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First attempt at robart hinges FAILED, now what?? - 8/2/2012 4:50 AM   
Muddin_Mavric


 

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Status: offline 		im putting together a phoenix models edge 540 with a dle 20 for power. all i have ever used before for hinges is the CA type hing. every one says the robart hinges are suppose to be way better so i though i would give them a try on this plane. i used gorilla wood glue to hold them in. well about 2/3 of the way though my first tank of fuel just running it up on the ground my right elevator half falls off. all of the hinges pulled out of my horz. stab. after the glue was dry i pulled on all of the hinges as hard as i could and they all felt solid and none pulled out. at this point im not real sure what i should do. do i cut off all the robart hinges and put the ca hinges in right next to them? do i just re glue the elevator half and hope the rest are ok?



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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 5:15 AM   
Gray Beard


 

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Status: offline 		These are the flat Roberts I assume.just use a bit of oil between the hinge, use more gorilla glue to install them again. Then from the bottom of the LE and TE you drill a hole through the wood bottom just through the hinge and use a round cut off tooth pick and CA to hold the tooth pick in, cut off the picks and sand. You can paint or put a strip of covering to cover over the tooth picks. This is what we call pinning the hings. With both CA, and flat hinges like the Dubro you want to cut the slot then drill a hole in the center of the slots so you can get glue all the way into the hinge slot or they aren't going to hold very well. I drill the hole and use the free syringes I get at the drug store to shoot the glue into the slots. Some people use epoxy for the glue. Soak the hinges in alcohol to clean them before you glue them in. I also use diabetic syringes to put the oil in the hinge center, you don't need much, just enough to keep the glue from sticking to the hinge center.

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 11:18 AM   
Muddin_Mavric


 

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Status: offline 		these are the round hinges not the flat ones. i thought about trying to drill into them and pin them but im not sure how well that would work.

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 4:35 PM   
pdm52956


 

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Status: offline 		Were your hinges mounted into a hinge block or just into a balsa trailing edge stick? If they weren't glued into a block behind the trailing edge, they will pull loose. Using CA hinges, the CA wicks into the balsa and the hinges don't come loose and that isn't the case with robart hinges. The Robart hinge needs something more to glue to.

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 6:04 PM   
Gray Beard


 

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quote:

ORIGINAL: pdm52956

Were your hinges mounted into a hinge block or just into a balsa trailing edge stick? If they weren't glued into a block behind the trailing edge, they will pull loose. Using CA hinges, the CA wicks into the balsa and the hinges don't come loose and that isn't the case with robart hinges. The Robart hinge needs something more to glue to.

100% what PDM said. ARFs have different needs then a kit or scratch built plane and theydon't do well with hinge pins for a good reason. Wood cost money so ARFs have very little of it. The leading and trainling edges are often just 1/4 or 3/16 balsa, I have found them with just 3/32. Hinge pins require wood to glue to to. When building a plane I mark out where I plan on hinging if using hinge pins and glue in extra wood blocks so the pins have something to stick to.
What happened to you is there isn't enough wood to glue to, it's hollow, the gorilla glue expands but it takes the path with the least resistence which is towards the inside of the wing and control surfaces. Very little glue got onto the hinges at all.. Hinge pins and ARFs that weren't designed for them don't work well. Some of the better giant scale ARFs are designed for pins but most ARFs are designed for flat hinges. That is why a CA hinge installed correctly in an ARF work so well, they don't require a lot of wood to stick.

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 6:23 PM   
Muddin_Mavric


 

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Status: offline 		Thanks for all the replies. In the build thread for this plane one of the first people to post said he used the robarts instead of the ca hinges. I hear of a lot of people not liking ca hinges so i figured i would give the robarts a try. I will never use them again in an arf. So i guess i will have to re hinge everything. What would be better the ca hinges that came with the plane or some of those flat hinges you can pin from the bottom?

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 6:32 PM   
Gray Beard


 

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Status: offline 		I would guess the poster was refering to the Robart flat hinges and not hinge pins? I have use them on ARFs during a rebuild when I could add the wood behind the edges but that was something different. Robart flat hinges are stronger then CA hinges but if you know how to install CA hinges correctly they are as good as anything you can use. If you use the Robart flat hinges then use epoxy, make sure you don't get it inside the hinge joint and make sure you get the epoxy into the slot!!!!!!!! If you get the eopxy into the hinge center then Acetone will release it but you have to go slow and work the hinges to break them free. Goodc luck to you.

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 9:06 PM   
JohnBuckner



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quote:

ORIGINAL: Muddin_Mavric

these are the round hinges not the flat ones. i thought about trying to drill into them and pin them but im not sure how well that would work.



I think mavric is talking about single point hinges.

John

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 9:16 PM   
JohnBuckner



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quote:

ORIGINAL: Muddin_Mavric
In the build thread for this plane one of the first people to post said he used the robarts instead of the ca hinges.

I hear of a lot of people not liking ca hinges try. What would be better the ca hinges that came with the plane or some of those flat hinges you can pin from the bottom?




The first mistake is making decisions by strick concensus on some thread or forum. I love CA hinges and beleve they are a milestone development in the progress of our model airplanes. In fact they are the one thing that allowed for major improvements of our modern ARF's and I am sure many will hate me for saying such a thing and thats fine.

The answer to your last question is what do You think, sure use them (CA).


