olnico

Yes.
Thanks for the link.

DrScoles

My Feedback: (18)

Good stuff Oli. Its funny that I opened the forum, and saw this topic and hit it first. We are an odd bunch to get excited about glue strengths! Refreshing to see a building topic. I'm sure there are a ton of people here who could share some great information to make us all better modelers.

CraigG

My Feedback: (40)

+1 Jack ......and the deterioration issue is something you only discover over time. I still have my F-4, which is one of the first models I recall using Hysol on, and as far as I can tell, it is still solid. That was some 15 years ago.

In any case, these tests are still interesting.

Craig

olnico

Yes, this is why I made dots: to counteract the torsional moment.

This is anyway representative of what can be experienced on a servo bracket.

My aim is not to show how to crash proof a model but to compare glue joint strength so that people know what they can expect in terms of resistance when they choose a certain type of glue.
Structure resistance in another story and not the purpose of this thread.

olnico

I absolutely 100% agree with you, Jack. Especially as a professional operating aero structures in the Middle-East.
This is why we only sell Hysol products at the shop. I have been using this brand for 15+ years with 100% satisfaction apart from the 9462 air bubbles issue ( see my bulletin here
in the download section of the product page http://www.ultimate-jets.net/collect...cts/hysol-9462 )

DISCUS54

My Feedback: (211)

Very informative Oli...thanks for sharing.

Zor

olnico,

Thanks for your comments 'olnico'.
I will be out of here.

I figure that comparing glues and/or adhesives is one of the many factors that makes a model airplane strong and resistant to damages in a crash.

The same or the strongest glue is not necessarily recommended for all gluing.
The strenght needed at a servo is very small compared to other areas of a model structure.

I have models here that were built more than 50 years ago and are still sturdy. They were glued with what was then the glue to fasten asphalt tiles to the floor. That glue is ( was ) plenty strong for model airplanes and is water and humidity proof when cured.

Enjoy your initiated thread _ _ _ I am now out.

Zor

roger.alli

A good discussion Oli. And yes, I bet dropping 25 kg steel weight on the floor it not without its hazards!!!

My impression of your result of the 5 min epoxy test, is that the resin only failed over approximately 50% of the tested area. Surely the resin that remains under the bit of hardwood that split off, is still intact, and didn't fail at all. It was the hardwood natural fibre cellulose bonds that failed in this ½ of the glued area, so should not the bond strength be closer to twice what you calculated??.

Adhesives tend to be very specialised nowadays, some are good with wood, some plastic, some metal. Some adhesives chemically bond to the substrate, while others just form a mechanical grip. Some are fast cure just for convenience. Some glues allow for flexibility, some are completely solid. Some are selected simply because they can be easily sanded.

My point is, that while your tests might be interesting as to comparing a group of similar epoxies, I feel it to be unfair to compare say Hysol to Cyno, or clear silicone to PVA. All these adhesives are exceptionally good at their specialized tasks, but will all perform quite differently when asked to attach a servo mount to a piece of hardwood.

In my humble opinion, correct selection and proper application, is far more important than the overall strength of the cured glue.

Roger

Jgwright

Oli

I agree with the comments made especially Jack Diaz. I bought an old part built plane a while ago and the Robart hinge pins had been gluued with epoxy that had completely denatured over the years and I could pull them all out without much force. Thankfully our planes rarely last this long!

When we were flying last week one of our group had a jet that he bought fairly new second hand and the aileron servo just dropped out on landing! On inspection the servo hardwood blocks were glued to some 'Chinese' ply. The glue bond had not failed but with very little force the ply had delaminated. When you have finished you tests and selected the 'best' adhesive it will be interesting if you could use it on different commonly used mounting materials. I am certain that the Chinese ply faced plates will delaminate before the servo would fail and would surprise some. The better airframes like the JL Viperjet use a moulded plastic plate so gluing is not required at all. Your tests while good for comparison are not what we normally see in our airframes.

John

davevh

Formaldehyde based glue? Eeek, if the formaldehyde molecules are free roaming then I hope you used a respirator. Formaldehyde and paraformaldehyde (PFA) are fixing agents in biology (they freeze the cell mechanics for preservation), and the fumes can be deadly since your wet lungs readily absorb the agent. I once mixed up a batch of PFA in a biology lab, and very stupidly opened the hot bottle that the solid chips of sodium hydroxide were melting in to adjust the pH, and caught a whiff of the vapour which poured out readily. I felt terrible for the rest of the day, and should have gone to the ER since you can die from a big inhalation.

Did the glue get warm when you mixed the powder and water? If it did, a reaction was taking place and could release fumes. Over time this could destroy lung tissue.
Could be why it is not used for models!

Quandry

Hi Oli, nice experiment, can you include BVM aeropoxy in the test?



all the best...

olnico

Test protocol for Hysol 9462 in progress.

olnico

100% agree with you on Chinese ply. This is why we use aero grade Finnish birch ply. Millions of miles away in terms of quality...

Yep, the purpose of this test is mostly for comparison.
However this is also relevant to what we experience on the airframe we sell. The Mibo A-10 is using above ply/ glassfiber laminated servo hatches and we glue our PYCABS servo brackets or the original Mibo plywood servo bracket on them. In fact lots of the kits we sell use this technique and it is very relevant for me and for all further designs to have a precise idea of glue joints resistance.
I have two large model kits being designed right now and these will use the same technique. I have a resistance module in the CAD software I use and I need that data to implement glue joint resistance in the assembly of these models...

olnico

Thanks Roger.

