# Flight Club - Ultralight Build Log

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#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
If you want the ultimate in cheap and light - Skip to 6:00. I have seen this type of hinge on man carying Experimental made with 2" Dacron tape.

#### memde

##### New Member
20 each AN42 bolts would be needed for the ailerons, elevators and rudder. Total cost would be in the $200 to$300 range, depending on the sizes selected.

Edit. Just looking around, it looks like some may be available for about half of the above.

BJC
We used fork bolts and eye bolts for hinges and other control linkages on our E-Hawk (EMG-6). They are a clean solution but I would have to echo the sentiments above regarding cost. I recall having to pay ~$25 per for some of the AN fork bolts (the mating eye bolts are more reasonably priced at around$5).

#### Victor Bravo

##### Well-Known Member
I'm sorry to noisily disagree with anyone or be heavy-handed with my opinions here, but... No, just no, on fabric or laced hinges.

Yes for the Goldberg Stunt Man 23, yes for the Top Flite Baby Flite Streak, no for a man-carrying ultralight.

Our new friends and HBA participants will be flying a bit higher than they are willing to fall. Primary structure and primary controls should use components that are low risk and high reliability.

IMHO this is not the place to save a couple of dollars... and that is one of the most important lessons these students need to learn for their school project.

I'm not saying that a $750 NASA approved aerospace hinge is what they need to use. A$5 hardware store hinge may be capable of taking these loads with a perfectly good safety factor. But safety wire or zip ties or fabric is not right for this.

#### jedi

##### Well-Known Member
As
I'm not quite sure I understand the design you're describing. Do you have any examples you could refer us to (model or full size)?
As in Post # 101 but VB has spoken and needs to be heard.

I am not suggesting the tape used in the #101 example but a 5,000 pound test strap from Harbor Freight riveted to an external aluminum gusset should certainly hold up and would be field replaceable when worn or degraded by UV radiation. Sounds like some serious overkill to me. I welcome more comments and discussion as I plan to use similar concepts for primary structure.

I also understand the resistance to wire ties but there is also 1/16 multistrand flexible steel cable over a suitable rub strip. Don't forget kevlar paraglider lines or monofiliment fish line (monofiliment is less redundent for the failure mode). Remember the 2,000 wire ties at Sun n Fun years ago? Trying to remember the bird and builders name. Worked fine for him.

Needle and thread are used to sew on fabric covering when rib stitching but then that is not a moveable surface just primary structure. I would look at material like the climbing straps from REI. Think outside the box.

Don't like the zig zag hinge, the same can be accomplished by sewing between the front and rear hinge members.

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#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
No, just no, on fabric or laced hinges.
Why? Because it carries the stigma of being developed for - models?
If there exists a real reason, rather than an emotional reaction, then I would genuinely like to hear it.
Dacron has a pretty good fatigue profile, and with multiple strips a quite progressive and observable failure rate. On top of that you have an automatically sealed control gap.

#### Bill-Higdon

##### Well-Known Member
Why? Because it carries the stigma of being developed for - models?
If there exists a real reason, rather than an emotional reaction, then I would genuinely like to hear it.
Dacron has a pretty good fatigue profile, and with multiple strips a quite progressive and observable failure rate. On top of that you have an automatically sealed control gap.
The Skypup uses sewn hinges

#### proppastie

##### Well-Known Member
Log Member
Because it is not "standard aircraft parts or process".....Is there one LSA, or Certified aircraft or STC that uses it, I would be interested to see it. Were one such as a Rutan to do all the analysis and testing such as he did for the Vari-Easy and was at a FISDO with understanding inspectors perhaps,..... but to suggest it as a high-school project is not what I believe is appropriate.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
but to suggest it as a high-school project is not what I believe is appropriate.
Maybe, but part of this project is learning how to evaluate the options presented. So far they appear to be doing an excellent job. If I thought the option was inherently unsafe I would not have suggested it.

This isn't a completely novel idea in the man carrying aircraft world and, in my mental history data base, predates the use of the use of the AN eye bolt type hinge that does have a documented failure mode of twisting in flight and locking the control surface. There is a similar commercially available one piece product using Kevlar for the hinge fabric* that has been tested for this type of application.

I'm hoping that VB will add some relevant observations from the model world.

*Kevler fatigue properties are significantly inferior to Dacron

#### proppastie

##### Well-Known Member
Log Member
my mental history data base, predates the use of the use of the AN eye bolt type hinge that does have a documented failure mode of twisting in flight and locking the control surface.
Good point, post if not too much trouble, certainly a wing that deflects is going to want to twist two eye bolts, perhaps piano hinge is better where it still deflects but does not twist, and if the hinge is short pieces (2" ?) the deflection through the pin is very small, plus one would be able to have at least 4 maybe more rivets....The tabs of post #91 also would allow deflection without lockup.

When I first joined EAA 1970 the operand method was "aircraft materials and process" this pre-dates the Vari-Easy, the big controversy was "pop-rivets" instead of AD rivets.

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##### Well-Known Member
This isn't a completely novel idea in the man carrying aircraft world and, in my mental history data base, predates the use of the use of the AN eye bolt type hinge that does have a documented failure mode of twisting in flight and locking the control surface.
Instead of using one eyebolt/one forkbolt you could use three eyebolts. This arrangement is impossible to twist.

