Hello all,

I'm building my first plane. A Kadet LT-40. I've decided to go electric. I've followed the kit, except for a couple mods for the electric stuff.

I've covered it, and now I'm to the point of final assembly.

I don't know why, but I decided to use the Great Planes hinges, the ones with the pins, instead of the hinges that came with the kit.

The instructions said to cut grooves for the hinges.. which I did. I test fitted everything before I covered it, and everything seemed OK.

Then I covered the surfaces, and I've started finally assembly. Now it seems the hinge action is stiff, it squeaks. The elevator springs from extreme up, to extreme down, with tension in between. And I noticed this morning one of the hinges actually broke. Gosh Darn it!

Anyway... I'm punting the hinges I installed. And I'll install the kits hinges...

What I need to do, is cut hinge grooves that I know are going to be aligned and accurate. I need the control surfaces to move easily and smoothly.

So.. After that long diatribe..

What are some good technics, tools, tips, for cutting hinge grooves. And for installing hinges afterwards....


Thanks in advance,

Lyndon

Hi,

For hinges, you need to ensure they are all parallel and operating on the same axis. But one will always be higher / lower than the others, and one will always be at an angle to the rest. You get better with practice! Mis aligned hinges will result in binding.

I love GP hinges!

You can get a set of hinging tools from Du Bro, and I beioeve Carl Goldburg once made a set. A set of 2 prong forks & a gouger (to remove the wood froem h e\center of teh slot)

There is also a parallelogram 'hinge slot centering tool' that helps guide teh above tool into the center of teh TE, and paralleel to teh TE. But I ralrey use it. As long as teh hinge pin is parallel to each other and to the axis of rotation

There is also the center finder marker. Both GP & CG make them.. a lttiel device, with two tabs, and a central point. The tabs ride on teh top & bottom of the TE, while the cdnter point scribes your center line.

Once teh slots are cut, drive th inhnes hiome, and give a bit of a opush to 'dent' teh balsa. this, for me, is enough of a groove. Then try teh control surface, adn ensrue all fits & works as intended.

Next, you need to glue them hinges in. Typically I use epoxy, and as you've seen, gettin gehright amount in the slot takes expericent (i usually get too much in!!) a sanded donw popcicle stick helps get the epoxy into the slot. I glue the hinges into the control surface, let cure, then glue teh control surface to teh airframe.

Grease teh hinges at teh pin. Brush a bit of vaseline on the hinge knuckes (both sides). This prevents teh epoxy from sticking the hinge halves together.

Glue teh hinge in place. Wipe up any excess with a rag & Methyl Hydrate (denatured achohol) flex the hinge a few times, and wipe again. Ensure it is well seated.

There is usually a bit of stiffness when you first flex the surface.

Drilling a hole at the center of the hinge and first inserting triangle shaped hinges and then an Exacto knife has helped me to keep the hinge parallel to the surface. The triangle hinges are used only as a guide for the knife and other hinges are used at final installation.

Bill

Ok, think I need to add some to this thread. The first question would be, "Are you planning on building more models"? If so, then it would be in your best interest and safety to purchase the Great Planes Slotting tool and plastic centering guide from Tower Hobbies, or?
This tool will simplify the slotting job while getting all of the slots parallel. As for pin type hinges, before epoxing in the hinge the pin area should be carefully filled with petroleum jelly, or light grease, and then all of the glue surface areas cotton swabbed with alcohol to make sure there is no grease contamination. The method I was taught for gluing these pin hinges was to use a flat blade to spread the epoxy around in the slots, and then a light coat over the attaching surfaces of the hinge filling all of the holes, if any, then carefully slide the hinge into the slot making sure the extra epoxy that oozes out gets wipe off with a cotton swab. It is important to make sure all of the hinge pins are parallel to the stab or flight surface before the epoxy sets up. For safety, I drill a hole through the center of each hinge glued area, and install a round tooth pick section after the epoxy is dry. Now I know that the hinge will not come out until a crash.

This procedure make seem like a long job for just installing hinges, but after a few hinging jobs it will become old hat. Glad you have joined the hobby, and have choosen a swell model to start with. You will really enjoy flying this model.

Rich S.

