Author: "pepeborja925mb" <pepeborja925mb@...> Time: Tue Nov 29, 2005 1:53 pm PST Link
Instructions are not clear on this but do the 704 bulkhead (you know,
the two big beefy ones for the center spar section) flanges that attach
to the center bottom skin get dimpled or machined c-sunk? Dan C's site
appears to have it dimpled, but I just want a second opinion before I
let loose 90 psi's of force on that lovely flange.
The only thing on the instructions is a note to skip 5 holes and
instead c-sink to the skins for a flush finish with the forward floor
ribs. This last instruction seems odd to me since a guy could just
dimple the rib to match the flange, which seems odd too again because I
think I just answered my own question: Dimples; otherwise, why the
advice on c-sinking skins.
Jose Borja
Elk Mound, WI Finally pounded a few rivets on the rear fuselage
Author: "Dan Checkoway" <dan@...> Time: Tue Nov 29, 2005 2:35 pm PST Link
Dimple the F-704 flanges.
Rule of thumb...countersink for AN426AD3-x rivets only when the material is
.040" or thicker. Dimple when it's .040" or thinner.
How's that for ambiguity? So what do you do if it's .040"? I always dimple
whenever possible. When given a choice, I would rather dimple than *remove*
material.
Unrelated note: when installing nutplates, use NAS1097AD3-3.5 rivets (Van's
sells them) and countersink -- only slight c-sink is needed with those
rivets, so you don't bottom out through the material.
)_( Dan
RV-7 N714D (708 hours)
http://www.rvproject.com
----- Original Message -----
From: "pepeborja925mb" <pepeborja925mb@...>
To: <RV7and7A@yahoogroups.com>
Sent: Tuesday, November 29, 2005 12:48 PM
Subject: [RV7Yahoo] 704 bulkead - csink or dimple?
> Instructions are not clear on this but do the 704 bulkhead (you know,
> the two big beefy ones for the center spar section) flanges that attach
> to the center bottom skin get dimpled or machined c-sunk? Dan C's site
> appears to have it dimpled, but I just want a second opinion before I
> let loose 90 psi's of force on that lovely flange.
>
> The only thing on the instructions is a note to skip 5 holes and
> instead c-sink to the skins for a flush finish with the forward floor
> ribs. This last instruction seems odd to me since a guy could just
> dimple the rib to match the flange, which seems odd too again because I
> think I just answered my own question: Dimples; otherwise, why the
> advice on c-sinking skins.
>
> Jose Borja
> Elk Mound, WI Finally pounded a few rivets on the rear fuselage
> Van's Air Force - World Wide Wing
> www.vansaircraft.net
> Yahoo! Groups Links
Author: "Bob Collins" <bcollinsrv7a@...> Time: Tue Nov 29, 2005 4:07 pm PST Link
I countersunk. The thickness was of sufficient amount to allow
countersinking, but I was also mindful of not wanting to distort the
flanges in any way (you may remember a similar warning for the flanges
of the wing spar.
But most folks I've run across have dimpled here.
I doubt it much matters because that whole section is just a frickin'
tank. It's built solid.
--- In RV7and7A@yahoogroups.com, "pepeborja925mb"
<pepeborja925mb@y...> wrote:
>
> Instructions are not clear on this but do the 704 bulkhead (you
know,
> the two big beefy ones for the center spar section) flanges that
attach
> to the center bottom skin get dimpled or machined c-sunk?
Author: "Brad Bellamy" <rvbuilder@...> Time: Tue Nov 29, 2005 4:48 pm PST Link
I had to think about this one a little bit also.
I ended up dimpling except for the 4 places they specifically say to CS on
the 704 fwd bulkhead.
The dimples turned out really nice. No distortion of the flange. The
flange is much thinner than the flange of the main wing spar.
Brad
Austin
-----Original Message-----
From: RV7and7A@yahoogroups.com [mailto:RV7and7A@yahoogroups.com]On Behalf Of
pepeborja925mb
Sent: Tuesday, November 29, 2005 2:48 PM
To: RV7and7A@yahoogroups.com
Subject: [RV7Yahoo] 704 bulkead - csink or dimple?
Instructions are not clear on this but do the 704 bulkhead (you know,
the two big beefy ones for the center spar section) flanges that attach
to the center bottom skin get dimpled or machined c-sunk? Dan C's site
appears to have it dimpled, but I just want a second opinion before I
let loose 90 psi's of force on that lovely flange.
The only thing on the instructions is a note to skip 5 holes and
instead c-sink to the skins for a flush finish with the forward floor
ribs. This last instruction seems odd to me since a guy could just
dimple the rib to match the flange, which seems odd too again because I
think I just answered my own question: Dimples; otherwise, why the
advice on c-sinking skins.
Jose Borja
Elk Mound, WI Finally pounded a few rivets on the rear fuselage
[Non-text portions of this message have been removed]
Author: "Bruce" <wingtime@...> Time: Tue Nov 29, 2005 10:03 pm PST Link
I countersunk the center skin here all the way. They did this on the
Orndoff video. I was talking to Vans about something or another I made
a bo-bo on and they said either way would work. I went for the c-sink
since it left the whole flange smooth on the inside and I didn't have
to worry about certain rivets.
Author: "pepeborja925mb" <pepeborja925mb@...> Time: Wed Nov 30, 2005 7:24 am PST Link
Thanks for all the replies. After a closer look I saw the flange on
704 was a thin one and dimpling was done. I actually built the entire
skeleton yesterday in the evening.
