RVators article about heating the skins

[papalima]

In the mid 90th there was an article in RVators about heating the skins before riveting.

Does anyone know which RVator and how I can get it?

Thanks!

[rlmccarter]

There is an article dated 2/93 titled "Heat Shrinking Wing Skins" discussing heating before riveting to give a tighter fit. It says if you heat a skin 80 degrees over a 48" span the free edges move 0.050".

Vans part number CD RVATOR 27 YEARS will get you years of RVAtor on CD.

[rbibb]

When I built my RV4 I riveted my wings with them sitting on saw horses out in the sun. They were plenty warm. When I built new ones years later I opted for my air conditioned basement.

Could discern no difference in skin ?tightness?

YMMV.

[Kyle Boatright]

Does that technique have any merit with prepunched skins? I can't imagine why it would...

[akabud]

.050? Are you sure it's not .005.

[Snowflake]

Unless you match-drilled them with heated skins, and kept the frame cool, i'd be surprised if you could have any effect on skin tightness. Once dimpled, the dimples will key each hole and prevent any significant shifting... That's kind of the point of a dimple.

[Kyle Boatright]

Originally Posted by Snowflake

Unless you match-drilled them with heated skins, and kept the frame cool, i'd be surprised if you could have any effect on skin tightness. Once dimpled, the dimples will key each hole and prevent any significant shifting... That's kind of the point of a dimple.

I can't imagine the self centering function of the prepunched holes isn't going to negate whatever skin growth comes from heating. My opinion is the ribs are going to flex that 0.00whatever so the prepunched holes match the skins when you're drilling to size.

[RV7A Flyer]

https://books.google.com/books?id=4d...ins%22&f=false

Put me in the camp that this is a silly thing to do.

ETA lists

CTE, linear 68°F 23.2 µm/m-°C 12.9 µin/in-°F AA; Typical; Average over 68-212°F range.
CTE, linear 250°C 24.7 µm/m-°C 13.7 µin/in-°F Average over the range 20-300ºC

for Al 2024-T4. The rather miniscule effect a perfectly managed (very) hot skin instantaneously attached to a cool substructure is left as an exercise for the reader.

[rvbuilder2002]

Skepticism aside, the influence of heating skins during installation is real. That is why it was featured in the RVator at one point.

Understanding this requires thinking about the physics involved.
The dimensional difference between a skin being loose or tight in any give rib bay is probably only a couple thousandths of an inch.
A couple thou can be tolerated between ribs without even noticing it when the skin is clecoed on (remember, when rivet holes get dimple countersunk, the hole enlarges slightly).

There is no difference between punched skins or traditionally drilled in place skins. in both cases the holes were put into all of the parts with the intent that they match each other.

The degree of difference noted will always be directly proportional to the high to low temp delta that the airplane operating in.
Example-
If the skins are riveted on when the shop temp is 40 F, when the airplane is parked out in the sun on a 100 F day, there will be a noticeable amount of looseness/oil canning when compared to my first RV that got the top skins riveted on with them sitting outside in the Arizona sun on an 85 F day (the temp delta is small).
Conversely, the wing skins on my airplane were like a Jamaican steel drum when the weather was cold.

What makes this work is for the heating to occur in a way that heats the skin more than the interior structure. If this occurs, the skin will always be tighter in any given temp condition than if it wasn't done. Think of it this way.... the interior sub structure is always in the shade under the wing skins. The substructure material will always be cooler than the top skins in any situation where there is any level of solar influence, and when there is not any, the skins will still be slightly tighter than they would have been otherwise.

Having said all of that, I would suggest the going to the trouble is not worth it for the majority of builders. There are many other things you can do more easily to assure a high quality finish (proper rib fluting and flange angle adjusting, proper quality dimpling, good riveting technique with a 2X gun, etc.). In fact I would suggest that if you are not sure you have all of these other details covered the best they can be, then heating skins is a total waste of time.
I would also suggest that you can cause yourself problems if you decide to do this and you do it incorrectly. I would not recommend attempting this in a cold shop and only heating a portion of the skin with a localized heat source.

[RV7A Flyer]

Originally Posted by rvbuilder2002

Skepticism aside, the influence of heating skins during installation is real. That is why it was featured in the RVator at one point.

Understanding this requires thinking about the physics involved.
The dimensional difference between a skin being loose or tight in any give rib bay is probably only a couple thousandths of an inch.
A couple thou can be tolerated between ribs without even noticing it when the skin is clecoed on (remember, when rivet holes get dimple countersunk, the hole enlarges slightly).

There is no difference between punched skins or traditionally drilled in place skins. in both cases the holes were put into all of the parts with the intent that they match each other.

The degree of difference noted will always be directly proportional to the high to low temp delta that the airplane operating in.
Example-
If the skins are riveted on when the shop temp is 40 F, when the airplane is parked out in the sun on a 100 F day, there will be a noticeable amount of looseness/oil canning when compared to my first RV that got the top skins riveted on with them sitting outside in the Arizona sun on an 85 F day (the temp delta is small).
Conversely, the wing skins on my airplane were like a Jamaican steel drum when the weather was cold.

What makes this work is for the heating to occur in a way that heats the skin more than the interior structure. If this occurs, the skin will always be tighter in any given temp condition than if it wasn't done. Think of it this way.... the interior sub structure is always in the shade under the wing skins. The substructure material will always be cooler than the top skins in any situation where there is any level of solar influence, and when there is not any, the skins will still be slightly tighter than they would have been otherwise.

Having said all of that, I would suggest the going to the trouble is not worth it for the majority of builders. There are many other things you can do more easily to assure a high quality finish (proper rib fluting and flange angle adjusting, proper quality dimpling, good riveting technique with a 2X gun, etc.). In fact I would suggest that if you are not sure you have all of these other details covered the best they can be, then heating skins is a total waste of time.
I would also suggest that you can cause yourself problems if you decide to do this and you do it incorrectly. I would not recommend attempting this in a cold shop and only heating a portion of the skin with a localized heat source.

Nobody is arguing the physics or the principles behind...just that unless done with a pretty extreme difference in temperatures between skin and structure (and that temp difference is *maintained* throughout the riveting process) that the effect is swamped by all the factors (flex in the substructure, size of the rivet holes, fluting, flange angle, etc., as you noted).