NCIS

I am laminating my main horizontal spar on my monster Corsair out of 1/8"x3/8" spruce. There will be 3 layers to equal a 3/8" sq. stick. I am doing it this way because if you have built the center section of a Corsair you know how much trouble it is to steam or wet with amonia a piece of spruce so it will bend. It usually crushes the inside of the bend weakening the spar. Not to mention the undo pressure it puts on the center section when it dries and you remove it from the building board. I have had this cause a center section to twist because of the spring in it. I have done a test and have yet to see the winning adhesive product. I used West Systems 105 resin which claims to be a great bonding agent and the old stand by Great Planes 30 minute epoxy. Which one do you vote for or have used to tell us about. I will test the strength of each joint tomorrow at 4:30pm to see which one comes out the winner.


Barry
www.canopyrailsforwarbirds.com

jmohn

Best stuff is called "Smooth-On" that I used for bow laminations. You can get it at: http://www.binghamprojects.com/Catalog.pdf

Tough and flexible. Can be cured overnight on a warm day or several days on colder days. You can also use a heat lamp too.



Jeff

flyguy

My Feedback: (20)

Try T88 I heard from a friend that it is used on full scale spars. You can get it from Wicks aircraft. [link]http://www.wicksaircraft.com/catalog/product_cat.php/subid=8462/index.html[/link]

F4u5

My Feedback: (81)

Yes, T-88.....used in full scale and available from Aircraft Spruce or here in MN at Rockler woodworking stores. I used it back in my A7P days, and works great for models. Take about 12 hours to set up and 24 to fully cure, but you get a good deep penetrating bond, which is what you want.

WhiteRook

My Feedback: (38)

could you possibly bolt it along with gluing it? mabey number six bolts

ampeater

My Feedback: (1)

Good idea to laminate it for the shape. If you're using it as a top or bottom spar, then the adhesive doesn't really matter. Since the spars are separated by a dihedral brace or shear webs they'll always be in tension or compression and the strength comes from the wood. The main thing you need is adhesive strength (as opposed to tensile or shear strength) since it'll be trying to hold together the shape of the laminations. In that case, I'd go with something that's made for it, sounds like the T-88 gives a penetrating adhesive bond.

AH1G

I prefer West Systems in this type of application.
If twisting and warping is a problem after curing consider including graphite fiber strands in between layers of spruce/basswood/ whatever. If you intend to use this in the center section of the wing, make up a jig in the shape you want and secure it on its side to a flat sheet of Aluminum or steel. Make sure you use some type of mold release or use clear packing tape to prevent bonding to the metal.

mboland

Dash7ATP

Laminating 1/8 spruce to get a 3/8 square section should not be a problem, depending on how much curve you need. You may still have to steam it and hold it to your forms until it dries, and THENglue it. This should ensure you are not gluing in bending stresses. I should think any slow setting epoxy will do what you need. The longer the cure, the stronger the joint. Also, the more pressure you can apply to the joint while it's curing, the better your bond. That can be read, the less epoxy, the better. I still have a little Hobby Poxy 2 adhesive. It's thick and takes an overnight cure. Idon't think it's available now, so Isave it for those occasions when Ineed a bond like you're talking about.

Don't overlook the slow curing wood glues, like Gorilla Glue. That also should be done under pressure.

Good luck.

Dash

vertical grimmace

My Feedback: (1)

Why does it have to be bent? Cant you cut this shape out of ply on the bandsaw and eliminate the possibility of spring back or all of the other issues that come with bending? To improve yield of material you can face glue and scarf the ply together, cut to close shape on the bandsaw and then sand to exact size with your drum or belt sander.

Just a thought.

NCIS

I am using this in my gull section of my blown up Ziroli Corsair. I blew up the plans 133% so the wingspan is 10' 4". I don't want to mess with plywood and the plan calls for spruce anyway. All I did to make the bend in the 3/8"x1/8" spruce is wet it some with hot water. Then it bent easily. It followed the contour of the wings verticle spar and ribs perfectly. The fist layer is already glued in with Gap Filling CA. Here is a pic of the 1st layer glued in. I'm curious now about the T88. Is it a thick or thin product when mixxed properly. I am leaning toward the thinest product I can find for more penetration. Thats why I was thinking of West systems resin or the EZ Lam Laminating product. Has anyone used EZ Lam before for laminating hardwood?

Barry

Also my test of the West Systems vs 30 minute epoxy is finished. They both held and the wood let loose first. So they are about the same and here is a picture of the test results.

F4u5

My Feedback: (81)

Thin is not necessarily an indication of penetration. You could just soak it in to the wood, and end up with a "starved" (of glue) joint. If you look at T-88, it is the same consistency of 30 minute epoxy...more or less, maybe a bit thicker, but it take a long time to set up and cure. This allows good penetration of the glue in to the wood, which will be evident in the staining you will see in the wood once it dries. Clamping, but not so tight as to squeeze out all the glue, is the key. T-88 is used in full scale, so there is absolutely no reason to question it in the RC world. You need to look at the MSDS for T-88 and you will find just how strong it is. I believe the tensile strength is around 7or 8,000 psi., and I think the lap joint strength, such as yours, is around 3K psi., but typically the wood will always fail first, at a lower rating.

That being said, I don't think you needed to bend that wood along the center spar as you did. I don't recall Nick's plans showing that. On all of mine, I brought the wood strainght in and tied them with a gusset, but yours will work fine, just a lot of extra effort.

Jeff

fw190

My Feedback: (37)

Most epoxy will work for our application, however having to wait 12-24hrs for it to completely dry... is a waste of time. Sometimes 12 minute epoxy takes too long. If I was to sit inside a plane yeah by all means use the best.

G-Pete

Proven and simple, like this one here [link=http://www.dap.com/product_details.aspx?BrandID=64&SubcatID=10]click here for weldwood-resorcinol[/link]

The picture below shows a 35 year old 1100+ flying hours Fly Baby, build with that glue - still airworthy....
BTW- it is a full scale[8D]

F4u5

My Feedback: (81)

You're correct Vic, the strength is there with regular epoxy, but since I sleep at night, I am fine to glue it up with T-88 and let it dry overnight. My A&P mentality I guess, plus, I prefer a little "extra" with a 100 pound airplane. Good 'ole Devcon 30 minute is good for my 1/5 scale birds, but I never use 5 minute for structural joints....just don't trust the short potting life.

Jeff

G-Pete

One more Barry - per OZ, it is the cheapest one Guess now I have your attention....

NCIS

[quote]ORIGINAL: G-Pete

One more Barry - per OZ, it is the cheapest one Guess now I have your attention....
[/quote

I pulled up the Weldwood but there wasn't anywhere to order it. What gives?

Barry

fw190

My Feedback: (37)

I don't sleep and agree those 5min is way too fast sometimes. Nothing is as strong as terra firma! 100lbs [X(], I cant even lift myself up in the morning.

NCIS

Thanks for the info on the T88. It seems like the way to go. I only need a small amount so I hate to buy a 1/2 pint bottle of the stuff. Times are tough in the WI apartment business. To many unemployed tenants. That means evictions and loss of revenue. I need to stay on a narrow budget fo the time being. I think I'll just have to chance using 3 hour epoxy instead of 30 minute. That should make it about the same as T88 and I have it on hand. It also has a 24 hr. cure time.

Barry

G-Pete

[link=http://www.shopwiki.com/resorcinol+glue]click here[/link]

NCIS

Thanks Pete.

Barry