adhesive vs rivets?

[Lumpyguy]

just a curious comparison, what peoples opinions would be of using structural adhesive (like the automakers use) vs riveting all the main aluminum panels onto the chassis? I know that once its glued on its on! but it would save allot of drilling and drilled holes in the chassis. I would almost think it would stiffen the chassis as well. I see the big super car companies gluing there main structures together.

thanks

[Mechie3]

If you can get ahold of good stuff and do proper prep I don't see why not. It might be harder as some panels are positioned and held in with clecos temporarily to help align things, but the end result would be cleaner. My only concern would be that I don't know if the industrial stuff can be purchased and what kind of surface prep it requires and if those items are available over the counter. Lots of times the commercial version of industrial products just really don't cut it. I have no knowledge of these types of adhesives though.

[Turboguy]

FFR roadster builders have been using adhesives between the panels and frame for ages. Do both, like they do.

[edwardb]

Roadster guy here, but I'm assuming FFR is using the same method for the 818 as the Roadster. The Roadster instructions state to use adhesive (usually silicone glue) and rivets. Creates a very strong bond. Much stronger than the aluminum. Try to get the joint apart after it's dried. Just adhesive holds strong enough you probably will damage the aluminum beyond repair. Ask me how I know. Additionally, the panels aren't structural to the strength of the frame. So in theory, only adhesive would probably work OK. But IMO the drilling, cleco and ultimately setting the rivets is a quick a quite practical solution. It would take a lot more work IMO to try to clamp the pieces in place until the adhesive dried. In some cases, it would be nearly impossible to do so. Get 5-10 high quality #30 drill bits, and toss them when they aren't cutting well. Don't try to keep drilling with a dull bit. Also, consider a pneumatic rivet puller. I found a Campbell Hausfeld at a local tool store that works perfectly. Built my first Roadster pulling the rivets by hand. Built the second with the air powered gun. What a difference. Not only because they're (obviously) way easier to set, I think they pull down even better.

[skullandbones]

Here's where other FFR builds translate to the 818. I'm also a roadster builder. In this case, the whole is greater than the sum of it's parts. The silicone adhesive at the very least reduces the shear limit of the rivets by themselves. As mentioned above you probably won't be able to take the panels off after curing without damaging the aluminum. I've seen some airplane kits that are put together the same way. You should follow instructions to the letter on this one! IMO, WEK.

[Turboguy]

Additionally, the panels aren't structural to the strength of the frame. So in theory, only adhesive would probably work OK.


Actually, I believe using adhesive AND rivets to attach the aluminum panels will effectively increase the strength and rigidity of the frame -- it will change FFR's "tube frame" chassis into a "semi-monocoque" chassis.

[edwardb]

Actually, I believe using adhesive AND rivets to attach the aluminum panels will effectively increase the strength and rigidity of the frame -- it will change FFR's "tube frame" chassis into a "semi-monocoque" chassis.

Could be. Hard to argue that the aluminum panels don't add some measure of strength to the steel chassis. And I'm certainly not a structural engineer. Just my general impression based on what I've seen/heard in the last several years regarding the panels. Plus Factory Five's own advertisements where SolidWorks is frequently mentioned as the tool used to design and test their chassis, always pictured without the aluminum panels. Even the "Chassis testing video" for the 818 on their website shows them running without any panels. Steel chassis frame only. Personally, I wouldn't want to count on that .040 aluminum for too much. Would be interesting if someone has any empirical evidence. But getting the thread a little of course.

[RM1SepEx]

Very detailed FEA has been done on other tube frames with aluminum. A sheet of aluminum can provide rigidity like a steel member making a triangle. Bottom line, there is significant stiffness gained by bonding and riveting them together.

[mjazzka]

Could be. Hard to argue that the aluminum panels don't add some measure of strength to the steel chassis. And I'm certainly not a structural engineer. Just my general impression based on what I've seen/heard in the last several years regarding the panels. Plus Factory Five's own advertisements where SolidWorks is frequently mentioned as the tool used to design and test their chassis, always pictured without the aluminum panels. Even the "Chassis testing video" for the 818 on their website shows them running without any panels. Steel chassis frame only. Personally, I wouldn't want to count on that .040 aluminum for too much. Would be interesting if someone has any empirical evidence. But getting the thread a little of course.

I don't think it's off course at all, OP definitely wants pros and cons of doing adhesive vs. rivets. You guys have given some good info!

I agree with the semi-monocoque statement of Turboguy, using industrial automotive adhesive can only help. Stiffening a whole portion of the frame with a panel attached at all points will have a great effect. I think the best option would be to use both, although you could use less rivets with adhesive.

