Seaplane Grommets

[harneymaki]

Hello all.

I bought all my covering material yesterday and asked for seaplane grommets. I was advised by the Poly-Fiber salesman to just make holes with a sharpened piece of tubing. He said this will work fine and is approved in the STC as long as it is through at least 2 layers of fabric and has done this on several a/c. I saw them on his Hatz bi-plane and they looked really clean.

Any thoughts on the subject.


Thanks

[behindpropellers]

I have seen the holes poked with a soldering iron to prevent fraying.

[Speedo]

I think you've been given bum information.

When I took the Stits covering course offered by EAA through what was Alexander, they emphasised that seaplanes needed to have seaplane grommets, and that punched holes were not acceptable. They also said it's impractical to retrofit a plane with grommets.

Best to install grommets now.

[Torch]

I think you've been given bum information.

When I took the Stits covering course offered by EAA through what was Alexander, they emphasised that seaplanes needed to have seaplane grommets, and that punched holes were not acceptable. They also said it's impractical to retrofit a plane with grommets.

Best to install grommets now.

I just took the seminar here in Fairbanks and the lady that taught the class showed us how to use the grommets and attach them. I would say DO NOT just punch holes. She made absolutely no mention of that. If she did, I completely missed it. I agree, I think you got some bad information. At least if it was my airplane there is no way I would do that. Just put the grommets in and do it right.

[StewartB]

Both methods discussed are contained in the manual and are perfectly legal. There is no mention that either drain style is required or prohibited in any gear configuration. That isn't to say that grommets aren't a good idea. My plane's on tires and has seaplane grommets.

Stewart

[harneymaki]

Thanks for the input. I'm leaning toward putting them in with dollar patches over them.

Torch--- I'm going with Pontiac Red and Juneau White again but small N-Numbers this time.

[Marty57]

My understanding is that seaplane grommets are also a must in any wing with a wood spar, seaplane or not. Does that sound right?

Marty

[Yard Dart]

For what it is worth CC just use holes.

[mvivion]

If I'm not mistaken, NONE of the current manufacturers of fabric airplanes uses seaplane grommets.

They are not required.

Which doesn't mean they're not a good idea.

MTV

[Dave Calkins]

I'll not get into the fight of whether or not you need them.

However, best to use a soldering iron or hot poker when making holes. Also, a large-area washer makes the perfect guide for melting the holes. I'd not use the 'sharpened tubing' method!!

And make sure you put the holes as far into the corners you wish to drain as possible.

Also, if you choose to use seaplane grommets, do yourself and your mechanic a favor that you'll appreciate in about five years. INSTALL dollar doiles over the top of the seaplane gromets.

PS my preference is to leave off the grommets and just melt a hole. It saves ALOT!!!! of time.

Also, if you're the kind of guy that ties his stick back with a seatbelt. Put drain holes at the FRONT of the elevators, not just the back!

Have fun! DAVE

[Torch]

Thanks for the input. I'm leaning toward putting them in with dollar patches over them.

Torch--- I'm going with Pontiac Red and Juneau White again but small N-Numbers this time.

Well you can't go wrong. If it ain't RED it ain't RIGHT!

[bob turner]

I use fabric over everything I glue on to the fabric - inspection rings, those odd celluloid shapes that hold aluminum covers (I imbed aluminum; it holds #4s longer) and grommets - and even those canvas reinforcements. Regular grommets are now quite expensive, so I make them out of aluminum, too - a Whitney punch makes them quickly.

[RedEye]

Paul, take the time, put em on with a dollar patch over them. You wont regret it. The difference between them and just putting a hole is the seaplane grommets creat a vacuum that pulls moisture out rather than just draining out the hole. If done right they look better too !!!

[Phil Kite]

Several years ago I restored 2 identical PA-12's. One had seaplane grommets the other just had holes made with a small soldering gun and penny washer. When I looked back at the tail of each while flying them, the fabric on the stab with seaplane grommets was "sucked in" and touching the diagonal braces in the stab. The fabric on the one with no seaplane grommets was flat with no puckering. The same fabric, shrinking temperature and covering process was used on each plane. Since I saw this, I have never used seaplane grommets again. I feel that with the fabric sucked in a touching the bracing, it will crack and fail sooner than the flat flying fabric.

