HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Dec 28, 2004, 09:13 AM
TLAR Black Belt
ejett's Avatar
Athens, LA, United States
Joined Apr 2002
1,249 Posts
AJ, Jack:

Are the carbon sparcaps tapered too? If so, how'd you do that?

EJ
ejett is offline Find More Posts by ejett
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 28, 2004, 12:01 PM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
1,317 Posts
The tapered spar is used on the outboard panels. Believe it or not, there is no carbon there. Spruce top, and balsa bottom spar caps. Shear webs at the tip graduate down to 1/16 balsa. Light.

AJ
solo6796 is offline Find More Posts by solo6796
Reply With Quote
Old Dec 28, 2004, 12:10 PM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
1,317 Posts
Jeff,

The bench sander idea sounds reasonable for tapering the spars. Clamp them together and do all of them at once.

AJ

Wish I had some real tools when I was building this.
solo6796 is offline Find More Posts by solo6796
Reply With Quote
Old Dec 28, 2004, 12:55 PM
Jeff
USA, CA, Redondo Beach
Joined Aug 2003
645 Posts
Quote:
Originally Posted by solo6796
Jeff,

The bench sander idea sounds reasonable for tapering the spars. Clamp them together and do all of them at once.

AJ

Wish I had some real tools when I was building this.

Thanks to everyone. Yes, spot gluing together is an excellent solution. And I have a little antique razor plane (uses safety razors!). Then touch up with a long flat sanding block. In case anyone is wondering what happened to getting started, I realized I did not have all the wood in the materials list I hate starting something without having most of materials on hand. Quirk of mine, amongst others. So I have to wait till Thursday (Payday) when I can get over to Superior Balsa and get the spruce. I had one 1/2" x 1/8" stick, I thought I had two. I thought I had the trailing edge stock and tiny spruce stick, nope. Did anyone forego the spruce on the trailing edge and substitute carbon Heat-Tac ribbon on the bottom of the TE stock?? I just used that stuff to great effect on a really thin trailing edge on a DHLG (Gambler+) kit.

Big thread that first one. Lots of info. But takes some mining. Glad I made that build notes document from posts in the original thread.

So I'll take the Bill of Materials to the shop today and verify that which I have and have not.

Best wishes,
Jeff
gdjsky01 is offline Find More Posts by gdjsky01
Reply With Quote
Old Dec 28, 2004, 05:48 PM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
1,317 Posts
There has been plywood trailing edges and some carbon modifications, no spruce, and with lightening holes. Also, the tail feathers have been lightened/stiffened by some. As more are built, tastes may vary. I prefer a little less dihedral in the center but others like maximum dihedral. I think this plane will fly well as long as the basics are there. The center spar is WAY stronger than it really needs to be, but the design leaves a margin for inexperienced winch operators, or competition launches. As long as you can come in around 55 oz., all that I have seen fly very well.

Good luck on your build. It really goes pretty fast, after the spar is done. I'd be interested in any mods you may make...part of the evolution in the Hawk.

AJ
solo6796 is offline Find More Posts by solo6796
Reply With Quote
Old Dec 28, 2004, 06:18 PM
Jeff
USA, CA, Redondo Beach
Joined Aug 2003
645 Posts
Quote:
Originally Posted by solo6796
Good luck on your build. It really goes pretty fast, after the spar is done. I'd be interested in any mods you may make...part of the evolution in the Hawk.

AJ
Thanks for the info AJ! Problem is I tend to build to plan, spec, instructions. I have always been one to RTFM. I have tried to tell other kit manufacturers that I (and I bet a whole bunch of others that are silent) prefer instructions and plans that are complete and if followed, ensure success. As opposed to those that assume the builder will simply figure it out. Good thing the Houston Hawk has decent instructions (better than a magazine article from a billion years ago), and the great support group here!

I'll try and look back and see if I can find the references to lighter tail feathers and carbon on the TE. Lighter tail feathers are always helpful. I may go the Heat-tac route if I have enough on hand. If not, I'll go stock with spruce.

If anyone has a PDF of the lighter tail plan pass it on.

Best wishes,
Jeff
gdjsky01 is offline Find More Posts by gdjsky01
Reply With Quote
Old Dec 28, 2004, 07:15 PM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
1,317 Posts
Jeff,

I've used that heat tack .007 CF on other projects, but I have always used thinned epoxy to secure it. Are good results obtained by just ironing it on?

