CHAPTER FOUR

STABS AND RUDDER

I do not remember the hot wire machine for the rudder and stabs. I do remember that they were cut with multiple wires. I have a vague image of the foam blocks, from the same foam as the wings, sitting vertically with a clamp that held the block in place. The arm with the wires was brought down around templates and cut the stabs and a different jig cut the rudder foam blanks. As I remember it, we got four or more elevators and four or more rudders from each block.

The horizontal stabs had hardwood leading edges glued in place and the root injected molded pieces were glued on. They were then sanded and prepared for the 1/64th (.4mm) ply skins to be applied. Special aluminum platens were also used to vacuum bag the horizontal pieces. Like the wings, there were holes in the foam, die-cut ply skins with holes for alignment and glued, vacuumed bagged and cured.

On the rudder, after the foam cores were cut and prepared, the injected molded rudder piece with control horn was glued into place and a wood wedge was glued to the bottom and a wood piece glued to the leading edge. As with the stabs, the die-cut 1/64th in. (.4mm) ply skins had glue applied, aligned and vacuum bagged in their special platens.

If you go to, and I highly recommend you do, www.hobiehawk.com, click on History on the left, scroll down to the Shop Tour of Ross models and check out the photos. On the left, second one down shows the air router that cut all those bays in the Hobie Hawk wings. Also notice the fixtures that routed the stabs and rudders. We told you the wings were done in pairs, back to back and notice that the rudders were done two at a time and the stabs were done stacked 4 deep.

NOTE: Most all of the photos in this article came from www.hobiehawk.com. Our sincere thanks to Brian Joder for their use.

Once the rudders and stabs were routed, like the wings, light sanding around all of the bays and final inspection. They are ready for shipment unless they were finished so the injected molded stab tips and the rudder top were glued into place and sanded smooth. The rudder bottom had to be sanded round too.

SPECIAL TIP BEFORE COVERING

Because when shrinking, the covering will also heat the air in each bay and cause ballooning. For this reason I will drill a small hole or take a large paper clip and poke a hole in the foam rib between each bay. These holes allow air to move between bays and reduces the ballooning considerably. Try to keep the holes in a line for appearance purposes.

FINISHING THE WINGS & TAIL FEATHERS

As with everything else, the Hobie Hawk required a different approach in finishing. The elevators and rudder were pretty much the same as with other planes, but care had to be taken not to get the foam too hot or it could melt.

The wings however were a different story. Many people have covered the wings very carefully and slowly. Having manufactured the Hobie Hawk and insight into how Hobie covered them wings, I have always covered them by flattening out the wing on a special board designed for covering the wing. At the end of this chapter is a picture of the board Brent Daily built for me to cover his stock Hobie Hawk wings.

The idea is that with the elliptical dihedral and curve of the airfoil, covering material does not like to bend two directions at the same time, so if you flatten the wing, you only have the curve of the airfoil to contend with. This is accomplished by the building board.

HOBIE HAWK COVERING BOARD

If you want to build a board for covering your Hobie Hawks wings the way the original was done, here is how to build a covering board. The plan form is the shape of the wing only 1/4” smaller and you have the left and right. You have to make a metal end plate, it can be 1/16” up to 1/4” and aluminum is easiest to work with. First thing I would do is drill the 5/16” hole in the end plate. Using your wing, slide the main wing rod through the end plate into your wing. Clamp the wing to the covering board so the bottom is flush with the end of the board. Using a small drill, drill a hole near the leading edge and one near the trailing edge through the end plate and into the covering board. You will need to open up the holes through the end plate to accommodate the screws and mount the end plate onto the board. Next draw a line over the airfoil and one at the bottom of the board. Remove your end plate and wing. Saw, grind, file the end plate so that when mounted it will hold your wing in place and be aligned with the bottom of the board and the top of the wing. Mark and drill the holes and mount the end plate on the other board.

Originally they used a U shaped piece of plastic to hold the tip down flat, but as you can see in the photo below, I used a clamp.

Now that you have the covering board, covering is much easier. Place the covering on the wing, tack around the parameter, then seal leading edge and trailing edge, iron down to the ribs. Just be sure to leave a few extra inches at the tip so you can heat and pull the covering over the round wing tip.