[edwardb]

Very detailed FEA has been done on other tube frames with aluminum. A sheet of aluminum can provide rigidity like a steel member making a triangle. Bottom line, there is significant stiffness gained by bonding and riveting them together.

Interesting and good to know! Certainly this is new info for me. Makes the integrity of the mounted panels even more important. Seems the recommended adhesive and rivet method is the best choice. Back to what the instructions said to do.

[mjazzka]

Interesting and good to know! Certainly this is new info for me. Makes the integrity of the mounted panels even more important. Seems the recommended adhesive and rivet method is the best choice. Back to what the instructions said to do.

Almost makes it seem like they know what they're doing, don't it? :p

[tirod]

Space frames are already inherently stiff, entirely the point of having the tubing welded into the pattern at various places the way it is. Some FEA has been done and it's entirely arguable that it does help - in that if there is any increase in stiffness, other aspects of the suspension, drivetrain, etc may not be able to exploit the incremental increase.

Panel bond adhesive and VHB tape have been done, it does eliminate most of the rivets. The two were actually developed by 3M and others with the knowledge they allowed some flex. Thirty years ago 3M put a VHB box body in a flex tester and subjected it to hours of vibration and twist. The result was that the welds on some major members broke, but not the bond on the panel seams because they flexed enough to prevent fatigue.

From there, VHB tape and panel bond adhesive has been used in the construction of complete honeycomb board chassis for high end race cars and projects. The main issue with them is getting the sub assemblies mounted to the chassis thru proper reinforcements and thru bolting. Those fasteners become the critical weak link, not the honeycomb or adhesive.

If honeycomb board was cheap and plentiful there would already be kits built with it for the flooring, etc, but for now it seems cost prohibitive. What the rivets and silicone do for the F5 kit is get a floor pan and cabin wall installed at the builder level simply because tube framing doesn't support any other method. It's nearly impossible to get a full floor pan installed without having the tubes welded in after, which defeats the purpose of the kit. Because it is a tube frame, tho, the unwanted consequence is that there is no "wall to wall" separation of the cabin that creates an effective shield against inclement weather. These things are leaky at best in a full rainstorm, even with a roof. Plenty of roadster builders add even more panels at the body to frame joints where none are supplied in the kit. Surf "pool noodles" for the number of threads on that.

For the actual results in keeping the panels attached and not squeaking or chattering, rivets and silicone are cost effective and work. Going further to reinforce the existing framing is a nice idea, what would deliver more speed and cornering would be a track day with Koni engineers with a pile of shocks and springs. Which Wayne Presley already did for F5. Panel rigidity in a tube frame chassis is a very low return and incrementally insignificant issue in the perspective of the whole scope of the car.

[Boog]

I like the idea of being able to remove any body panel if needed and have been considering going with less frequently spaced rivnuts and a flexible sealant rather than rivets and an adhesive sealant.

Is the consensus that this would reduce chassis rigidity? Would the loss be enough to notice?

[billjr212]

some have done this with strategically placed body panels (such as the rear bulkhead on the 818, the center console on the Roadster, and trunk panels on the hot rod). My concerns with doing it everywhere would be rattles and water infiltration. I can't imagine you'd feel a performance difference unless you are racing very regularly. Even then, it seems the impact would be limited based on comments above.

[STLMARSHALL]

As mentioned above you probably won't be able to take the panels off after curing without damaging the aluminum.

Actually the panels come off quite easily. I just made new rear hatch panels for my FFR Coupe. I had to take the old one out in one piece which was going to be difficult....until I got an idea. I drilled out all the rivets 1st. I then got out my propane torch and lightly heated up the panels starting at the corners. Once I got one corner up I just pulled up one corner at a time while heating the sealed edge with the torch. It was almost too easy!

[Lumpyguy]

Thanks guys, lots of good advice! I think I will just stick with the tried and trued sealant and rivets.

[tirod]

https://www.google.com/search?q=rivet+fan+spacing+tool&es_sm=93&source=lnms&tbm=isch&sa=X&ei=Tl7zU4fXG4P3oAT5gYHgAQ&ved=0CAkQ_AUoAg&biw=1024&bih=515

I'm of the mind it should come with the kit.

[AZPete]

For a rivet spacer, you can cut the elastic from a pair of jockey shorts and then mark it every 2 - 3 inches. Clamp one end at the start of your rivet run, stretch it to the end and mark the aluminum at each mark on the elastic. Perfect proportional spacing, the "tool" folds up small, and it's FREE!

Oh, and wash the jockies first.

[Oppenheimer]

I guess this is one tool no one ever wants to borrow.