Riveting of the top hole on each rib on the 705 bulkhead was awkward
due to the slope of the seat rib interfering with the tools, so I ended
up using blind rivets for the top holes. Quick and easy that way,
actually the whole thing would have been easier to do with blind
rivets. I am not sure why Van's always insists on using machined
fasteners to join ribs to bulkheads. It's not like we are building a
14G Jet fighter here. My current airplane is built entirely with
pulled rivets, uses a 23 foot one piece cantilevered wing, GW is
1200lbs and is rated for 6Gs. If the job looks hard to do I opt for
pulled rivets, otherwise I bang them in.
Jose Borja
Elk Mound WI, Rear Fuse and Center Section in progress
Author: "Bill" <flybill7@...> Time: Wed Nov 30, 2005 7:24 am PST Link
Just this past week I dimpled them -- except for the holes noted for
countersinking. The 704 flanges dimpled fine.
http://www.aircobratech.com/Bill/Fuselage/F-25Nov05.html
... Bill Cloughley
Severna Park, MD
RV-7 Fuse
Author: "Bill" <flybill7@...> Time: Wed Nov 30, 2005 7:25 am PST Link
Just this past week I dimpled them -- except for the holes noted for
countersinking. The 704 flanges dimpled fine.
http://www.aircobratech.com/Bill/Fuselage/F-25Nov05.html
... Bill Cloughley
Severna Park, MD
RV-7 Fuse
Author: "Bob Collins" <bcollinsrv7a@...> Time: Wed Nov 30, 2005 7:44 am PST Link
The one aspect of the instructions that I didn't understand -- whether one
countersinks or dimples in this case isn't the issue -- is the suggestion to
countersink THROUGH the skin. I didn't see any reason to do that, even
though I did. I remember asking about this while I was looking it over and
someone said it's so the stiffeners fit flush on the flange. That's true,
they need to. But if you dimpled the skin and countersunk those holes, there
would be no impact on the stiffeners. So I'm not sure why Van's suggests
countersinking through the skin there and not just dimpling the skin and
countersinking those holes.
B
-----Original Message-----
From: RV7and7A@yahoogroups.com [mailto:RV7and7A@yahoogroups.com] On Behalf
Of Bill
Sent: Wednesday, November 30, 2005 8:19 AM
To: RV7and7A@yahoogroups.com
Subject: [RV7Yahoo] Re: 704 bulkead - csink or dimple?
Just this past week I dimpled them -- except for the holes noted for
countersinking. The 704 flanges dimpled fine.
http://www.aircobratech.com/Bill/Fuselage/F-25Nov05.html
... Bill Cloughley
Severna Park, MD
RV-7 Fuse
Van's Air Force - World Wide Wing
www.vansaircraft.net
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[Non-text portions of this message have been removed]
Author: "jmjula" <jmjula@...> Time: Wed Nov 30, 2005 4:11 pm PST Link
There was not much of an edge distance on those floor stiffiners at
that joint when I drilled them. I would believe a countersink might
further compromise the strength of that joint. I am speculating this
is the reason for Vans recomendation.
One note, at least to 7A builders, when you do dimple the rest of
704A, leave the outside 5 holes on both ends flat. These need to be
double countersunk for double flush rivets. A few of us have had to
flatten those oops dimples and then countersink...
James
--- In RV7and7A@yahoogroups.com, "Bob Collins" <bcollinsrv7a@c...>
wrote:
>
> The one aspect of the instructions that I didn't understand --
whether one
> countersinks or dimples in this case isn't the issue -- is the
suggestion to
> countersink THROUGH the skin. I didn't see any reason to do that,
even
> though I did. I remember asking about this while I was looking it
over and
> someone said it's so the stiffeners fit flush on the flange. That's
true,
> they need to. But if you dimpled the skin and countersunk those
holes, there
> would be no impact on the stiffeners. So I'm not sure why Van's
suggests
> countersinking through the skin there and not just dimpling the
skin and
> countersinking those holes.
>
> B
Author: "Dan Checkoway" <dan@...> Time: Wed Nov 30, 2005 4:13 pm PST Link
> The one aspect of the instructions that I didn't understand -- whether one
> countersinks or dimples in this case isn't the issue -- is the suggestion
> to
> countersink THROUGH the skin. I didn't see any reason to do that, even
> though I did. I remember asking about this while I was looking it over and
> someone said it's so the stiffeners fit flush on the flange. That's true,
> they need to. But if you dimpled the skin and countersunk those holes,
> there
> would be no impact on the stiffeners. So I'm not sure why Van's suggests
> countersinking through the skin there and not just dimpling the skin and
> countersinking those holes.
I'll say it again... Because you'd be *removing* material from F-704, a key
structure and a key joint. Because you'd be *losing* anti-shear strength
that nested dimples provide.
I'm not saying your plane is gonna "unzip," and obviously through what
builders on this list have mentioned, Van's has approved dimpling the skin &
c-sinking the F-704 flanges. But it's my belief that dimpling in this area
provides superior strength in every way.
