Has anybody here used structural foam on their 914 to increase structural rigidity?

Here is the original Abstract of that SAE paper 1999-01-1785

"Stability and structural integrity are extremely important in the design of a vehicle. Structural foams, when used to fill body cavities and joints, can greatly improve the stiffness of the vehicle, and provide additional acoustical and structural benefits.This study involves modal testing and finite element analysis on a Sport utility vehicle to understand the effect of structural foam on modal behavior. The modal analysis studies are performed on this vehicle to investigate the dynamic characteristics, joint stiffness and overall body behavior. A design of experiments (DOE) study was performed to understand how the foam's density and placement in the body influences vehicle stiffness. Prior to the design of experiments, a design sensitivity analysis (DSA) was done to identify the sensitive joints in the body structure and to minimize the number of design variables in the DOE Study."

And the Conclusion:

"The most sensitive area of the body were found to be the A-pillar, the D-pillar and their joints. With structural foam injected into this sensitive areas, the vehicle body was significantly stiffened, as shown by the increase in modal frequencies. The 1st torsional mode was most effected with an increase of 29.1% in modal frequency.The design sensitivity analysis and design of experiments described here, can be used to identify the sensitive ares of the body structure. This results are useful in the determining the best application locations for structural foam."

Foam doesn’t have a good rep in our cars.

Peeps take the foam out of their 914's.

Rear/trunk and the rollbar have foam, consensus is it attracts rust (moisture).

I understand that the foam originally used attracted moisture and was generally the cause of rusty mayhem.

This modern structural foam, appears to posses different characteristics... Amongst them, it does not retain but repels moisture.

I've used commercial structural foam on large steel tanks, exposed to the elements and was amazed at its durability and performance. Then I saw the SAE paper and thought I'd ask the Gurus.

Thanks for the input

Sounds interesting.
Could you post the full address to the paper?
My phone wants to call that number above.

I think it might be the same issue as trying to use adhesives instead of welding in our cars. The structure needs to be designed for the construction materials and meathods.

In my opinion, this is something a modern OEM would do, in order to build a car as cheaply as possible. I don't see it being relevant to restoring an old Porsche -- metal is relatively inexpensive for us.

Maybe if there was a foam that absorbed rust...

Here's the paper:

http://www.mwsmotorsports.com/z32/foam/1999-01-1785.pdf

Thanks for posting.

Agree on foam being a source of horrors historically but I think this deserves a second look today. Sprayed inside a properly rust proofed cavity (with venting) I think this could be a viable option for people who don't weld.

The structural improvements all the car makers are chasing can't be arrived at via more metal due to weight issues - I believe this is part of their solution.

All that said - someone else can go first. Grin.

I'm also looking for some articles by Mike Kojima - He foamed a 300ZX! Since then I've been reading more and more about the benefits... it appears that the 8# foam offers the best results.

On the matter of applying this technology to a 914, I think I'm going to try it. I just don't see any downsides... yet

I also am going to get rid of the targa roof and replace it with a hard roof. The idea is to make the chassis as rigid as possible without the use of a roll-cage.

Please keep us posted and document what you do.

We should ideally come up with some independent and repeatable measure or it's all subjective.

Well firstly, I just settled with the USPS (after 2+ years!) and can now straighten my car and put it back to factory specs. Then we will head into the great unknown. I'll be sure and keep everybody abreast of anything and everything.

BTW, There was a dark blue 914 that had a hardtop (w/sunroof!) from a 944 grafted on. Does anybody here own that car? When last I read about it, it was for sale in Las Vegas, I believe.. It would be interesting, from a historical perspective, to see how that 914 has held up. and maybe do an A-B comparison, if possible.

Anyway, if anybody finds out anything please post it, as I read these forums constantly.

The build was (sort of) documented here. I say "sort of" because some parts were skipped...

Here's the thread: http://www.914world.com/bbs2/index.php?sho...=76305&st=0

It has been sold on here a number of times; TC seems to keep buying it back and then re-selling it.



Here is a thread about AA fabricating a 916 type roof: http://www.914world.com/bbs2/index.php?sho...c=66687&hl=

--DD

Is there any data / observations as to how its dynamics differ from a conventional 914?

Anybody here driven it?

Is it for sale?

I'd love to hear about it.

Thanks!

Modern car bodies are built from steel that is already rust protected from the mill and then the fully welded chassis is dipped in an ED coat bath to further protect it and seal all welds etc. I think that any foaming operations are performed after the ED coat which means that to do it on a 914 with the same level of protection you'd need to acid dip and e-coat the chassis. The foam wont perform as intended if all it bonds too is surface rust which sadly coats the inner panels on most of our cars.

I have owned it twice - the roof was the best part of the car. When I got it the 2nd time, the carbs had been gone thru my MotorScheister and it was a different car. It's in New Hampshire now or as far as I know

Thanks for the info. I always thought that car was a brilliant interpretation of what the 914 was supposed to be, had production continued. Did you notice any difference in driving characteristics? Did the durability of the chassis / car change? Any other observations of note?

Only twice? It seemed like more....

--DD

Yes, it is in NH - or technically in MA in storage. Bought it from TC with plans to put a 3.2 in it, but life got in the way. I bought another 914-6 conversion to keep me entertained until I have time to address this.

Can you share any differences in driving the hardtop? Anything noticeable?

@jss297 See the post above Beebo Kanelle has a question? Beebo you can send a notification to a user by using the @Username, does not work for you as you have a space in your name.

hope that helps you get the answer your looking for.

Foam in older cars not good idea. I am a firm believer in foam for structural enhancement, it is used all the time in Marine applications. I used it on the retoration of my boat, installed drain channels into the bilge and then foamed all under deck cavities. But it is fiberglass with wood stringers, and a 3/4" pressure treated deck. I never want to go back and redo the floor on that boat.

I will most likely purchase a different one, and it will most likely have a floor made of pulp, and do it all again.

Foam in a car that has rust = bad idea, and all 914s have rust, unless acid dipped metal repaired, proper holes installed and the EDM coated.

Also if you foam the logs, you will crush the paper tubes that are in there to keep the heat going in the proper direction.