Adding a provision for tie-down eye bolt

[pecanflyboy]

Adding wing tie-down receivers: F-1 with the sport (RV4) wing which was built with no provision to screw-in eye bolts. How hard is it to add tie downs receivers, or is there another way to tie down the F-1?

 

[Freemasm]

If I understand what you're questioning, it's in the drawings. Square extrusion mounted/drilled/tapped. Will look tonight if I get a chance.

 

[pecanflyboy]

If I understand what you're questioning, it's in the drawings. Square extrusion mounted/drilled/tapped. Will look tonight if I get a chance.

Thanks. Anything is possible. But, to install it according to the plans I'd either have to cut a large access or remove a skin. Just wondering if there is an alternative.

 

[Freemasm]

Thanks. Anything is possible. But, to install it according to the plans I'd either have to cut a large access or remove a skin. Just wondering if there is an alternative.

Forgive my lack of comprehension. Retrofitting the required sub-structure into an essentially completed wing is going to be quite the challenge, even if access holes were added. Sorry but I haven’t seen and can’t conceive of a solution I’d trust. Again my apologies for not grasping your predicament.

 

[andoman]

Is there any chance that the extrusions are installed but the access holes weren’t cut?
From an engineering standpoint: you mentioned tiedowns but not jack points. I think that, structurally, you need less for tying down than is needed for jacking up. If desiring jack point duty as well then proceed with caution.

 

[pecanflyboy]

Forgive my lack of comprehension. Retrofitting the required sub-structure into an essentially completed wing is going to be quite the challenge, even if access holes were added. Sorry but I haven’t seen and can’t conceive of a solution I’d trust. Again my apologies for not grasping your predicament.

That is exactly my predicament. Why is was not installed, I haven't a clue. There airframe is so clean, I don't see any other options but possibly making a fitting in the wingtip at the end of the spar.

 

[pecanflyboy]

Is there any chance that the extrusions are installed but the access holes weren’t cut?
From an engineering standpoint: you mentioned tiedowns but not jack points. I think that, structurally, you need less for tying down than is needed for jacking up. If desiring jack point duty as well then proceed with caution.

I need tiedown points. I typically jack from the gear.

 

[Freemasm]

That is exactly my predicament. Why is was not installed, I haven't a clue. There airframe is so clean, I don't see any other options but possibly making a fitting in the wingtip at the end of the spar.

I wouldn’t do that. Wings are basically meant for a distributed load. The spar extension out near the tip is only 032 IIRC. The resulting mechanical advantage associated securing your aircraft at the wingtips is pretty huge. A small amount of loading from wind, a prop blast, etc. would have an easy time permanent deforming the wing.

 

[pecanflyboy]

I wouldn’t do that. Wings are basically meant for a distributed load. The spar extension out near the tip is only 032 IIRC. The resulting mechanical advantage associated securing your aircraft at the wingtips is pretty huge. A small amount of loading from wind, a prop blast, etc. would have an easy time permanent deforming the wing.

Agreed.

 

[Freemasm]

OK. Assuming yours is the same configuration, I’m gonna say it shouldn’t be that hard.

I was able to get a small angle drill on the head of each bolt (drawing shows three but calls out four. Go figure) If you pre drill the extrusion with say #30 pilot holes and then xfer those pilots to the wing structure, you could upsize each from there. The longitudinal hole will be a be-yatch to drill straight but I believe very do-able; maybe cheat ever so slightly to the near side. Buy or borrow and angle drill with a small head and give it a shot. A little piece of mind = the weak point in the installation, in tension at least will be the aluminum threads where the tie down ring is inserted. Keep us informed.

Edit = I would have lost this bet BTW.

 

[PaulvS]

Here is a pic of the tie down point for RV-6 wing, probably applicable also to -4 wing. There are three bolts per wing and the position of the tie down bar will be determined by the position of the wing rib.

 

[David Paule]

..... There airframe is so clean, end of the spar.

I actually ran the numbers for that on my RV-3B and determined that the spar wasn't strong enough to do that.

Dave

 

[pecanflyboy]

Thanks, everyone. I have a game plan.

First of all, installing the tie down towards the wingtip is not a good idea. The spar is just a "C" channel in that area, with not enough structure to support a tie down.



I'm going to remove the tanks and install the extrusion between the front of the spar and the tank. I will install it close to the inspection panel for the aileron bell crank to have access to the back of the spar. I'll be using the Cleaveland Aircraft Tool threaded extrusions. I will be able to easily drill straight through the spar and install the extrusion with AN hardware.



Thanks Vince Frazier for the pics. I'll keep you updated.

 

[Norman CYYJ]

Thanks, everyone. I have a game plan.

First of all, installing the tie down towards the wingtip is not a good idea. The spar is just a "C" channel in that area, with not enough structure to support a tie down.

View attachment 99193

I'm going to remove the tanks and install the extrusion between the front of the spar and the tank. I will install it close to the inspection panel for the aileron bell crank to have access to the back of the spar. I'll be using the Cleaveland Aircraft Tool threaded extrusions. I will be able to easily drill straight through the spar and install the extrusion with AN hardware.

View attachment 99192

Thanks Vince Frazier for the pics. I'll keep you updated.

When you install them make sure that the tie down ropes don't run interference with the pitot tube. It might cause tou to learn a second language the first time you go to tie the plane down.