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Door opening rebuild


Well Known Member
A number of months ago when I was working on the RV-10 Cabin top I cut the door openings to what I thought would properly fit the Mcmaster seals. However given some overzealous trimming I cut the bottoms about 1/4 inch to 1/2 too much and I don't have the recommended spacing from the cabin spacing to the inner door frame which should be about 1/4" gap all the way around.

I feel this is a multistage process the first being getting the lip depths where I want them to be. Here's a picture showing...

The Top is fine the side will take some very minor rebuilding <3/16th in some spots and the bottom needs a good 1/2" like mentioned above. My thought process is to get some cardboard or something semi rigid and put that around the entire back edge area. Measure and mark any area not to those specs. Then cover the cardboard with some non fiberglass sticking clear tape. Sand/scarf appropriately where I plan to do some rebuilding. Mix up some epoxy and milled fiber and build it up and out using the cardboard as backing. Once cured take the cardboard out and sand the edge to make sure it smooth and clean.

Next I want to build up the 1/4 thickness for the Mcmaster seal but also ensure I have the 1/4 gap between the frame and the door. Like this....

My thought on this is to use glass fabric and build up the area's that need it and sand down and possible build up on the backside area's that get thinner than 1/4". Some area's like the curve on the top are actually going to need to get built up by an 1/4 or so.

After all the spacing I imagine I'll have to micro and sand to get everything looking clean.

Another thought which I don't know if it would be 'easier' is to get some 1/4" Masonite and use 2-3" strips on the inner side of the door. Then mix up milled fibers and epoxy and put that down in area's that need to get built up and then close the door and let cure. Then I can go back and clean the edges and rebuild the backside using some seal as a form to build any depth of the lip I need.

Any tips or advice would be welcomed!

So looking for some advice on the best way to approach this. Right now what I'm thinking of doing is scarf the edges I need to build out.
Hi Justin,

Like you, I misunderstood how much needed to be cut back and cut too much. I've spent way to much time over the past several months correcting this mistake. Here's what I would do if I had to do it again.

- use scrap aluminum, excess fiberglass from the doors or whatever you can to make a flat surface to the door opening to build up a handful of layers in plane with the door opening. Build up ~5-6 layers of fiberglass cloth.

- I built up a 1/4" feeler gauge using a piece of angle aluminum. I just cut down and sanded a piece to have a 1/4" thickness. I used this to check the fit between the door and cabin top. Identified areas that were too close and sanded. Areas that were not thick enough and added a bit more fabric.

- Once I got this close, I'd sand the door opening to ~ the measurements shown on Ivan's site. Once happy with the opening edges, then I'd use the McMaster-Carr Seal, fill it with flox and press it on to the cabin top. Close the door and let the epoxy/ fabric cure. Also note that when you slide the McMaster-Carr Seal on, make sure that the edge nearest the door (the bulb edge) is flat against the cabin top so you don't mess up your 1/4" spacing.

- After the epoxy cures, remove the McMaster-Carr seal and sand/ fill wherever you need to to maintain the 1/4" spacings. You might need to redo a few areas but this should get you very close in a fraction of the time I spent!!

Happy to talk you through what I did if you want to PM me.
I did some of the original build up using the Mcmaster seal as a form as you mentioned. I may end up doing that, will have to start though with the sizing around the edge correct.
Installation tip:

It won't help Justin in this case, but for those of you getting ready to install your McMaster-Carr door seal and trim the cabin cover door flanges, this worked great for me to get a perfect gap all the way around the door: I can not remember the exact gap I needed but I'll use this as an example. IIRC, I needed a 5/16" gap to give me about 1/16" compression on the seal when the door was closed with the pins engaged. I used a 2" long piece of 5/16" square tool steel with a sharp pointed tip, closed and locked the doors and rested the scribe against the door and ran it around the a couple times. I filled the scribe line with a pencil to make the line more visible. Cut and finish sand to the line and it was a perfect fit and seal first time.
I'm approaching this step (still debating the McMaster-Carr seal at all if you want to know the truth) and would love to see a picture of the "square tool steel" scribe you mention. I'm not sure I'm visualizing your tip well.
That scribe probably would of worked out fantastic!

Eric's post about making some tools out of scrap aluminium got me thinking about what I could make to help out in this process. I decided to use some L shaped aluminium to make some gauges/sanders to use on the sides and top flanges. The idea is that one is 1" for the sides and bottom and the other is 1 1/4" for the top.

I also put some self adhesive 80 grit sand paper on the back which will help me get a precise size.

The fantastic news is with these gauges it's not obvious that I do have enough flange material that the only flanges I need to build up.. or out.. make taller are the bottom ones. So I did that last night.

I used some cardboard, painters tape and some clamps to reinforce the back. Then I make some fiber/epoxy "dry" so it was pretty thick and lathered it on. Then covered with peel ply and used another piece of cardboard to flatten it all out quite a bit. Went out a couple times after 30 mins and reworked it to push back up any that was starting to settle out. After a few hours went back out there and used some tape to pull the back cardboard piece to flare it out just a bit. Then used a small wooden block to again flatten out the front of it. This morning pulled the tape, molds and peel ply and it turned out nice. The back will take some minor sanding, I'll have to trim it to the 1" length and them clean it up a bit but over all happy with it.
I'm approaching this step (still debating the McMaster-Carr seal at all if you want to know the truth) and would love to see a picture of the "square tool steel" scribe you mention. I'm not sure I'm visualizing your tip well.

They are cutter blanks commonly used in a lathe. Anything that is metal and sharp would work. I happen to have an assortment of bits as I have a lathe. You do this step sitting in the plane with the door closed and pins engaged. You may have to cut some fiberglass first if your door hits the lip anywhere first. The door has a pretty flat surface and you place the tool bit flat on it and just rub the sharpened tip against the lip as you work it around the door to scribe a mark.
Just a quick follow up, yesterday I sanded the sides and bottom to 1" and the top to 1.25". Once that was all clean looking I put some 1" fairly thick fiber glass tape about 1/2" down the edges and covered with some peel ply. That tape should give some reinforcement to the edges, especially the bottom which I'm sure people will step on.

Also got the left door hung today and ran a little 1/4 gauge to see the spacing between the inner door shell and the cabin door flange. Happy to say for the most part I have the gap I want. My newly created bottom flanges and the corners on the top will need some building and the very top flange will need some sanding. Shouldn't be much of an issue at all.
Here's the close to end results-

Here's what I figured out in the process. Instead of doing the 1/4 thick lip and having to do a lot of building back up I instead ordered some new 3/16th grip McMaster seals and then sanded down everything to meet that. Now in doing this I also roughed up a bit of the back, hence the dry micro. Also 1" on the bottom was too tall, the PlaneAround Cam was pushing down on it, so I took a little more than an 1/8th off the top. So it's more like 13/16th tall vs a good inch.

I said close to end because I need to do some final sanding on all this and some general clean up and then I can repaint the inside. Actually have quite a bit of cabin top stuff I need to get done. Either way it turned out with a consistent 1/4 gap between the door and the flange which is what I was looking for.