aframe2

My Feedback: (5)

I am putting together a 50cc airplane with a DLE-55 engine. The kit came with metal 1/4 20 wing bolts. I am on the bubble with weight, and for that
reason I would like to use nylon bolts instead of metal. It is a pitts challenger bi-plane. Does anyone know if the nylon wing bolts are a safe
replacement for the metal ones? Aframe 2

dasintex

My Feedback: (10)

You need to wonder why they provided Metal bolts instead of Nylon, a lot of ARFs even 50cc sized ones such as Warbird Arfs come with Nylon Wing Bolts and the Nylon bolts on those plane are adequate; but on a Pitts, with 2 wings, Nylon may not be enough to hold the wings on, I'm no expert on this, I'm sure others will chime in, but they provided Metal bolts for a reason?

da Rock

I've been replacing steel bolts that sized with nylon since the first model with that sized bolts. Why? Because I'd been replacing the smaller bolts all the previous planes, which of course were smaller planes.

Why? For weight savings, savings of course that aren't major.

The plan to begin with was that some of the joints were planned to fail in catastrophies, thereby reducing damages overall. Darned if the plan didn't work great. Then one day a new model was bolted together with one bolt, and it seemed barely strong enough for the steel. So the plan was rewritten. Now I often add another bolt.

It also makes sense to get rid of the steel blind nuts that usually pair up with those bolts. When both have been replaced, nuts and bolts, with nylon, you really have saved weight. When doing that, adding a couple of additional nylons results in truly enough strength, if you are worried about that.

da Rock

BTW, replacing steel with nylon actually adds an extra level of safety. Steel on steel is a poor setup when vibration is present. There is little friction holding things together unless the bolt is tight. As soon as the tightness is gone, the bolt will immediately walk right out. A nylon bolt screwed into threaded wood has friction resisting every bit of the bolt that's touching wood.

SrTelemaster150

1/4X20 STEEL! That's crazy. I've used 8X32 steel on wing struts that were being subjected to perpendicular shear, but I doubt that the wing would take the loading to break 1/4 x 20 nylon in a pull-out application from flight induced strain. Besides, the design should be such that ther load will not be direct on the wing bolts.

SrTelemaster150

Double post.

HighPlains

My Feedback: (1)

The tensile strength of a 1/4-20 nylon bolt is a little over 300 lbs. When you figure out the amount of air load on a bolt, figure on at least 20g's as the most that an average sport model will achieve (due to their slow speed). Take the total weight of the model with fuel, but subtract the weight of the wings, since their weight at any g load does not go through the bolts.

jetmech05

I flew a Aeroworks Pitts Python for a few years before I sold her she had nylon bolts holding in the lower wing. Metal screws and nuts on the struts and just metal screws into blinds for the cabines

Rodney

Actually, 10x32 nylon bolts will hold the wings on any of the large scale planes, even 1/4x20 is over kill. Nylon is much safer than metal bolts for that application due to their resistance to backing out under vibration.

Lightspeed1551

My Feedback: (4)

Over the last 12 years my dad and I have put a couple of planes (kits and ARF's) in to the dirt and the 1/4-20 nylon bolts never break! They either pull through the wing or pull the wing mounting block out of the fuselage.

I also agree with da Rock, steel on steel WILL vibrate out.

SRQFlyer

My Feedback: (17)

About metal-to-metal not being vibration proof:
I had built a 40-size low-wing semi kit a few years back with a dieselized OS FP40 in it. It had four #8 metal bolts into blind nuts (from the bottom). I was tuning up the engine on the test bench for a while and didn't notice that the front two bolts had vibrated out and were laying on the bench. Then, I re-started the engine and took off, but that didn't last very long! That will teach me - no more metal bolts!
Jim

2walla

My Feedback: (10)

Silicon sealant on the steel bolts will prevent them from backing out. With age nylon can become brittle or it may be of suspect origins to begin with. Good nylon is usually strong enough as most wings have dowels too carry the load but to carry 100 percent of the load maybe not. Do some research, our little planes can pull 30-40g and depending how rigid the airframe is the load may or may not be transferred equally to the bolts or you could have combined shear and tensile loading. How do the wings attach? If you are concerned about weight order some aluminum bolts.