Nothing at all beats this set. Well worth the minor investment, cuts perfectly straight hinge slots EVERYTIME, and extremely fast. First time I tried mine I wondered why I hadn’t gotten it from the start. And the Slot Machine tool comes with the CA hinge blades already included.

GREAT PLANES SLOT MACHINE
http://www2.towerhobbies.com/cgi-bin...?&I=LXK263&P=7


SLOT MACHINE CUTTING GUIDE
http://www2.towerhobbies.com/cgi-bin...?&I=LXPU13&P=7


SLOT MACHINE MEDIUM NYLON HINGE BLADES (2)
http://www2.towerhobbies.com/cgi-bin...?&I=LXK266&P=7


SLOT MACHINE HD NYLON HINGE BLADES (2)
http://www2.towerhobbies.com/cgi-bin...?&I=LXPT33&P=7



All RC builders should have these in their toolbox.

If it is stiff, you could have got glue in it a little! There are ways to fix the problem![:-]

Thank-you all for advice. I ordered and received the slot cutting equipment. While I was waiting for it to arrive I proceeded re-installing hinges. Hopefully the pictures below will help explain what I did.

First, I cut the old hinges out of the control surfaces. In doing so, I made the holes pretty big (relatively speaking of course). But far too big for friction to hold the hinges in place. I needed to devise a way to hold all the hinges in place while epoxy filled the holes and cured.

I took pictures of my work on the elevator.
1. I marked the position of the hinge.
2. Then I transfered that mark to a length of angle aluminum. It has to be angle stock because it is by nature straight.
3. I clamped the hinges onto the angle aluminum, I made sure both "flaps" of the hinges sat flush on the angle. With four hinges needed for the elevator, this assured all hinges pivoted along the same line.
4. I clamed the aluminum to my workbench. You can see in the pictures I test fitted the elevator to make sure everything was set.
5. I mixed up some 15 minute epoxy, and put the hinges in place on the elevator. And let it cure for a couple hours.
6. Then I epoxied the elevator/hinge assembly in place.

The end result, spectacular! Night and day difference. As I type this, I've just finished the aeleron. Once this is cured, I can finally install the aeleron servo, and finish radio installation.. I... gorsh I can hardly believe it.. I'm only a few hours of work from being flight ready!!!

For future use, if you are using "hinged" hinges, cut a little piece out on both sides around the hinge itself. This will set the hinge in closer and eliminate the large gap you have. You should really seal the gap you have, otherwise it may feel mushy.

I've got to post a follow up to this thread.

While my wallet saved up money for the batteries to fly this bird, I did more and more reading.

Last week, I came across a build thread by RCKen. Seeing how well he did on the hinges on his build, and see how blankety-blankety-blank-blank bad I did on mine. I decided "make it right."

I ripped the monocoat off my wings. And I'm rebuilding it now. The wing's TE is so buggered up, it wasn't useable. So I ordered a new TE and ailerons from Sig. (Should be here next week)

In the meantime, I've modded the wing for independent aileron servos (flaperon if I want).

The biggie, I practiced cutting slots. I used scrap TE and aileron stock to make practice.

I have the slot cutting tool from GP. Works great!

I do have a couple questions. Hopefully RCKen will see this and respond. I followed his technique.

When CAing the hinges, should there be any gap between the TE and the aileron?

The first picture shows my first attempt. No intentional gab between TE and aileron. Seems OK, not sure. The second picture, I left the pin in while I moved the aileron to it's extreme, before CAing the hinges. There is a gap, slight. The pin is being held in place by friction, that's how close it is.

Which did I do correctly?

Good idea using test pieces... That's a great way to learn without messing up your project.

I leave a gap for CA hinges, exactly the way you have it in your pics. But if the hinges have a pin, I get as close as possbile - no gap necessary. With a pin, I just make sure the pin is exactly on the pivot point and that they don't bind.

Nice job btw. "Make it right" is what it's all about, as long as it keeps it fun for you. Just make sure it doesn't get in the way of completing the project at hand.

-Todd

I vote for the Great Planes Hinge Slotting Machine. I use mine a bunch. I built a small table with a fence to position and hold the parts for slotting and a mount for the hinge slotter. Speed and accuracy and it makes the job so much easier and faster as well.

JEB

OK.. I'll bite...

Pictures / demonstration / description of jig please.....

Here is the fixture I built out of plastics materials. In that business so it was a natural for me.

JEB