Author Topic: Ply nose doubler laminateing glue . (Read 1605 times)

Air Ministry . · « **on:** December 02, 2019, 08:30:43 PM »

Is PVA a adequate solution ? .

Been using epoxy , both surfaces , lately ' thinned ' with micro ballons .

PVA bot sufaces , spead even thinn , clamped . - Would it hold up long term , or other objections .

Would still epoxy bearers to doublers .

Steve Berry · « **Reply #1 on:** December 02, 2019, 08:51:21 PM »

Personally, I'd use Z-Poxy finishing resin for this. Plenty strong, thin so it penetrates well, and long enough working time to get everything aligned. Can also use some carbon fiber cloth (the light veil stuff) in between the balsa and ply to help add strength. Watch the latest Stunthanger video Sparky did over the weekend with some of his Tucker build and John's Nobler (he shows the actual installation of his doubles using this very method).

Brett Buck · « **Reply #2 on:** December 02, 2019, 09:30:10 PM »

Quote from: Air Ministry . on December 02, 2019, 08:30:43 PM

Is PVA a adequate solution ? .

Been using epoxy , both surfaces , lately ' thinned ' with micro ballons .

PVA bot sufaces , spead even thinn , clamped . - Would it hold up long term , or other objections .

Would still epoxy bearers to doublers .

I would recommend continuing to use epoxy.

Brett

Kim Doherty · « **Reply #3 on:** December 03, 2019, 10:38:20 AM »

Just to amplify:

The MOMENT you place PVA (or any water based adhesive) on wood it starts to swell.
The MOMENT you place two relatively large surfaces with PVA on them together a "S#$T Storm" starts happening.
A film forms at the edges preventing anything from escaping.
The wood continues to expand... and expand...
Warpage ensues. (it does not matter if you clamp it because it will still not be dry when you take the clamps off)
The moisture is now trapped between the layers. (it could take a long time for this to become completely dry!
Forces build up.
Delamination ensues. (even if you can not see it!)

PVA type glues (I.E. most wood glues) need lots of circulating air to properly harden.

PVA is for edge gluing/butt jointing - not laminating!

PVA adhesive (other than TiteBond III) is also not likely to be waterproof!

EPOXY is for laminating. (not finishing epoxy either - too thin - not hard enough) (use only 24 hour cure industrial epoxy) (do not use micro balloons!!)

Use only a very (very) thin film of epoxy. (you really only need 1 molecules worth of epoxy between the layers. More makes it weaker)

This is where vacuum bagging/pressing should be used if possible. Otherwise use a full surface clamping caul and lots of clamps - shaped if the part is shaped.

To register two parts together consider using two adhesive systems at the same time. A few drops of medium or thick CA well inboard of the edges and evenly laid out in little "Islands" with epoxy all around. You can set the position easily by holding the two pieces at the CA locations then once you have a bond finish clamping.

Kim.
(someone who has worked on literally dozens of full sized composite sailboats with CS Yachts)... and a couple of toy model airplanes.

BillP · « **Reply #4 on:** December 04, 2019, 09:05:02 AM »

Quote from: Kim Doherty on December 03, 2019, 10:38:20 AM

Just to amplify:

The MOMENT you place PVA (or any water based adhesive) on wood it starts to swell.
The MOMENT you place two relatively large surfaces with PVA on them together a "S#$T Storm" starts happening.
A film forms at the edges preventing anything from escaping.
The wood continues to expand... and expand...
Warpage ensues. (it does not matter if you clamp it because it will still not be dry when you take the clamps off)
The moisture is now trapped between the layers. (it could take a long time for this to become completely dry!
Forces build up.
Delamination ensues. (even if you can not see it!)

PVA type glues (I.E. most wood glues) need lots of circulating air to properly harden.

PVA is for edge gluing/butt jointing - not laminating!

PVA adhesive (other than TiteBond III) is also not likely to be waterproof!

EPOXY is for laminating. (not finishing epoxy either - too thin - not hard enough) (use only 24 hour cure industrial epoxy) (do not use micro balloons!!)

