DB-4 rebuild

[Westroc #19]

I thought it would be fun to document our new project. If anyone has some advice that they would like to offer, please do. This is our first Atlantic and this car looks to be pretty difficult to work on. Should be fun.

[Steve O'Hara]

Look just about the same as mine! Here are a few pics....

I took the back off today to remove the fuel cell and allow access to the seatbelt mounts that have to be relocated for use with a HANS device. Cell shows signs of small leakage and there was a lot of crap on the cell cavity that could cause trouble if it got under the bladder.

I have all the front suspension bulkheads and steering rack out of mine for inspection and cleaning. Needed to get the stuff out of the way to replace the pedal mounts as mine had been hacked up by someone along the way.

I have found only one very small area where the aluminum skin has detached from the honeycomb..... anyone out there know of any way to fix that problem? Maybe some kind of resin that can be injected in some manner?
Regards,
Steve O'Hara

HAPPY NEW YEAR!

[Dave Welsh]

There is some good info in this thread. http://www.apexspeed.com/forums/show...&highlight=db4

[Paddy O'Brien]

The only real weak link on the now 15-20 year old DB4 is the tub. Now that you guys have your cars down to the bare tub, I highly suggest that you closely inspect the aluminum bottom of the tub. Even if your car was never raced I would bet that if the tub is original,at the very least the honeycomb glue is dried out by now. And if your car has been raced before, you can be sure that it is no secret that the DB4 works best the lower you can drop the car so the tubs get bounced off the pavement alot(use lots of jabroc!) Althought it is a pain in the ass, I would pull the floor(replace it) and have a good look as well as do an x-ray of the top. Or at least get another opinion of someone who is really familiar with the DB4. Otherwise if your tubs are like most DB4's out there, shock changes won't do much and you will need a ton of pre-load at the front to get the car to turn-in......ask me how I know!!!

[Charles Warner]

I have found only one very small area where the aluminum skin has detached from the honeycomb..... anyone out there know of any way to fix that problem? Maybe some kind of resin that can be injected in some manner?

Steve,

As is mentioned in the thread shown above, delamination is a problem in these older tubs. If you can see any delamination at all (as you state) then there is a lot more happening than you probably want to know (but you need to find out) and the admonition to get the tub x-rayed is a good one. Take care of the issue now while the tub is accessible and repairs can be made. You might even consider a complete retub by someone really familiary with these cars.

[Steve O'Hara]

Charles, Paddy,

Thanks for your suggestions. I now have my tub stripped down to the bare aluminum and original gel coat on the top glass section, the rear panel removed to access the fuel cell compartment and the cockpit side panels that cover all of the wiring and plumbing removed. Using careful visual inspection and "sound" testing over the entire tub I have found only one area of about 1" x 2" where delamination can be detected. It's a small area just below the oval shaped opening in the tub where the rear brake line, clutch line ARB cable etc exit the tub. To my surprise, the tub is in very good condition from a structural point of view. The car has been fitted with jabrock so the floor is in great shape. I have inspected every rivet on the tub I have not found a single one missing or loose and the panel adhesive has been fully bonded in each location where I have removed pieces.
This one seems to have survived the 17 years in pretty good shape so it will be interesting to see how it behaves.

Paddy, I'm curious about your remark
>>>Otherwise if your tubs are like most DB4's out there, shock changes won't do much and you will need a ton of pre-load at the front to get the car to turn-in<<<<

I assume you felt your tub was flexing but I wonder why you felt eliminating the front suspension was the way to address that problem?
Regards,
Steve O'Hara

[Paddy O'Brien]

Steve, Please take my comments with a grain of salt because I usually only race my DB4 about 4-5 times a year so I may not be the most sensitive to minor changes. My original tub also looked pristine but developed a small delam area on the lower front of the tub. I could never actually feel the tub flex but a few seasons ago I noticed that shock changes(rebound in particular) became less and less effective. Finally, by the 2004 season the car just would not turn into corners as quickly as it used to. I would turn the wheel and there would be a noticeable delay before the car would turn. With most DB4 setups the car likes a little bit if pre-load on the front springs, maybe half a turn, but eventually we cranked in almost three full turns which did help the car turn in better but then corner exit traction suffered. My lap times increased about a second or so at most tracks and I just figured that the problem was me getting older and slower. With the new tub installed the lap times have dropped back down(I am young again!) and we are back to only using a small amount of pre-load at the front, but I can not actually say that I can "feel" a difference.

[Paul LeCain]

I've replaced/reglued the bottom of a DB-4. Given where you are in stripping this one, it's not an awful job. In the long run, you'll save yourself a lot of grief by doing it now.

