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Hobie Hawk Restoration

One of the things I like to do with basket case donations like this is trying to figure out what the last flight may have looked like.
With the broken dorsal fin (stab mount) and this broken rudder. I’m confident that the last flight ended in violent ground loop that came to rest inverted.

The other issue is that the wing tip was damaged. I’m thinking that this might have been part of that same violent ground loop. I’ve also noticed that the aluminum wing rod is bent. But there is no damage to the carry through structure in the fuselage. This indicates that the force to bend the rod didn’t have too high a shock load, indicating again the ground loop or ground loops!

I’d like to show the wing root. You will notice that is has a distinctive serpentine look. You can see that the trailing edge is coming back under the fuselage. This wing root is as distinctive as the elliptical dihedral. I really don’t want to loose this esthetic feature by lowering the wing incidence.

I’ve been doing some research on the Hobie Hawk and I’ve come to the conclusion that there are two very polar camps on this bird. There are those that love the Hobie Hawk and think it is the pinnacle of sailplane design. And then there are those that think in was a horrible sailplane used to experiment with manufacturing processes and never should have been brought to market.

I have to admit I’m a bit ambivalent on the Hobie Hawk. I’ve loved her lines for decades, lusting after one ever since I saw ads for her in the model press. She is deeply rooted in the dreams of my youth.

Now I have to say that the last “high performance” 2 channel sailplane I owned was a Mark Smith’s Windfree. I loved the Windfree as it was my first standard class ship. I actually learned to find and work strong thermals with the Windfree. But I also learned that I didn’t like the lack of control one had with an aileronless model!

When the time came for me to actually fly a Hobie Hawk I actually had strong ideas (feelings) as to what made a great sailplane. I’m sorry to say the Hobie Hawk is NOT a great flying sailplane. It wasn’t back in 1975 and it isn’t today. But she is a beauty! And this is why I want to try to rebuild this example and try to address some of the crippling flight characteristics without compromising her esthetic appeal.

All the best,
Konrad

HH inverted stop.jpg


HH damaged tip.jpg


HH Serpentine Root.jpg
 
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I’ve been given a lot of documentation on the Hobie Hawk (thanks GP49). It looks like my example is an “original" Hobie, Hobie Hawk, not the Midwest production. It was a bit of a surprise to learn that the Monokote covering was used to hold the washout in the wing tip. I’d have thought that this would have been cut into the cores or pressed into the wing during the manufacturing process. This bring up a question of what materials to use when recovering the wing. I believe the original covering was MonoKote (a Mylar film?). It has been my experience that MonoKote is a bit stiffer than polyester film (Oracover). This makes MonoKote a bit better at holding film induced trim settings.

My question is what happened to the modern formulation for MonoKote. It smells and performs nothing like the MonoKoat of old (I have a few rolls of the 80’s MonoKote) Has Top Flite admitted that there has been at least one reformulation of MonoKote. Will the new formulation of MonoKote give the properties I need to hold the washout. I have to admit that over the years I much prefered to cover with Oracover.

I notice that Paul Naton is using Ultracoat in his renovation.

All the best,
Konrad
 
Yeah, Monokote had to switch to a lower VOC content along time ago, and it has sucked ever since. Either find some vintage film or use another brand. Some colors of the new Monokote are REALLY horrible. As I recall the lime green is the worst. I dragged a stash of vintage film back to the shop a while back, but think the good rolls have already found new homes.
 
We really do live in interesting times!

LVOC, this would have been for the adhesive? I've also noticed that the actual (new) film is horrible, much more brittle and it doesn't shrink. I wonder what the shelf life is of the old good stuff might be. Even in the original shrink wrap covering it is exposed to the air.
If I have old rolls it will be of odd colors, like pink or orange. I just can't bring myself to cover a Hobie Hawk in pink!

Is there a known date that the LVOC switch occurred? I assume it was around the turn of the millennium.

