Bell XP-77

[stuart murdoch]

Guys,

I've been asked a question I can't answer, hope some of you can.

The Bell XP-77 was of wooden construction, there is little information available about the a/c.

The question I have been asked is was it built similar to the Mosquito or was it built as a frame sheathed in ply then over sheathed with metal?

What was the construction method used?

Stuart

[Juke]

Interesting !

Finns had also a plan to build Mosquitos with DB engines on it.

rgds,

Juke

[turbo_NZ]

Hi Stuart,

I got this from http://home.att.net/~jbaugher1/p77.html

The two XP-77s were finally delivered in the spring of 1944. Serial numbers were 43-34915 and 43-34916. The low-mounted cantilever wing had a single-spar structure with stressed skin. The wing and the fuselage were largely constructed of resin-bonded laminated wood. The tricycle landing gear was electrically-operated. The nosewheel retracted rearwards into the fuselage, and the main landing gear retracted inwards into wheel wells in the wing. The flaps were manually controlled.

Hope this helps,

Cheers
Chris

[stuart murdoch]

Thks Chris,

I had already tracked this down for my mate Sci Fi Bri the Intergalatic Womble.

He is assuming that the wing structures would be the normal construction method, but,
he seems to think that it was a monocoque structure on the fuselage but he is stumped with the "metal laminate skin" comment he has no idea if this was bonded on during or after the forming of the fuselage, any ideas?

If anyone can track down how this a/c was constructed, you would make a lunatic carpenter/cabinet maker very happy, and save my sanity trying to get answers about something I know squat about.
He is driving me crazy since I introduced him to warbirds in general, but now he has a thing about this a/c, he thinks its cute!!!!

Stuart

[Cvairwerks]

Stuart: From what I've been able to find over the years, Bell used essentially the DuraMold process to mold the exterior skins for the fuselage and most likely the wings too. It's basically a wet layup to full thickness in a female mold and then a male section is closed onto it. Steam at a carefully regulated flow is piped throught the mold sections to cure the resins. The skins are then bonded to bulkheads just like a big model airplane. BTW, mold halves are considerably larger than each skin section and weigh in the tens of tons each. Cold molding ala boat hull fabrication process would be a possible method to replicate the skins, but would require some testing to verify that they are reaching the necessary structrual strengths.
I'm slowly researching this too, as the Fairchild made extensive use of the DuraMold process.

[stuart murdoch]

cvairwerks,

I think the two of you are thinking on the same lines, the cold moulding process I am lead to understand was used by DeHavilland on the Mosquito or something else, not sure.
However another woodworking nut friend of his suggested that the fuselage could be made in three sections, firewall to aft of the cockpit, aft fuselage and finally tailcone, with bulkheads which would allow for the metal laminate to cover the joints.

According to Bri, the wings are the "simplest???" structure to fabricate, he goes into wood tech speak which is incomprehensible to the normal person, but feels that the internal structure would be similar to the norm with the ply leading edge being formed in a mould then laminated with metal, likewise the wing tips.

I am trying to get him to post on the board, then you guys could talk tech speak all day long.

Stuart

[Cvairwerks]

Stuart: If I remember correctly, the XP-77 was done with just two skins for the entire fuselage from the firewall aft. There was some sort of wing spar carrythru structure and then the two skins were slipped on and glued together over and to the ring formers at several fuselage stations. Think typical plastic model airplane construction...

The AT was done with four major skins with the front two going on over the wing center section and glued to the 4 or 5 built up ring formers that were bolted to the steel tubing structure. These two skins were light enough that one person could pick either of them up.
The section from the rear spar aft was done the same way, but with heavier skins and ring formers, as it is designed as a monocoque with a steel support structure for attaching and transferring the air loads from the tail.

If you can find a copy of "Revolutions in the Sky", which is a history of Lockheed aircraft prior to WW2, it has some great pictures taken on the Vega production line showing the molds and some of the details on how they were assembled. I've also got some stuff taken from different magazine articles on how the AT was built that shows more details. One of these days I'll get around to chasing the patent data on DuraMold for more of the technical stuff.

You woodworking pal may think the wings are easy, but just a rough count shows around 1100 individual pieces of wood in the two center section main spars.......spars that are nearly 30' in length! These things look like they were designed by Chicago Bridge and Iron and then had Grumman Iron Works to add some additional beefing.

[stuart murdoch]

cvairwerks,

Sorry if I made you think that Bri thought the wings were easy, he had assumed they were of "Normal" construction, spars, ribs etc.

I've passed all your info on to him, and hopefully I will get some peace at last.

Thanks for all the help

Stuart

[Jeffrey]

cvairwerks,
I've passed all your info on to him, and hopefully I will get some peace at last.