Once you are done covering the wing top, release the clamp and finish shrinking the covering with a heat iron or heat gun. Be careful not to put too much heat anywhere as damage to the foam core can occur.

Covering the bottoms is pretty simple. I always tack the parameter and then I seal the covering to the center of the under camber ribs before I finish sealing to the leading and trailing edges. Once again, be careful not to over heat the foam core.

The horizontal stabs and the rudder were covered in a normal fashion. Again the Monokote was die cut to shape.

NOTE: I have read various reports from individuals that talk about doing piece work on covering wings, rudders and elevators. They also talk about when Hobie sold the business that he told these individuals to keep the wings, rudders and elevators and the rolls of covering. I am not disputing these claims in any way, but in my conversations with Hobie he stated that he had ladies in house that did the covering. He also stated that he had the Monokote die-cut for wings, rudders and elevators. To support his statement when I had the wing, rudder and elevator ply skins die-cut for my production runs, they told me they use to die-cut Monokote too. At the rate that Hobie was producing Hobie Hawks, it is quite possible that the ladies could not keep up and Hobie had out side sources sand and cover the parts on a piece basis. In any case, here I only make reference to the facts that I am sure of.

PUSH RODS

The push rods were fiberglass and the 2-56 threaded metal rods were bent into a tight U shape on the non threaded end and with hot melt glue, were glued into the fiberglass rods. You could adjust the rods by heating the hot melt glue with your covering iron, and then small final adjustments could be done with the clevises.
NOTE: If you get out your old Hawk or acquire one, test the firmness of the rod in the push-rod. If these come loose in flight, chances are that you will severely damage your Hawk. If the rod is solid after giving it a good pull, fine, but if it moves just a little I would recommend rebuilding the push-rod. Originally they were glued with hot melt glue, but epoxy with mico-balloons can be used.

The hardest part for most people was getting the elevator clevis attached to the bell crank in the tail piece. Nylon clevises were stock but some would replace them with metal clevises but both were difficult to attach.

THE READY TO FLY (RTF) VERSION

Hobie told my that he wanted a sailplane that he could fly at or near his house on the beach. The went into various Hobby stores and there simply was nothing available ready to fly. If you ever met Hobie, he may seem very laid back with his causal clothing but his mind was always in high gear, so he did not want to spend a lot of time building....he wanted to fly. This is when he began to conceive the Hobie Hawk. He really did not want to create a sailplane because it represented a lot of time and work away from his REAL JOB! Eventually he decided if he was to design a sailplane, he wanted it to be the best he could make, typical Hobie. He decided to create two, actually three versions of his plane.

For those use to and willing to put a little time into the plane he created the kit version. Finishing this version entailed shaping the leading edge on the wings, elevators and rudder, covering them. Unlike future manufacturers of the Hobie Hawk, Hobie's kit version had a painted fuselage.

Next came the covered version where the fuselage was painted with an automotive urethane paint, the wings and tail feathers were covered in a variety of colors, yellow, red, orange and blue. I believe you could have opaque or transparent in those colors.
I do not remember any other colors available.

Finally there was the ultimate RTF.....a real Ready to Fly sailplane, I believe the first in the world. This version was not only covered, but it had a radio installed and was balanced. Just charge the batteries and FLY!

I cannot in a million years explain to you the balancing apparatus Hobie had, but you would set the finished Hobie Hawk with radio gear installed on this contraption, add the weight through the hole cut in the cockpit until it was balanced. I know that it also was able to balance the Hobie Hawk, nose to tail, wing tip to wing tip at the same time.