Rodney

Here is an old list I got from Weckesser many years ago. I think it is still quite valid as to relative strengths of the various nylon screw sizes.
As you can see, an 8x32 screw would probably work for all your planes in so far as holding a wing on. I've used many a 6x32 on up to 60 size planes and use 4x40's on all the smaller ones with never a failure. Nice thing is, in a violent crash, you want low shear strength as it lets a wing shear off without tearing up the fuse or the wing mounting area.

MetallicaJunkie

ive been using metal bolt wing nuts with bonded washers for that snug security...ive been doing it for years, not because i feel that the nylon bolts will fail, but because its convenient that i can tightem them with no tools....

on my glow planes that use tapped out hard wood blocks, i make sure to CA the bolt holes then run a 1/4 20 tap ...CA again and retap, and never an issue.

MetallicaJunkie

Excellent point there, metal on metal can be an issue, especially iwhen vibrations are present .ive been using metal bolt wing nuts with bonded washers for that snug security the rubber washer dampens it...ive been doing it for years, not because i feel that the nylon bolts will fail, but because its convenient that i can tightem them with no tools....

on my glow planes that use tapped out hard wood blocks, i make sure to CA the bolt holes then run a 1/4 20 tap ...CA again and retap, and never an issue.

aframe2

My Feedback: (5)

With all the advice given, should I keep the steel bolts or change to a nylon washer, and what is a bonded washers? Aframe2

SrTelemaster150

cloudancer03

My Feedback: (22)

Iused nylon bolts on an ugly stick many years back after a bad landing ripped out my landing gear.the next time I used nylon bolts and a bad landing this time just sheared off the bolt.i fixed it in a matter of minutes and have used nylon bolts ever since.and my landings improved lol.

MetallicaJunkie

bonded washers are a washer with a rubber cushion glue to the metal washer

nylon or steel bolts will both work....however if you keep the steel bolts, go by your local hardware store or home depot type store and get some bonded washers for extra security

they make bonded washers in all sizes... i use them to mount cowls, mount wheel pants and canopy hatches, landing gears....loose bolts are now pretty much a thing of the past...try em out[ATTACH]1959712[/IMG]

*edit how do i attach a pic so it will show ....my attachment came out like a link

Gray Beard

My Feedback: (-1)

I use both and have never had anything vibrate loose. I have had more then one nylon bolt break though. Not all bolts are made in the USA so some are just better then others.
If bolts are vibrating loose then there is a bigger issue at hand. I haven't seen anyone using nylon on motor mounts and it isn't like engines are falling off. Nylon, steel, just a choice thing. I'm putting together a 68 inch bipe right now and it has Nylon bolts holding on the bottom wing and I have steel bolts holding on the wing on a 90 inch plane. Wing hold downs isn't a place to worry about the added weight of steel or nylon unless your name is Bob!!

JohnBuckner

My Feedback: (1)

It most certainly is more that just a "choice thing" In the case of many typical 40/60 sized ARF's coming out of china that include metal bolts for the typical two bolt wing hold down, high or low wing. These things spit those bolts out like they are greased berings. I have seen two complete inflight wing separations and caught a loose floppy wing with just one flight of a students airplane after double checking the tightness myself when I could not convince him to change out those Metric ball berings that they called wing bolts.

What has not been mentioned yet in this thread is the fact that the metal bolts that are most prone for this are those china arfs with metal bolts that are metric. The reason they are more prone is the metric fine threads. These bolts are typicallly just under a 1/4 inch and are a very fine thread when compared to a 1/4 20 and it is this fine thread that contributes to this constant loosening with vibration in additon to the fact it is metal.

