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Search: Posts Made By: Marc Bourget
Forum: Traditional Aircraft Engines 07-15-2018, 08:17 PM
Replies: 11
Views: 909
Posted By Marc Bourget
With the piston at the bottom of its stroke, the...

With the piston at the bottom of its stroke, the pressures are minimal.

As the factory says, size it for the top end where the "work" is done!
Forum: RV-14 07-15-2018, 11:17 AM
Replies: 8
Views: 778
Posted By Marc Bourget
The "bow" occurs because of the compression of...

The "bow" occurs because of the compression of material inside the neutral axis of sheet (when looking on edge.) from bending the material.

It can (as suggested) be pulled into line, or you can use...
Forum: RV General Discussion/News 06-30-2018, 11:15 AM
Replies: 15
Views: 1,548
Posted By Marc Bourget
These results have been reported many times,...

These results have been reported many times, since the NACA studies during WW-II. That being said, I compliment you on the effort! Unusual and laudatory! Good Man!

I do have concerns with the...
Forum: Electrical Systems 06-30-2018, 09:47 AM
Replies: 20
Views: 1,792
Posted By Marc Bourget
My comment about operating altitudes came from a...

My comment about operating altitudes came from a conversation with an actual engineer buried in the back- shop of Plane Power.

I recall two points of interest, rpm and brushes. After further...
Forum: Electrical Systems 06-28-2018, 11:57 PM
Replies: 20
Views: 1,792
Posted By Marc Bourget
You don't plan to fly over about 6000 ft? :D:):D

You don't plan to fly over about 6000 ft?

:D:):D
Forum: RV General Discussion/News 06-26-2018, 08:45 PM
Replies: 19
Views: 2,305
Posted By Marc Bourget
Like the emphasis on rivet gun control. Direct...

Like the emphasis on rivet gun control. Direct and to the point.

The majority of the previous were all good hints, but gun control was not stressed.

I solo riveted wings on another design that had...
Forum: Propellers 06-22-2018, 05:35 PM
Replies: 5
Views: 734
Posted By Marc Bourget
John, Thanks for the picture, but I'd like to...

John,

Thanks for the picture, but I'd like to see a view from a step back.

Is is possible to "color" the cracked areas with a sharpie and wipe clean for more contrast?

Thanks
Forum: VAF Classifieds (posts in here deleted after 30 days) 06-20-2018, 08:46 AM
Replies: 6
Views: 620
Posted By Marc Bourget
If you cleeco the nutplate to use it as a jig, ...

If you cleeco the nutplate to use it as a jig, then use a small of drill as possible to avoid losing center tolerance. If your trying to match holes, say for AD-4 rivets, better to drill 1/8"...
Forum: Traditional Aircraft Engines 05-28-2018, 04:25 PM
Replies: 9
Views: 770
Posted By Marc Bourget
See if you can get access to an ultrasonic...

See if you can get access to an ultrasonic cleaner of sufficient size.

Not guaranteed, but it will do better than simple flushing/reverse flushing.

There was an article in Kitplanes some years back...
Forum: RV General Discussion/News 05-24-2018, 07:34 AM
Replies: 2
Views: 470
Posted By Marc Bourget
I do not recall the placement point. I believe...

I do not recall the placement point.

I believe there are plenty of other factors that prevent laminar flow that far back on the (any) fuselage.

The slipstream is generally at ambient pressure as...
Forum: RV-14 05-06-2018, 12:29 PM
Replies: 20
Views: 2,906
Posted By Marc Bourget
Smile Good to be cautious, but how is that rib loaded...

Good to be cautious, but how is that rib loaded when in use?

It mainly serves in compression and I don't think much stretch or bending takes place in the vicinity of the deformation.

I'd lightly...
Forum: RV-8/8A 05-05-2018, 08:10 AM
Replies: 20
Views: 3,075
Posted By Marc Bourget
I believe there is much more dynamic pressure...

I believe there is much more dynamic pressure possible than "lift" from slipstream airflow.
Forum: RV-8/8A 05-03-2018, 05:29 AM
Replies: 16
Views: 3,551
Posted By Marc Bourget
It's not black magic. I watched an industrial...

