North American ESO-7618 ("Jet T-28") to spec OS-141 (VTB Basic Jet Trainer)

[Jemiba]

Ok, ok, got several points wrong, most worrying to me is the overall length. For some
of those points, I would simply blame the model maker, e.g. the too long wind screen.
But what's strange to my opinion , is that although the 7618 actually would have been
smaller, than calculated by me, the landing gear in the manufacturers drawing actually
seems to be much smaller, than anticipated by me, although it should be just the other
way round, IF the T-28 landing gear would have been used. I checked this again using
a T-28 3-view, with wing chord as reference. I actually used 3 different drawings, in the
cut-out only one is shown, because results were the same. May it be, that it's a similar
case,as we had with the Douglas D-890/895/900 and others, where the reason for such
drawings seems have been to give exact dimensions, but not necessarily precise details ?
Nevertheless, thanks for sharing it .. could just have saved me some hours, if I had seen
it before, but exercising's always worthwhile !

 

[Tailspin Turtle]

Jemiba,

I've tried to create a three-view from dimensions and pictures several times, with poor results compared to a three-view from the manufacturer when I eventually came across one. Your drawing is much closer to correct than any I ever did. I am impressed.

 

[Jemiba]

Thank you !
Just let us put together the parts of this puzzle we now have:

- A manufacturers drawing giving very precise dimensions and maybe somewhat doubtful details

- Photos of a model,showing the general appearance and details like hinge lines, some panels and
so on. And at least two of them taken from the side precisely enough to allow for some estimations
of proportions of these parts (tail and nose/canopy)

- Precise drawings of the ancestor, the T-28, giving details and proportions of components.

I've checked the GA drawing and found it actually to be quite precise with regards to fuselage shape
and dimensions, but lacking precision with regards to overall height and the landing gear. Must admit,
that I was quite glad about the latter ! The top view is clinched and too short ! Comparison with
the T-28 shows (to my opinion), that the proportions of the rear fuselage (wing-tailplane distance)
were unchanged. The red lines in the "check" drawing just show the dimensions in scale, indicating
that height, ground clearance and wheel bas in the side view aren't shown correctly (green lines are
from comparison with a T-28 3-view). The front view isn't exactly the same scale !
In the latest version of my drawing, I changed the canopy (a little bit longer), height of the fin, span
of the tailplane, span and dihedral of the wing and size of the intake (considerably smaller). And some
minor details, like airbrake and others.
Well, I think, we've improved precision and SOURCEGRADE just by teamwork !

 

[Stargazer]

After looking at your new version I still get exactly the same feeling as with the previous one: it doesn't have the "feel" of the model and original three-view. I usually like your line art but with this one something just wasn't right... so I superimposed the "real" profile with yours just to find out what it was, and it turns out they are quite different:

1. Windshield is much smaller in your version that it actually is on the original plan.
2. Bubble canopy mount is wider in the original plan.
3. You've extended the shape of the nose well underneath the canopy, while the original drawing shows the air intake protruding over the fuselage.
4. Wing shape is completely different.
5. You've added a weird appendix underneath the tail which doesn't exist in the original plan.
6. You've given the rudder more width than it has in the original drawing.
7. The nose wheel seems way too large.
8. The nose wheel's hatch is further behind in the original design.
9. The dorsal fin is differently angled.

 

[Stargazer]

I have tried to stay true to the original profile view while integrating the various panels and details from your version.


Also I have considered that your calculations regarding the height of the landing gear are correct, BUT I have changed the nose gear because 1°) your nose wheel was as big as the main wheels (which didn't seem normal to me) and 2°) though sketchy, the original drawing showed a wheel axle that was quite different from yours. Presumably a not everything would have been kept from the Trojan, and when there's the weight of a jet engine involved, this is one of the parts that get redesigned; I have also kept the design of the main gear as original drawn but enlarged it a bit to correspond to the corrected height.

 

[Jemiba]

about 1 : Think you meant, that the windshield in the original plan is smaller, than in my drawing. To my opinion, the model shows it to be larger, than in the plan.
about 2: I compared it to the model, where to my opinion the pointed rear end shows it to be narrower
about 3: Model shows it to be different, I think.
about 4: Wing shape was taken from the T-28, but I will check it against other T-28 3-views.
about 5: “Appendix” recognizable in the photo of the raer fuselage of the model.
about 6: As point 4 taken from T-28 drawig, will check again.
about 7: Landing gear in original plan way too small ! The later marks of the T-28 got a larger nose wheel,
which I used for the Jet, too. the lines on the mode show, that the landing gear was te same, I think. I

used a profile from Squadron Signal N°89, but will check size of the nosewheel.

about 8: see point 7
abou 9: see point 6


I've the feeling, you are putting too much faith in the plan, which, as I already pointed out ,to my opinion was mainly a way to

show the dimensions, but not a production drawing. With regards to shape and details te model and the T-28 is a more reliable
source, I think, but discussion keeps us strong !

