreader on the bottom of the open container. organize and straighten the canopy lines.

3.With the leading edge on your left, collapse the canopy placing all cells together with rib edges straight and aligned.

4.Hold the chute by its leading and trailing edges and raise it upward to a normal position of exit and inflation. (The leading edge comes out of the pack first).

5. Check that all lines hang in normal flight position.

6. Lay the canopy down with the leading edge on your left. The lines will cross but will be in correct position when folding is completed).

7.Check that all lines are straight away from and not within the chute in any manner.

8.Fold the canopy top up overlapping the sides. The width of this fold approximates the length of the container full length of the canopy cord.

9.Fold the trailing edge, about a hand width, down and under.

10. Make the next three folds Z fashion from right to left. The folds thus completed approximate the width of the container. NOTE (IN THIS CONFIGURATION THE LEADING EDGE IS INCORRECTLY ON THE ON THE BOTTOM OF THE PACK)

11.Rotate the folded pack one half turn leftover right. The leading edge should now be on top of the pack with all lines toward the jumper. Place the pack, in this position on top of neatly coiled lines in the in the container.