Yes, the instructions are a little ambiguous in this area, but the "process
of elimination" comes into play. If they *only* call out countersinking the
skin in four spots, well, then, if you put enough thought into it, you can
deduce that dimpling the rest was implied. The stiffeners need to lay flat
on the flange in only those four spots? Ok, then that must mean the rest
are dimpled. You need to "infer" Van's intentions here...they could have
just as easily left out the 4-spot countersinking instructions, and have you
countersink the floor stiffener instead...but they didn't. Why? Because
that would be *removing* key material from a key structure unnecessarily.
And that is the implied goal here, to avoid that. At least that's my take
on it!
I agree that the plans & instructions are not intended to be a "puzzle," but
on the flip side, less is more. There's some point at which more clutter on
the plans would cause more confusion and mistakes.
Read your plans carefully, and ask Van's and/or people on this list if and
when you have trouble interpreting them. I would not leap ahead if you are
unsure.
)_( Dan
RV-7 N714D
http://www.rvproject.com
Author: "Bob Collins" <bcollinsrv7a@...> Time: Thu Dec 1, 2005 8:19 am PST Link
// There was not much of an edge distance on those floor stiffiners at
that joint when I drilled them. I would believe a countersink might
further compromise the strength of that joint. I am speculating this
is the reason for Vans recomendation.
Van's recommendation on the F-704 holes where the stiffeners attached is
perfectly clear. They are countersunk. You don't have any choice there or
else your stiffener is going to sit up off the F-704 and the first few
rivets of the stiffener to the skin is going to be ugly (not that the first
one is all that great with the joggle joint). There's no recommendation --
either from Van's or from me -- to do anything to the stiffener other than
drill a hole.
Where the Van's instructions fail is on note 1 where it says to countersink
THROUGH the bottom skin into the F-704. There's no reason to countersink
through the skin in that location.
[Non-text portions of this message have been removed]
Author: "Bob Collins" <bcollinsrv7a@...> Time: Thu Dec 1, 2005 8:20 am PST Link
--- In RV7and7A@yahoogroups.com, "Dan Checkoway" <dan@r...> wrote:
> Read your plans carefully, and ask Van's and/or people on this list
if and
> when you have trouble interpreting them.
Dan, if you go back and read the original message again about these
*four* hole locations, you will see that I indicated that at the time
I had the question about these *four* holes and the need to
countersink *through the skin,* you'll see I noted at the time that I
did ask why there was a need to countersink the skin by countersinking
the F-704 *through the skin*. The response was that it's so the
stiffeners can lie flat.
The advice was incorrect. There's no relationship between taking a
countersink cutter to the skin portion of that joint and the ability
of the stiffener to lie flat.
Now, if you review 5E, you'll note that Van's gives situations where
countersinking a thin skin is acceptable, and this is one of those
times -- when a thin skin is sandwiched between two other units.
But the fact one CAN safely countersink a thin skin doesn't
necessarily give me a good reason as to why one HAS to in that location.
Author: "Bob Collins" <bcollinsrv7a@...> Time: Thu Dec 1, 2005 8:21 am PST Link
// I'll say it again... Because you'd be *removing* material from F-704, a
key
structure and a key joint. Because you'd be *losing* anti-shear strength
that nested dimples provide.
Well, then I'll *ASK* again.... why do you have to countersink (here's the
key phrase...)**through the skin** on those holes (the ones where the
stiffeners attach, not all of them)? Why NOT dimple the skin and countersink
those holes (that is, we're told to countersink THOSE holes, my question
isn't about countersinking the 704, it's about also using the countersink on
the skin)?
You've answered a question I didn't ask.
// Yes, the instructions are a little ambiguous in this area, but the
"process
of elimination" comes into play. If they *only* call out countersinking the
skin in four spots, well, then, if you put enough thought into it, you can
deduce that dimpling the rest was implied.
Agai, you seem to be taking me to task for a question I did not ask. And,
for the record, I did not countersink the holes in the skin. I dimpled the
holes in the skin. But on those holes indicated, it doesn't say "dimple the
skin and countersink the holes," it says countersink through the skin on
those holes (we're talking four holes here).
// The stiffeners need to lay flat
on the flange in only those four spots? Ok, then that must mean the rest
are dimpled. You need to "infer" Van's intentions here...they could have
just as easily left out the 4-spot countersinking instructions, and have you
countersink the floor stiffener instead...but they didn't. Why? Because
that would be *removing* key material from a key structure unnecessarily.
And that is the implied goal here, to avoid that. At least that's my take
on it!
Good point. But it's not my question. It could ALSO mean that the holes
pointed out are "countersunk through the skin" and the other holes are
dimpled in the skin and countersunk on the spar.
And I believe you're correct, removing material presents a weaker bond. So
I'm back to the original quesiton, agai. WHY does Van -- on those four holes
-- instruct one to countersink through the skin?
// Read your plans carefully, and ask Van's and/or people on this list if
and
when you have trouble interpreting them. I would not leap ahead if you are
unsure.
Whoa, slow down a little, pard'ner. I'm not at all confused about what the
plans do or do not say regarding countersinking or dimpling the F-704 to
accept dimples in the skin. The plans are VERY clear to me. On page 5-3
you'll see where it says (this is section 5E). "For AD3 rivets, .032 is the
minimum allowable skin thickness, and for AD4 rivets, .050 is the minimum
thickness. Metal thicker than this is difficult to dimple, so it is sommon
practice to machine countersink for AD4 rivets. "
I am also aware that Van's recommends dimpling in metal .040 and thinner.
for a number of reasons. So my choice here to countersink, while others may
disagree with it, is simply that, a choice, and is not the issue here. Nor
is understanding the instructions.
