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Help! new guy replacing WD-403 weldments

F

flying4food

Member
Hello everyone.
My name is Mark, Ive been lurking around this site for years and now Im finally an RV-4 owner. We have an older (s/n 548!!) -4, with the original, weaker engine mount brackets in the fuselage. I recently found some very fine cracks around the bolt heads in the steel bracket, Weve grounded the plane untill these weldments are replaced.
From what Ive read, this is a fairly common problem. Is there anyone on this list who has replaced the WD-402/403 weldments with the new design, who can reccomend the easiest method of replacement. Im hoping I can do this without having to completly remove the engine mount/landing gear.
Any insight on this procedure would be greatly appreciated.
Thanks,
Mark Jimenez
 
cracks in weldment

I had the same problem with my -3, and what I did was to use a motor lift to take the weight off of the mount, and changed each one seperatly. It is still a pain in the butt, but at least you don't have to remove the motor.
Hope this helps!

Mike Bauer
RV-3 flying N87LB
RV-4 building N742MC
 
Thanks Mike

Thats exactly my plan so far. Looks like the only trouble spot will be the vertical row of three rivits covered by the engine mount. Thinking I will go back together with AN-3 bolts in place, or Cherry Max. Ill talk to Vans about it and try and post a pic of the final product for future reference.
-Mark
 
Weldement varients

Mark - I have never done what you are setting out to do, but I did look into the firewall weldements in some detail at one time. I think in the life of the RV4 there have been 3 different varients and I am just slightly concerned that the first varient is different to the later two in that the bolt/rivet layout is changed.

I suggest if you are talking to VANS you discuss that.

The current varient is shown here.

I hope I am wrong.

Good luck,
 
Hi Steve,
Thanks for the input. I have spent quite a bit of time at you site, Thanks for posting so much info, its really helpful. It looks like the biggest change (other than material thickness) is the "arms" along the logerons are welded together for additional strength. As long as all the angles are the same I should be ok. # of fasteners and general layout is un-changed. Im Just hoping the parts are not pilot drilled.
-mark
 
I just got the WD-402/3 with the kit, and there are no drilled holes in them. But your plane is probably in the order of two decades older than mine. Maybe it is an idea to also get updated drawings? to be sure they are the only changes worth doing on that part of the fuselage.

I am just thinking out load here, but if you only change the weldings without changing the bolt spacing *and* the cracks are *not* in the weldings themselves, then you are not really strengthening the structure by any considerable degree. If larger bolts are used with the larger weldings, this will be an entirely different matter alltogether. There are alot of possible changes that *could* have been done over the years that are not obvious by just looking at the parts, so a new set of drawings for that area is probably a good idea no matter what.

I agree with Steve, whatever you do, check with Vans first.
 
Mark, thanks for the kind words. It frustrated me that I could not find the pictures I wanted, hence my efforts. The trouble for you out there is that I sometimes march to a different drum!

Glad if it helps. Good luck with the weldements. Let us know how it goes.

PS Why flying4food. Does this mean you are also a commercial pilot, or foodaid, or.....
 
Hi Steve,
yes, Im a comercial pilot. These days I fly for a little more than food, but I have had that e-mail and screen name in various forums since I was a flight instructor, and in those days, it was quite accurate!
Ill post an update when Ive made some progress, Im sure I wont be the last one to have to replace these as the -4 fleet ages so hopefully this info will help streamline the process for everyone.
-mark
 
Weldments

Mark,
I just recently purchased an RV4 that had the old style weldments in it. Several other RV4s in the area recommended that I upgrade them due to me being a student pilot. Anyways....I'll walk you through the experience of changing the brackets, don't let the job scare you.

First you will have to find the proper jacks that will work. I used 2 tripod jacks positioned under the wings at the tie down nut with 2 dummy bolts in the tie down loop location. Keep in mind I did not put pressure on this until I had an engine cherry picker also lifting the motor. I lifted the gear off the ground a 1/4 to a 1/2". Keep everything neutral. I pulled all six motor mount bolts. Theres enough movement between the motor mount and the bump out on the fireway that you are able to shift the motor left or right so that you are able to get to the 3 rivids on the face of the firewall. Also you will need to be able to get at the nuts that are incapcilated on the bottom of the airframe. I removed the front D shaped caps on the front bulk head, approx 4 or 5 rivits. The new weldments do not come drilled so you will need to deburn fit them, prime and paint, etc. (After removing old brackets) I put the new ones in place using quick clamps pushing from the left to the right and pushing forward. I then took a dental pick and reached in from the bottom side of airframe and scribed the locations for the bolts in the bracket. Removed center punch and drilled. Reinstalled the brackets and bolted in place. I went through and drilled all the rivet locations, removed brackets, debured and reinstalled by bolting them first, and then riveting (assure that you are keeping the brackets pushed into place to eliminate loose fit between layers). Once the brackets are bolted in place and riveted, I went back to bolting the motor mount to the firewall. The two upper bolts were put in place, the two centers were put in place and I set up a drill bit with a bushing shoulder and drilled the two new locations for the lower motor mounts and reinstalled bolts.

Good luck. If you have any further questions email me or give me a call 320-587-1114.
 
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