Use only a very (very) thin film of epoxy. (you really only need 1 molecules worth of epoxy between the layers. More makes it weaker)

This is where vacuum bagging/pressing should be used if possible. Otherwise use a full surface clamping caul and lots of clamps - shaped if the part is shaped.

To register two parts together consider using two adhesive systems at the same time. A few drops of medium or thick CA well inboard of the edges and evenly laid out in little "Islands" with epoxy all around. You can set the position easily by holding the two pieces at the CA locations then once you have a bond finish clamping.
ba
Kim.
(someone who has worked on literally dozens of full sized composite sailboats with CS Yachts)... and a couple of toy model airplanes.

I'm not sure where some info comes from but...epoxy (glue) is a structural gap filler and a thick glue line is stronger than most any wood it glues. High clamping pressure isn't required or desired with epoxy. Squeeze the glue out and you have a weaker joint. Regardless, the weakest epoxy known to man will pull balsa grain in a heartbeat...even laminating will pull balsa grain.

The only question I have with Elmer's Carpenter pva glue is whether it will dry on doublers...I think on this application it will but can't speak from experience. Brett previously posted of doubles being wet after a crash with Ambroid (but isn't the same experience I've had) so I suppose pva could suffer the same. It's definitely strong enough and doesn't expand (like the Gorilla Glue I use which looks like expanding foam).

bp

Kim Doherty · « **Reply #5 on:** December 04, 2019, 10:13:27 AM »

Quote from: BillP on December 04, 2019, 09:05:02 AM

I'm not sure where some info comes from but...epoxy (glue) is a structural gap filler and a thick glue line is stronger than most any wood it glues. High clamping pressure isn't required or desired with epoxy. Squeeze the glue out and you have a weaker joint. Regardless, the weakest epoxy known to man will pull balsa grain in a heartbeat...even laminating will pull balsa grain.

If "a thick glue line is stronger than most any wood it glues" then the proper glue line thickness (thin) with perfectly mating surfaces is stronger still. (and lighter) I never once said that high clamping pressure is required, however, uniform clamping pressure is and that is where bagging and pressing or the use of form fitting cauls with lots of clamps come into play. I routinely bag, press, or clamp pieces of wood with epoxy and adjust the pressure to the level required to achieve the desired glue line without damaging the substrates. Finishing resin (I think that is what you meant to say) is so thin that you may very well starve the joint. Horses for courses. Whether it works or not is not the point. It was not designed for this use.

Kim.

Brett Buck · « **Reply #6 on:** December 04, 2019, 10:48:57 AM »

Quote from: BillP on December 04, 2019, 09:05:02 AM

The only question I have with Elmer's Carpenter pva glue is whether it will dry on doublers...I think on this application it will but can't speak from experience. Brett previously posted of doubles being wet after a crash with Ambroid (but isn't the same experience I've had) so I suppose pva could suffer the same. It's definitely strong enough and doesn't expand (like the Gorilla Glue I use which looks like expanding foam).

Being water-based, PVA and Aliphatic *will* dry, they wet the wood, the wood subsequently dries. It's not really a matter of strength in this case - even on hardwood, if you glue two pieces together, clamp them tightly, you can remove the clamps 15 minutes later and you cannot get them apart, you will have to use a chisel and cut the wood. Alphipatic, particularly, has tremendous "grab", even in a few seconds in tight joints - a fact that many model rocket people can attest to, if you are sliding an engine mount into a body tube and pause even briefly, or slow down, it will stick and be stuck forever.

It's different from Ambroid or other model cement - they are acetone or other solvent - based, not water-based, and will not wet the wood in the same way.

The best reason to use epoxy or cyanoactrylate (which is what I use), is to prevent it from warping from the contact with water.

Brett

Tom Vieira · « **Reply #7 on:** December 04, 2019, 12:56:49 PM »

Brett's right..... even on highpower rockets (G80 motors and up), Titebond holds exceedingly well! My Madcow 4" Patriot on a I500T motor holds up quite nicely, built completely with titebond except for the nosecone attachment, that was epoxy (dissimilar materials...).....

