biton

Hello all,

I am in the midst of assembling the P-51D kit and ran into some trobule with the supplied parts.

While examining the 1/8" balsa fuselage sides against the side view plan, I noticed the upper edge is not straight (in both parts). It seems the parts fit OK to the wing saddle section but when pinned to the plan to aft section appears lower than it should be (it doesn't seem to be shorter but rathe displaced downwards by 3-4 mm measured at the end of the fuselage).

See attached photo. It demonstrates the aft section displacement when the fuse base is situated over the plan so the wing saddle fits the plan and the front edge aligns with the FRONT of F1 (as instructed in the manual in step 1 of the fuselage assembly).

Has anyone else encountered this problem ? how is it possible to assemble the fuse on a flat surface when the top surfaces are supposed to stay straight ?

Any information would be appreciated.
Biton

tschuy

My Feedback: (1)

What kit is it?

Cheers,

biton

GP P-51D 40 kit

goatboy

I have built quite a few great plane trainers for people over the years and have always found problems in either the plan alignment or bad die cuts I recently built a pt-60 that was terrible in the wood cuts. its possible that may be the problem. depending on humidity it could slightly alter the paper the plans are on.I would try to keep the alignment with the wing saddle as your point of reference, I dont claim to be an expert,but going on my own experiance. you might want to contact GP also. good luck!!

Daryl_y

I agree, If both sides match just line it up with the wing saddle and the front and you will be fine. Your fuse sides are probably cut correctly and it is the print that is wrong. I've ran into this problem a few times recently with a Lanier Shrike. As long as both sides are the same its really not a problem at all.

biton

Hey guys,

The problem in using the supplied parts is that I'm supposed to assemble the fuselage bottom-up so that the top surfaces (one of which is the stabilazer base) are placed on the building surface and the fuse sides are attached to them. Since the parts' top edge is not straight I won't be able to connect them to these surfaces correctly (unless I try to bend the sides which is extremely difficult).
What do you say ?
Biton

R8893

My Feedback: (20)

Biton,
Warpped wood is not uncommon in kits. In this situation what I would suggest is that you trim the top edge of your wood straight and then add back a piece of wood to make up for what you cut off. Then use a good staight edge to align the top of your fuselage.
Chuck

paladin

My Feedback: (9)

Biton, I've built two of these kits but that makes no difference here. Wheather the wood is warped or smaller than needed is also in consequetial. Where it is located is also unimportant. The most important thing is that the stab and wing keep the same relationship to one another. Now the delta you show in your picture will easaly trim out on the maden flight. Also are you sure that your plans have not expanded? It is very commomn for bond paper to expand and contract with humidity. Now that would allow plans that have been roled to expand on the ends (because the outside layers will absorb moisture) making any plan long parts look warped. That is why you should tape the plans down on the work bench overnight before building on them. I cant tell you how meny times I've come back the next day and the plans are buckled from the expansion.

Now I'm trying to remember but I believe this model has ply inserts that are placed in the balsa fuse sides. If so mount them where they should be. Now that means checking the angle of attach for the stab and the wing from the plans, then checking the final product (the stab should be 1/2 to 1.5 degrees negitive to the wing). Once the relationship of wing to stab is known exactly where it is becomes unimportant as long as the relation ship is maintained. That means you can add material to the area in question or remove it its all up to you and what you feel is the best way to do this taking your scale fidelity need and strenth of assembly in to account.

Good luck its a grest flying plan!
Joe

biton

Hey Joe,

Thank for the info.

The strange thing is the top edge on the plan is perfectly straight. Its hard to believe that the plan has expanded in such a way to produce that result.
Its the fuse sides that are not straight. This causes a few problems :
1. Attaching the part to the plan so its in good fit.
2. Edge gluing the bottom section to the fuse sides (both 1/8" hard balsa).

You're right - there are doublers that attach to the inner sides of the fuse sides (also hard balsa). The doublersreinforce the sides in the wing saddle section (I measured them against the plan - they fit perfectly).