John

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 9:21 PM   
dbacque


 

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Status: offline 		Robart Hinge Points are great but they must be installed correctly. There are several tutorials around here on how to use them. First, use the Robart drilling jig. Then there are several ways to fit the hinge up to the knuckle, some use a Dremel, I prefer to square out the entry of the hole with an X-acto. The manufacturer specifically calls out that these hinges are designed for use with epoxy. I know some people do use Gorilla Glue but I prefer to "stick" with the mfgr. recommendations. Besides, keeping the GG out of the hinge knuckle but getting enough for a complete glue joint is problematic. If the surface literally fell off, then you did not get much of a glue joint. Even without an internal glue block it should have held better than that.

Dave

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 10:45 PM   
Rodney



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Status: offline 		As Dave in post #10 says, alignment is critical. The hinges must line up perfectly. If one is off line, when you activate the surface, one or more will be severely stressed. Also, the rotational axis of each hinge MUST be a right angles to the surface being moved.

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 11:29 PM   
Muddin_Mavric


 

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Status: offline 		i tried to get everything lined up the best i could. and i rammed as much glue in the hole as i could and put glue on the hinge before pushing it in. i could not beleave it when all the hinges in a control surface fell out just from the vibration of the motor. i guess i will just cut all the hinges and put CA hinges in i really don't want to crash it because a aileron falls off in the air. i spent a fair amount of time on here searching and reading trying to make sure i installed them right, guess i will just stick with ca hinges, they have never failed on me yet.

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RE: First attempt at robart hinges FAILED, now what?? - 8/2/2012 11:44 PM   
dbacque


 

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Status: offline 		What did the hinges that pulled out look like? Did the glue mostly pull clean off, leaving just a little or no glue on the hinge? Or are the hinges completely covered in glue and pieces of wood?

Dave

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 12:35 AM   
Boeing



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Status: offline 		I have had outstanding success using Gorilla Glue and the round Robart hinge points.
Question: Did you moisten the hinge hole with water prior to adding the glue and the hinge? Using liquid vaseline on the hinge knukle will prevent the glue from messing up the hinge.

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 12:57 AM   
pmerritt


 

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Gorilla glue specifically states that it will SWELL.  This can't be a good thing when one is trying to get a snug fit into a soft wood such as balsa.
After very careful alignment in one half of the install, whether that be in the control surface or the air frame itself, I use 30 minute epoxy.  First I treat all the hinge pin areas with oil not to get any on the barrel of the hinge itself.  If you do, clean it off with acetone before continuing.
You can put blue masking tape around each hinge hole to keep the epoxy off of the monokote and gently remove it just after everything lines up and there is enough time for the epoxy to hold but not harden.
With a 30 minute window, you can work the control surface and make sure the movement is satisfactory.  This also can be done as a dry run before the final expoxy step. 
If you want, you can lightly sand the plastic barrels so they rough up some for a better bond. 
Have some cleaner handy so you can clean up right after the install. 



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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 1:21 AM   
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Status: offline 		As others have said, Robarts need a block glued in on the forward side of the LE or they can pull out...

At this point I would go with a Dubro flat hinge, they are strong, easy to install and work great.. I always use them on my ARF'S that are cut for CA hinges..

Jimbo

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 1:31 AM   
Mustangman40


 

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Status: offline 		This is what I use... If you do them right, no need to pin them.. I have used them on planes going 130+mph and never had one pull out... If you recess  the knuckle into the control surface and install with regular wood glue, no need to lube the hinge with anything and you end up with a tight hinge gap that wont come out...

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD941&P=0

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 1:49 AM   
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Status: online 		Just a view of the required structure for Robart Hinges.  The hinges need an added block on both sides of the hinge to allow enough material depth for the barbs to engage the wood.

Not a lot of ARFs will have this feature unless they are designed for Rubart Style hinges.

SunDevilPilot 

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 4:36 AM   
Muddin_Mavric


 

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Status: offline 		i did not wet the wood before putting in the glue. when the hinges pulled out there was a little bit of glue on the end part that was probably sticking out the other side into nothing. the part that was in the wood has nothing on it, the glue either wasnt on it good enough or pulled right off of it. at least these hinges should be easy to get out, i ran another tank though the dle 20 getting it tuned in a bit and now my rudder has fallen off lol. i probably should have bolted the wings on maybe i could have gotten a aileron off too.

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 2:27 PM   
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Status: offline 		That shows that your hole went all the way through the wood so when you installed the hinge points they just pushed the glue out.

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 2:38 PM   
Live Wire


 

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Status: online 		Just what Gorrilla glue did you use, the original or the wood. I have put in hinges with the original and with out water it just takes longer to set up. When they come out it is with a lot of Wood when it swells it come out of the hinge no matter what you do.
Larry K

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 2:41 PM   
Live Wire


 

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 2:43 PM   
Muddin_Mavric


 

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 2:52 PM   
Live Wire


 

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Status: online 		I will bet that was the problem. The original works great but you have to watch how you aply it, it sticks to any and every thing. Water will speed up the time it takes to expand and I use a windex sprayer to mist the hinge after installed. The excess glue that comes out of the hinge can be easly be removed if the hinge has been lubed befor installation.
Larry K

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RE: First attempt at robart hinges FAILED, now what?? - 8/3/2012 2:59 PM   
Live Wire


 

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Status: online 		Just another thought
All bonding surfaces should be scuffed or sanded to make sure the glue has some thing to grab onto, that is why most flat type hinges are pined
When you clip the top of the glue bottle, make the hole where the hinge will just fit. Then when the hinge is inserted into the hole you get the glue on the part of the hinge you want it on and when you pull it out it leaves the grooves filled. A small amount in the h holes and you are on your way.

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