composite tie-in

[jack]

the issue of monocoque vs. tube frame has been debated fairly thouroughly on this forum, but i dont think anyone has addressed the practice of "tying in" composites with tube frames. do many schools do this? how effective is it in stiffening up a tube frame?? anyone have any prefered methods or materials? got pics? just wondering what you guys think...

JACK
www.etec.wwu.edu (http://www.etec.wwu.edu)

[Schumi_Jr]

It is 5:06 in the &*(#&^*@ morning. After starting laying up a stupid cf shear plane on the rear of our car at 9 we finally got the stupid vacuum bag to seal. If you want to do composites go ahead, lose your sleep! I guarantee you that none of your lay-ups will finish before 3. good luck

OUT!

Aaron Johnston
University of Waterloo FSAE

www.eng.uwaterloo.ca/~fsae (http://www.eng.uwaterloo.ca/~fsae)

[Schumi_Jr]

ya 14 inHg on the vacuum! I'm goin the $%*#&*^ home!

Aaron Johnston
University of Waterloo FSAE

www.eng.uwaterloo.ca/~fsae (http://www.eng.uwaterloo.ca/~fsae)

[vinHonda]

I didn't know it was called "tying in". But it is very effective. I don't think many schools do it.

Vinh

University of Toronto Formula SAE Racing Team
www.fsae.utoronto.ca (http://www.fsae.utoronto.ca)

[jack]

i dont know if it is called "tie in" or something else. that is just what i have heard it called, i am refering to the technique of building a space frame, and then laying up composites between the tubes.

JACK
www.etec.wwu.edu (http://www.etec.wwu.edu)

[tommy]

Its called a stressed skin if i remember right, and Rensselaer did it in 2002.

[Garbo]

We do it, too... cheaper than monocoque, lighter than equivalent all-tube frames. Nice and stiff and lets you use all sorts of fun things as structure :-) The issue is at the edge of the core, next to the tube, and the bond between the carbon and the tube. Good surface preparation on the tubes is essential. Also, make sure the stiffness of the tube and carbon are as close as possible (the traditional carbon design mistake).

www.formulamun.com (http://www.formulamun.com)

[Schumi_Jr]

To save face for my stupid previous comments...

Waterloo extensively used cf shear panels on our 1999 and 2000 cars. It was very effective and the concept progressed to a full-front monocoque for 2001.

Stressed composite panels are way more feasable to do than a pre-preg tub for FSAE (you don't need access to a 'clave). I personally think that for the target of FSAE vehicle design (weekend autocrosser) a tube frame or tube frame with shear panels is a better design. Our tub is sooo damn sexy though http://fsae.com/groupee_common/emoticons/icon_wink.gif

Aaron Johnston
University of Waterloo FSAE

www.eng.uwaterloo.ca/~fsae (http://www.eng.uwaterloo.ca/~fsae)

[Gareth]

Jeeze Schumi_Jr, don't you think you're a little OFF-TRACK? Hope you don't DNF on the DRIVE home from work. It'd be the first time in 25 days of driving, right? And with all that EXPERIENCE... Okay okay. You gotta love race season. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Garbo]

I keep wanting to do do the full monocoque deal but something in the back of my mind (an/or the fist of the treasurer) always makes me draw tubes. I think I can rationalise the monocoque because it _should_ be easier to bag. Sealing a vacuum around the chassis tubes is a raving slut! (I dunno whay everyone else does, but we lay up most of our panels in place on the car...). No matter what, though... it seems like almost all of the really late nights involve epoxy and cloth. I guess that's the hazzard of 'glass bodywork, once you mix a batch of epoxy, you can't leave!

As of thursday, I will be saying goodbye to Finland and resuming the 20 hour per day fabbing marathon.... mmmmm... racing is in the air!

[Howard]

We should have some stressed skins on this year's car. I'm not sure if they'll be carbon or al sheet this year though.

Vacuum bagging a frame is a major PITA. Good luck forcing a bag to seal if you have just a small leak in the suspension mounting points. Getting consistant surface finish across a carbon panel on the frame is next to impossible. I know I get all sorts of small air bubbles and I'm double sealing my bags.

It is not something to be done on a whim.