Covering was another item we did not offer in the Hobie Hawks we sold. To my knowledge, Hobie was the only one that offered a pre-covered, pre-painted and in some cases available with a radio installed and balanced. Hobie wanted to ship complete airplanes, some even with radios as well as the unfinished kit versions we sold.
Hobie told me that he had ladies that sat at a special table with a jig that allowed the wing to be flattened, clamped and covered. At one end of this jig was an aluminum plate with the shape of the top of the airfoil and flush with the top when held in place. Using a main aluminum wing rod through the plate and into the wing would hold the root down while she would flatten the wing and use a U shaped plastic clip to hold down the tip. She would then take the color of Monokote for that wing, lay it on the flattened out wing panel and seal it around the edges and onto the ribs. She then released the tip, finished sealing the Monokote and using a heat gun, finish shrinking the covering. Next she or someone else would apply the bottom covering in normal fashion, without flattening and finish the wing. I am not sure if each lady did the same thing over and over or if she did a whole wing. I do know that the Monokote was die cut to the shape so there was very little if any trimming. I have also heard from other sources that the prep of each wing (installing the wing tips, sanding the fuzz from the ply in the bays and rounding the leading edges) and also covering was out sourced and paid as piece work.

BALANCING

Hobie came up with a unique way for customers to balance their Hobie Hawk, a way I have not seen before or since but obviously works.

Pictures cover most questions so at end of this chapter is a copy of the balancing page from the manual.

Because the Hobie Hawk can be temperamental if slowed too much, I would error on the nose heavy side, at least until you become proficient flying this great sailplane. That means more like 20 to 20 ½ ” from the table up to the base of the tail skid.

End of Chapter 4

Chapter 5 will be the final chapter and I am still trying to locate, scan and present promotions and ads for the Hobie Hawk over the years. Some very creative and beautiful ads were run by the various companies that produced the Hobie Hawk. One such ad prompted a phone call from a Madison Avenue Ad agency, looking to get a piece of the action. When asked what they would charge for such an ad, they calmly said they could do an ad like this one for around $20,000.00. That is just the production cost folks, and has nothing to do with the placement in a magazine......They obviously do not understand the hobby industry but shows the quality and creative effort the Hobie Hawk inspired. I will keep looking and will present as many as I can.
If any of you have access to any Hobie Hawk ads or reviews, please let me know.
Until then.....I hope you have enjoyed the look inside the manufacture of the magnificent Hobie Hawk.
Bob

Great read, as always...I can vouch on seeing women covering ...I think I saw them at both locations...on picking up parts

Curt

Originally Posted by bob57hdt

CHAPTER FOUR

STABS AND RUDDER

I do not remember the hot wire machine for the rudder and stabs. I do remember that they were cut with multiple wires. I have a vague image of the foam blocks, from the same foam as the wings, sitting vertically with a clamp that held the block in place. The arm with the wires was brought down around templates and cut the stabs and a different jig cut the rudder foam blanks. As I remember it, we got four or more elevators and four or more rudders from each block.

The horizontal stabs had hardwood leading edges glued in place and the root injected molded pieces were glued on. They were then sanded and prepared for the 1/64th (.4mm) ply skins to be applied. Special aluminum platens were also used to vacuum bag the horizontal pieces. Like the wings, there were holes in the foam, die-cut ply skins with holes for alignment and glued, vacuumed bagged and cured.

On the rudder, after the foam cores were cut and prepared, the injected molded rudder piece with control horn was glued into place and a wood wedge was glued to the bottom and a wood piece glued to the leading edge. As with the stabs, the die-cut 1/64th in. (.4mm) ply skins had glue applied, aligned and vacuum bagged in their special platens.

If you go to, and I highly recommend you do, www.hobiehawk.com, click on History on the left, scroll down to the Shop Tour of Ross models and check out the photos. On the left, second one down shows the air router that cut all those bays in the Hobie Hawk wings. Also notice the fixtures that routed the stabs and rudders. We told you the wings were done in pairs, back to back and notice that the rudders were done two at a time and the stabs were done stacked 4 deep.

NOTE: Most all of the photos in this article came from www.hobiehawk.com. Our sincere thanks to Brian Joder for their use.

Once the rudders and stabs were routed, like the wings, light sanding around all of the bays and final inspection. They are ready for shipment unless they were finished so the injected molded stab tips and the rudder top were glued into place and sanded smooth. The rudder bottom had to be sanded round too.

SPECIAL TIP BEFORE COVERING

Because when shrinking, the covering will also heat the air in each bay and cause ballooning. For this reason I will drill a small hole or take a large paper clip and poke a hole in the foam rib between each bay. These holes allow air to move between bays and reduces the ballooning considerably. Try to keep the holes in a line for appearance purposes.