It's not black magic. I watched an industrial arts teacher, (Don Pridham, author of the GPU Conversion book), laminate some plywood, drill holes for a home-made vacuum table, and, with a canister...
Forum: RV General Discussion/News 04-25-2018, 02:24 PM
Replies: 26
Views: 2,683
Posted By Marc Bourget
First, I'm away from my reference material. I've...

First, I'm away from my reference material.

I've seen many installations where the mass flow to the cooler is choked off by a long SCAT hose, or other things that defeat flow.

Have you checked the...
Forum: RV-8/8A 04-18-2018, 08:31 AM
Replies: 31
Views: 5,916
Posted By Marc Bourget
Tom said: " I have no proof, but I feel that if...

Tom said: " I have no proof, but I feel that if you get your outlet air flow in the right direction, the outside air may even help to pull the air out."

It doesn't, as there's nothing between the...
Forum: Alternative Engines 04-09-2018, 05:24 PM
Replies: 47
Views: 6,170
Posted By Marc Bourget
I looked at the Eggenfelder efforts some years...

I looked at the Eggenfelder efforts some years ago and inspected his efforts at OSH and a local Sonex owner. One question Jan refused to answer was what investigation he made into modifications...
Forum: RV Building Tips/Techniques 04-06-2018, 03:11 PM
Replies: 9
Views: 1,125
Posted By Marc Bourget
Lot's of good points, above. I think I spent an...

Lot's of good points, above. I think I spent an average of 15 minutes or so just on riveting in my Sun'nFun and Air Venture sheet metal forums. So many points popped into my mind reading this...
Forum: RV General Discussion/News 03-27-2018, 05:39 AM
Replies: 19
Views: 1,540
Posted By Marc Bourget
Talking Check the spec sheet to verify from what surface...

Check the spec sheet to verify from what surface or plane you measure the length of a flush vs. brazier head rivet :D
Forum: Traditional Aircraft Engines 03-26-2018, 02:15 PM
Replies: 13
Views: 1,615
Posted By Marc Bourget
Michael, I think he meant moving the ramp a...

Michael,

I think he meant moving the ramp a short distance away from the cylinder (at about the midline of the cylinder?) but I believe he kept the baffle tight towards the "6 O'Clock" position or...
Forum: RV General Discussion/News 03-19-2018, 09:17 AM
Replies: 11
Views: 950
Posted By Marc Bourget
Didn't remember this when I first viewed the...

Didn't remember this when I first viewed the thread.

A definitive NACA Cooling report described placing something like 34 Thermocouples on the downstream side of the cylinder. Interesting but...
Forum: RV General Discussion/News 03-15-2018, 08:07 AM
Replies: 5
Views: 781
Posted By Marc Bourget
Bill, If you meet the pressure differential...

Bill,

If you meet the pressure differential specs for the engine, you should get the necessary mass flow.

As far as inlet size, if properly designed you should experience little, if any, increase...
Forum: RV General Discussion/News 03-09-2018, 08:13 PM
Replies: 13
Views: 1,672
Posted By Marc Bourget
Talking That might be an "apples vs. oranges" point, but...

That might be an "apples vs. oranges" point, but I agree yours is a more accurate technical description.

There was a "How it's Made" episode that described submersing formed ribs in a salt bath as...
Forum: RV General Discussion/News 03-09-2018, 07:10 PM
Replies: 13
Views: 1,672
Posted By Marc Bourget
The benefit to be gained from “icebox rivets”...

The benefit to be gained from “icebox rivets” (2024) is achieved when you alter (expand) the rivet spacing to take advantage of their greater strength. Almost irrelevant in structure designed for...
Forum: RV-7/7A 03-04-2018, 06:25 PM
Replies: 5
Views: 900
Posted By Marc Bourget
I think you can go larger than 2.2" if you design...

I think you can go larger than 2.2" if you design the intake opening correctly, Same as for cooling intake.

With engine intake, a superior installation would have a smooth intake duct with...
Forum: RV-7/7A 03-04-2018, 06:20 PM
Replies: 6
Views: 764
Posted By Marc Bourget
I think it is easy to assume the baffles are...