Even though you can find only one delamination, I'm betting there are more. It can delaminate between the honeycomb and the outer skin, and also between the honeycomb and the inner skin. The second one is next to impossible to detect without removing the bottom.

[GregoryJ]

I stripped mine down to the bare tub as well to remove layers of paint (very few) and inspect. The belly showed no signs of any de lamination and all the rivets were tight and in place. There is no jabroc on the tub only the tunnels at the moment.

Regards,
GregoryJ

[Charles Warner]

I stripped mine down to the bare tub as well to remove layers of paint (very few) and inspect. The belly showed no signs of any de lamination and all the rivets were tight and in place. There is no jabroc on the tub only the tunnels at the moment.

Gregory,

Simply because there are no signs of delamination visible does not really mean anything. Paul is trying to explain that, like an iceberg, the vast majority of the nasty stuff will be unseen - below the surface.

Probably the best thing a small shop can do is, as Paul explained, pull the bottom skin allowing for much better examination and, of course, regluing of (preferably) a new outer skin with new rivits. Just because rivits are tight to the feel means little.

With very little delamination, in areas you'd never expect, setup can be a nightmare. The first indication is when you put the car on the scales and none of your adjustments are repeatable or they are way off relative to side to side adjustments.

You can always test the rigidity of your tub. Contact Richard Pare as he has a fairly easy method of doing this and I'm sure he'll share it with you. Might as well take care of the important stuff at this stage on the rebuild.

[Steve O'Hara]

Charles, Paul,

I'm not sure I understand what you are saying when you suggest removing the "bottom skin". To do so would effectively destroy the bottom half of the tub in my opinion. You can't remove the "bottom skin" without also removing the outside sheet aluminum from the sides of the tub all the way up to the intersection of the upper and lower portions. Doing so would almost certainly damage or destroy the fragile "honeycomb" material that bonds the inner and outer sheets together and even if it didn't I doubt a new outer/bottom skin can be fabricated and glued back to the original honeycomb material with any greater assurance of a complete bond than the original material even in an aged condition.
I also take issue with the remarks about the the condition of the rivets not meaning anything. If structure has weakend such that it will deflect under load the movement would compromise the integrity of the rivets.
Paul, any chance you took pictures of the process you describe as "I've replaced/reglued the bottom of a DB-4"..... I would be very interested in seeing exactly what you did.
Thanks,
Steve O'Hara

[Charles Warner]

Steve,

Any tub can be re-skinned if needed in case of damage. My suggestion is to find a shop near you that is experienced with the DB-4 and ask them for their suggestions. It would be great if you could take the tub to them for inspection. These cars have been beat pretty hard and there are all sorts of weaknesses that can be hidden. I inspected my Shadow tub carefully and had it professionally looked at. However, a season later the tub was flexing so much that suspension changes did very little. Rivits may seem tight but if the bond of the epoxy is broken or weak then they do very little. A damaged area that is rivited back together without proper preparation of the flanges and epoxying is not much of a repair. The epoxy IMO is what keeps the monocoque's strength, not the rivits. The rivits hold the structure together so the epoxy can bond. Obviously the rivits provide strength as well, but not the primary force. Of course, a structural engineer can expound and prove me out to lunch.

As has been stated, if you are at this stage of prep it is the proper time to get the tub back to as good as you can. Sort of like Fram's commercials - pay me now or pay me later. Might as well have as good a car as you can. Nothing worse than a car that doesn't respond to changes.

[Steve O'Hara]

Charles,

Sorry to be so full of questions so bear with me here.... when you say re-skin are you saying that the outer/bottom layer of sheet aluminum is detached from the honeycomb aluminum leaving the honeycomb attached to the inner sheet of aluminum? If so, how does one go about peeling the outer sheet off without damaging the honeycomb or detaching it from the inner sheet?

Thanks,
Steve O'Hara

[Paul LeCain]

On mine, when I drilled out the rivets, including the hard ones around the seat area, the bottom skin turned out to be more delaminated than I thought. Even so, it did mess up the honeycomb somewhat to remove it.

The honeycomb was also, in a few places, separated from the inner skin. That's what I meant when I said you'd never see that if you didn't remove the bottom.

I had a new bottom made, using slightly thicker aluminum. I replaced/reglued to the inner skin all the damaged honeycomb.

At this point I took the opportunity to add some extra nutplates and holes in the new bottom. I wanted to be able to replace the skid plate in two parts and needed more holes than were there originally.

Before gluing/riveting the new bottom, I washed it with a pre-paint solution and went over all the gluing surfaces with a 36 grit wheel to help the glue's adhesion.