Now, if you look aat DWG 28, you'll see those four (4) holes pointed out
where the stiffener attaches to the F-704. You'll also see that it refers
one to Note 1. Note 1 says as follows:
"Machine countersink THROUGH THE F-776 and F-704A. Do not dimple. 4
places."
I GOT the reason for not dimpling thge F-704A in that location. Simple. The
stiffener has to lie flush against the F-704. But the question I originally
asked, Dan, is WHY would you have to countersink the bottom skin (F-776). I
can see no logical reason for doing so. That should be dimpled
In answering the question I didn't ask, you provided -- perfectly -- my
reason for asking it in the first place.
As near as I can tell, the instructions are incorrect there and should read:
"Machine countersink the F-704A to accept the dimple in the F-776."
To your point about deduction, that wold also lead one to a more logical
conclusion that the REST of the holes on F-704 are dimpled. But as written,
the note does not at all lead to the conclusion you based. It could. but it
could also mean you dimple the rest of the holes in the bottom skin.
[Non-text portions of this message have been removed]
Author: "microsmurfer" <microsmurfer@...> Time: Thu Dec 1, 2005 9:59 am PST Link
--- In RV7and7A@yahoogroups.com, "Bob Collins" <bcollinsrv7a@c...>
wrote:
> Well, then I'll *ASK* again.... why do you have to countersink
(here's the
> key phrase...)**through the skin** on those holes (the ones where
the
> stiffeners attach, not all of them)? Why NOT dimple the skin and
countersink
> those holes (that is, we're told to countersink THOSE holes, my
question
> isn't about countersinking the 704, it's about also using the
countersink on
> the skin)?
Because they assume you'll dimple the forward bottom skin, so the
dimple needs to sit in the countersunk hole in the rear bottom skin.
That's what it is. Otherwise you'd dimple all three parts (forward
bottom skin, rear bottom skin, and F-704 flange). The idea is to
avoid dimpliing those holes in 704 flange so stiffener can sit flat.
Obviously, another approach is to countersink those holes in forward
bottom skin, and do absolutely nothing with rear bottom skin or 704
flange. This is what I did.
As implied, all other holes were dimpled on 704 flange....
HTH
Radomir
Author: "pepeborja925mb" <pepeborja925mb@...> Time: Thu Dec 1, 2005 1:00 pm PST Link
<SNIP>The idea is to avoid dimpliing those holes in 704 flange so
stiffener can sit flat.<SNIP>
So, if the idea is to keep the stiffener flat, why not countersink (or
dimple) the stiffener to match the dimpled 704 and get it done and over
with?
Seems to me this could be revised to align with the "less is more"
philosophy.
Jose Borja
Elk Mound, WI rear fuse and center section in progress.
Author: "Bob Collins" <bcollinsrv7a@...> Time: Thu Dec 1, 2005 1:01 pm PST Link
--- In RV7and7A@yahoogroups.com, "microsmurfer" <microsmurfer@y...>
wrote:
>
> That's what it is. Otherwise you'd dimple all three parts
(forward
> bottom skin, rear bottom skin, and F-704 flange). The idea is to
> avoid dimpliing those holes in 704 flange so stiffener can sit
flat.
Right, I've acknowledge the fact the F-704 flange is countersunk and
the minute it is -- independent of the treatment of all other of the
four components of that joint, the stiffener is assured to lie flat.
Dimpling the center skin would have no impact at all in whether the
stiffner lies flush on the flange of the F-704. The dimple of the
skin would simply rest in the counterink of the F-704.
> Obviously, another approach is to countersink those holes in
forward
> bottom skin, and do absolutely nothing with rear bottom skin or
704
> flange. This is what I did.
>
> As implied, all other holes were dimpled on 704 flange....
That's an inteesting approach. But I'll just point out again in NOTE
1 on the drawing cited earlier, the instruction to "countersink
through the (bottom skin) and F-704. Do not dimple" just as easily
implies countersinking the F-704 flange as dimpling it. I agree,
though, that if it hadn't included the bottom skin in the
instruction to countersink, THAT would have implied dimpling the F-
704 flange.
In any event, I reckon that joint there consists of .040 on the
flange, .032 on the forward skin, and .025 on the center skin. .097?
I ain't worried.
Author: "microsmurfer" <microsmurfer@...> Time: Thu Dec 1, 2005 7:03 pm PST Link
Because there's no hole to countersink, so to speak :) The idea is
to keep the stiffener flat while centering it and drilling all those
holes. After the holes are drilled, it wouldn't matter which
approach to take... The whole "keep it flat" is about ease of
drilling initially...
This is one area where it pays to look ahead and think of
alternative ways. As I mentioned, I didn't like countersinking
through the skin.. just didn't sound right to me.
HTH
Radomir
--- In RV7and7A@yahoogroups.com, "pepeborja925mb"
<pepeborja925mb@y...> wrote:
>
> <SNIP>The idea is to avoid dimpliing those holes in 704 flange so
> stiffener can sit flat.<SNIP>
>
> So, if the idea is to keep the stiffener flat, why not countersink
(or
> dimple) the stiffener to match the dimpled 704 and get it done and
over
> with?
>
> Seems to me this could be revised to align with the "less is more"
> philosophy.