I think it is easy to assume the baffles are identical by appearance, but are they identical in Delta-P?

Hook up a manometer to each and verify they perform the same.
Forum: Interiors 02-27-2018, 08:50 AM
Replies: 22
Views: 4,661
Posted By Marc Bourget
I recall an article about sound proofing. The...

I recall an article about sound proofing. The author installed sensors in all the panel areas (between bulkheads and stringers for example) turned out just a few panels generated the majority of...
Forum: RV-14 02-13-2018, 08:05 AM
Replies: 20
Views: 1,997
Posted By Marc Bourget
IMHO, the differing amount of gap is a result of...

IMHO, the differing amount of gap is a result of incomplete execution of the "dimpling process." Technically, between the upper and lower skins when joining sheets and a special angle (110 deg)...
Forum: RV-14 02-12-2018, 08:37 AM
Replies: 20
Views: 1,997
Posted By Marc Bourget
Keep in mind, "so it lays flat" means no more...

Keep in mind, "so it lays flat" means no more than .002" between the countersunk member and the dimpled skin."
Forum: Traditional Aircraft Engines 02-06-2018, 07:58 PM
Replies: 13
Views: 1,537
Posted By Marc Bourget
The 4130 part was a safety piece. If the flange...

The 4130 part was a safety piece. If the flange failed, it kept the propeller with the aircraft. The spacer was used to stiffen the flange as an assembly with the intent of not needing the safety...
Forum: Traditional Aircraft Engines 02-05-2018, 05:51 PM
Replies: 13
Views: 1,537
Posted By Marc Bourget
The 0-290G the Lycoming GPU had a thin flange...

The 0-290G the Lycoming GPU had a thin flange because all it had to do was drive a pretty much immovable alternator.

When John Thorp started converting the GPU for the T-18 project he advised...
Forum: RV Building Tips/Techniques 11-25-2017, 09:02 AM
Replies: 20
Views: 2,545
Posted By Marc Bourget
Slightly swelling a rivet is helpful in assembly...

Slightly swelling a rivet is helpful in assembly when skins (particularly "formed" shikns) don't fit "exactly."

You can either pre-swell, or insert and "swell" (takes practice). Then follow up by...
Forum: RV-7/7A 11-25-2017, 08:54 AM
Replies: 17
Views: 2,850
Posted By Marc Bourget
I'd do some dimples in a piece of scrap and see...

I'd do some dimples in a piece of scrap and see how they "fit" in the CS.

Should be less than .002" between the skin and spar. (If more, too shallow of a C/S. If it "slides" or "wiggles" C/S is...
Forum: Traditional Aircraft Engines 09-29-2017, 01:30 AM
Replies: 18
Views: 2,952
Posted By Marc Bourget
An unmentioned issue is what is the proper way to...

An unmentioned issue is what is the proper way to check the crank.

A friend of mine is a long time auto engineer. He was on several initial design team for new OEM engines in Detroit.

The...
Forum: RV-14 07-05-2017, 11:09 PM
Replies: 8
Views: 1,477
Posted By Marc Bourget
No smilies when you keep things under control and...

No smilies when you keep things under control and in alignment. (i.e., if you don't over-drive)
Forum: RV-10 06-04-2017, 10:16 AM
Replies: 4
Views: 723
Posted By Marc Bourget
I was taught, (and teach in my sheet metal...

I was taught, (and teach in my sheet metal seminars) by men who'd learned their trade in the WW-II factories in So Cal that if you're matching parts, you drill holes with a 1/8" or .125 drill, at,...
Forum: RV-7/7A 05-01-2017, 07:46 AM
Replies: 22
Views: 4,688
Posted By Marc Bourget
Will somebody favor me by posting a picture of a...

Will somebody favor me by posting a picture of a "pillow effect"?
Forum: RV General Discussion/News 04-24-2017, 10:23 AM
Replies: 32
Views: 4,167
Posted By Marc Bourget
I like to cover my benches with the "original"...

I like to cover my benches with the "original" Astro-turf, not the carpet "grass".
Forum: RV General Discussion/News 04-24-2017, 10:13 AM
Replies: 1
Views: 751
Posted By Marc Bourget
Although some would venture there are as many...