FINISHING THE WINGS & TAIL FEATHERS

As with everything else, the Hobie Hawk required a different approach in finishing. The elevators and rudder were pretty much the same as with other planes, but care had to be taken not to get the foam too hot or it could melt.

The wings however were a different story. Many people have covered the wings very carefully and slowly. Having manufactured the Hobie Hawk and insight into how Hobie covered them wings, I have always covered them by flattening out the wing on a special board designed for covering the wing. At the end of this chapter is a picture of the board Brent Daily built for me to cover his stock Hobie Hawk wings.

The idea is that with the elliptical dihedral and curve of the airfoil, covering material does not like to bend two directions at the same time, so if you flatten the wing, you only have the curve of the airfoil to contend with. This is accomplished by the building board.

HOBIE HAWK COVERING BOARD

If you want to build a board for covering your Hobie Hawks wings the way the original was done, here is how to build a covering board. The plan form is the shape of the wing only 1/4” smaller and you have the left and right. You have to make a metal end plate, it can be 1/16” up to 1/4” and aluminum is easiest to work with. First thing I would do is drill the 5/16” hole in the end plate. Using your wing, slide the main wing rod through the end plate into your wing. Clamp the wing to the covering board so the bottom is flush with the end of the board. Using a small drill, drill a hole near the leading edge and one near the trailing edge through the end plate and into the covering board. You will need to open up the holes through the end plate to accommodate the screws and mount the end plate onto the board. Next draw a line over the airfoil and one at the bottom of the board. Remove your end plate and wing. Saw, grind, file the end plate so that when mounted it will hold your wing in place and be aligned with the bottom of the board and the top of the wing. Mark and drill the holes and mount the end plate on the other board.

Originally they used a U shaped piece of plastic to hold the tip down flat, but as you can see in the photo below, I used a clamp.

Now that you have the covering board, covering is much easier. Place the covering on the wing, tack around the parameter, then seal leading edge and trailing edge, iron down to the ribs. Just be sure to leave a few extra inches at the tip so you can heat and pull the covering over the round wing tip.

Once you are done covering the wing top, release the clamp and finish shrinking the covering with a heat iron or heat gun. Be careful not to put too much heat anywhere as damage to the foam core can occur.

Covering the bottoms is pretty simple. I always tack the parameter and then I seal the covering to the center of the under camber ribs before I finish sealing to the leading and trailing edges. Once again, be careful not to over heat the foam core.

The horizontal stabs and the rudder were covered in a normal fashion. Again the Monokote was die cut to shape.

NOTE: I have read various reports from individuals that talk about doing piece work on covering wings, rudders and elevators. They also talk about when Hobie sold the business that he told these individuals to keep the wings, rudders and elevators and the rolls of covering. I am not disputing these claims in any way, but in my conversations with Hobie he stated that he had ladies in house that did the covering. He also stated that he had the Monokote die-cut for wings, rudders and elevators. To support his statement when I had the wing, rudder and elevator ply skins die-cut for my production runs, they told me they use to die-cut Monokote too. At the rate that Hobie was producing Hobie Hawks, it is quite possible that the ladies could not keep up and Hobie had out side sources sand and cover the parts on a piece basis. In any case, here I only make reference to the facts that I am sure of.

PUSH RODS

The push rods were fiberglass and the 2-56 threaded metal rods were bent into a tight U shape on the non threaded end and with hot melt glue, were glued into the fiberglass rods. You could adjust the rods by heating the hot melt glue with your covering iron, and then small final adjustments could be done with the clevises.
NOTE: If you get out your old Hawk or acquire one, test the firmness of the rod in the push-rod. If these come loose in flight, chances are that you will severely damage your Hawk. If the rod is solid after giving it a good pull, fine, but if it moves just a little I would recommend rebuilding the push-rod. Originally they were glued with hot melt glue, but epoxy with mico-balloons can be used.

The hardest part for most people was getting the elevator clevis attached to the bell crank in the tail piece. Nylon clevises were stock but some would replace them with metal clevises but both were difficult to attach.

