Thorp Air Command - T18.net

Deciphering the plans on Drawing 227. Called out are 144 AN470 AD 4-8 rivets between BL18.0816 and BL41.375

Does this mean there are 36 rivets on the top Spar Cap and 36 on the bottom angle cap at each end.

Thanks for the help

Rob

Rob
My DWG 227 only shows 18 rivets between BL18 and BL41. I may have an old set of plans. I was able to come up with 144 by counting the 18 rivets called out in my plans on the top cap (between BL 18 and BL41), and then I doubled that number to get 36 rivets across the top cap (for one side, I assume to address the smoking rivet issue). Then multiply 36 by 4 for each upper and lower cap to get to 144?

Im sorry, thats really not any help at all....

I know this thread is a couple years old, but I am currently building/assembling my inner wing and I have run across the same question. My inner wing skins and center upper/lower caps are drilled with the single row of rivets per S-18 drawing 227 (and drawing 200) how Rob explains.

When I look at my plans, however, the notes left by the previous builder (who seemed to be very knowledgeable) says the stagger pattern was for the T-18 wing (longer inner wing section?). The SDR does not specify whether it is specific to the T-18/T-18C/S-18. Reads, "Extra Rivets Added To Main Spar- Refer to T-18 Drawing A-532, -537, Newsletter# 49".

Is there anyone who has built both wings and can provide experience/advice? I have only seen one other S-18 that is local to me and it it built per plans and only has the single row of rivets per plans. Currently thinking for S-18 a single row is acceptable as designed.

Thoughts?

Rob
rv3maker
S-18 SN46 - building inner wing

I have built both T and S wings. Double row on each version. On the T, I had already single riveted the skins to the spar. A conversation with John Thorp assured me that beacause I had used .032 alclad on the inner wings, I could countersink the added row. I did and no problems after1500 hrs

_________________
Bob Highley
N711SH
SN 835
KLAL

I recommend a staggered double row.
Cubes

Staggered second row marked and drilled out with #40 drill bit. I will transfer drill to the already drilled skins with a #40 13" strap duplicater on each end and then cleco and enlarge to #30. Then remove skins and debur/countersink.

Some pics. Thanks for the inputs...onward!

RH inner skin fitted and staggered rivet holes drilled. Now to disassemble, debur, countersink and dimple.

And you made the skins wider than plans because you are fitting it on a T fuselage, correct?
Cubes

Hey Cubes,

Verified skins are width of S-18 drawing 200 (-1L/-1R). There is one minor difference I see at the outer flap mount bracket cutout. I may have to make a filler piece there - still assessing.

Fitting to a S-18 fuselage.

Rob

I could move this thread over to the S-18 wing section. Started here since I was initially discussing the added staggered rivet pattern on the spar caps.

Oh. Sorry. I thought you were fitting to a T fuselage. My bad.
Cubes