Another idea instead of foam and microballons is a clear polyureathane glue with a drop or two of water the glue will foam and fill all the voids.

Soar Dude

Originally Posted by Soar_dude

Another idea instead of foam and microballons is a clear polyureathane glue with a drop or two of water the glue will foam and fill all the voids.

Soar Dude

I debated that but have had bad issues with controlling the foaming. We were most worried about the foam building up pressure and bloating the plywood outward.

I just used this technique on my old Turbo I'm also restoring. The results were poor. It did not fill the area I was after, and the foam that did expand into an area I wanted to fill fell off as it had no adhesion to the wood, and below that were large air voids. I'll be smearing the area with some microballons.

My buddy showed me his cleaned up repair and it looks pretty good. I forgot to take a picture though..

While on the subject of filler materials, I just thought I'd interject another, that I'd like to explore a little more myself, but was really interested at the results I had.
a few months ago I was fixing a pylon racer that the gear was getting kinda smooshy. there were some hardwood longerons that the wire gear legs bolted into that had cracked and cracked and so forth so much that the end that stck into the wing core was actually flexing fore and aft in torsion. think aileron torque rod with a wheel on the servo side. I mixed up a quarter of a dixie cup full of 5 min epoxy, then an equal (or 1 1/2 part) of microballoons or even more and it got too thick to pour. so I thinned it back down (a bit too far) with isopropyl alcohol and it ended up the consistency of a melted Mcdonalds shake. I poured it into this void in the wing that was pretty big. I poured, and poured, ...and POURED, until the 3/4 cup of "mix" was gone. I jammed the gear into the groove/hole and turned it right side up, to let it envelop the gear, and walked away to the other end of the shop for a while. OK, like a minute. then all hell broke loose, and I re-invented EPP. Fluorescent yellow EPP! Whoo hoo! A BIG PILE OF IT! seriously, it was like expansion foam, but with no swelling of the wing- What's more, when the plane met it's demise, I broke open the wing to check out the inside of my repair, and it was light, not flexible, and kind of honeycomb "ish"..

I'm going to experiment with this stuff once I get my new laboratory, I mean "shop" set up! lol

Interesting..

Originally Posted by exciter900rr

While on the subject of filler materials, I just thought I'd interject another, that I'd like to explore a little more myself, but was really interested at the results I had.
a few months ago I was fixing a pylon racer that the gear was getting kinda smooshy. there were some hardwood longerons that the wire gear legs bolted into that had cracked and cracked and so forth so much that the end that stck into the wing core was actually flexing fore and aft in torsion. think aileron torque rod with a wheel on the servo side. I mixed up a quarter of a dixie cup full of 5 min epoxy, then an equal (or 1 1/2 part) of microballoons or even more and it got too thick to pour. so I thinned it back down (a bit too far) with isopropyl alcohol and it ended up the consistency of a melted Mcdonalds shake. I poured it into this void in the wing that was pretty big. I poured, and poured, ...and POURED, until the 3/4 cup of "mix" was gone. I jammed the gear into the groove/hole and turned it right side up, to let it envelop the gear, and walked away to the other end of the shop for a while. OK, like a minute. then all hell broke loose, and I re-invented EPP. Fluorescent yellow EPP! Whoo hoo! A BIG PILE OF IT! seriously, it was like expansion foam, but with no swelling of the wing- What's more, when the plane met it's demise, I broke open the wing to check out the inside of my repair, and it was light, not flexible, and kind of honeycomb "ish"..

I'm going to experiment with this stuff once I get my new laboratory, I mean "shop" set up! lol

This brings to mind an "experiment" I made a few years ago.
I used spray-can foam to do some weatherproofing around the house.
When I was done I had about a half can left. I was already familiar with how forcefully this stuff can expand, so I did this:
I had a balsa glider fuse that had seen better days, all cracked and formers busted out, etc.
Shot it full of foam from the aft end of the compartment under the wing all the way to the nose (hatch removed).
As the stuff foamed up I would stir it up with a stick, making it liquid again. As it foamed up again I would stir it some more. As time went on, the foaming action slowed, until at the end of the day it was pretty much done.
Anyway the stuff was very hard and tough. I cut holes for radio gear and put that old wreck back to work. I eventually gave it to a newbie who used it to learn to fly on, and it was still going strong a couple years later.

This may be off-topic, but I figger you guys can always use info like this.
I think another way to use the stuff would be to squirt a plastic bag full of it, with a plastic tube secured in a corner of the bag. Knead the bag to break it down as it tries to foam up, then when it's about done, but still foaming a little, squeeze it into a mold for a wing or fuselage.
As I recall it was resistant to solvents, I tried cleaning the stuff up after it cured and not even acetone would budge it. It has very minimal adhesion when cured, so if you wanted it to stick you might have to apply a glue to the inside of whatever you're trying to reinforce with it.
It takes time but you only have to stir it every once in a while, so you'll want to do it while working on some other thing at the same time.