AJ
solo6796 is offline Find More Posts by solo6796
Reply With Quote
Old Dec 28, 2004, 07:24 PM
solo6796's Avatar
United States, TX, Richmond
Joined Aug 2003
1,317 Posts
If built to the instructions provided, you will have a great flying model...

I flew mine yesterday, coming back down, I messed around with a loop or two, then a fast flyby, a 180 degree and land... Very responsive on high rates.

AJ
solo6796 is offline Find More Posts by solo6796
Reply With Quote
Old Dec 28, 2004, 07:49 PM
Hot Dawg Glider Pilot
schrederman's Avatar
United States, TX, Weatherford
Joined Nov 2002
7,761 Posts
New Trailing Edges

Jeff and everyone,

I see some questions popping up. My next Hawk is under way and basically framed and sheeted. I used balsa trailing edges and no spruce on the wing. It is flimsey to say the least. These newer airfoils are really thin back there. This time I got some .2 oz. carbon mat from the same folks that sent me the spar material. It works great. I cut some strips 7/8" wide and used medium ca to attach it. I used the clear plastic from Monokote to spread it. I added another strip 1/2" wide to the center panels, and then decided it wasn't needed.

Ed,

The main panel spars are not tapered. I wanted it to be easy to build so I made the thickness constant. I tapered the outer spars to bring the outboard weight down. I did it by clamping them together and using a jack-plane and a long sanding bar. I'll describe the process in the next post. I cut off the ends that were tightly clamped. I have never seen wing panels flex... no surprise there... and any additional strength added to the outboard panels is wasted weight. Not tapering the spars is also wasted weight - outboard where it affects the handling. Remember that the bending load at mid span is only 1/4 what it is in the center, and that's if it was a constant chord. With the wing taper, at the poly joint, it's probably 1/5 or less. That's why the outer spars are spruce and balsa. Also, the compression strength of spruce is roughly twice that of balsa, so the top spar cap is spruce instead of balsa twice as thick. That way the tension and compression loads are about matched in the wing. About the only weak point in the model is the stock joiner. Most people will never launch hard enough to bend it but I have to constantly fight to keep my center dihedral at 7 degrees. I think AJ has his bent down to about 4 or 5 in the middle. I have had mine there once but launched pretty hard and it's back to 8... My Hawks will have 1/2" joiners from now on.

And you guys thought I was lost to being Martin Lithier King....

Jack Womack
schrederman is offline Find More Posts by schrederman
Reply With Quote
Old Dec 28, 2004, 08:18 PM
Hot Dawg Glider Pilot
schrederman's Avatar
United States, TX, Weatherford
Joined Nov 2002
7,761 Posts
Tapering outer spars.

One of my favorite tools is my jack-plane. I keep it razor sharp with an India Oil Stone. They are not cheap but worth every cent. Once I get it close on 2 progressively finer Arkansas stones, I hit it with the India stone and the result is a really sharp blade. My left arm always has bald spots on it from checking blades. It prolongs the life of #11 baldes, too. Make sure your plane isn't set to cut too deep. It needs to shave the wood off in long, translucent, smooth, curly strips. If your plane isn't sharp, the balsa will ball up in it and make this a real frustrating time, so get to whettin'...

Clamp 1 end of the 1/8 X 1/2 spar caps together, with them stacked spruce-balsa-balsa-spruce. If you spot glue them, make sure they are glued only in an area that will be cut off, as the entire 36" isn't needed. With them standing on the 1/8" edge, begin about 2" from the outboard end and make a cut to the outboard end. You should be making only a 2" plane cut. Come back 2" more for the next cut and progress back almost all the way at 2" intervals. Each cut will start in the factory edge and progress through where your plane has already been, and go all the way to the outboard end. Stop about 4 " from the poly joint end, and start over. This second pass will have you close. With your outboard panel plan taped down, check the stack of spar caps for fit into the ribs. If they need more work, make note of how much and proceed carefully. By this point, you may need to just sand them using 80 grit on a hard block.

One other point about the outboard panels - The laser doesn't cut the angled spar slots so when you are making the outer panel. you will need to relieve the spar slots in the ribs slightly for a good fit. That means you will need to keep the spar caps fitting tightly at this point.

I hope those answers help you with your Hawk...

Back to sanding leading edges.....