Another option is available. The Aerodrome Aeroplane WWI replicas use an extruded aluminum device for hinges. The extrusion slips over a 1" tube and has an AN-3 bolt hinge pin. This is easy and reliable. You could probably purchase a supply of these hinges from Aerodrome. Airdrome Aeroplanes ~ Holden, MO

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member

Both good observations. I'd forgotten about those extrusions. Of all the options so far they seem to me to be the best for their project - if they are available in the proper tube size.

This tangent kind of reminds me of the first time I ran across plastic rivets to hold inner fenders in place rather than the then standard Tinnerman nuts. Of course the first experience involved a broken fastener and I condemned the whole change as "just cheap". I'll never again use a metal Tinnerman nut for that application. The plastic is just better.

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#### syclone

##### Member
I love what you’re doing. From a crashworthy standpoint I’d like to see you end the (brown) upper tube one junction further aft. That might be another reason to consider turning the triangle over. You might need more triangulation in the forward cockpit area and perhaps an “X” arrangement on the cockpit floor. Keep us informed of your progress.

#### Victor Bravo

##### Well-Known Member
Well I was just promoting the safest possible method of hinging a control surface... I didn't expect the Spanish Inquisition.

If Robert Baslee at Aerodrome manufactures an extruded tube hinge material then this will be by far the best option, because it is certainly cheaper than welding up the ones I drew. From everything I have heard he is a great guy and would likly be supportive of the project to one degree or another.

(Perhaps RadfordC and one or two of the other HBA people might know Robert personally and put in a good word for him to help out in some way)

For Ollie and his design crew, once again I have a little bit of personal experience with aluminum tube ultralight/LSA ailerons that uses piano hinges (Kolb Firestar, Kolb Mark 3). Please trust me, absolutely do not use piano hinges on a light flexible structure. They do bind up under normal flight loads and make the ailerons unacceptably hard to move in flight.. Maybe Dana and others here who have flown the Kolb aircraft have had better luck than me with the piano hinges, and maybe the two Kolbs I flew were unusual, or built improperly.

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#### Dana

##### Super Moderator
Staff member
Please trust me, absolutely do not use piano hinges on a light flexible structure. They do bind up under normal flight loads and make the ailerons unacceptably hard to move in flight.. Maybe Dana and others here who have flown the Kolb aircraft have had better luck than me with the piano hinges, and maybe the two Kolbs I flew were unusual, or built improperly.
You're right, I did have better luck, never noticed any binding or excessive force... and the Ultrastar has a rather short side stick. I only flew my buddy's Firestar once, and I don't recall any issues there either.

OTOH, I'm not thrilled with the aileron friction on my piano hinged Hatz... but first I need to figure whether the friction is coming from the hinges or elsewhere in the system.

#### BBerson

##### Well-Known Member
HBA Supporter
I am planning to make hinges similar to eye bolts by welding a hinge bushing to the head of a 1/4" AN bolt.
The 1/2" long steel bushings are similar as used on Grob. Side by side pair, no fork.

#### proppastie

##### Well-Known Member
Log Member
You're right, I did have better luck, never noticed any binding or excessive force... and the Ultrastar has a rather short side stick. I only flew my buddy's Firestar once, and I don't recall any issues there either.
maybe the two Kolbs I flew were unusual, or built improperly.
It is really important that the hinges are in line and square for lack of a better term...Also if the wing was not rigged properly or was loose and deflected much more that it should have, that would be another problem. You once posted about the bad flight you had, did you ever find out what the problem was?...Is your friend flying that machine?...There are many Kolbs flying if it was a design problem I would think there would be more noise about it.

#### Victor Bravo

##### Well-Known Member
There was a lot of noise about it on the Kolb internet list once. People were told or decided to simply accept the Kolb's heavy ailerons as part of the charm, the same way owners of old British cars wear "Lucas: The Prince of Darkness" T-shirts and people in Chicago accept the cold wind. "Kolbs have heavy ailerons" is frequently discussed.

On the two that I flew, it wasn't that the hinges were poorly aligned during the build. If that were true, then the ailerons would have a lot of friction on the ground, which they did not. Only when the lift on the wing bent the wings slightly upward (which misaligns the hinges) did the problem become an issue.

#### Ollie Krause

##### Well-Known Member

Both good observations. I'd forgotten about those extrusions. Of all the options so far they seem to me to be the best for their project - if they are available in the proper tube size.
Do you have a photo/drawing/link of these extrusions? I wasn't able to find them on Airdrome's website...

Thanks for all the great feedback and discussion, everyone!

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Do you have a photo/drawing/link of these extrusions? I wasn't able to find them on Airdrome's website...
Strictly from memory - couldn't find a pic either:

#### Ollie Krause

##### Well-Known Member
I love what you’re doing. From a crashworthy standpoint I’d like to see you end the (brown) upper tube one junction further aft. That might be another reason to consider turning the triangle over. You might need more triangulation in the forward cockpit area and perhaps an “X” arrangement on the cockpit floor. Keep us informed of your progress.
Sorry, could you send a screenshot of the exact beam you're referring to? I couldn't find a brown beam so it's probably just my computer's crappy display and low res screenshots that are messing things up. If it's easier, you can view/copy/download the full 3D model from our public Onshape document. We were thinking of using honeycomb aluminum paneling for any floor panels that may be stepped on or have control mechanisms mounted to. Out of curiosity, what would adding a full X to the bottom of the cabin do that a single diagonal beam wouldn't? It would add some rigidity and ensure that one beam is always in compression but our initial calculations suggest that the 1x0.035" 6061 aluminum tubing is already plenty strong in compression or tension.

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