The bond sheared pretty clean in fact. The hard wood block you see on the picture was pulled out by 3 of the dots I made with the Dremel that were deeper than the other ones. the block is not bonded to the bracket any more. From what I can observe, I think that the failure on this one was representative enough. However if I have enough spare time, I will do this test again.

You are right, glues are very specialized. However it is interesting to know the glue jont resistance anyway. Even if it is unfair to compare CA with Hysol on a certain matter, one would still choose CA over Hysol on given application because of the ability to set instantly with activator. So knowing the strength of a CA glue joint is still relevant.

Also the purpose of this comparative study is to educate newer modelers and demonstrate the difference betweeen types of glue. I have seen more than once people using CA on servo brackets. Even on Chinese ARF kits...
And frankly, while I can guess what silicon compound will do on the stress test, I am still extremely curious to see the result for real.

Correct selection and application is important, but glue joint strength is equally important. The bond will be only as strong as the weakest link, as always...

olnico

Why? Your point of view is extremely appreciated here. You provided constructive interesting comments, which is the purpose of this thread!

BTW thanks you to all the contributors of this thread to provide so many interesting technical insights.

Carbon-Customs

what if the strongest glue in your test will be brittle and a "weaker" one is more soft, and therefore maybe a "better" glue for models?

it must be hard to test glue, so that we can name a "winner"

Selleri

CA with and without activator?

DISCUS54

My Feedback: (211)

Reading through the thread I had a deja vu' to Recurrent where there is always one guy double pumping his hand for another hypothetical question. There may be a "winner" declared here but we all realize it isn't the winner for every application....Once Oli finishes his testing perhaps we can glean some information. Aeropoxy is repackaged Hysol. I would agree with Jack about the "longevity" of Hysol. It is more flexible than standard 30 minute epoxy and maintains its bond longer because it doesnt micro fracture or chemically degrade from the vibrations, and temperature variations over time like regular epoxy but is exponentially more expensive. A good choice for the Kingcat but overkill for the Kadet. I am putting together a field box with Aeropoxy because the last box I built failed at the joints after some 20 years...plenty of service life for that item, but I will be passing this one on to the next generation so it is getting additional attention to detail.

roger.alli

All good points Oli. Knowing adhesives comparative shear strength will be interesting. I hope and am fairly confident, that Hysol/Aeropoxy will be the outright winner.

Educating people on how to use adhesives correctly is a very good idea.. I just wish some the ARF manufacturers would take care in this area. It grinds my goat to see these mass produced ARFs with great lumps and globs of what is passed off for epoxy smeared all over the place.. And while I’m on my high horse regarding glues, It would be great to get a sample of the famous Chinese ARF “epoxy” for you to test!!

My favourite Epoxy (when I don’t wish to use Hysol) is the West System 105 Epoxy, with 403 microfiber glue filler. This recipe makes a slow cure, thixotropic glue which is immensely strong, and very economical when compared to Hysol. I don’t know it longevity potential, but West Systems Epoxy is a very reputable brand.



Roger

drac1

My Feedback: (4)

Using aircraft grade ply, you can use a thinner ply as well which also saves weight.

In regards to CA versus epoxy for servo mounts, (I always use epoxy), it may be surprising as to how well CA would work with correct materials and preparation. Looking forward to that test.

dbsonic

My Feedback: (3)

I am not sure I agree with the notion that epoxy resins deteriorate that badly over time. If it were true then standard class(15m) fiberglass gliders made in the 80's would end of life. Which is certainly not the case. In fact, Libelles are still flying as well and they are even older as being some of the first glass ships. I suspect what we have available to us in the modeling community is not quite up to par with something like an MGS or similar.

lightningmcnulty

My Feedback: (11)

Good point, although most know I think when the community refers to 'epoxy' they are talking about the cheap Loctite product that home depot sells or equivalent, it will last at most 5 years before it starts to crack normally

Clearly there are a bunch of really good and really long lasting epoxy's

Jgwright

I agree, but there are many types of epoxy out there. I am sure the quick setting types are the ones that cause the most problems. In the plane I bought the glue had gone light brown in colour and was soft. It surely was not like that when originally used. The plane was a composite plane and the whole of the original structure was quite sound. Unfortunately this test will not pick up long term deterioration.

John

CraigG

My Feedback: (40)

There is also the issue of fuel affecting the deterioration of adhesives. Glow fuel certainly had an effect on the epoxies we used to use and I suspect turbine fuel might as well. Here again, Hysol is impervious....another reason I like to use it areas that might experience fuel contamination.

sensei

Building and gluing to crash proof as suggested is a waste of time and only hinders the performance of an airplane IMO... We build to fly. The proper choice of airframe materials, adhesives, and a properly designed structure that includes proper bond lines is what is needed.

Personally I only use thin and medium CA on all my wood airframe structures including firewalls and landing gear blocks, I do use thin laminating epoxy on my sheeted foam wings and tail feathers though. There are many really great adhesives out there, most are much stronger than the materials that make up our airframes, so again bond lines are key.

Bob