Jack
schrederman is offline Find More Posts by schrederman
Reply With Quote
Old Dec 28, 2004, 08:21 PM
Hot Dawg Glider Pilot
schrederman's Avatar
United States, TX, Weatherford
Joined Nov 2002
7,761 Posts
AJ,

The iron on cf is just for convenience. For the strength to be there, it has to be wetted out with epoxy or ca.

Jack
schrederman is offline Find More Posts by schrederman
Reply With Quote
Old Dec 28, 2004, 08:29 PM
Jeff
USA, CA, Redondo Beach
Joined Aug 2003
645 Posts
Quote:
Originally Posted by schrederman
AJ,

The iron on cf is just for convenience. For the strength to be there, it has to be wetted out with epoxy or ca.

Jack

That is correct. The melting plastic binder is only to hold it in place. Then you hit it with thin CA or medium CA and use monokote backing material (as a spreader).

Jack Thanks for the advice. Actually I believe you did tell that in the first thread. Or atleast you talked about the Jack Plane. I have a cheap one ut fear the blade is no where near as sharp as need be and I have no experience sharpening them. So I think I'll try shaving it with a razor plane as I think AJ did.

Now I understand the process. So perhaps I'll forego the thin spruce on the TE and use .007 carbon. If I understand what you were say about the ribs, they do not make a 90 degree angle with the spar.

Thanks
gdjsky01 is offline Find More Posts by gdjsky01
Last edited by gdjsky01; Dec 28, 2004 at 08:38 PM.
Reply With Quote
Old Dec 31, 2004, 06:26 PM
Hot Dawg Glider Pilot
schrederman's Avatar
United States, TX, Weatherford
Joined Nov 2002
7,761 Posts
New Hawk Rising - has some changes!!

In a constant effort to improve and lighten this model, I've had some brain storms lately. I have made the following changes: Lighter stab with NACA 008 airfoil; vented spoilers; 1/2" joiner; stronger stab belcrank mount; aluminum stab belcrank; and a few very minor things that are not obvious.

I am not sure where we fall in the serial numbers, but #1 is being retired as soon as this one is painted and covered. The next one is already started.

Anyhow, I'll miss the Postal Contest tomorrow going to get my real glider from the Austin atea. I didn't think about that when I got the call that the deal was made. I'll have a nice Pik-20B to float around in this summer. While you're hot and looking up, I'll be at cloudbase looking down .

Here's a pic or 2 with done descriptive language attached.

Jack Womack
schrederman is offline Find More Posts by schrederman
Reply With Quote
Old Dec 31, 2004, 06:30 PM
Hot Dawg Glider Pilot
schrederman's Avatar
United States, TX, Weatherford
Joined Nov 2002
7,761 Posts
Yet another new tail group

This tail has tarered carbon spars, and the belcrank is backward from the original.

JW
schrederman is offline Find More Posts by schrederman
Reply With Quote
Old Dec 31, 2004, 06:41 PM
Hot Dawg Glider Pilot
schrederman's Avatar
United States, TX, Weatherford
Joined Nov 2002
7,761 Posts
Spoilers and Tail

I built 2 Magnum 12s back in the 70s. They had an interesting concept for spoilers. They were vented. I would never have thought that those tiny spoilers would bring all that wing down, but they were very affective. With that thought, now you know the credit goes to Hugh Stock, and not Jack Womack...

Also visible is the carbon fiber spar material in the horizontal tail. The sheeting is 1/20" sheet from Lone Star Balsa. Saved a little weight. In case you are wondering, the stab is smaller in area but not much. The span is reduced but the root chord is increased. The rudder is stock size but a bit lighter. I'm waiting to fly it to pass judgement. If it's good, I'll gladly send a plan to anyone that sends a SASE.

Should fly next weekend, depending on my real sailplane stuff, weather, work, etc., etc., etc.

Happy New Year, everyone!

Jack th' Wood Butcher Womack
schrederman is offline Find More Posts by schrederman
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Winter Project, newest Houston Hawk erichj Sailplane Talk 15 May 06, 2007 04:49 AM
The Houston Hawk Project schrederman Thermal 1004 Nov 23, 2004 02:01 AM
Schreiner F-18 Project - Part #2 TedLarson Electric Ducted Fan Jet Talk 115 Feb 22, 2003 01:52 PM
Jim Bourke's Moving Sale Part 2 -- Brushless motors jbourke Aircraft - Electric - Airplanes (FS/W) 1 Aug 07, 2001 02:00 AM