35-11: dimpling versus countersinking canopy deck parts

[TASEsq]

I was curious why the plans ask to dimple the 0.040” canopy deck parts. These seem fairly thick to dimple.

Does anyone know why?

For those that dimpled as per plans did they come out ok?

Did anyone countersink the canopy deck instead of countersinking the longeron?

[trying hard to ignore what’s going on and keep building - hoping it’s not for nothing!]

 

[Jetmart]

I dimpled mine as they called out very specifically to do so. Mine came out fine.
Not sure why they have you dimple it though.

 

[mc607]

I was curious why the plans ask to dimple the 0.040” canopy deck parts. These seem fairly thick to dimple.

Does anyone know why?

For those that dimpled as per plans did they come out ok?

Did anyone countersink the canopy deck instead of countersinking the longeron?

[trying hard to ignore what’s going on and keep building - hoping it’s not for nothing!]

I would say it’s to create a stronger joint along that area. A dimple locked in to a countersink is typically stronger than a countersink sitting on a flush surface. I practiced on scrap first and then dimpled it as per the plans. Came out fine.

 

[czechsix]

Dimple instead of countersink whenever possible

I was curious why the plans ask to dimple the 0.040” canopy deck parts. These seem fairly thick to dimple.

Does anyone know why?

My rule of thumb is always dimple wherever possible. Countersink only if dimpling can't be done.* Dimpling results in a stronger joint, almost always comes out looking better, and isn't prone to 'smoking rivets' like countersinking (where the rivet heads tend to move around as vibration takes its toll).

FWIW, I also dimpled the wing skins in the wing walk area and the fuel tank aft baffles on my -14. Came out way better than the countersunk skins on my -8 and was easier to do as well. These areas have been discussed in other threads...

*Note: one example on the -14 where you must countersink and not dimple is if you want to use flush screws in the lower empennage gap fairings. If you dimpled the fuselage skin for a #6 screw, you would then need to countersink the upper longeron for that dimple to nest into, and Van's told me that would remove a bit too much material structurally from the longeron. Instead, you first rivet the skin to the longeron, then countersink the skin/longeron in combination which results in less material removed from the longeron. This is covered in the plans although the rationale isn't spelled out.

 

[TASEsq]

*Note: one example on the -14 where you must countersink and not dimple is if you want to use flush screws in the lower empennage gap fairings. If you dimpled the fuselage skin for a #6 screw, you would then need to countersink the upper longeron for that dimple to nest into, and Van's told me that would remove a bit too much material structurally from the longeron. Instead, you first rivet the skin to the longeron, then countersink the skin/longeron in combination which results in less material removed from the longeron. This is covered in the plans although the rationale isn't spelled out.

I did think it was a strange way to do it at the time, but your explanation makes perfect sense now.

I went ahead a made dimple in some spare 0.040 and it actually dimpled fine. I did find when I did a couple of dimples in the canopy decks themselves as a test, that the edge deformed a bit and didn’t sit so nice against the skins, as it did prior to dimpling. So I just slightly broke the edges of the deck pieces.

With the Proseal installed under them, I’ll just smoosh them down tight using tape after the rivets are set and it should be good.

Thanks for all the assistance. Hopefully my finish kit order will work itself out and I will have a canopy to close against these pieces. Or I’ve just made the world’s most useless canoe.

 

[dmattmul]

Longeron protection

This area gets a lot of abuse getting in and out and mine received some ugly scratches. This seems to have protected it pretty good and easier to install before the interior (And canopy alignment plate) is installed.

https://www.amazon.com/gp/product/B092MN8WDF/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Lots of colors offered.

 

[TASEsq]

The thickness of the leather doesn’t affect the canopy closing at all?

I was thinking some prop tape might be the go.

https://www.aircraftspruce.com/catalog/cspages/3mproptape2.php

 

[rv12iS-builder]

Perhaps paint-protection film would work?

https://flyboyaccessories.com/products/paint-protection-film?variant=46474496311604

 

[dmattmul]

The thickness of the leather doesn’t affect the canopy closing at all?

I was thinking some prop tape might be the go.

https://www.aircraftspruce.com/catalog/cspages/3mproptape2.php

Not at all, if anything the seal was better. Clear film probably ok (3M) but you need to do it before you scratch it. It would be easier later on (If you scratch the leather or clear tape) to replace the leather I think but to date have not had to. (Yet)