Nose Cowl Problem....wont fit

[paul]

Nose Cowl is far too small to slip over former B1.
I would have to sand approx 3mm for the Cowl to fit, but as you can see there would be no balsa left
Same the other side
Any solution to this problem would be appreciated

Paul



P-40 Warhawk 500 Series

[Bill Gaylord]

When you sand the entire perimeter, a small amount will drastically reduce the circumference. You don't want to remove it all from one area, as the plastic cowl can flex a considerable amount to fit over the firewall profile. I've never encountered a firewall requiring anywhere near 3mm of reduction, as I remove material from the entire perimeter. I'm not sure if it's on every plan, but they do suggest a slight amount of sanding in the fitting process, which is preferred to the firewall being undersized. It allows for cleaning up any imperfections in the shape of the firewall, including making all the stringers even with the perimeter.

[Mitch]

Paul

I would continue to sand the fuselage... all around and evenly. Sometimes my stingers get very thin on the bottom. If that happens you can remove them, cut the notch deeper. and replace with new section of stringer.

It may be to late now but be careful NOT to trim back the plastic cowling too far, as it tappers quickly. I ussually leave that little curl, so I know I have the total diameter. When I test fit, I will continue to sand the plastic to remove that curl and get things smooth. When that happens I usually need to sand the fuselage just a bit more.

The good thing is you are dealing with wood. Keep sanding until it fits and replace with new stringers on bottom if necessary! Mitch

[Wildpig]

I"ve got to ask..... did you put the Former B1 in upside down? Just because the letters B1 are right side up, doesn't mean the part goes that way.

[solumn_eagle]

I"ve got to ask..... did you put the Former B1 in upside down? Just because the letters B1 are right side up, doesn't mean the part goes that way.

I've done that a couple times when I first started building Balsa wood kits. It's probably more common than people think, and definately a pain to fix...lol

[paul]

Thanks guys

The answer was staring me in the face, sand perimeter of B1 former,cut notches deeper and replace stringers
What a plonk I am

Building this one to fly, so no landing gear or dope will be applied. Read a thread somewhere, dope not needed. Not had the best of luck with dope, always looks splotchy
A sucker for cosmetic perfection

Thanks Again
Paul

[Phugoid]

Paul,

Going without dope isn't that wise IMO, especially given the dampness of the air here in blighty. All my models are to fly and I always dope the tissue. Doping won't stop the tissue going saggy in humid conditions, but in my experience stops the tissue shrinking any more than the controlled shrinking that you put in. Thus it serves to stabilise the structure avoiding future warps and wonkiness.

My own form with tissue is this:

I glue in to the frames with PVA thinned with water. I only use Esaki tissue, the stuff in the kits is usable but I think it takes up a lot of dope and does not shrink a lot (this can be an advantage on delicate structures however) Esaki is also lighter

Water (or "cold steam" on delicate parts) shrink, this process should get the tissue taught. You can locally shrink to get rid of wrinkles with some spit (a bit yucky, but it works) make sure you have flying surfaces pinned down when they are shrunk

Two coats of Banana oil, which is a very light and thin non shrinking dope, applied with a large soft brush. I only use shrinking dope if the tissue is not taught enough or some reason, or if the structure is stiff enough to sake the extra shrink. Again the flying surfaces must be pinned down.

To avoid the possibility of a white bloom or splotchiness, make sure the tissue is completely dry before you dope.

Most of the above is in the Cessna 180 group build.

IMO If you want your model to fly then put the structure on a diet rather than skimping on doping the tissue....

Andrew

[Mitch]

I agree with Andrew. I always dope my models. I believe it give the whole model much more strength as well. I use Lite Tissue from EasyBuilt and it comes in about 27 different colors, and is alot cheaper than Esaki. Whatever paper you use and however you seal it, I believe your model will... 1. Look Better 2. Fly Better and 3. Last Longer, Good Luck and keep us posted. Mitch

[joecrouse]

EVERY FRIGGEN P40 I have ever built has has that problem

I always wind up building a double thick firewall and a nose block to mount the plastic on, then cutting a modest sized hole for the rubber band pass through.

For the longest time I wouldnt build an P40 for this very reason.


Oh BTW Burt Rutan of Scaled Composites Is on CSPAN giving a talk.

[joecrouse]

EVERY FRIGGEN P40 I have ever built has has that problem

I always wind up building a double thick firewall and a nose block to mount the plastic on, then cutting a modest sized hole for the rubber band pass through.

For the longest time I wouldn't build an P40 for this very reason.


Oh BTW Burt Rutan of Scaled Composites Is on CSPAN giving a talk.

[paul]

Update.......

That was scary sanding the entire perimeter. managed not to replace any stringers, although it was very close.
Stringers now probably the width of a cigarette paper, but yet still feels strong.
Next build I think I will test Cowl against B1 former before adding stringers.
Then cut notches if need be,then add stringers. Don't want to go through that again.



Bit more sanding to top of Cowl

[Bill Gaylord]

Sounds good Paul. Thin CA is really good for strengthening those thin sanded stringers. I imagine you discovered that the cowl will stretch a bit also without cracking it, when fitting around the firewall. I've had to do that a few times, since I sheet some of these planes with 1/32" balsa.

[Walt]

I ran into the same problem but I used a different solution. I wanted to sand down B1 but I did not want to sand the stringers. So I used my notcher to sand just the B1. My notcher is made from a piece of 1/16 thick spruce. I just stood the fuselage on end on the building board and laying the notcher on its side on the board carefully sanded the former until I got a good fit. (my notcher doesn't have a stop and is flat on both sides) I only had to sand about .015 inch all around. I thus achieved a good fit and it gave me a ledge to butt the plastic nose cowl up to.

[Terevet]

I read the post by Phugold mentioning banana oil. Where can one purchase banana oil?

Terevet

[Bill Gaylord]

I read the post by Phugold mentioning banana oil. Where can one purchase banana oil?

Terevet

If you don't find out here, there are a few other forums with stick and tissue builders that would probably know. My place as of late is to post on the Flying Models Facebook page, since I'm already signed up there. I've met a few old time stick and tissue builders there.

I was just thinking of a good cowl fit solution, with my Edge 540 build. Mine was a bit different, since I had to inset plank the nose, so that I could sand away the sheeting applied afterward, and match the cowl. The inset planking alone would provide good sanding latitude for a tissue covered kit, make a nice looking nose on a warbird, and the added weight would not be a big problem as they generally require nose ballast anyway.