Thanks for all the help

Stuart

unless he's decided it's a "doable" project then you'll be hounded for parts for years!

mind you would be a nice little plane to make and a valuable addition to the warbird scene

[airnutz]

Stuart, You guys have probably seen these, but they may give Bri an
idea of what he's getting hisself into... NZ-tech Glyn Powells version of
cold-molding a new fuse for static display NZ2308
www.mossie.org/NZ2308.htm

Bri might be better off thinking about conventional former/ply-wrapped
surfaces. Lotta time on molds for a non-production machine. But then,
there are guys who molded the 109's for 2 flying aircraft and statics...
so I guess it's up to the dreamer and his pockets.

Are the 500hp Rangers even available? Maybe a scaled-down version
using a smaller Ranger, or the 250hp LOM inverted supercharged 6 as
a more modern and reliable alternative?

Have fun!

Last edited by airnutz on Sun Nov 21, 2004 1:08 am, edited 1 time in total.

[Cvairwerks]

Stuart: I may have confused things a little, but if Bri is talking about the XP wings being simple, then he would be correct. There is less wood in te entire XP wing than in one of the outer panels for the AT.

Airnutz: Ranger VL-770's are available, but they've been cheap when I've been cash poor and people want diamond prices when I have the cash to spare. The last two that I called about, the guy wanted 15K for the pair, new in the boxes and there were no log books or records on them at all. I missed a chance last year to pick up 3 of them for a total of 1800$, all new in the boxes but with no logs. Up to about 2K for an engine with no logs is about the realistic max you want to spend. You are going to have to do a complete teardown anyway so much more than the 2K and you are going to end up with a pretty expensive engine.


Craig

[stuart murdoch]

Hi Guys,
Just back from the Macau GP, marvelous street racing madness, lots of shunts but no serious injuries on the day, great fun, hangover now in remission mode.

Airnutz,

Yes, seen it, that's what got the nut started in the first place, he has built or was involved in building static replicas of WW1 a/c, I think for a movie that never got made, I'll have to find out.

Craig, thks for the info on engines, now I know I'm never going to get any peace at all.

Jeffery, Yes, he has decided it's a do-able project.

However in saying that he assumes it will take some considerable time to research the construction method, any alternative construction method, materials, etc.
So guys don't hold your breath, he's a perfectionist, hence the nickname
"Sci Fi Bri the Intergalactic Womble"

If it starts I'll let you know and try to post some pics.

Thks
Stuart

[STURMVOGEL 262]

I wish your friend all the luck with this unusual aircraft design
Sound's like a fun and game's project .
Great link too thank's , Last time I was down at Point Cook with the Aussie Mossie Lad's.
I told them about the dude in N.Z. and could he help making Aus Moss a flyer .
But they said no , we simply don't have the fund's to make it happen, Static, no running engine's and ten year's roughly till completion , Bummer .
Cheer's all, Tally Ho! Phil .

[airnutz]

bump

[visaliaaviation]

XP-77 has been a subject we've considered several times over the last twenty years, or so. Our thought was to use molded ply over internal framework for wing, which is pretty standard(ala Whittman tailwind etc.).

Fuselage could use a molded system similar to duramold process, which IIRC, is explained in goverment report from 1943 (can arrange a copy if one is truly interested), but more user friendly for a 1-off build. We were thinking vacuum bagging ply sheet over an undersized foam/glass form.

BTW- several years back, we had to wrap a sharp LE with 1/16" 90 deg. mahogany ply from top of spar to bottom of spar, when we discovered that "steaming", as is used by boat builders WILL NOT WORK conveniently (less than 30seconds workable!) with large sheets of ply. However simply soaking each piece in water for three hours rendered it limp, puckery, andworkable for about 10-15 minutes. I have no doubt that considerable double curvature could be induced with appropriate molding. We found no advantage to using hot water vs cold(ambient) , but this took place in summer months. We used cargo straps to pull and hold it to a shaped leading edge form (constnt -no taper), but had to be carefull that it layed flat ,as it was quite easy to let a bubble to form btween straps during the strapping progress. When dry (24 hrs) the bubble would remain.

As for the aircraft itself,I have not heard that it was a metal bonded to wood structure. Corsairs DID use a metal over balsa sandwich in the tail feathers, I belive was called "Metal-Lite"(??). AFAIK, the XP-77 used metal only for hardware, cowling and spinner, etc.

Reliable data for the project is probably available. I would bet someone has it. A little digging may be in order. Persistence usually pays off. Try NASM. If all else fails, there is enough data available to reverse engineer a relatively close facsimile, using standard wood building practices.

The inverted V-12 Rangers engines are getting rarer, but are still around. I know of two still in their original crates. Be aware that these engines were fitted to a number of designs, but none too sucessfull.

A fellow named Robinson did fairly decent scale drawings which appeared in model mag some years back. It shows the airfoils and provides ordinates charts for root and tip. IIRC, a couple of articles regarding Bell and XP-77 have appeared inthe American Aviation Historical Society Journals over the years.

All in all, I feel an authentic FLYING reproduction XP-77 is well within possiblity for a serious homebuilder. Without guns it should have superior performance. Someone SHOULD do one!