>
> Jose Borja
> Elk Mound, WI rear fuse and center section in progress.
Author: "Bob Collins" <bcollinsrv7a@...> Time: Thu Dec 1, 2005 7:03 pm PST Link
--- In RV7and7A@yahoogroups.com, "pepeborja925mb"
<pepeborja925mb@y...> wrote:
>
> So, if the idea is to keep the stiffener flat, why not countersink
(or
> dimple) the stiffener to match the dimpled 704 and get it done and
over
> with?
I think the stiffener is .063 (don't quote me) so dimpling wouldn't
work. But in theory countersinking could, except for one problem in
at least TWO of the stiffeners. There's no edge distance there. See
the landing gear mount (the two inboad "prongs") has to fit behind
that stiffener a little bit in order to mount flush against the Web
of the F-704. I would think -- and I have no engineering background
at all to call upon here -- that if you countersink the stiffener
there you have a really weak bond.
But maybe not.
Author: "Daryl Tolliver" <daryl.tolliver@...> Time: Thu Dec 1, 2005 7:03 pm PST Link
All
The reason you machine csink thru the skin is to not dimple the F-704 in only
the 4 holes where the stiffener sits against the 704. As Dan Suggested....
you can dimple the 704 because it is .040 the max allowable to dimple
according to Vans. If you dimpled in these 4 places the 704 would have a
raised area.... (the back side of the dimple) and that would not allow the
stiffener to sit flush.
Again as Dan pointed out. You could Csink all of this but you would loose
the shear strength of dimpled skin sitting in the dimpled flange of the 704.
In only these 4 places Vans recommends machine csinking.
Sounds like a more robust stronger structure to me. Hope this helps clear
things up.
_____
From: Bob Collins [mailto:bcollinsrv7a@...]
Sent: Thursday, December 01, 2005 1:32 PM
To: RV7and7A@yahoogroups.com
Subject: [RV7Yahoo] Re: 704 bulkead - csink or dimple?
--- In RV7and7A@yahoogroups.com, "microsmurfer" <microsmurfer@y...>
wrote:
>
> That's what it is. Otherwise you'd dimple all three parts
(forward
> bottom skin, rear bottom skin, and F-704 flange). The idea is to
> avoid dimpliing those holes in 704 flange so stiffener can sit
flat.
Right, I've acknowledge the fact the F-704 flange is countersunk and
the minute it is -- independent of the treatment of all other of the
four components of that joint, the stiffener is assured to lie flat.
Dimpling the center skin would have no impact at all in whether the
stiffner lies flush on the flange of the F-704. The dimple of the
skin would simply rest in the counterink of the F-704.
> Obviously, another approach is to countersink those holes in
forward
> bottom skin, and do absolutely nothing with rear bottom skin or
704
> flange. This is what I did.
>
> As implied, all other holes were dimpled on 704 flange....
That's an inteesting approach. But I'll just point out again in NOTE
1 on the drawing cited earlier, the instruction to "countersink
through the (bottom skin) and F-704. Do not dimple" just as easily
implies countersinking the F-704 flange as dimpling it. I agree,
though, that if it hadn't included the bottom skin in the
instruction to countersink, THAT would have implied dimpling the F-
704 flange.
In any event, I reckon that joint there consists of .040 on the
flange, .032 on the forward skin, and .025 on the center skin. .097?
I ain't worried.
Van's Air Force - World Wide Wing
www.vansaircraft.net
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Author: "bobbarrow747" <bobbarrow10@...> Time: Thu Dec 1, 2005 7:04 pm PST Link
I would suggest that there is not one slow builder who has not
pondered this very question for hours. I have a number of builder
friends who have done completely different things. Some have dimpled
the entire 704 flange, some have countersunk etc.
The point is that the instructions are not clear on this issue. And
there is no reason for them not to be clear. Vans has probably had
over a 100 questions on this one topic directed at them. But do they
ever change their instructions....I don't think so. And it could be
so easily rectified.
The same goes for their drawings. There are many very bad mistakes
and inconsistencies on their drawings. Some of them are very simple
things like telling you to drill the wrong size hole for a fuel
vent. They must receive dozens of enquiries regarding these
errors...but they won't change the drawings. You'll note that most
of their drawings haven't had a revision for years, if at all. I'm
not saying that their drawings are a total disaster....they're not.
But RV builders who come from an engineering background and are used
to reading drawings will know that they could be so much better.
My further opinion is that the RV7(A) construction manual is a
throwover of the RV6 manual. For instance a lot of the sequence in
the fuselage doesn't make that much sense.
I think Vans is a very good company and they have always treated me
fairly. But they desperately need to get some-one clever to
completely revamp both their drawings and their fabrication
instructions. It's a sad statement regarding the quality of their
instructions and drawings that many builders need to go to Dan
Checkoways site every second day to work out what is going on.
Author: "Bob Collins" <bcollinsrv7a@...> Time: Fri Dec 2, 2005 10:43 am PST Link
// The reason you machine csink thru the skin is to not dimple the F-704 in
only
the 4 holes where the stiffener sits against the 704.
Yeah, that's what people keep saying but I don't see where dimpling the skin
would prevent you from countersinking the 704. That doesn't make sense to
me.
// If you dimpled in these 4 places the 704 would have a
raised area.... (the back side of the dimple) and that would not allow the
stiffener to sit flush.