[Nathan K. Hammond]

2 months late, I never was good at punctuality.

So I'm a PolyFiber Instructor, but I'll be the first to admit I'm always learning new things. That being said, heres the skinny on grommets:

Grommets are optional and in no way mandatory; seaplane, woodspar or not. Melting a hole with a soldering iron is perfectly acceptable, AS LONG AS it goes through 2 layers of fabric (usually the fabric and trailing edge tape.) After you melt the hole, take a sharp pencil and spin it in the hole to clean out any slag. If you decide to use grommets, they must be covered by a tape. Reason being; the plastic ones are CAB plastic which tends to warp, if that happens it's sure to get ripped off by the slip stream leaving a real ugly spot. The metal ones run the same risk, but not nearly as bad. But still the STC says grommets must have a tape over them.
Seaplane Grommets: they have 2 distinct traits that make them nice to have in wet environments. First being, the hood acts as a shield, preventing water from splashing in the surface. Second, the hood creates a low pressure area around the hole, and that helps evacuate any moisture ( evident in the case of Phil Kites PA-12's, for example.) Unfortunately, you have to cut individual dollar patches for each grommet. Further, and this is strictly opinion, they tend to detract from an otherwise sleek, smooth finish. So then the question arrises, "Do I need Seaplane Grommets?" The answer is purely personal preference, and a balance of how much time is spent on floats. Personally, if it were my plane and it spent it's time 50/50 floats/wheels, I'd stay with the melted hole and no grommet.

Hope this helps some.

nkh

[AK-HUNT]

I must be missing something. You say:

"If you decide to use grommets, they must be covered by a tape. Reason being; the plastic ones are CAB plastic which tends to warp, if that happens it's sure to get ripped off by the slip stream leaving a real ugly spot. The metal ones run the same risk, but not nearly as bad. But still the STC says grommets must have a tape over them. "

Is there some change to the STC or manual? Am I missing something? I use seaplane grommets with dollar patches on all my stuff so I am really asking out of curiosity, but on page 51 of the manual it says "This is a good idea in propwash areas" and "You can (not must) cover them with a mini-doily".
I can't find anywhere where you are required to cover any grommet with a patch. Didn't sound familiar so I looked for it but I can't find any reference to that. What's the scoop?? Thanks

[Nathan K. Hammond]

AK,

Sorry for the confusion, I jumped the gun a little. The latest revision for the manual (rev. 21) is currently at the Feds. It was explained to us at the Instructor meeting, that this would be one of the changes (tapes over grommets.)

PolyFiber kept getting feedback from customers who were upset when a grommet would peel off, taking the top coat of paint. So hopefully this will solve that problem.

Once again, I apologize for giving premature information and causing any fuss.

nkh

[AK-HUNT]

Understood. Thanks

[Glidertow]

Planning to use the burned hole method. Is this done before or after painting?

[Steve Pierce]

I do it before. Looks kinda bad to have all these black burnt looking holes in your newly recovered wings.

[Rob Murray]

I learned the hard way what happens when you don't have adequate drainage in your tail sections, even with seaplane grommets. They're not only a good idea, make sure the holes in the fabric are large enough (grinding and bending the tip of a small soldering iron works real well) and check the openings each season. And if you rejuvinate and redope or repaint your Cub you will likely have to redo the burn outs.

[bob turner]

Why should the feds care if the grommets fall off? Is there a safety of flight issue here, or are they legislating ugliness?

[12Geezer2]

Mud Daubers made a nest in every one of my seaplane grommets. If you live where these bugs live; check your grommets. Easy enough to clean but takes time away from flying.

[Nathan K. Hammond]

When you melt a hole, take a sharpened pencil and spin it in the hole immediately. Does a couple things; makes the hole perfectly round, cleans out any slag and pushes any discolored material into the hole and out of sight.