 

[Jemiba]

Not meant as bossiness and the last time I'll bother you with this type, but I got support from a forum member, sending me
better 3-views of the T-28 and giving additional clues (Many thanks, Stanley, hope your scanner didn't melt ! ):
- I modified the fin/rudder according to the 3-views from Steve Ginters T-28 book, the lower edge is somewhat different
and the rudder is wider.
- I checked the landing gear and especially the size of the nose wheel and actually for the USAF variants of the T-28 the nose
wheel was just slightly smaller, than the main wheels ...but : The USN versions got a smaller nosewheel with a high pressure
tyre to prevent bounces during carrier landings. Not sure about aircraft, that were used solely from land bases, so I have both
variants now, but at least the manufacturers drawing supports that version. I stayed with the attitude of the fuselage on the
ground given by tailspins drawing (somewhat nose up), the nose wheel leg seems to be longer, than that of the T-28. May have
been a modification, but I was pointed to the possibility, that due to the lower forward fuselage (compared to the T-28), the
attachement point/junction may just have been positioned lower in the forward fuselage.
- And I corrected the canopy length on the upper view, sorry, my mistake, I used the wrong aid line (Well spotted, Stéphane)

Not sure, that I met the "feel" of the model or manufacturers 3-view better now, but clearly both are different with respect to
several details and the latter is not precise with regards to dimensions and proportions. So I again was mainly clinging to the
model and the T-28, with the 3-view a most welcome aid.
Thanks again for support and participation !

 

[Stargazer]

Not meant as bossiness and the last time I'll bother you with this type

If we were "bothered" by this type, we wouldn't click on this page and therefore wouldn't read your prose or see your work Jens! Any contribution to the subject is most welcome. Your approximations, my mistakes, everything advances the topic! I wish though that for such topics, which can be found via Google or such as soon as anything is posted, there could be a "sandbox" kind of status to keep it out of the search engines! That was exactly my idea in creating two separate General Aircraft designations topics last month: one is a sandbox to exchange ideas, the other one is the "presentable" topic!

 

[Jemiba]

Principally a good idea, problem to my opinion, that it isn't accessible to all members then,
so you could lose worthwhile input, as I got here.
You know better than me, that reconstructing a project from incomplete sources in most cases
includes interpretation and so bringing in a kind of personal opinion. And that's why it will always
be debatable and probably there will be never a final solution, at least not until complete set of
manufacturers construction drawing appears.

About being bothered, well, sorry for that, was just kind of irony, will try to avoid it the next time,
or at least make this clearer by puting a smiley behind it .

 

[hesham]

Not meant as bossiness and the last time I'll bother you with this type, but I got support from a forum member, sending me
better 3-views of the T-28 and giving additional clues (Many thanks, Stanley, hope your scanner didn't melt ! ):
- I modified the fin/rudder according to the 3-views from Steve Ginters T-28 book, the lower edge is somewhat different
and the rudder is wider.
- I checked the landing gear and especially the size of the nose wheel and actually for the USAF variants of the T-28 the nose
wheel was just slightly smaller, than the main wheels ...but : The USN versions got a smaller nosewheel with a high pressure
tyre to prevent bounces during carrier landings. Not sure about aircraft, that were used solely from land bases, so I have both
variants now, but at least the manufacturers drawing supports that version. I stayed with the attitude of the fuselage on the
ground given by tailspins drawing (somewhat nose up), the nose wheel leg seems to be longer, than that of the T-28. May have
been a modification, but I was pointed to the possibility, that due to the lower forward fuselage (compared to the T-28), the
attachement point/junction may just have been positioned lower in the forward fuselage.
- And I corrected the canopy length on the upper view, sorry, my mistake, I used the wrong aid line (Well spotted, Stéphane)

Not sure, that I met the "feel" of the model or manufacturers 3-view better now, but clearly both are different with respect to
several details and the latter is not precise with regards to dimensions and proportions. So I again was mainly clinging to the
model and the T-28, with the 3-view a most welcome aid.
Thanks again for support and participation !

Well done my dear Jemiba.

 

[circle-5]

From piston radials to turboprop and turbojet: T-28 evolution in models from the manufacturer.

 

[hesham]

From piston radials to turboprop and turbojet: T-28 evolution in models from the manufacturer.

Wow,very beauty my dear Circle-5.

 

[Mark Nankivil]

Stunning! Thanks for sharing!

Enjoy the Day! Mark