Ken Culbertson · « **Reply #8 on:** December 04, 2019, 02:34:21 PM »

"He Loved CA" will probably be on my tombstone. I have been using JB Superweld for just about everything. It is perhaps as strong as Epoxy in a laminating application. It spreads super thin and even and gives you a couple of seconds to position the parts then sets almost instantly when you apply pressure. In every case where I have had to separate things it took a layer of balsa with it. Biggest advantage - Wallmart carries it. Not quite as strong on a joint as the thin stuff but you also don't have to worry about gluing your dog to the floor by accident, plus, it sands fairly easily. One use I have found for it is to provide a quick fix for sanding into polyspan.

I have even made a "Blind Nut" for a hatch out of it by filling the hole then running a 4-40 tap - it works.

ken

BillP · « **Reply #9 on:** December 04, 2019, 03:03:35 PM »

Quote from: Kim Doherty on December 04, 2019, 10:13:27 AM

If "a thick glue line is stronger than most any wood it glues" then the proper glue line thickness (thin) with perfectly mating surfaces is stronger still. (and lighter) I never once said that high clamping pressure is required, however, uniform clamping pressure is and that is where bagging and pressing or the use of form fitting cauls with lots of clamps come into play. I routinely bag, press, or clamp pieces of wood with epoxy and adjust the pressure to the level required to achieve the desired glue line without damaging the substrates. Finishing resin (I think that is what you meant to say) is so thin that you may very well starve the joint. Horses for courses. Whether it works or not is not the point. It was not designed for this use.

Kim.

Sorry but a thicker epoxy glue line isn't "weaker". I was commenting to you posting this:

"Use only a very (very) thin film of epoxy. (you really only need 1 molecules worth of epoxy between the layers. More makes it weaker)"

Show me one epoxy mfg that says a thick epoxy glue line is weaker than a thin epoxy glue line. If applied correctly, either one will pull wood grain long before glue failure.

Serge_Krauss · « **Reply #10 on:** December 09, 2019, 02:22:39 PM »

I've never had a problem just using normal 30-minute epoxy, thin, but not microscopic. It sets up, is fuel resistant, does not warp, and never lets go. No fuss. CA is not fuel resistant, as I hear it.

Brett Buck · « **Reply #11 on:** December 09, 2019, 05:23:42 PM »

Quote from: Serge_Krauss on December 09, 2019, 02:22:39 PM

I've never had a problem just using normal 30-minute epoxy, thin, but not microscopic. It sets up, is fuel resistant, does not warp, and never lets go. No fuss. CA is not fuel resistant, as I hear it.

I have used CA in the "line method" for many years now, and my airplanes generally last long enough (14 years and counting on the current one). Its pretty hard for raw fuel to get all the way into the doublers - usually it is falling apart from other problems if you can do that.

Almost anything will work, even model cement (which is the worst possible thing), if you use proper technique. Plenty of people, myself included, built entirely acceptable airplanes with only Ambroid.

Brett

Angelo Smyth · « **Reply #12 on:** December 09, 2019, 06:19:41 PM »

The use of caul plates (whether plain or shaped) along with vacuum-bagging helps to ensure that you use the correct amount of adhesive for the job. Too much epoxy only adds weight and does nothing for the strength of the overall joint beyond what the correct amount would have already accomplished. To be sure, you'll want to ensure there are no "dry" spots for the pieces being bonded together. Vacuum-bagging, even clamping and weighing-down all accomplish (to varying degrees) the same things: to promote the bond and helps squeeze out any excess epoxy. I work in the aviation industry dealing with the manufacture of composite components: excess epoxy use in parts are rejected for the above reasons (weight and strength considerations).

I would strongly recommend against using glass beads, or micro beads with epoxy in any joint requiring strength. To mix in as a filler however, it's just fine.

Now, if I were an adhesives manufacturer, I'd tell you to use all the adhesive you can. And to buy more of my product!

Curare · « **Reply #13 on:** December 10, 2019, 08:11:26 PM »

Quote from: Brett Buck on December 09, 2019, 05:23:42 PM

I have used CA in the "line method" for many years now, and my airplanes generally last long enough (14 years and counting on the current one). Its pretty hard for raw fuel to get all the way into the doublers - usually it is falling apart from other problems if you can do that.

Almost anything will work, even model cement (which is the worst possible thing), if you use proper technique. Plenty of people, myself included, built entirely acceptable airplanes with only Ambroid.

