Hobie Hawk Restoration

[Wayne]

I don't use the thin stuff very often, usually medium. But my experience is a small amount of thin will pretty much cure on contact with a towel. I have never managed to have any glue get past the towel. If I am using thin CA, I will glue it up in the garage if I can.

 

[Glenn Beer]

I really disliked the aluminum wing rods.
They bent with a dirty look, and if both sides bend, the only thing to do was to find a hacksaw. Even when the didn’t bend they sometimes gualled. I finally sleeved the fuse and wings with brass tubing and started buying unhardened drill rod for wing rods. They still bent, but they never got stuck in the fuse. Kept a couple on hand all the time.

 

[Glenn Beer]

Imron is what I remember as being one of the paints used, that or the now unavailable Formula-U polyurethane.

 

[Konrad]

Yikes, Dupont's Imron is what ended my career as a body and paint man. This was in the 70’s before Dupont’s recommendation of positive air suits. Face masks with Organic filters weren’t sufficient. Imron put me in the hospital for 3 day, the resultant torn muscles and tendons didn’t heal for 6 month. Then there was this issue of neurological damage. The upside is it forced me to become a machinist /engineer.

I hope Hobie, Midwest, Ross and all the OEM’s didn’t actually use Imron paint for our toys.

Dupont’s Catalyzed Centari paint was flexible and had a good bond with most plastics.

I’ve never had good luck with Pactra’s un-catalyzed polyurethane (Formula U) paint. It never really cured. (It always stayed soft, never really stood up to glow fuel above 5% nitro and was heavy.

All the best,
Konrad

 

[gp49]

KLASS KOTE EPOXY PAINTS, CLEAR COATS, MODEL PAINT

Color Formulae

 

[Konrad]

This is mainly to keep the pressure on. I've removed all the covering from the top of one wing. I still have a slight blue hue to the wing. Also there is some blue, deep in the wood grain. I'm hoping that when covered this will look like strong grained oak veneer.

Any of you artist out there know if there is a way to hide this? like with a complementary transparent color to blue. If I stay with MoneyKote this means transparent red or transparent orange. I might go with transparent orange as I think this was an OEM color for the Hobie Hawk. But it is a lighter color and I fear any and all repairs to the wing will show through the covering.

All the best,
Konrad

 

[Wayne]

How did you get it off so well? It was very stubborn on my old one.

I have seen a number of restorations that painted the wood black. This looks really shard when working with something like the transparent blue. Looks good with yellow also. But yours is in such good shae would be a shame to cover up the wood.. Maybe use a dark colored film for the leading edge back towards the bays.

 

[Konrad]

Thanks!
I too am surprised at how good the wing cleaned up! I've only cleaned up 25% of the wing, but it does look promising.

I found that using an iron to release the adhesive counter productive. Removing the iron on film the way Paul Naton shows in his videos, I found actually drove the adhesive deep into the wood veneer grain. Yes, more of the adhesive came up with the film. But at the same time more was pushed deep into the wood.

I used a heat gun to soften the adhesive. Them I pulled straight up on the film to remove it. This worked well, but often left thick areas of adhesive on the wood.

To remove this adhesive I let the wing cool down to room temperature. I'd then use a sharp scrapper held 90° to the surface of the wood. Running the scrapper (A Stanley carpet knife blade) with the grain of the wood would remove the adhesive. After a few passes one learned how to hold the blade so as to not shave the veneer. Make sure the removed adhesive shaving was clear of the wing before bring back the blade for another pass. If the shaving was caught it was likely to be smeared into the wood grain.

All the best,
Konrad

 

[Konrad]

Paint under MoneyKote has never worked well for me. Even Paul Natan made a comment to the same effect. I've tried dye (water based) and this also has produced less than satisfactory results. As the dye often wasn't uniform over the whole surface. I had the same issues with stains (Oil based). If I did get a nice sub-surface it blotched badly when expossed to the heat of the iron. Heat, Paint and MonoKote don't mix.

All the best,
Konrad

 

[Konrad]

Stripped all the covering off the bottom. And have finished the first step of clean off the adhesive. I was pleasently surprises not to find any more damage to this wing panel.

Now as expected the bottom wing has a lot more adhesive stuck to the wood. This was because the under cambered airfoil needed to actually have the iron on film pressed down on to the ribs at the factory. This drove a lot of the adhesive into the wood grain. It doesn't look too bad. But the bottom of the wing has a blue hue that is about twice as strong as the top of the wing.

As you can see there has been at least two repairs to the wing tip. I will have to fail these repairs and try to align the pieces a bit closer together. It really is fine as is, but it is holding a bit more wash in (less wash out) than what I see in the other wing.

All the best,
Konrad

 

[Konrad]

Again this is mainly to keep the pressure on so that Hank GBZ's prophecy doesn't come to be. (See post#30)

The left wing cleaned up really well.

