F19 Wing Spar Crack

[wesley2012]

This winter I have been looking for a Taylorcraft to purchase. My plan is to have it on floats so want a minimum of 85 horsepower. While inspecting an F19 recently I came across the following. In the right rear spar there is a crack on top on the end where the spar atttaches to the fuselage. See the attached photos. The first photos show the damage and the others are some I found online of a Taylorcraft wing being rebuilt that show what structure is in the vicinity of the crack. It appears that the nail through the first wing rib caused the split. I do not know how far the crack goes along the top under the fabric or down the vertical face of the spar.

I am interested in opinions on this crack. I have no experience with wood spars. My thought is a crack in the spar would require either repair or replacement, particularily in this location where the wing fastens to the fuselage. Anyone else seen cracking in this area? I greatly appreciate any and all guidance. Thank you.

Wes

[Hank Jarrett]

This is NOT uncommon. In even a LIGHT hit on the wing tip there is a lot of force on the root end of the rear spar. Look at the leverage generated and think about it for a moment. You push back on the wing tip and the wing tries to rotate around the front spar attach to the fuselage. That is a BIG LONG lever! As the wing tries to rotate it acts on a short lever between the front and rear attach points. The force of the original hit is multiplied by the ratio of the wing half span over the distance between the spars. Something has to give, and unfortunately what gives is usually the grain at the root of the aft spar where it goes through the bolt holes for the spar attach fitting. Those holes are stress risers that concentrate the load. That's why the spar attach fitting is bolted on at an angle. So the load doesn't have multiple stress risers on the same grain boundary.
The most common place for a split is through the bolt hole closest to the root end. I have seen several spars split this way and it is an area that should be looked at on EVERY annual and any time ANYTHING hits the wing tip pushing it aft. It is HARD TO SEE but well worth the effort. We found a split spar after a wing tip light hit a hangar door that wasn't opened quite far enough. The hit didn't leave a mark and didn't break the glass on the light but it put a nasty split in the rear spar!

Hank

[Ragwing nut]

It will require replacement. You could do a spar splice, but in todays world no one would want it.

[Hank Jarrett]

SAVE THE WOOD!!! The wood in old spars as BEAUTIFUL tight grain Sitka Spruce! You just can't find as good a wood as that any more. A spar with root end cracks may be good for a clip wing or a home builder. I have seen far too many cut up or burned!

Hank

[Scott]

This demonstrates the problem of butyrate dope and its continuous shrinkage throughout its life. It also shows a Taylorcraft weekness which is the design of the root rib.

(This also demonstrates that nails are adaquate for holding parts together while adhiesive cures, but should not be relied on for anything else!)

The fabric/dope has deformed the root rib, ripping the nails through the wood, and exposing the area to moisture. If your finger nail penetrates the wood, rot has already started.

If the wood is still sound and the damage from the nail does not progress further than what's visible in the photo, you could potentially repair and protect the area with structural epoxy adhesive.

What tends to happen is the moisture gets down to the attach fitting bolts and the spar cracks from the bolt holes to the root, under the plywood doublers. Check the wood at the root between the doublers. Any signs of cracks, or soft discolored wood there and the spar is pretty much done.

[Jim Herpst]

Scotts 5th sentence is key here. Going to be difficult to inspect the end without removing the wing and perhaps (hopefully not) some fabric.

[Mark Bowden]

+1 on both Scott’s and Jim’s comments.

What does it look like through the inspection access covers for this rib bay? Any evidence of damage outboard of the upper bolt? Bolt hardware looks new, when was the last recover?

I would suggest that further review is necessary before pronouncing the spar is junk and must be replaced based on two photos.

Why is spar splicing suddenly not an accepted repair.? Lot of wood spar aircraft flying fine with splices.

Is the wood in the crack soft or any dry/wet rot started? Was the aircraft always hangered? When was the last annual? Who did it, the owner, owner’s IA buddy or a shop you can go talk to? It doesn't look like something new.

Where the nail is located there is really no stress in this part of the spar. Stress is in compression outboard of the bolts in positive g loading. Even in negative g loading, not much if any stress here as stress is circular around the bolt out to the tangent points of the spar edges.

Load path is wood to bolts to fitting plate and to the bolt in the fuselage.

If the wood is sound in the surrounding area you could pull the wing and use a saw blade to remove the cracked area and bond in a tiny filler splice. Or just fill it with epoxy like Scott said. Leave the nail out. If the wood is soft based on further review, pull the wing, get in and remove the compression member, drag/anti drag wire and fittings. Then see if any rot extends to the bolt hole. Then determine a repair plan with your IA based on how far the damage goes outboard.

However, as a buyer you need to have the seller verify condition at their expense and have a repair plan and cost estimate prepared by YOUR shop and IA, not the owner’s so you can negotiate a sale price to offset the defect.
Or wait until the owner repairs it then buy it.

Either way she is grounded until further inspection to determine extent of the crack.

[Jim Herpst]

Mark,

Agreed . It would be great IF one can inspect this with out too.much angst. Then upon the findings hopefully remove the offending nail and fill with epoxy on move along. I do believe many spars have been needlessly replaced "see my sermon rant"

[Ragwing nut]

Mark,

Agreed . It would be great IF one can inspect this with out too.much angst. Then upon the findings hopefully remove the offending nail and fill with epoxy on move along. I do believe many spars have been needlessly replaced "see my sermon rant"

Cracks are not repairable within a reinforcement plate per AC43.13. It would need spliced or replaced.

[Scott]

It may not be a crack. What's visible is local damage from the nail.

A small inspection mirror will allow the root end-grain condition to be checked. If the varnish is in good shape and no evidence of cracks, the spar is probably salvageable.

Frankly the most likely showstopper is at the aux tank strap location. Not a good design and compression damage to the spar in this crtical area results from over tightening the straps.

[N96337]

At the very least, pull the fitting and get a good look at this. Like Mike said, cracks aren't repairable. If it's a gouge, it's repairability is questionable. I'd want some paperwork if I was to want to sign off an annual. If you just fill and hide, that's definitely not good. Think of the next person that signs it off.
JH