Gluing A Lamination

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lake_harley

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I'm working on building a RW-2 biplane in my nice warm basement during these cold days. In constructing the tail leading and trailing edge it requires a 6 layer lamination of 3/4" X 1/8" strips that are then rounded to a "D" profile after gluing them up around form blocks. It makes me cringe to build something so heavy compared to the "light tail" leading and trailing edges that were on my MiniMAX build, but I guess I'll be a good boy and not stray from the plans. I've been using T-88 for the work I've done so far on the ribs, spars and fuselage, but building up 6 layers with T-88 seems it will be a challenge time-wise to get all of the parts coated, put into place and then clamped tight to allow it to cure before the T-88 starts "going off" on the first couple layers. Maybe I'll have to do it in at least a couple stages of 2 to 3 layers at a time with cure time in between? I have considered using Tightbond III on these laminations, but would continue using T-88 through the rest of the project. Thoughts on using Tightbond III anywhere on an airplane build?


In the past, I have done some sample joints with Tightbond III and they were definitely good enough joints to break out wood at the joints rather than merely separating at the glue joint. I have read some build reports of people using Tightbond III when building wing ribs, but then I don't know if they lived through their test flights or not. :speechles


I'm all about building within plans and avoiding excess weight but this "heavy" lamination (about 30 linear feet) is making me cringe. I'm shooting to make Part 103 weight and it's going to be a challenge, at best.

Lynn
 

RUSTY

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I would use West Systems 105/206. Brush or roll it on. Good stuff. A little pricier than t88 but you can probably get it locally and save on shipping.
 

don january

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Lynn. I have lamination's on the Taylor-m that are 1/2" x 1/8th times 4 and about 12 ft. total. I used T-88 but personally I think Tightbond or weld wood would have been just fine. Is yours for the tip bows and h/s and elevator? it does seem rather large at 3/4". What type of wood to be Laminated? mine was Ash. Maybe you can go another route? I guess a couple of test pieces and a stress test will give you a better Idea on how the glue will hold up but it looks like weight is going to be a real challenge if you are staying under 254 lb. I wonder how Tightbond holds up after time?
 

lake_harley

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Thanks for the suggestion, RUSTY. I looked at some info on the 105/206 West System and it actually looks like the pot life, and in my case working time to get the 6 layer lamination done, would only be about 20-25 minutes. I think that's a bit shorter pot life than I've found T-88 to have. Unless there's an extended pot life hardener, or adhesive system to give more like 45 minutes to do the build-up and clamping I may have to do it in two stages; #1-3 on day 1, and then 4-6 a day later.

Lynn
 

TFF

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I would not worry about test flights, I would worry about 10 years of exposure. I would go with the Wests especially if I ever sold it. TB would be easyer but I still only use it on models. I don't know if System Three Clear Coat could be used; I think it would be ok. It seems like thinned T88. Slower the better if mixing a lot, and even then you want a set of small batches vs one big one.
 

BBerson

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I noticed crutches are nicely laminated of 1/8" strip. Can almost always get a pair at Goodwill for about $10, I think.
 

RUSTY

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There is a hardener with a longer pot life. It will also take considerably less time to roll on the 105 than to spread t88.

Edit: 209 is the extra slow cure hardener.
Pot life 40 -50 minutes
Working time 3 -4 hours
 

Pops

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I use T-88 and mix small batches at a time. I also do a trial fit to make sure I have everything I will be needing. Nothing worse than running out of clamps with the epoxy mixed.
 

lake_harley

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Don... we must have been posting at the same time. I'll be using Northern White Pine for the lamination. I did do a non-scientific calculation of the weight of the total linear feet of the leading and trailing edge laminations. Without taking into account the removal of material for the radius of the piece I came up with just under 3.2#, which was not as heavy as I feared it might be. I used 27# per cubic foot for the pine, which is a "average" weight for NWP that I saw at one time. I have thought the lamination thickness at 3/4" was a bit much and perhaps it could be reduced to 5 layers for 5/8" thickness, or even to 4 layers at 1/2". The RW-2 plans do point out various places where material dimensions are reduced if the plan is to build it as an ultralight. Perhaps this is one area that a bit of weight could be removed too, but that's altering the plans pretty significantly and that's not something I would do lightly. In ultralight for the RW-2 would be a 55-60 MPH plane at best, but flutter and/or inviting structural failure isn't something I want to build into the plane.