Although some would venture there are as many approaches as aircraft, at some point, the baffles are best placed in contact with the fins, although some use high temp adhesive to reduce chafing,...
Forum: RV General Discussion/News 04-24-2017, 10:09 AM
Replies: 8
Views: 2,145
Posted By Marc Bourget
I agree, but considering the external...

I agree, but considering the external environment and the fact that the relatively low pressure in the bottom half of the cowl and low flow volume from the hinge gaps is faint by comparison with jet...
Forum: RV General Discussion/News 04-23-2017, 09:47 AM
Replies: 8
Views: 2,145
Posted By Marc Bourget
Wonder if it's significant enough to worry about....

Wonder if it's significant enough to worry about. Seems the helical airflow from the propeller will cause more turbulence/drag than leakage from the cowl hinge.

Second thing is I do not believe...
Forum: RV General Discussion/News 04-23-2017, 09:42 AM
Replies: 32
Views: 4,167
Posted By Marc Bourget
You guys are missing a technique to fix a "factor...

You guys are missing a technique to fix a "factor " only a few pointed out.

You have to get some movement of the skin in order to drive the rivet. This will often lead to a depression like...
Forum: RV Ongoing Maintenance Issues 04-18-2017, 10:00 AM
Replies: 11
Views: 2,536
Posted By Marc Bourget
You have nothing to lose, Don't think the gear...

You have nothing to lose, Don't think the gear is heat treated. Why not try bringing the ring gear up to a dull red heat and let it cool to see if it will "heat shrink" enough to tighten up and...
Forum: California 04-16-2017, 12:56 PM
Replies: 11
Views: 2,176
Posted By Marc Bourget
I suspect that this is an attempt to verify...

I suspect that this is an attempt to verify actual cost of sale - suspecting the actual cost of sale is under reported.

CA BOE has an extensive, sophisticated process for "mining" data. I know of...
Forum: RV Ongoing Maintenance Issues 04-13-2017, 12:34 AM
Replies: 8
Views: 1,851
Posted By Marc Bourget
I believe that a significant factor in the...

I believe that a significant factor in the development of "smoking rivets" is poor dimpling/countersinking practice. It results in the dimples not "nesting" well, kinda like stacking tea cups, they...
Forum: RV General Discussion/News 04-13-2017, 12:19 AM
Replies: 12
Views: 2,984
Posted By Marc Bourget
Best to start with a sharp drill. Leaves less of...

Best to start with a sharp drill. Leaves less of a "burr" when the drill punches through.

Whether flat or dimpled, you want to debur the minimum amount possible, retaining as much of the...
Forum: Texas (South) 03-15-2017, 09:59 AM
Replies: 8
Views: 2,061
Posted By Marc Bourget
Gisnar said: "Typically, after welding, the...

Gisnar said:

"Typically, after welding, the properties near the weld are those of 6061-O, a loss of strength of around 80%."

I like Alcoa's "Forming Alcoa Aluminum" (in addition to "Welding Alcoa...
Forum: Texas (South) 03-15-2017, 12:19 AM
Replies: 8
Views: 2,061
Posted By Marc Bourget
I don't think 6061 goes "dead soft" upon welding....

I don't think 6061 goes "dead soft" upon welding. The annealing protocol for 6061 is not consistent with the heat cycling achieved with welding.

More likely, you'll achieve a "W" temper condition -...
Forum: Tools 03-04-2017, 12:07 AM
Replies: 11
Views: 1,969
Posted By Marc Bourget
Charlie, I'm understanding that you don't agree...

Charlie,

I'm understanding that you don't agree with my 110 deg statement?

If so, please re-read the first sentence to my post.

The skin, as it's dimpled "down" is stretched. Poisson's ratio...
Forum: RV-9/9A 03-04-2017, 12:01 AM
Replies: 5
Views: 1,915
Posted By Marc Bourget
Few observations: Sequence becomes more of an...

Few observations:

Sequence becomes more of an issue the older the rivet and thinner the skin(s).

Since the question applies to more than just the rudder mentioned, On some parts you have to worry...
Forum: RV General Discussion/News 03-02-2017, 11:34 PM
Replies: 51
Views: 9,004
Posted By Marc Bourget
I've seen installations where the breather tube...