What I am most concerned about is what will happen once I try to asemble the fuse UPSIDE-DOWN. It seems to me that since the stab base and fuse top are on the workbench the fuse sides wont attach to rear stab base because of the gap.
Could you elaborate a bit on how to determine the angle of attack from the plan ?
Thanks,
Biton

bayareajeff

Biton,
i just got a 1/2 finished kit from a friend, He has lost the Fuse plans. The Fuselage is half built. I was wondeing if you could do me a favor and measure how far the center line of the engine is from the top of the piece in your pic. (the top of the Fuselage side) I am running the engine inverted and want to make sure that I have it right. Thanks again..

Peace,

Jeff

paladin

My Feedback: (9)

Biton, In the old days they would write the angle of attack right on the plans. That ment the angle would be shown some how near the wing and stab. I’m pretty sure your stab does not have that so we will have to glean it. The stab is glued to the top of the fuse, the fuse initial assembly is built with the top of the fuse against the work bench. You said the top of the slab balsa is supposed to be flat and the slab stab glues directly to it, that tells me that the top of the fuse is parallel to the slab stab angle of attack. With that assumption you need to measure from the center of the LE to the top of the slab fuse sides on the on the plans. Then also on the plans measure the distance from the wing TE to the top of the slab fuse sides.

The measurements them selves are not important but the delta is! If you measure the cord of the wing on the plans using Sin of and angle you can find the angle of attack of the wing in relationship to the stab. This number can help you to trim the plane before the maiden flight. You know that you want to maiden with that relation ship between the wing and stab so with a incidence meter you can insure that. Now that does not mean the plane will be in trim from lift off your power choice will affect the final position. The model is built for a 45 engine if you put a 60 in it or anything more powerful than a 45 that will require the wing to reduce the angle of attack to achieve level flight.

Now that we know the angle of attack set up by the stab we can check our work once we get to that point in the build. For now you build the fuse as the destructions say, when it comes time to mount the wing you know what angle to mount it at. When its time to mount the stab you know its relationship to the wing and can set that in the assembly of that part by measuring and shimming. Weather the fuse side is twisted, or wavy or what makes no difference any more.

From what I saw in your picture I would build the model than set the stab angle when it is being attached after the wing has been attached.

I hope this helps? I usually have to show this in person.
Joe

Fragmentum

My Feedback: (8)

biton,

I am also building the same plane and have not yet started on the fuse but I will check my wood against the plan this evening and drop a note in here somewhere....

Don

bayareajeff

any Chance any one can measure the Vertical centerline of the engine for me from the top of the side??

Thanks...
Jeff

Fragmentum

My Feedback: (8)

Biton,

After checking my plan, my upper fuse side matches the plan almost perfectly. The tail end height is just a little wider than the plan, but better than a little narrow.
My suggestion may be to make sure your lines on the plan are straight, and if so, cut a whole new set of upper fuse sides and use what came in the kit as scrap.
The saddle 'notch' for the main wing seems to be the most important fit for the fuse sides, IMO....

bayareajeff,
Not sure exactly what measurements you need, but here is a pic with a steel ruller. The one inch mark is at the top of the firewall.
If you need a plan, you can buy one from Great Planes for $21.75 from here; http://www.greatplanes.com/parts/gpma0175pl.html

bayareajeff

Biton,

Perfect.. Thank you very much. I really appreciate it!


Peace,

Jeff

Fragmentum

My Feedback: (8)

Jeff,
The image was from me...

Anyway, you got the dimensions you need!

Fragmentum

bayareajeff

Fragmentum,
You are right.. Sorry about that.. I appreciate you doing that for me. Great idea about the ruler and all with the pic.
Sorry again for the name.. I just went up and copied the message and went out to measure and see if the marks were off - which they were... I apologize. .

Peace,
Jeff

Fragmentum

My Feedback: (8)

Jeff,
No sweat, my friend.
Let me know if ya need any further help.
Drop me an email or post here if your needy, OK?