Thank heavens that more and more of the Arfs are now starting to abandon the inclusion of these metal metric bolts in arfs for wing hold downs and starting to include nylon and in some cases with even with nylon in the 1/4 20 SAE course thread.

Prior to the what some called the ARF invasion wing bolts backing out was rather rare but when all those Arfs came along with those metal metric anyone that would deny the problem was just had a bad case of tunnel vision.

I would urge anyone with say a 90 sized and down arf of any kind that included metal metric bolts for the conventional two bolt wing hold down to rethink using them.


Now for those of us who do like to use quarter twentys for landing gear hold down. There just may come a day when you peel the main gear on a poor landing (happens) but perhaps you did not peel the fuselage structure along with it. Well thats a success and guess what that is the whole idea in the first place huh, kinda trading a minor repair for a major one

So OK when this happens lots of time one of those pesky broken nylon bolts broke off so you cannot grab hold or even reach it from the inside. The solution is real slick. Just grind a cheap small screwdrive down so the flat blade is sharpened and narrowed to less that an eighth inch wide. Next heat the tip of the screwdriver with a propane torch till the tip glows red hot then quickly shut down the torch and plunge it into the broken off bolt and hold it still untill it cools quite a bit.

Its only necessary to insert the tool no more that 1/16 inch. You will now find you can simply back the broken nylon bolt tip out very easily. When the scewdriver cools you will find the nylon will be welded to the screwdriver and very difficult to remove which is why I usually just grind the nylon off my little special tool on the grinding wheel at home.

When I was still active racing Q-500 after driving a long distance a bad landing in just one heat could end your entire day or event if you ripped out the gear plate so for this reason I preferred to use two nylon !/4 20's and usually peeling the main gear was not a big deal and it was easy to get ready for the next round. So I always carried the little 'special screwdriver' and a cheap torch.



John

SRQFlyer

My Feedback: (17)

+1 for everything John has said about the (5mm) ARF metal bolts. Throw them away and use 1/4-20 nylon!

About the landing gear bolts snapping off flush with the fuse bottom: The heated screwdriver works real well, but I've found that a (nylon) washer between the fuse and the gear will usually cause the bolt to break with enough sticking out to grab with needle nose pliers. While this is OK for sport planes, it probably won't do for racing planes.
Regards,
Jim

SrTelemaster150

Comparing wing bolts to engine mount bolts is just plain ludacrous!

If you torque your wings down like you would an engine mount you will crush most wings! There's no good reason to use steel 1/4 X 20 bolts for the wings. Way overkill & heavy. If you want to use metal bolts or the wings use 8 X 32 W/nylock nuts to prevent the lightly torqued bolts from vibrating out.

BarracudaHockey

My Feedback: (11)

Nylon all the way.

Though the weight savings on a 50cc plane would be pretty negligible

HighPlains

My Feedback: (1)

Hey John, I used four #8 steel flathead screws to hold my landing gear on a quickie. I never worried about ripping out the bottom of the fuselage, because my structure was strong enough that the gear would just twist up and absorb the shock. I didn't want the gear banging into the tail.

But most quickies are not that strong. The designers make the mistake that if the gear is 1.25 inches wide, then the plywood block they mount it to is also 1.25 inches wide and 1/4" thick. Not enough glue surface to withstand the torque of catching a weed or two. My gear plate is about 3" long (it's only 1/8" ply), with a doubler on each side that doubles the glue surface and also holds the screws. It also ties into a plywood bulkhead that goes up and grabs the wing hold down. The entire fuselage is built from 1/8" ply, 1/32" ply and 1/8" balsa. and ends up at 6 oz. Part of the reason that I always carried an oz or two of lead even when the minimum weigh was 3 1/2 lbs. In essence, the fuselage from the trailing edge forward is all plywood with a balsa skin, and glassed on the outside. Something like a bit over 30 pieces of plywood.

Must have built too many Goldberg models as a kid.