It sure did work well for restoring useful life into that beat up fuselage.

Exciter and all;

Nice thread, thank you. I just picked up a hawk and will prepare it to fly. My question(s) is; it came with a large aluminum wing rod. Is this acceptable to use, or should I find something else.. carbon, etc.??

Also, should the dorsal part be reinforced in any way, or is stock ok?

Thanks in advance for your time.

John

Originally Posted by John Cole

Exciter and all;

Nice thread, thank you. I just picked up a hawk and will prepare it to fly. My question(s) is; it came with a large aluminum wing rod. Is this acceptable to use, or should I find something else.. carbon, etc.??

Also, should the dorsal part be reinforced in any way, or is stock ok?

Thanks in advance for your time.

John

John,
the aluminum rod is just fine- you can substitute it for something else if it's bent, but the general concensus is they it allows the wings to flex rather than break.
The stock tail is fragile to a point, but plenty strong if it is still intact and not cracked or poorly repaired. Remember, it's pretty much an antique! Lol good luck, and thanks for the post!

Exciter, thank you for the reply! The rod is new, as is the whole model. I will plan on using it then. It's never been flown, but I'm still going through it and will also refinish it since the existing paint and covering have aged poorly. Another Hawk to join the fleet!

John

While the aluminum may help prevent wing damage, they are a P.I.A. to remove from the fuse once they are bent. I used to replace them with steel ones, but I can't remember if that caused more cases of wing damage or not.
What would be nice is one that could flex some under crash loads then spring back. Carbon or glass?
When I bent one so bad I couldn't remove it I had to hacksaw it off and get a new one. But if you're patient and creative you can straighten it while it's still in the fuse.

I'll be honest, and tell you that there is a 5/16" stainless rod in mine, but I know that I'm not gonna flog the hell out of it- just be careful of winch launching it, and pouring on the g's from diving/looping and the stronger ones are cool-
my "default" is to recommend what's "supposed" to be, or better.

I think a popular replacement is something like 7075 alloy. It can bend under load, but is very hard to actually bend and keep bent.

I need to do a little research and see if that is the right alloy..

Well, I broke down and finally nabbed a great looking Hobie this week. No restoration required on this baby (yet). I'm really stoked!

All I did was replace the old 72mhz radio with a 2.4Ghz rx, and replaced the old slider power switch with a blackjack plug for external charging and power-switching, Tonite, check the CG and washout, and she's basically ready to go. Even my wife likes it. She says it looks like a piece of art in our living room. (I agree!)

mdine1us - I hate you too. Great looking plane, and you wife is right, it looks great on your coffee table.

Just sent a lot of cash off for a tail assembly so I can get back to work on mine. Lets just say the price of these parts has gone way up!

Ran into a great example at Long Beach on Sunday. Was flying with an equally nice looking Aquilla (sp?). Didn't bring my camera though..

Be warned - the Hobie at Long Beach had been recovered recently. Even though the plane had no damage history the wing now has flat spots - Why you ask? Well, he used the new Monokote, and it required a lot more heat to pull the wrinkles. The heat melted the foam. You have been warned. We plan to use Ultracoat on ours.

-Wayne

Thanks Wayne. I feel an addiction coming on... And I will likely be getting another Hawk to do some restoration work on very soon, so I will be looking at all of the good information in this thread when I take that project on! Ultracote it is!

Marty

I think I spelled it right... Anyway I remember a day flying a Hobie in an east wind on Table Rock Dam near Branson, Missouri. It was a great day with 10-15 mph wind and thermals.
In those days (early/mid '80's) I was young and very go-4-it.
I flew my Hobies with the CG at the aft limit (19"?) and plenty of throw on the surfaces. No computer radio, in "normal" flying the top of the stick never moved more than 1/8"-3/16". And my snap rolls were wild...

I was flying in a "spirited" manner. Some guy showed up with a Sig Ninja, fresh on the market at that time. He marveled that I had a faster roll rate than he did...
My flying buddy says "Hey Steve, show this guy your lomcevak."

So I found a thermal and got her way up there, I'm sure no less than 300' over.
Vertical dive, when she got level with us she was really moving.
I eased the stick back to bring her to a vertical climb with minimal speed loss...
Then I pulled full left and full up. Hobie was a blur, spinning wildly.
The climb stopped immediately but all that energy was now in a rapid positive G spin, with Hobie on her back. As she fell she wanted to nose down, but the gyroscopic forces interfered, and the result was a combination of spin and tumble, really wild. Recovery must have used 100' at least.
It looked very much like the famous maneuver seen at airshows.

Ninja guy just shook his head in disbelief.

Yep, them Hobie Hawks were really something.