THE READY TO FLY (RTF) VERSION

Hobie told my that he wanted a sailplane that he could fly at or near his house on the beach. The went into various Hobby stores and there simply was nothing available ready to fly. If you ever met Hobie, he may seem very laid back with his causal clothing but his mind was always in high gear, so he did not want to spend a lot of time building....he wanted to fly. This is when he began to conceive the Hobie Hawk. He really did not want to create a sailplane because it represented a lot of time and work away from his REAL JOB! Eventually he decided if he was to design a sailplane, he wanted it to be the best he could make, typical Hobie. He decided to create two, actually three versions of his plane.

For those use to and willing to put a little time into the plane he created the kit version. Finishing this version entailed shaping the leading edge on the wings, elevators and rudder, covering them. Unlike future manufacturers of the Hobie Hawk, Hobie's kit version had a painted fuselage.

Next came the covered version where the fuselage was painted with an automotive urethane paint, the wings and tail feathers were covered in a variety of colors, yellow, red, orange and blue. I believe you could have opaque or transparent in those colors.
I do not remember any other colors available.

Finally there was the ultimate RTF.....a real Ready to Fly sailplane, I believe the first in the world. This version was not only covered, but it had a radio installed and was balanced. Just charge the batteries and FLY!

I cannot in a million years explain to you the balancing apparatus Hobie had, but you would set the finished Hobie Hawk with radio gear installed on this contraption, add the weight through the hole cut in the cockpit until it was balanced. I know that it also was able to balance the Hobie Hawk, nose to tail, wing tip to wing tip at the same time.

Covering was another item we did not offer in the Hobie Hawks we sold. To my knowledge, Hobie was the only one that offered a pre-covered, pre-painted and in some cases available with a radio installed and balanced. Hobie wanted to ship complete airplanes, some even with radios as well as the unfinished kit versions we sold.
Hobie told me that he had ladies that sat at a special table with a jig that allowed the wing to be flattened, clamped and covered. At one end of this jig was an aluminum plate with the shape of the top of the airfoil and flush with the top when held in place. Using a main aluminum wing rod through the plate and into the wing would hold the root down while she would flatten the wing and use a U shaped plastic clip to hold down the tip. She would then take the color of Monokote for that wing, lay it on the flattened out wing panel and seal it around the edges and onto the ribs. She then released the tip, finished sealing the Monokote and using a heat gun, finish shrinking the covering. Next she or someone else would apply the bottom covering in normal fashion, without flattening and finish the wing. I am not sure if each lady did the same thing over and over or if she did a whole wing. I do know that the Monokote was die cut to the shape so there was very little if any trimming. I have also heard from other sources that the prep of each wing (installing the wing tips, sanding the fuzz from the ply in the bays and rounding the leading edges) and also covering was out sourced and paid as piece work.

BALANCING

Hobie came up with a unique way for customers to balance their Hobie Hawk, a way I have not seen before or since but obviously works.

Pictures cover most questions so at end of this chapter is a copy of the balancing page from the manual.

Because the Hobie Hawk can be temperamental if slowed too much, I would error on the nose heavy side, at least until you become proficient flying this great sailplane. That means more like 20 to 20 ½ ” from the table up to the base of the tail skid.

End of Chapter 4

Chapter 5 will be the final chapter and I am still trying to locate, scan and present promotions and ads for the Hobie Hawk over the years. Some very creative and beautiful ads were run by the various companies that produced the Hobie Hawk. One such ad prompted a phone call from a Madison Avenue Ad agency, looking to get a piece of the action. When asked what they would charge for such an ad, they calmly said they could do an ad like this one for around $20,000.00. That is just the production cost folks, and has nothing to do with the placement in a magazine......They obviously do not understand the hobby industry but shows the quality and creative effort the Hobie Hawk inspired. I will keep looking and will present as many as I can.
If any of you have access to any Hobie Hawk ads or reviews, please let me know.
Until then.....I hope you have enjoyed the look inside the manufacture of the magnificent Hobie Hawk.
Bob

Thanks Bob. Very interesting to say the least.