You'd only have a raised area on the skin. If you countersink the F-704,
that would accept the dimple and the topside of the F-704 flange is still
virgin and the stiffener would lie perfectly flat against it as desired.
Again, we're only talking about those 4 holes (I think folks are getting
distracted by my choice to countersink all the F-704 holes but that's not
the issue. That's done, that's acceptable building. Not an issue). I can see
no reaason for countersinking THROUGH (that's the keyword) the skin in those
locations.
It creates a weaker bond in those locations and it doesn't do anything to
help the stiffener sit flush that a more acceptable approach (dimple the
skin, countersink the 704) wouldn't accomplish.
Like I said in the initial message, I can't figure out what Van's sees as
the advantae of countersinking (THROUGH) the skin in that location. I get
countersinking the 704 there, but not the skin. That's all.
[Non-text portions of this message have been removed]
Author: "Bob Collins" <bcollinsrv7a@...> Time: Fri Dec 2, 2005 10:43 am PST Link
// My further opinion is that the RV7(A) construction manual is a
throwover of the RV6 manual. For instance a lot of the sequence in
the fuselage doesn't make that much sense.
I gotta believe that eventually the 7A model plans will be like the 10
plans. No manual. More drawings. That would be cool, becuas by the time you
get around to the fuselage, the plans are where it's at. Unfortunately, it's
also where some nagging mistakes -- not fatal, just annoying -- mistakes
reside.
In the meantime, some enterprising individual looking to build a useful Web
site could organize correctons to the drawings as they're found. (although I
think somebody tried to put the plans online once and got into some hot
water doing so...or at least the threat of hot water).
DWG 28 for example (that's the rivet chart for the fuselage that I depended
on heavily) shows an AN426AD4-6 rivet at the intersectionof the lower
longeron/stiffener on the forward fuselage. Nope. DWG 38 reveals that
there's a flush AN509-10R12 screw in that location. I read ahead and saw
that, but I'm also aware of other folks who "charged ahead" and ended up
with a rivet there to drill out later. A pain in the neck and I called it to
Van's attention and they admitted that "that needs to be revised," and since
that was almost a year ago, I thought RVAtor would be the perfect place to
do it. But I imagine what they've got in mind is just revising the next set
of plans.
By the way, there's ANOTHER location where Van's recommends countersinking
"through the skin" that appears to be unneccessary. But maybe it's because
they drew DWG 38 later (that's where the instruction appears) and onc eyou
stick a "4" rivet in there, it's too late, yo've got no choice BUT to
countersinkink through the skin. (the instruction says ""machine countersink
F-770 side skin and F717 lower longeron"). Again, absolutely no need to do
that. DIMPLE the skin in that location for a #10 screw before you put the
skin on and countersink the longeron. Stronger bond.
Anyway, there's lot of little places that could be improved, it's also one
of the reasons I'm not at all concerned about counersinking the F-704.
Heck, whatever I "lost" there in structural integrity I more than made up
for by using the proper size rivets on the entire side skin/longeron,
rather than those Van's recommends on the drawings that would be substandard
and definitely weaker. (heck, if structural integrity were the only issue in
building airplanes, we'd be using universal heads in these locations, but
the fact is the design allows for more rivets in these locations because the
loss of structural integirty -- whether by hot dimpling or countersinking --
is assumed). So is a countersunk joint less strong than a dimpled joint?
Sure. And a 426 riveted joint is less strong than a universal head joint.
(Source: Aircraft Sheet Metal - Jeppesen). You just have to evaluate degree.
(By the way, I'll bet if an airplane "unzips" in flight, it's going to be at
one of the more inboard ribs in the wing before the bottom of the fuse)
I can also see some areas where some of the red end bearings could use a
washer to protect the system in the event of bearing failure.
But in those situations, it's educational to know if those incompatabilities
are the result of an actual intent, or just a mistake. I guess that's part
of the educational aspect of homebuilding.
But I don't have ny real qualms with Van's design at all. I just
occasionally like to know what their thinking is on certain things because
it's entirely possible I'm missing certain areas where their recommendation
is incompatible with AC43.13-B -- A manual I tend to open at this stage of
building MUCH more often than the Van's manual.
I don't think you can go wrong staying with in the "acceptable" methods,
techniues, and practices specified.
YMMV
[Non-text portions of this message have been removed]
Author: "pepeborja925mb" <pepeborja925mb@...> Time: Fri Dec 2, 2005 10:45 am PST Link
Sorry I started this whole debacle on the 704 bulkhead deal.
I am not concerned at all about the joint and it being strong or weak
as much by either method as I was about the ease in which task can be
achieved. I much prefer dimpling and wanted to ensure that's what
others did (unless dimpling had the risk of buggering the flange).
I have spent a lot of time in the lighter side of aviation and know
what a few NAS bolts and Carbon Steel rivets can do. The amount of
fasteners used in the RV make it virtually indestructible (sans the
RV8 episode of a few years back).
If it were up to me I would use a lot of blind rivets to handle a lot
of the internal structures, like rib to bulkheads, etc but that would
deviate from the plans and open the doors to our lawyer friends if
something were to go wrong over the 18 year period of liability.
If the rivet is too hard to buck and the risk is there where the tail
will get messed up, I use a blind rivet and move on. The joint will
be just as good.