I have also considered patterning the tail components to build more like the MiniMAX "light tail", but that's a rather boxy structure that doesn't have the biplane shapes and appeal.

I guess some testing of various laminations and adhesives would be in order to get more scientific, but I don't know at what point I'd feel comfortable with my findings.

Lynn
 

lake_harley

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Again, more simultaneous posts. Perhaps the 209 hardener would be the trick. I agree rolling on an adhesive would be much faster than spreading or brushing on T-88.

For clamping the lamination I thought that using a band that could be tightened/pulled around the entire "C" curved shapes would be a good way to get even clamping pressure. There would definitely have to be something in place to keep the strips evenly lined up while clamping took place, since adhesives are a bit "greasy" when wet.

Edit/addition.....I just took a look at the System Three Clear Coat. Info says that it can be used for laminations and has a pot life of about 60 minutes. Hmm...I think I can work at that pace even considering my advanced years. ;)

Lynn
 
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wsimpso1

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Thanks for the suggestion, RUSTY. I looked at some info on the 105/206 West System and it actually looks like the pot life, and in my case working time to get the 6 layer lamination done, would only be about 20-25 minutes. I think that's a bit shorter pot life than I've found T-88 to have. Unless there's an extended pot life hardener, or adhesive system to give more like 45 minutes to do the build-up and clamping I may have to do it in two stages; #1-3 on day 1, and then 4-6 a day later.

Lynn
West System does have a slow hardener. Find a stocking dealer on their website.
 

Kyle Boatright

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When I glued up the center section bow for my sidelined Hatz project, I made a fixture to hold the bow. It had 2" holes near the edge of the fixture so I could soak the wood, clamp it in place against the properly shaped fixture, allow it to dry, pull apart, and then glue together using the fixture. It was from several layers of 1/8" spruce and I used several glue sessions - glue a couple of plies together, clamp 'em in the fixture, unclamp the part the next day, and add another lamination or two, then clamp to the fixture to cure. Lather rinse repeat. Springback was negligible, and by using multiple glue sessions, I didn't have to worry about the epoxy curing prematurely.
 

lake_harley

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It was from several layers of 1/8" spruce and I used several glue sessions - glue a couple of plies together, clamp 'em in the fixture, unclamp the part the next day, and add another lamination or two, then clamp to the fixture to cure. Lather rinse repeat. Springback was negligible, and by using multiple glue sessions, I didn't have to worry about the epoxy curing prematurely.
Kyle...what you did is probably what I will end up doing. I was hoping to avoid making the laminations a couple days project for each of the 5 lamination sections. In the overall scheme of building a plane I suppose it's not really that big of a deal or slow down. I'll just have to temper my impatience.

In some of the larger glue-up sessions on my MiniMAX build I did mix multiple, smaller batches of T-88, but you hit the nail on the head with the same reservations I had...epoxy curing prematurely. I feared that layers 1 to 2 epoxy would have started to cure before I got finished with layers 5 to 6 to properly clamp everything up well, and the 1 to 2 layer and perhaps 2 to 3 as well would be compromised by the total time start to finish. Doing it in 2 or 3 sessions is probably the ticket.

Thanks, one and all, for the suggestions.

Lynn
 

Basil

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Why not use Aerolite 306. Spend as long as you like spreading glue on alternate laminations and when you are done paint the acid on the other pieces and assemble.
 

lake_harley

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Bob Hoovers blog seems to make the point that a discussion of glues is about as productive as a discussion about the "best" oil to use. :ermm:

Lynn
 

Pops

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I like his style of writing. To the point.
 
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