Endor

Hi all,

I have a World Models Zero 60-size plane with some tail structure problems. Basically, I need to get to the inside stringers/bulkheads to firm things up on in the LE area of the rear horizontal stab.

This is a fiberglass fuse (not sure if it's painted or gelcoated) that is VERY narrow... no chance of getting that far back into the tail section through the wing saddle. I need to cut an "access hatch" in the rear bottom quadrant and start surgery, then somehow replace the hatch or fix it up.

My questions are....

1) What is the best way to cut the access hatch if I'm trying to reattach it? I was thinking of just using a hobby knife to slowly work through it. A Dremmel cutoff disc would likely remove too much material, which may not matter depending on the answer to my next question...

2) What is the best way to reattach the hatch after surgery is complete? Options I can see are a) use some balsa triangle stock epoxied from the inside as a platform to screw it back onto the fuse, b) use some fiberglass cloth over the hatch and overlapping onto the fuse to permamently re-attach it, c) discard old hatch and create new one via cloth/epoxy. Option B and C are obviously more difficult since I want it to be a smooth surface... how do I do that? And how do I paint it once I'm done?

Sorry for asking such a basic question, just never worked on fiberglass fuses before and am afraid of messing things up... I have fixed FG cowlings before, though, so I understand some of the basics. Thanks in advance for any advice you can provide!!

flyierjon

im interested as to what people have to say on this topic as well!

Thanks all
Jon

saramos

One approach would be to cover the area with a sheet of monokote. Tape it down along the edges, don't try and iron it to your finished model. Next, lay 4 or so layers of 3 oz fiberglass right on top of the monokote. The monokote is acting as a parting film for the fiberglass. Once the glass has cured, remove it and the monokote from the plane. Now, when you make your access hole, you have a piece of fiberglass that you can cut a hatch cover from, and get a nice close fit. This would be easier than trying to cut out the access hole and trying to use the cutout piece for the cover.

I am using this technique on a hatch that I am making on my Spitfire ABS cowl. I did laminate the piece that was cut out to the inside of the new fiberglass hatch cover for a stiffer hatch. I also cut the fiberglass hatch cover slightly larger than the access hole, then used a mini rabbiting bit to cut a recess around the hole that the cover fits into.

In my case, this hatch will only be used during static display. To attach it, I glued two small blocks on the inside of the cowl, to which I epoxied a small steel washer. On the hatch cover, I epoxied two small rare earth magnets.

Scott

Endor

saramos, thanks, a good idea that I hadn't thought of.

However, I jumped the gun since I figured out that a hobby knife cut through the fiberglass with no problem. Plus, I found a decal that came with the kit (that, fortunate for me, I was too lazy to apply when building) that I can use to "cover over" my little hatch.

So, surgery is complete and now I have an square access hole that is about the same size as a standard servo cutout. I'm thinking the easiest way to deal with it would be to use a piece of clear Ultracote a little larger than the hole, glue it down and shrink it tight, and the decal over that to cover my handiwork.

Will a small piece of clear Ultracote stick to a painted glass fuse? A search here has returned mixed results.... some say yes and some say no. Thoughts?

saramos

I've never tried to apply Ultracote to a painted surface. I have applied opaic Ultracote to a primed surface, and it stuck very well. If you have some of the paint, you could paint a scrap of balsa and give it a test. I would suspect that the big question will be, how well will the paint hold up to the heat of the iron. Using a low temp film like Ultracote would probably work better than high temp Monocote.
Another question would be, what will the cosmetic results of ironing a clear film onto a painted surface? I have no idea on this.

Scott

Endor

I looked through my Ultracote stash (various colors from various planes) and found a light gray that matched the stock paint in that area almost perfectly, maybe a half-shade off. Since it's underneath the rear horizontal stab and somewhat "hidden", I gave it a try. Indeed, it stuck very well to the paint.... I was surprised myself.

So, after sticking it down at 225F and a bit of shrinking, all is good... barely noticable.

Thanks for your help and advice saramos. I will certainly use the Monokote parting film method the next time I need to get in that fuse... a great tip!