I've seen installations where the breather tube is run down the landing gear and out the back of the wheel pant.

There appears to be sufficient separation that none migrates back to the tail...
Forum: Tools 03-02-2017, 11:30 PM
Replies: 11
Views: 1,969
Posted By Marc Bourget
The "bottom" of the dimpled skin is at a wider...

The "bottom" of the dimpled skin is at a wider angle than the 100 degree dimple die because the skin thins as it is stretched forming the dimple.

I second the observation about inadequate dimpling....
Forum: RV General Discussion/News 03-02-2017, 04:06 PM
Replies: 9
Views: 1,604
Posted By Marc Bourget
I began learning my sheet metal practices at John...

I began learning my sheet metal practices at John Thorp's Burbank shop from retired professionals from the WW-II Lockheed, Northrup and North American factories.

I've served as a Tech Counselor at...
Forum: RV General Discussion/News 03-02-2017, 03:57 PM
Replies: 9
Views: 1,604
Posted By Marc Bourget
I began learning my sheet metal practices at John...

I began learning my sheet metal practices at John Thorp's Burbank shop from retired professionals from the WW-II Lockheed, Northrup and North American factories.

I've served as a Tech Counselor at...
Forum: Safety 02-07-2017, 01:06 PM
Replies: 42
Views: 14,388
Posted By Marc Bourget
These lens shaped clouds are Alto-Cumulus...

These lens shaped clouds are Alto-Cumulus Standing Lenticulars (ACSL) and vertical velocities in excess of 10,000 FPM have been reported. What can’t be seen are the “rollers” that persist miles...
Forum: RV General Discussion/News 02-05-2017, 09:36 AM
Replies: 10
Views: 2,219
Posted By Marc Bourget
Advise you look at the cutting edges with a loupe...

Advise you look at the cutting edges with a loupe or inspection microscope?
Forum: RV Friends Who Have Passed On 01-21-2017, 09:14 AM
Replies: 27
Views: 18,701
Posted By Marc Bourget
Harnesses are a preventative device, they are...

Harnesses are a preventative device, they are not a "cure" No impact with the head is necessary. Recalling the fatal injuries to Dale Earnhart (sp?). The sudden deceleration caused a fracture...
Forum: RV General Discussion/News 01-10-2017, 05:45 PM
Replies: 61
Views: 16,762
Posted By Marc Bourget
Identifying criteria may be related to ensuring...

Identifying criteria may be related to ensuring no substitutes presented to the doctor. Use the info for verification/quality control back in OK.
Forum: RV General Discussion/News 01-10-2017, 12:53 AM
Replies: 28
Views: 6,178
Posted By Marc Bourget
Would appear to ba a lot of spanwise flow at the...

Would appear to ba a lot of spanwise flow at the tip on the Grumman.

IIRC, if you want "undisturbed air" you have to position the inlet about 18" ahead of the leading edge
Forum: RV General Discussion/News 01-07-2017, 08:24 AM
Replies: 12
Views: 3,199
Posted By Marc Bourget
JRS has it right. Add the "venturi" effect to...

JRS has it right. Add the "venturi" effect to low altitude winds aloft.

Here in California Central Valley, light winds at sea level can easily translate to 30+ at 10-12K over the Sierra's, and...
Forum: RV-10 01-06-2017, 08:36 AM
Replies: 11
Views: 2,759
Posted By Marc Bourget
For general information (I'm sure it's been...

For general information (I'm sure it's been raised before) Back riveting in commercial/certificated use isn't compliant without special procedures.

I understand this is related to poor...
Forum: RV-10 12-28-2016, 08:14 AM
Replies: 37
Views: 11,945
Posted By Marc Bourget
I don't recall the conversation exactly, but I...

I don't recall the conversation exactly, but I have a friend who was a member of the "core" engineering design group for several OEM engines.

We got to discussing crankshafts, including why/how you...
Forum: RV General Discussion/News 12-27-2016, 10:38 AM
Replies: 3
Views: 1,961
Posted By Marc Bourget
Have a HF SKU#?

Have a HF SKU#?
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