Unlike the right wing the left wing has too much of a foam core. You can see this in that the top and bottom skins don't meet at the Trailing Edge (TE). There is a sandwich of blue foam in the TE for about 6 bays. I think I'll have to use a thin kerf saw to remove this 0,7mm thick foam to allow the top and bottom skins to actually bond to each other.

You can also see that the left wing actually is a bit too thick as it doesn't fit the plastic end caps very well. I think I'll just have to live with this manufacturing error.

The wing does have some very minor damage. There is a small dent in the bottom of the leading edge from contact with a rock. I also found a kink in one of the ribs near the TE.

All this should be easy to fix.

A question I have for owners of the Hobie Hawk. What is your possition on the ABS wing tips? They appear to be rather heavy for what they are. I'm guessing 5 grams each. To help make the Hobie Hawk track and respond better I'm thinking to replacing these tips with much lighter balsa ones.

All the best,
Konrad

 

[gp49]

The wing tips used to be made from wood at one point on the early wings. Don't think it was balsa, but if you replace them only you will know. Some used to cut a few bays off the wing to shorten length for use on slope. I'm sure they made the new tips from whatever was available.

BTW, I wish my wings looked this good. Great job cleaning them up.

Mark

 

[Konrad]

Thank you, but I fear the camera may be hiding some blemishes.

I think the more durable wing tip would be made from hollowed out Basswood rather than balsa. I need to remember that the Hobie Hawk is NOT a high performance or even a performance glider. A little weight out at the tips while not a good idea won't destroy the charm of the Hobie Hawk.

Working with the wing I see that the ”core thickness” real was a factory assembly error. The top skin had shifted out of position and was riding on top of the plastic wing root. With a razor saw I cut back the shin that was riding high on the wing root. I then tried to push the wing skin back down into the recess provided by the wing root. I did get a bit of movement, but unfortunately there has been a lot of glue that has filled the recess.

All the best,
Konrad

 

[Hank GB Z]

Looking good Konrad. Glad to see you're trying to keep my prediction from coming true.

Hank

 

[Konrad]

Looking good Konrad. Glad to see you're trying to keep my prediction from coming true.

Hank

Yep, I’ve been told I’m a very trying person.

 

[Hank GB Z]

Yeah well we all have our cruciform tails to bear...

Hank

 

[Glenn Beer]

Thank you, but I fear the camera may be hiding some blemishes.

I think the more durable wing tip would be made from hollowed out Basswood rather than balsa. I need to remember that the Hobie Hawk is NOT a high performance or even a performance glider. A little weight out at the tips while not a good idea won't destroy the charm of the Hobie Hawk.

Working with the wing I see that the ”core thickness” real was a factory assembly error. The top skin had shifted out of position and was riding on top of the plastic wing root. With a razor saw I cut back the shin that was riding high on the wing root. I then tried to push the wing skin back down into the recess provided by the wing root. I did get a bit of movement, but unfortunately there has been a lot of glue that has filled the recess.

All the best,
Konrad

View attachment 2943

A little bondo to build up the root?

 

[Konrad]

I find that Bondo (polyester filler) is problematic when used next to polystyrene foam.

I much prefer epoxy based fillers like "SuperFil". SuperFil is much more stable and is about half the weight.

All the best,
Konrad

 

[Konrad]

Time waits for no man!

So as to not see HanksGB prophecy come true, I’m working on my wings. The biggest flight damage is the broken off wing tip. To make things a bit challenging there are what looks like 2 other repair attempts done to this wing tip. Just for the record the biggest issue with the wings happened at the point of manufacture. The skins shifted and there is some missing foam as a result of poor cutting of the wing cores.

I had to re-break some of the wing tip “ribs” to take out some of the built in stress (from previous repairs) that was messing with the wing washout. To fill in the void left from the crushing of the wing tip and the removal of a lot of old 5 minute epoxy I’m using expanding urethane glue.

All the best,
Konrad

 

[gp49]

If someone, with money, wants to to buy a NEW build Hawk, there is a guy name Tony (V1VrV2) on rcgroups that builds a G1 Super Hawk from scratch. He is about to start his next batch and is staring to look for buyers. Here is a little blurp about the Super Hawk from the Hobie forum :

"
Guys,

Is anyone interested in a Superhawk G1?

I have possible plans to make some this Fall/Winter. If there is enough interest I will build some for you guys. Builds would be pre-paid. I don't want crickets when it is done. It takes way too much time to make these for tire kickers. I have enough materials to build 200+ of them but a severe lack of personal time. Builds would be 3 meter span, SD-7037 airfoil, dual spoiler panel cutouts, Carbon fiber dorsals, Tintable canopy, 3/8" wing Joiner rods. PM me for interest and I'll see if its worth the build time. Should be ready for the Katie Tribute next season.

If not that's OK. I will work on one of the 100's of other "Honey Do's" I have waiting for me! Ha! "