Then I glued/riveted it all back together. The glue was something called Furane 420, an aircraft structural glue. It had an 'open' time of about 6 hours which was real handy when you're putting back a couple hundred rivets. I don't know if it's still available, but there are other glues available.

The car, I'm happy to report was a lot better after all this work.

[Steve O'Hara]

Paul,

Thanks for the thorough description of the proceess.... sounds like an interesting project! I'll be studying my tub very closely over the weekend to hunt for evidence of additional trouble spots.
Regards,
Steve O'Hara

[Westroc #19]

Wow. I forgot I started this thread. Car is coming along. Slower than we had hoped. Racing keeps getting in the way

We have the motor back and may be installed soon. Depends how things go for us at Grattan at the end of the month.

[H82BSLO]

So...how was the tub in the end ??

[Westroc #19]

Tub was sent to Pat Prince. Tub was inspected and given a clean bill of health. We did have Pat fab a new rear bulk head, which we installed.

[DB4 Tim]

Any pictures of it finished ?

Tub was sent to Pat Prince. Tub was inspected and given a clean bill of health. We did have Pat fab a new rear bulk head, which we installed.

[H82BSLO]

Good news...I just bought one and I have no intention of ripping the tub apart to check inside either !!

[Westroc]

To H8slo and all:
You may not have intentions of ripping it apart and really I didn't either but stuff happens. One of the reasons I THOUGHT something might be suspect was as follows. The aluminum wall at the end of the tub [actually it's a honeycomb piece] has a row of rivets right along the bottom in the centre. If ANY of them are loose or worse not there anymore then Houston you have a problem. Why? Since the engine is stressed it is moving becuse of issues [perhaps yet undiscovered] and the bulkhead has flexed enough to allow the rivets to get loose or fall out.
No there are no completed pics. The engine and hence the back of the car needs to go in.
For a laugh when I started typing this I made a typo and typed DB-$ with the dollars sign. Had it right the first time !

[DB4 Tim]

Which one did you get?

Good news...I just bought one and I have no intention of ripping the tub apart to check inside either !!

[H82BSLO]

It used to belong to Bill Pratt from Texas for many years, I bought it from Charles Duncan. It hasn't been used much for the last 15 years but seems to handle well enough.

[DB4 Tim]

Is it Toyota....got to get some pictures up here.

It used to belong to Bill Pratt from Texas for many years, I bought it from Charles Duncan. It hasn't been used much for the last 15 years but seems to handle well enough.

[H82BSLO]

Toyota.....

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[DB4 Tim]

SWEET....love the looks of DB's...very good looking ride

It used to belong to Bill Pratt from Texas for many years, I bought it from Charles Duncan. It hasn't been used much for the last 15 years but seems to handle well enough.

[Charles Warner]

It used to belong to Bill Pratt from Texas for many years, I bought it from Charles Duncan. It hasn't been used much for the last 15 years but seems to handle well enough.

I believe there were two Bill Pratts. One was a serious amateur Club racer and the other was a serious pro racer. It would be instructive to determine which this was and contact him regarding the history (I.e. damage/repair) of the car. I was acquainted with the Club racer and he was always very easy to get to know and took care of his equipment well. He eventually graduated to an RT-41 and I sold him all of the remaining RT-41 factory parts. His crew chief was Mike Mitchell of Midland-Odessa IIRC.

[H82BSLO]

if there were two (I think they are one and the same) it belonged to the amateur one. I do know Curtis Farley drive it in its first race, Long Beach GP. And I know it has been damaged a couple of times. would love to talk to BP. number anyone ?

[Charles Warner]

Mike Mitchell was at 915.687.4666

If there was any serious damage the tub should be x-rayed, especially if any corners were taken off.

[H82BSLO]

Thanks, will try him.

[Westroc #19]

There is light at the end of the tunnel. We need to finish up some plumbing and wiring and we'll bring this thing to life.

[DB4 Tim]

VERY cool...but we need more pictures

[Westroc #19]

I'll be out at the shop by the end of the week. If we make more progress, more pics will be posted.

Can't wait to mount up the side pods and get this car on the ground.

[DB4 Tim]

It looks great....

[Westroc #19]

Thanks. It's been a long build. Very rewarding though.

[DB4 Tim]

Do you happen to have any more pictures of the rear wing and mounting of it...very interested in how different wings are mounted on DB4's

Toyota.....

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[Westroc #19]

We still haven't fired it up, but she's on the ground.

[Rick Ross]

Very nice work. Can you post a picture without the engine cover?

[DB4 Tim]

you should be very proud....

[LAJ]

You Guy's Know how to do it RIGHT!!
First Class Rebuild !!
A clip of it running on Youtube soon?
Lee