I prefer after painting.

nkh

[Steve Pierce]

I am installing sea plane grommets on wings and tail surfaces and am looking for an easier, softer way. I see how Howard did his in the picture below. My main concern is if I don't cover the scoop with fabric is it gonna break and crack in a few years? Any words of wisdom?

seaplane_grommet.jpg

100_04861.JPG

[Roger Peterson]

I never use grommets, just burn a hole before painting.

[kevin]

Same here. use your soldering iron and burn a hole in the TAPE. This counts as the second layer. I've heard some guys after they pull the iron out to rotate a pencil in the hole to clean the hole and have a smooth transition.

[kevin]

Oops, just read 3 posts up from mine. same advice.

[12 Geezer]

I used to have 'em on my 12, and they never cracked in quite a few years, with no fabric over them. However they did have the silver and color dope over them (Stits process). Glued 'em on with Pliobond. However this time I just melted a hole, per jgerard's advice (Stewart System this time).

[mike mcs repair]

I am installing sea plane grommets on wings and tail surfaces and am looking for an easier, softer way. I see how Howard did his in the picture below. My main concern is if I don't cover the scoop with fabric is it gonna break and crack in a few years? Any words of wisdom?

seaplane_grommet.jpg

100_04861.JPG

Thats how i do mine. Dollar patches. But i beat a piece of cromolly right shape and ground sharp and hammer through 25 at a time to cut center hole.

[spinner2]

Seaplane grommets also make a neat exit point for wiring, like from the fuselage to the rudder for a tail position light. They can be pointed down or at a 45 degree down and back position to keep water out.

I haven't done it but I've also seen them used as an exit point for the rudder cables also.

[Roger Peterson]

i take a blunt end of a drill bit and push through the hole. kill some dirt dobbers, measure their head and use a drill bit just a little bit smaller
have yrouble ttyping.P1010663.jpg

[aktango58]

slickest way I have seen is a dollar patch with just a snip in the middle. When you glue the patch over the top of the SpG, the slit will allow one part over the scoop, and the other to lay flat. Smooth and do the next one...

Hot poker... or if you are Tim Taylor, a torch, and then you will have plenty of airflow

[Dave Calkins]

If doing the "slit", experiment with cutting the slit diagonally to the warp/weft. It may form more nicely over the seaplane grommet.

I've seen the way Mike and Howard do it. It looks really nice and clean and easy to do. Surely you lose a bit of protection for the plastic, though.

I'm still a "burn a hole" in it guy. It works well, is fast, and clean and less "stuff". I'm in to "less is more" these days.

[aktango58]

I'm in to "less is more" these days.

If wanting to reduce, I can come up and get any 'more' type aircraft so you have less....

FYI: still interested in the fuselage? I should have it ready to be sold in February... will have many parts, but lower longerons are TOAST from rust.

[Steve Pierce]

Here is how we ended up installing the sea plane grommets and the dollies. Pattern and the finished product.
DSCF0114.JPG

[mike mcs repair]

Here is how we ended up installing the sea plane grommets and the dollies. Pattern and the finished product.
DSCF0114.JPG

wow, pretty...

did it lay down without a lot of fuss???

I never have worried about/seen an issue with the plastic exposed under the dope and silver.... but our sunlight is so much less brutal up here...

[gpepperd]

I'm with Dave in the "burn a hole" method. It's much cleaner and less drag if the plane is not intended for sea plane destiny. Greg

[Superchub]

Burn a hole after paint works great, just keep the solder iron clean with some sand paper as it gets dirty!! I always wait till after I am done painting...

[Steve Pierce]

wow, pretty...

did it lay down without a lot of fuss???

I never have worried about/seen an issue with the plastic exposed under the dope and silver.... but our sunlight is so much less brutal up here...

Worked very well mike. Only had to iron a few of them. This is for a Super cub going on floats. I too prefer just burning the holes but usually do it before I start spraying.

Brandon, why do you like to burn after paint?