Jose Borja
Elk Mound, WI
Author: "Bob Collins" <bcollinsrv7a@...> Time: Fri Dec 2, 2005 3:16 pm PST Link
--- In RV7and7A@yahoogroups.com, "pepeborja925mb"
<pepeborja925mb@y...> wrote:
>
> Sorry I started this whole debacle on the 704 bulkhead deal.
It's not a debacle. It's just kicking the can around a bit. Nothing
wrong with that. That's what homebuilders should do when they sitting
around and it's 12 degrees outside and you can only hold a rivet gun
for about 1 1/2 minutes before you have to run back inside and warm
up.
Not that it ever gets cold over there in Elk Mound, of course. (g)
Author: "bobbarrow747" <bobbarrow10@...> Time: Fri Dec 2, 2005 10:17 pm PST Link
--- In RV7and7A@yahoogroups.com, "Bob Collins" <bcollinsrv7a@c...>
wrote:
> But I don't have ny real qualms with Van's design at all. I just
> occasionally like to know what their thinking is on certain things
because
> it's entirely possible I'm missing certain areas where their
recommendation
> is incompatible with AC43.13-B -- A manual I tend to open at this
stage of
> building MUCH more often than the Van's manual.
> I don't think you can go wrong staying with in the "acceptable"
methods,
> techniues, and practices specified.
A very good posting Bob. Many good points. In particular I endorse
AC43.13. To build an RV without it....well, it's a bit like having
religion but having no bible.
Incidentally while we're discussing Vans errors. A friend of mine
bought his RV7 slo-build fuselage about 6 months before me. When he
got to installing the forward fuse gussett plate F-695 (the plate
the ties the firewall to the main longeron) he found that Vans had
fabricated it to the wrong shape. Instead of the tie corner being
greater than 90 degrees it was less than 90 degrees. So he had to
contact Vans and received instructions on modifying this plate to
fit including a change to all the hole spacings indicated on the
relevant drawing.
Six months later I get to the same plate. Guess what..mine is wrong
too. Same problem. So I know that they have been sending out a
wrongly fabricated F-695 plate for at least 6 months. So I contacted
Vans and they said: "Oh yeh, we've known about that for years".
But then I thought to myself, hey wait a minute, this is an old RV6
plate (F-695). Is there any chance the problem goes way back
further. So I did an archive search...and guess what. People were
complaining about this plate back in 1999. You can refer to the
following archive:
http://www.matronics.com/searching/getmsg_script.cgi?INDEX=74489097?
KEYS=f695?LISTNAME=RV?HITNUMBER=1?SERIAL=16085622816?SHOWBUTTONS=YES
So it seems Vans has been sending out this incorrectly fabricated
plate for over 6 years despite the fact that they know it is
incorrect. It just beggars belief. In fact it is almost
incomprehensible as a business practice.
Has everyone else had the same problem with this plate. If the plate
is correctly fabricated as per the drawings it will form a perfect
angle with the firewall and the longeron.
Author: "Dan Checkoway" <dan@...> Time: Sat Dec 3, 2005 10:06 am PST Link
> Incidentally while we're discussing Vans errors. A friend of mine
> bought his RV7 slo-build fuselage about 6 months before me. When he
> got to installing the forward fuse gussett plate F-695 (the plate
> the ties the firewall to the main longeron) he found that Vans had
> fabricated it to the wrong shape. Instead of the tie corner being
> greater than 90 degrees it was less than 90 degrees. So he had to
> contact Vans and received instructions on modifying this plate to
> fit including a change to all the hole spacings indicated on the
> relevant drawing.
Bob,
It's obviously been a while. Can you show me a photo of this gusset and how
it's mal-formed, and maybe point me to the drawing where the hole spacings
either don't work or are incorrect? At least on my plane, the firewall
attaches to the longerons via weldments.
Just curious more than anything. My fuselage & firewall went together with
no issues -- at least that I know of! FWIW I'm serial # 70379 and have what
I believe is a fairly early (2002) RV-7 slow build fuselage.
)_( Dan
RV-7 N714D
http://www.rvproject.com
Author: "pepeborja925mb" <pepeborja925mb@...> Time: Sat Dec 3, 2005 10:07 am PST Link
<SNIP> It's not a debacle. It's just kicking the can around a bit.
Nothing wrong with that. That's what homebuilders should do when they
sitting around and it's 12 degrees outside and you can only hold a
rivet gun for about 1 1/2 minutes before you have to run back inside
and warm up.<SNIP>
Amen to that brother. I think folks need to relax a little and believe
that Van's does not really walk on water, that missing one fastener
will make the airplane a ticking bomb, or that choosing one method ver
another will make the airplane less safe. I have my brother-in-law's
books he used on his A&P school and it shows the different methods of
doing business when working with airplanes. I would recommend anyone
gets those books published by the FAA and get their answers there for
best practices.
I have been in this hobby for 14 years and have seen a lot of things.
Some of the odd stuff I have seen is a homebuilt UL with door hinges on
the ailerons. Another homebuilt made of wood lost the engine on
takeoff. It literally fell off as the glue softened from exposure to
fuel and oil. I have seen my share of crashes from seized 2 stroke
planes and seen all kinds of repairs made that mould make you believe
the thing is going to come apart but they don't.
The thing is these airplanes are way, way, way overbuilt and it will
take a lot of wrongs to make it unsafe. I tried to destroy two
aluminum sheets with overshoot rivets (wide and short tails) and no
matter how much hammering I did, the rivets never broke (i.e., put the
rivet gauge down and go by feel).
