Alternative to nails or staples

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b7gwap

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I will be building an ULF-1 in the near future and had a question about open truss wood rib fabrication in general.

I have watched several EAA videos and gone to look at some real examples to better understand the process and requirements, eg jig construction, bending of members, gusset design, adhesive squeeze-out.

I see some use nails to hold the gussets for cure, some use staples because it’s easier to remove, but has anyone ever used a vacuum bag? I was thinking a 1/4” ply caul in the shape of the rib with release film on it could be used to keep the force uniform. Would this perhaps squeeze too much glue out?
 

Pops

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When using T-88 to glue the gussets any weight or pressure will tend to slide the gusset out of position without a nail or staple to hold it in position. The plywood gusset tends to float on the film of glue even with the weight or pressure.
 

don january

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When using T-88 to glue the gussets any weight or pressure will tend to slide the gusset out of position without a nail or staple to hold it in position. The plywood gusset tends to float on the film of glue even with the weight or pressure.
Heck Pops that is the fun in chasing them gussets. Trying to get them to stay where ya want them before the glue firers off. :gig: when I did the gussets on my T-mono I didn't touch it with nail or staple gun so nothing to pull and dint's to fill up after being pulled.
 
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wsimpso1

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I see some use nails to hold the gussets for cure, some use staples because it’s easier to remove, but has anyone ever used a vacuum bag? I was thinking a 1/4” ply caul in the shape of the rib with release film on it could be used to keep the force uniform. Would this perhaps squeeze too much glue out?
Vacuum bag with a plate on top of the rib will work, but you will have to work up some supports in the jig to keep the gussets in place, as they will slide around. You won't need much pressure, a couple inches of vacuum at most. Also, when you go to apply gussets to the other side, you probably will need a mirror image jig to bond your gussets on the other side of the rib. A thick plate on top will also help when you have to make a rib that is fully skinned instead of just gusseted. Drawbacks to this are all the fuss of the vacuum bag and that you can only get one rib out of your process per cure time, usually 1 per day...

Having built ribs with a single jig and a staple gun, I can tell you that once stapled, you can pull the rib out of the jig, do the gussets on the other side, and do another rib or two while you are still rev'd up. I did three a day for a while, and I was only limited by how many capstrips I could get soaked and bent to rough shape per day. More bending jigs, and the rate could have gone up more, but life had others things in each day besides rib making.

I suspect that you are attempting to make these ribs much closer to perfect than has any use, which results in turning the process into a JOB. Do not do that to your airplane building. This is supposed to be fun. Try to enjoy the process, admire the beauty of the spruce capstrips and mahogony plywood and the nicely made jig, and then miss it a little when it is done and you are on to other processes.

Billski
 

Pops

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Vacuum bag with a plate on top of the rib will work, but you will have to work up some supports in the jig to keep the gussets in place, as they will slide around. You won't need much pressure, a couple inches of vacuum at most. Also, when you go to apply gussets to the other side, you probably will need a mirror image jig to bond your gussets on the other side of the rib. A thick plate on top will also help when you have to make a rib that is fully skinned instead of just gusseted. Drawbacks to this are all the fuss of the vacuum bag and that you can only get one rib out of your process per cure time, usually 1 per day...

Having built ribs with a single jig and a staple gun, I can tell you that once stapled, you can pull the rib out of the jig, do the gussets on the other side, and do another rib or two while you are still rev'd up. I did three a day for a while, and I was only limited by how many capstrips I could get soaked and bent to rough shape per day. More bending jigs, and the rate could have gone up more, but life had others things in each day besides rib making.

I suspect that you are attempting to make these ribs much closer to perfect than has any use, which results in turning the process into a JOB. Do not do that to your airplane building. This is supposed to be fun. Try to enjoy the process, admire the beauty of the spruce capstrips and mahogony plywood and the nicely made jig, and then miss it a little when it is done and you are on to other processes.

Billski
Yery true. I do enjoy the process, I set and build the ribs and use 1/4" aircraft nails with tweezer and a small tack hammer. ( My favorite tack hammer is made from a welding slag pick) While watching old 1950's westerns in the evening while building.
 

b7gwap

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Vacuum bag with a plate on top of the rib will work, but you will have to work up some supports in the jig to keep the gussets in place, as they will slide around. You won't need much pressure, a couple inches of vacuum at most. Also, when you go to apply gussets to the other side, you probably will need a mirror image jig to bond your gussets on the other side of the rib. A thick plate on top will also help when you have to make a rib that is fully skinned instead of just gusseted. Drawbacks to this are all the fuss of the vacuum bag and that you can only get one rib out of your process per cure time, usually 1 per day...

Having built ribs with a single jig and a staple gun, I can tell you that once stapled, you can pull the rib out of the jig, do the gussets on the other side, and do another rib or two while you are still rev'd up. I did three a day for a while, and I was only limited by how many capstrips I could get soaked and bent to rough shape per day. More bending jigs, and the rate could have gone up more, but life had others things in each day besides rib making.

I suspect that you are attempting to make these ribs much closer to perfect than has any use, which results in turning the process into a JOB. Do not do that to your airplane building. This is supposed to be fun. Try to enjoy the process, admire the beauty of the spruce capstrips and mahogony plywood and the nicely made jig, and then miss it a little when it is done and you are on to other processes.

Billski
I hadn’t considered the propensity of the gussets to wander without some fixture.