Brett

The "line method"? Can you elaborate?

Serge_Krauss · « **Reply #14 on:** December 12, 2019, 06:51:39 AM »

"Plenty of people, myself included, built entirely acceptable airplanes with only Ambroid."

Me too.

BillP · « **Reply #15 on:** December 12, 2019, 11:11:58 AM »

Vac bagging, caul plates, full scale aviation composite lamination...all a totally different league/application than gluing wood CL doublers. Regardless, it's easy to get empirical evidence on epoxy glue line strengths on your own.

Duco or CA is my preference for doublers and epoxy a distant third because it's messy...but I rebuilt a full scale wood/fabric ultralight and used T-88 structural epoxy glue. It was the preferred glue by exp home builders at that time and the mfg specs as a structural gap filler (no thickeners required). Stitch N Glue boats are built the same with less costly generic epoxy resin mixed with various thickeners for joints and large fillets.

Geoff Goodworth · « **Reply #16 on:** December 12, 2019, 02:52:02 PM »

A few comments about PVA and aliphatic glues.

I was first introduced to PVA in high school — late fifties. My dad was still using casein glue in a pot of boiling water for his wood working adventures.

The glue soaks into the timber and makes the timber around the glue line stronger than the timber around it.

Fast forward about 20 years and I'm development engineer for a building products company. In one product development, it became very clear that there was a limit to the amount of glue applied before the joint became weaker, not stronger — and it's not much.

The concern about moisture and warping is valid but I've not had problems.

I apply the glue very thinly to both surfaces and complete the assembly. I put the part between two sheets of plate glass, weight down the assembly and set it aside to cure. I then start building the other bits of the model.

When I'm ready to work on a fuselage, I return to it — for me that's at least several weeks. Maybe I'm lucky but I've always had space and a flat surface to set aside a Vector 40 fuselage side — that's the biggest I've built.

I've used this technique for full fuselage and profile models and I use ply offcuts to ensure that the fuselage side is weighed down on the glass for its entire length

I've crashed plenty of models built that way and I've never had a warp or a delamination.

FLOYD CARTER · « **Reply #17 on:** December 12, 2019, 05:17:11 PM »

I don't see the advantage trying something "new". I've always used good old Dave Brown 15 minute epoxy for ply doublers of all sorts. It's 100% effective.

Avaiojet · « **Reply #18 on:** December 12, 2019, 07:19:16 PM »

Quote from: FLOYD CARTER on December 12, 2019, 05:17:11 PM

I don't see the advantage trying something "new". I've always used good old Dave Brown 15 minute epoxy for ply doublers of all sorts. It's 100% effective.

Absolutely!

I align the pieces then clamp them. I drill two 1/8" holes. I remove the clamps, skim the surface with 5 minute epoxy then put the pieces back together. I stick bamboo skewers into the holes for correct alignment then re-clamp. I show this in my builds.

Works every time.

Yes, I used Ambroid when I was a kid. I'm still a kid but I would never use Ambroid.

Air Ministry . · « **Reply #19 on:** December 12, 2019, 08:25:41 PM »

Im thinking now , Winter is not the time to do it , with P V A .
Even Std epoxy kick off varies from two hours , temp over 30 C 9 likely 36 / 40 + i.e. 90 to 105 F .or so . To sub zero where its 28 hours .

The PVA & Aliphatic say sub 16 degrees is a no no .We wont go into that .

Brett Buck · « **Reply #20 on:** December 12, 2019, 11:06:59 PM »

Quote from: Curare on December 10, 2019, 08:11:26 PM

The "line method"? Can you elaborate?

Nothing clever, just applying it in grid lines to ensure full coverage. I could elaborate, but you will learn much more from the masters:

https://stunthanger.com/smf/building-techniques/laminating-glue-(fuselage)/msg317971/#msg317971

Both videos are long, but well worth the time, you *will* learn something useful. I rewatched these when I posted them, for the first time in close to 40 years, and I was amazed at how much of the techniques shown that I still use, and had forgotten where they came from.

Brett

Author Topic: Ply nose doubler laminateing glue . (Read 1605 times)

Tom Vieira