All the best,
Konrad
 
Yeah, I'm not sure, maybe around that time.. And I have no idea how long an old roll is good for, but seems to brittle a bit over time. I think storage temp would have more to do with it. Or just get some Oracover and be done with it.
 
But I recall all the dire warning about not using MonoKote with open structures. :eek: Like the wings will resist flutter about as well as a wet noodle!:unsure:;)

But as it looks like Paul Naton is using Oracover/ Ultracoat, I just may have too.
 
.....
If I have old rolls it will be of odd colors, like pink or orange. I just can't bring myself to cover a Hobie Hawk in pink!
.......
Konrad


There used to be a Hobie Cat with a nickname of Tequila-Sunrise. You can cover you Hawk to look like it with smaller scraps of older monokote.. :cool: Not sure what you could do with the pink


PS. I used to race a Hobie 16 when I was young and light...
 

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To put some pressure on me to actually finish this project in a reasonable time frame, I'm publicly announcing that I'd like to have this completed for the Sunset Beach fly in.
 
Konrad,

I will follow your Hobie Hawk chapter closely hopping that it makes me prioritize my many projects over the winter. I would like to have the Hobie Hawk ready by Sunset (Priority #3) . Also on my build sheet are a couple of classic EPP birds from DAW: Me163 and 3m Ka6 plus JW60 a Moth. I believe you met my son Alex while you were at Station B at ISR this past summer (thank you for letting him hang out). Well the bug has struck (him), and he would like to try to race next time at ISR. He now has a couple of old Jaro Muller Ellipse 3CAM's that we are going thru with help of local racers. Need to get these ready so that he can practice before next year (priority #1). Enough off subject rant. Onto building. Please post your progress!

Mark
 
Yes, I remember you and Alex,
I remember all the energy Alex had with that Alula! I have to be honest that part of me dreads new young blood coming on the racing scene.
This is because they often are faster than me, in what appears to be an unbelievably short amount of time. :eek: The other parts of me would like to see both you and Alex running the bases!

I was pleasantly surprised to learn that the MonoKote on this model was the original. And it still performed like real MonoKote! Too bad the top layer had become sun damaged and brittle. Now my Monokote is not acting like the MonoKote on Paul Naton’s Hobie Hawk. Using a hot iron actual is prone to leaving a lot of adhesive behind on the plywood skins. I’m finding that heating the MonoKote with a heat gun to just below the boiling point of water, maybe 90°C is working best. Note the aft part (open area) came off with no application of heat.

I’ve found that this wing tip has been damaged at least twice. I also noticed that the tip was looking like it was showing wash in, well definitely not wash out. So I separated it at the failed joint.

I also found a manufacturing flaw in that there is no foam in the trailing edge at the root. One could notice this as a dip in the trailing edge. I think I’ll separated the top and bottom skins and use expanding polyurethane glue to fill in the void. I’ll follow this repair with Periwinkle blue paint to try to hide the repair should I use a transparent covering.

All the best,
Konrad
HH broken tip.jpg


HH TE flaw.jpg
 
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Interesting on the missing foam.

Maybe I'll get my HH ready for Sunset too. It is a great site for them to fly at. I think someone had one there last year..? Might be a bit of a squeeze with the other project kicking in now.
GS - 1 (1).jpg
 
Glad to see you haven't lost focus as to what is important. I see that toy (sorry small) aircraft in the background!
 
Yep - I have moved most of my RC fleet to the office as the garage has been taken over. Luckily my wife lets me build the RC birds on the kitchen table from time to time. :)
 
How does the towel hold up against fast moving thin CA?

Digging through some of my Monokote stash I found a lot of colors I won’t admit to having. That might be why they are still around in my stash. But I found some new rolls, 2 rolls of transparent red, one roll of transparent green and one roll of opaque orange. The sales slips indicate that these are from around 1987. I’ll have to do some testing to see the real condition the film, so far they smell like real Monokote So this might help me stay motivated knowing I have options other than pink!
 
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