I’ve spent my career bagging things, so I don’t consider it a hassle, but if it’s not a good process I will follow the plan and use nails. I was wondering if anyone had tried this as it seems like the bag and caul plate might apply a more uniform pressure on the gusset than two or three nails each. But, as you say, maybe I’m painting the lily here.

Thanks for the input, looking forward to starting this project and taking little bites of the elephant every day.
 

TFF

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I like the jig that uses the clamps of plexiglass. Not the fastest but a clean way to do it. The other side is that many old planes, flying, were found to be held together with the nails after the old style glues had failed. Only found during restoration. The right staples are the round wire type rather than the standard type. They have a better chance of not splitting the wood.
 

Victor Bravo

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The most experienced and knowledgeable wood rib guy I have ever met uses really tiny brass nails (brads) and leaves them in. The weight savings for pulling them out is truly negligible,a nd the brads provide some shear strength to the joint.

Vacuum bagging the wib will bend and deform the gussets.

If you really REALLY wanted to not have nails or staples in the rib you could use the smallest size model airplane "T-pins", and then remove them after the glue sets.

If you are really trying to speed up production then it is worth the time to make three rib gig boards, so you can keep working while the glue sets.
 

Pops

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My first build was a KR-2 back in the 1970's after I seen the first one fly into Osh. In building the plywood covered fuselage I used 3/4" long aircraft nails driven into the spruce about 1/4" to hold the position of the plywood at the corners, mark the glue area from the inside, remove the plywood and slightly rough sand the glue area and vacuum with a shop vac. Had my children , girl 14 years old, boy 13 years old and youngest son of 11 years old to help brush the glue on between the lines and reposition the plywood with the 3/4" long nails. I had made nailing strips of thin wood and cardboard and stapled the strips and thru the plywood into the spruce. After the glue was set up, I bent a screwdriver end to slip down in the cardboard under the staples and removed. On the gussets for the ribs I use 1/4" long aircraft nails and do not remove.
My daughter still helps me and I wouldn't paint an airplane without her help and have flown behind 2 engines that she did the MOH on. Oldest son was AF. Youngest son was getting ready to get his pilots license at 24 years old but got hit head-on by a semi-tanker on the interstate and can't drive an auto. He oldest son is a ME just out of college and wanting to get his pilots license, maybe my other grandson that is an corp pilot and instructor will have time to instruct him.
When you get your children helping in the build, you never know where it will lead.
 

pictsidhe

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How about making the jig to fix one or two gusset edges with pins the gussets abut to. Then have springy lateral location to hold the gussets against the pins. Then drop a weight on?
 

pictsidhe

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If I were making ribs. I'd likely use a pneumatic wide crown stapler. With a spacer taped underneath so the staples would be proud. Then I'd flick them out using one of my staple pry bars which are these with a bit of extra grinding.
 

b7gwap

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The most experienced and knowledgeable wood rib guy I have ever met uses really tiny brass nails (brads) and leaves them in. The weight savings for pulling them out is truly negligible,a nd the brads provide some shear strength to the joint.

Vacuum bagging the wib will bend and deform the gussets.

If you really REALLY wanted to not have nails or staples in the rib you could use the smallest size model airplane "T-pins", and then remove them after the glue sets.

If you are really trying to speed up production then it is worth the time to make three rib gig boards, so you can keep working while the glue sets.
the brads provide some shear strength to the joint.
The nail would provide some shear strength, but nowhere near the shear strength imparted by the adhesive itself. My understanding of the function of the nail is primarily for clamping force and also alignment as discussed above.
Vacuum bagging the wib will bend and deform the gussets.
A bag used directly over the rib structure would indeed do this. However, if a caul plate is used under the bag and over the whole rib, the load is distributed evenly across the whole plate and would not deform the gussets, which was my original idea. However, this does not keep the gussets from squishing out of place as the atmosphere starts pressing them down.
If you are really trying to speed up production
For the record, I'm not. I'm mainly interested in getting the glue squeeze-out more uniform. An added benefit to using vacuum is that it would help assure flat alignment of the rib during cure.
it is worth the time to make three rib gig boards, so you can keep working while the glue sets.
Unfortunately the ULF-1 has a tapered wing planform so every rib is unique (except left to right of course). Thus I'll be building the next jig as the glue dries. I'm fine with this. :)
 

b7gwap

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How about making the jig to fix one or two gusset edges with pins the gussets abut to. Then have springy lateral location to hold the gussets against the pins. Then drop a weight on?
I like where you're going with this. The bag would be better than weight, however. More uniform and more force overall.

A part of the jig that is proud of the sticks but flush with the top gusset face could be used to prevent lateral movement of the gusset during vacuum bagging.

I will most certainly build some test ribs prior to the actual articles. I will test out some of these ideas and report back.

Vacuum bagging really doesn't have to be the high-end affair that it is though to be. If something doesn't have to go into an oven or autoclave, the materials used can be orders of magnitude less expensive and you might even already have them in your shop. For example, that clear plastic polyethylene painter's drop cloth makes a great bagging material, window caulking makes an excellent bag seal, a shop vac followed by an automotive hand brake bleeder makes a usable pump, etc.

Austin
 

TFF

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Epoxy does not need the clamping pressure like resorcinol or plastic resin. For epoxy, keeping it in position and in contact is the important part. the screw down plexi is really god at this as you tighten enough but not clamp tight. The beauty of epoxy is tolerance. There is really no best way. If my ply was laying flat, just pressing it on would be just fine; its when the edges curl or the sticks have a in perceivable crown is when you have to hold down an epoxy joint, which is most of the time.
 
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