My brother-in-law with 20 years in teh A&P side of the house with the
majors inspected my work during the TG holiday and I pointed out some
rivets I though looked bad. He said the plane has so many of them it
won't make a difference, besides it would do more damage to drill it
out and try to buck them in again in buggered out hole. The RV is not
a Jet fighter, it's a very light sport airplane.
Many airplanes like the Sonex, Tornado, Zenith are built using blind
1/8 inch rivets on 2 inch spacing and none of them has come apart and
the VNE's on those airplanes are 150MPH or higher. What makes anyone
think that the RV using 3/32 bucked rivets on 1" spacing would?. By
all intents all the airplanes I listed are basically in the same weight
and G rating category, so let's relax the grip a little and build with
peace of mind.
Do you attend the MN wing meetings? If weather is good, I may swing by
the 10th at Lake Elmo on my Tornado. A friend (Jim) has a -6 there.
Jose Borja
Elk Mound WI
Author: "Bob Collins" <bcollinsrv7a@...> Time: Sat Dec 3, 2005 10:08 am PST Link
// Vans and they said: "Oh yeh, we've known about that for years".
This is similar to their recommendations for 4-12 the plans recommend for
the landing gear to F-704 attach. Too short. That's kind of an important
part. Now, yeah, the 4-13 notation is floating around the Internet. But,
again, I think it would be nice to have a list of known "bugs" . What if we
set up a collection point for these? Would folks contribute to it. Maybe we
can get Doug Reeves to post it on his site if I put a page together. Is
anyone interested in working with me on it?
[Non-text portions of this message have been removed]
Author: "Bob Collins" <bcollinsrv7a@...> Time: Sat Dec 3, 2005 4:06 pm PST Link
// Do you attend the MN wing meetings? If weather is good, I may swing by
the 10th at Lake Elmo on my Tornado. A friend (Jim) has a -6 there.
I usually do, yes. You have to go just so you can see Doug Weiler's (RV4)
and Paul Hove's (RV7) hangar. That's what *I* want for Christmas.
I'm about 6 miles from Lake Elmo. So I'll try to get there. And if anyone
wants to come back to the house and do an "inspection" of my project, I'll
supply the beer/coffee..
[Non-text portions of this message have been removed]
Author: "bobbarrow747" <bobbarrow10@...> Time: Sat Dec 3, 2005 11:50 pm PST Link
> It's obviously been a while. Can you show me a photo of this
gusset and how
> it's mal-formed, and maybe point me to the drawing where the hole
spacings
> either don't work or are incorrect? At least on my plane, the
firewall
> attaches to the longerons via weldments.
Dan, I'm hoping that the following URL will take you to a photo of
the relevant gussett plate in position. You can see that it joins
the firewall to the main longeron. The longeron meets the firewall
at an angle of more than 90 degrees. However the plate as received
was less than 90 degrees. Therefore the plate had to be recut. This
resulted in the hole spacings on the longeron side needing to be
reduced (in order to end up with the same number of holes).
http://img202.imageshack.us/img202/5854/f6954lc.jpg
Author: "Dan Checkoway" <dan@...> Time: Sun Dec 4, 2005 10:04 am PST Link
Ah, I see what you mean. I honestly don't remember if I had to trim mine.
)_( Dan
RV-7 N714D
http://www.rvproject.com
----- Original Message -----
From: "bobbarrow747" <bobbarrow10@...>
To: <RV7and7A@yahoogroups.com>
Sent: Saturday, December 03, 2005 8:33 PM
Subject: [RV7Yahoo] Re: 704 bulkead - csink or dimple?
>> It's obviously been a while. Can you show me a photo of this
> gusset and how
>> it's mal-formed, and maybe point me to the drawing where the hole
> spacings
>> either don't work or are incorrect? At least on my plane, the
> firewall
>> attaches to the longerons via weldments.
> Dan, I'm hoping that the following URL will take you to a photo of
> the relevant gussett plate in position. You can see that it joins
> the firewall to the main longeron. The longeron meets the firewall
> at an angle of more than 90 degrees. However the plate as received
> was less than 90 degrees. Therefore the plate had to be recut. This
> resulted in the hole spacings on the longeron side needing to be
> reduced (in order to end up with the same number of holes).
>
> http://img202.imageshack.us/img202/5854/f6954lc.jpg
> Van's Air Force - World Wide Wing
> www.vansaircraft.net
> Yahoo! Groups Links
Author: "Bob Collins" <bcollinsrv7a@...> Time: Sun Dec 4, 2005 10:05 am PST Link
I noticed that too when I put the gusset in. I just ended up staying
relatively faithful to the centerline on the X and Y and making sure
the edge distance was acceptable on both and on the longeron.
--- In RV7and7A@yahoogroups.com, "bobbarrow747" <bobbarrow10@h...>
wrote:
> Dan, I'm hoping that the following URL will take you to a photo of
> the relevant gussett plate in position. You can see that it joins
> the firewall to the main longeron. The longeron meets the firewall
> at an angle of more than 90 degrees. However the plate as received
> was less than 90 degrees. Therefore the plate had to be recut.
This
> resulted in the hole spacings on the longeron side needing to be
> reduced (in order to end up with the same number of holes).
>
> http://img202.imageshack.us/img202/5854/f6954lc.jpg