sheet material attachment ???

[Art Smith]

as the time draws closer to adding sheet aluminum to the sides of the Crossle, I have a question on what's legal as far as attaching it to the frame.

D.6.d .............Sheet materials attached to the frame by welding, bonding, or by rivets or threaded fastners which are located closer than six (6) inch centers, are defined as stress bearing panels. ..........................

is the six (6) inch centers a linear dimension?? or spherical dimension?? or an undefined type of dimension?? the Crossle, has a number of internal and external corners (when viewed from the front) that aluminum sides need to be bent or formed around. assuming a 90 degree external corner with one leg vertical and the other horizontal, is there any relationship or linkage between fasteners in the adjacent planes attaching sheet material to a frame in the rules as currently written???

I'm not looking for personal opinions; like a number of things, we all have one! does anyone know of any precedents at the National level? as best I can remember the language in this particular paragraph hasn't been touched in at least 25 years so just about anything (in writing) is probably applicable. thanks!!

Art
artesmith@earthlink.net

[Steve Demeter]

Check the section on the 1986 FF construction rules.


They require some sort of side reinforcement and if I remember correctly it spells out exactly what it may be and how it must be attached.

If you follow that, I don't think that anyone could possiblt interpert it being contrary to the rules.

[EYERACE]

crossle? .....no idea where you're going with this but my 1978 Crossle 32F has alum panels on both sides of the chassis from the front [that is, the section that separates the pedals from the masters] all the way back to just behind the main hoop - these alum panels are riveted in place to the vertical chassis members and to the lower and upper frame rails. the upper part of the panels wraps over the top of the uper rail. if all this adds a little rigidity...good! was the recent frame up doing this to cheat?...no. this was done because that's the way the car was when i bought it. .....if anyone was to protest the panels of a 1978 car they'd have to be an idiot. no tech inspector has ever said a word. doubt i'm really any help here.... but i've no real idea what you're getting at. sounds like you should get a tech inspector over to look at the car and what you're thinking.

[Brian]

Non-stressed panels like the crossle side panels and similar can be riveted on with rivets no closer than 6" which seems straight forward to me. I confess I can't quite create a problem with this. Floors MUST be stressed, which implies that the rivets must be closer together and the floor can be bonded, and cockpit front and rear bulkheads may be stressed.

The only way I can come up with an issue is with a non-stressed panel that has a horizontal line of rivets at 6" spacing, then a vertical line of rivets tying the panel to a brace, and one of the vertical rivets wants to be closer than 6" to one of the horizontal rivets. In which case either do it and see if anyone cares, drill one out if some one does, or don't do it.

Brian

[EYERACE]

Can you imagine a tech inspector doing an annual......or a fellow racer.....going over to someone's car [that is from 1978] and measuring how far apart rivets are? maybe at the runoffs tech shed post race.

Hmmmmmm....eye should have thought of this before the frame up.

I might imagine a tech inspector doing so to a car trying to get a log book for the first time......but even thinking about this very long gives me a headache. Hey, recently, not only did no one protest the car but the officials let it go also when the winning FF at an event [where scales from the 14th century were the "official" scales of the event] ....and the car weighed 1090 instead of 1100......i think it was getting hot that day, so the impound officials decided to ignore their routine rivet measures. point: yes there are rules but the word latitude is in everyone's vocabulary for a reason....so that one might be a reasonable person.

If you must place a rivet or two a little closer than 6" to make the construction work, OK by me......apparently this is a rule, eye guess, .....so as long as your entire fabrication on the side panels is not terribly crammed in closely I doubt it will matter to anyone

[Art Smith]

it has become pretty obvious the previous post wasn't clear enough or was too criptic so attached is an illustration of the geometry in question. the question is posed in the hopes of better understanding what's compliant with the rules as currently written, not with what's reasonable. I'm looking for every bit of torsional stiffnes I can find that's compliant with the rules as currently written.

the rules as currently written includes a linear criteria on attachment spacing and says nothing about non-planar spacing.................. does anyone know of any applicable historic presedents dealing with out-of-plane attachment spacing???

Art
artesmith@earthlink.net

[Roland V. Johnson]

6 in centers, means 6 in centers. (ie within a 6 in radius) An extra rivet every now and then has been accepted, but not within a 6 in radius as standard practice. And yes I have seen someone dinged with 5 in spacing.

[Art Smith]

I understand and have NO questions about the criteria for fastener spacing in a single plane;
ie: X**2 + Y**2 ≥ 36.0 . my question is about historic precedents that might shed light on out-of-plane spacing. I see nothing in the rule as written that suggests or even hints at the spacing requirement being spherical spacing criteria (ie: X**2 + Y**2 + Z**2 ≥ 36.0); all the other distance criteria are linear (ie: planar)!!


Art
artesmith@earthlink.net

[Art Smith]

after a good night's sleep here's a better diagram of the question:

given a rivet on the vertical leg of the sheet material located at position "A", which of the two other positions shown on the horizontal leg of the sheet material would be compliant with the rule as currently written, "B1", "B2", BOTH, NEITHER. NOTE: the centerline of rivet "A" intersects the centerlines of rivets "B1" and "B2" so the distance between the center of rivet "A & B1" and the distance between the center of rivet "A & B2" are both zero..........................?

in thinking about the rationale for your answer to the rivet spacing question, keep in mind that structural adheasive bond lines are "areas" and it takes even less thought to manipulate the centerlines or centers of large areas to be greater than 6.00 inches......................................


Art
artesmith@earthlink.net