Damaged Carbon Frame - Power Loss?

A few months back an airline guerilla decided to smash up my wife's
carbon frame. (Stupidly it was being transported in cardboard... we
have learnt this lesson). The bottom tube was impacted such that the
impacted area felt like thick paper. (It felt like it could be pressed
all the way through with your thumb). Basically the integrity of that
area was completely compromised. I looked around for a while as to
whether this could be repaired. There are a lot of different opinions.
Eventually I found a shop that had a guy who makes carbon frames and
fixes them. His approach was to cut out the effected area and then do
some process to fill it all in. Sanded back and a new paint job and to
the eye and touch it seems brand new. However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

GH - Sydney wrote:
A few months back an airline guerilla decided to smash up my wife's
carbon frame. (Stupidly it was being transported in cardboard... we
have learnt this lesson). The bottom tube was impacted such that the
impacted area felt like thick paper. (It felt like it could be pressed
all the way through with your thumb). Basically the integrity of that
area was completely compromised. I looked around for a while as to
whether this could be repaired. There are a lot of different opinions.
Eventually I found a shop that had a guy who makes carbon frames and
fixes them. His approach was to cut out the effected area and then do
some process to fill it all in. Sanded back and a new paint job and to
the eye and touch it seems brand new. However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????


I'm no expert, but 20 minutes seems a lot of time for a bit of flex in
the frame.
Are these races time trials? If yes, you should be sure that conditions
are always the same (wind, etc), which is not easy.
If no, IMO it makes no sense to compare times.

Just my 0.2$
(I see a looooooong thread starting here :-) )

On 23 May 2005 21:26:35 -0700, "GH - Sydney"
wrote:

[snip]

. . . times
over 180 km are about 20 minutes down on normal and all other things
are equal . . .

[snip]

Dear G.,

A rider used to cover 180 km in X minutes, but is concerned
by recent times over the same course rising to X + 20
minutes.

Assuming that it used to take 300 minutes and now takes 320
minutes, the ride time has increased 6.7%.

For the same 111.85 miles, the average speed dropped from
22.37 mph to 20.97 mph, 1.4 mph slower.

It is highly unlikely that all other things are equal. No
gentleman would suggest that the rider's output could have
dropped, but the bike could have a problem or the wind could
have blown differently.

The wind is quite likely. Here's a calculator to play with:

http://www.kreuzotter.de/english/espeed.htm

When I place your wife on a triathlon bicycle, reduce her to
100 pounds and 5'4" (take her out to dinner after this
calculation), set the trip distance at the bottom of the web
page to 112 miles, and leave everything else at the
defaults, the results are a happy 22.4 mph and 5:00:00.

But if I increase the wind from a dead calm 0 mph to a
steady 2.2 mph headwind, your poor wife crosses the finish
line dead last at 5:20:00 at only 21.0 mph.

(Raising the temperature from 68F to 86F doesn't make up for
the headwind, but it does improve her time four-and-a-half
minutes, reducing it it to 5:15:30. The barometric pressure
will change things, too, but isn't available on this
calculator.)

Over a 112 mile course, a significantly cracked carbon frame
is much easier to detect than a 2.2 mph headwind increase,
which is little more than half a brisk 4 mph walking speed.

Carl Fogel

For clarification, the 20 minute decrease is a subjective assessment
compared to times ridden by other competitors she has competed against
many times. Its not a comparison between two events on the same course
under different conditions. So, the question is : could the damaged
carbon frame, even after the repair described, result in a significant
power output reduction (of say 5%)?

GH - Sydney wrote:

For clarification, the 20 minute decrease is a subjective assessment
compared to times ridden by other competitors she has competed against
many times. Its not a comparison between two events on the same course
under different conditions. So, the question is : could the damaged
carbon frame, even after the repair described, result in a significant
power output reduction (of say 5%)?

If this were to be the case it would be evident to someone not used to
the bike if he/she would be to ride it. If the repair doesn't show up
the tube isn't flexing very much at that point and stiffness should be
the same or even increased.

Check alignment and for changes in the seating position. Did you change
components, say tyres?
--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

"GH - Sydney" wrote in message
oups.com...
However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????


Borrow a new bike/frame, similar spec, and see what happens.

wrote:
On 23 May 2005 21:26:35 -0700, "GH - Sydney"
wrote:

[snip]


. . . times
over 180 km are about 20 minutes down on normal and all other things
are equal . . .


[snip]

Dear G.,

A rider used to cover 180 km in X minutes, but is concerned
by recent times over the same course rising to X + 20
minutes.

Assuming that it used to take 300 minutes and now takes 320
minutes, the ride time has increased 6.7%.

For the same 111.85 miles, the average speed dropped from
22.37 mph to 20.97 mph, 1.4 mph slower.

It is highly unlikely that all other things are equal. No
gentleman would suggest that the rider's output could have
dropped, but the bike could have a problem or the wind could
have blown differently.

The wind is quite likely. Here's a calculator to play with:

http://www.kreuzotter.de/english/espeed.htm

When I place your wife on a triathlon bicycle, reduce her to
100 pounds and 5'4" (take her out to dinner after this
calculation), set the trip distance at the bottom of the web
page to 112 miles, and leave everything else at the
defaults, the results are a happy 22.4 mph and 5:00:00.

But if I increase the wind from a dead calm 0 mph to a
steady 2.2 mph headwind, your poor wife crosses the finish
line dead last at 5:20:00 at only 21.0 mph.

(Raising the temperature from 68F to 86F doesn't make up for
the headwind, but it does improve her time four-and-a-half
minutes, reducing it it to 5:15:30. The barometric pressure
will change things, too, but isn't available on this
calculator.)

Over a 112 mile course, a significantly cracked carbon frame
is much easier to detect than a 2.2 mph headwind increase,
which is little more than half a brisk 4 mph walking speed.

Carl Fogel

What about her average pulse rate. Has that changed? Pulse rate is a
rough guide to energy expenditure. What does her pulse monitor say?

Marty

GH - Sydney wrote:
She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????


I find it very unlikely that a normal feeling downtube could be allowing
significantly more flex without other obvious symptoms (feeling very
flexy when pedaling hard standing). Even if the frame was flexing a bit
more now, it shouldn't affect TT riding, since that is pretty much
steady effort seated riding.

Of course none of this matters if she is convinced her frame is at
fault, sounds like new frame time to me.

"GH - Sydney" wrote:

Eventually I found a shop that had a guy who makes carbon frames and
fixes them. His approach was to cut out the effected area and then do
some process to fill it all in. Sanded back and a new paint job and to
the eye and touch it seems brand new. However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

If the frame was flexing enough to make THAT much difference, it would
be very obvious (she'd be scared to stand up to climb, for example).

The one thing you might check is the bottom bracket alignment. You
should be able to sight between the chainrings, and see the middle cog
on your cassette. This could be off to the right or left by a cog,
but should be very close, and the cogs and chainrings should be
obviously parallel (any misalignment should show up fairly well).

You might also think about checking the bottom bracket and wheel
bearings for wear, and toss on a new chain just to be safe.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

m-gineering wrote:
GH - Sydney wrote:


Check alignment and for changes in the seating position. Did you
change
components, say tyres?
--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

I think Martin is right with looking at the alignment, I would go a
step further and check the entire frame, rear dropouts forward. The
description of the repair seems odd to me but I didn't see it so ..