Andy Hill
Well Known Member
We have just finished fitting / drilling the Rear Spar for the RV-3.
Rear Spars, particularly the setting of sweep and incidence, cause much stress to RV builders, with limited room to keep ED and get the wings set correctly - as urged by Vans after the earlier RV-3 issues.
Some RV-3B builders even suggest using an oversize (hence overweight ) spar to keep minimise the issues - given the lack of matched holes etc., it would seem a good idea e.g.
We approached this from the other direction:
Rear Spars, particularly the setting of sweep and incidence, cause much stress to RV builders, with limited room to keep ED and get the wings set correctly - as urged by Vans after the earlier RV-3 issues.
Some RV-3B builders even suggest using an oversize (hence overweight ) spar to keep minimise the issues - given the lack of matched holes etc., it would seem a good idea e.g.
Do not use the rear spar supplied by Vans! It leaves no room for error when you drill the wing attachment hole. After mounting the wing and drilling the hole I realized the hole violated the edge distance requirements by 1/16". It doesnt sound like much, but at least one RV-3 pilot has died as a result of rear spar failure. I recommend replacing it with a 2" wide piece. It only costs about 40 bucks, you will be glad you did.
We approached this from the other direction:
- We made the fuselage "slots" for the rear spar
- We clamped the rear spar into the fuselage to set the rear / front spar distance as measured from the wings, during fuselage construction
- We drilled the wings for the rear spar bolts as per plans i.e. with good ED
- Drilled one end of the rear spar for the bolt - again "in the middle" so no ED issues
- Fitted the wings, and trimmed the rear spar length so the wings could establish the correct sweep, then drew a line on the rear spar where the other hole should go
- Drilled this hole centered vertically in the spar.
- Lightly clamp the rear spar to the fuselage and adjust laterally until wings square, and vertically for correct incidence.
- With undersize holes drilled in the rear spar, match drill into the fuselage bulkhead
- Final Drill holes through rear spar fuselage
- (After priming, will rivet Rear Spar into fuselage) This should not be an issue - there is good access to set these rivets.