Found, Surly LHT, Repair Help.

[Ajax Bay]

Question is how much would it change the ride of the bike by putting on a set of straight forks as opposed to curved ones that are on the bike? Best I can tell straight forks would shorten the wheelbase a cm or so.

If you wish to retain the steady handling characteristics for which the Surly LHT has a well-earned reputation, you need to try to find a fork with the same offset (some call this rake), that is: the perpendicular distance between the centre of the fork dropouts (before they were bent) and a (virtual) line drawn down the centre of the steerer tube. The shape of the fork blades doesn't matter (ie curved or straight) but its geometry will. If you choose a fork with a shorter offset, the handling will be more twitchy - fine for a racing bike but inappropriate for a touring bike, with or without a load. A longer offset will make the bike ride too steadily (tandem's have a long offset).

they used to think that longer fork trail was better for front end loading. This has been disputed in later years, and many people use short trail forks for touring now. It makes the bike more maneuverable, that's for sure

What is "longer" and what is "short"? Riding a Surly LHT, one doesn't want manoeuvrability, one wants steadiness, imo.
See my post from a while ago for more: https://www.cyclechat.net/threads/matching-fork-to-frame.205301/#post-4464435

 

[Gravity Aided]

What is "longer" and what is "short"?

Shorter fork trail is like many forks we see today, very little bend in the forks, almost with the wheel axle in line with the head tube. Longer has more curve, bringing the axle out in front of the head tube angle, and creating more wheelbase length thereby.

 

[Ajax Bay]

added to quote: "almost "with the wheel axle in line with the head tube

A bike with a fork (Edited "with the wheel axle [almost] in line with the head tube" will be borderline unrideable. Have a read of the other thread to which I linked (I've copied an extract below) and perhaps this compatriot site:
https://calfeedesign.com/geometry-of-bike-handling/

"There is a spectrum between 'twitchy'/fast response/racing and 'slow/stable response' (eg suitable for tandem) and the Tony Oliver graph of head tube angle (aka 'rake') against offset is the best representation I have seen. It shows limits of combinations outside which a frame builder/fork choice should only stray with due and deliberate consideration."
"A tandem must steer only where the handlebars dictate: you don't want a tandem to 'self-steer' like a road frame. The machine must not alter its line just because the stoker leans or sways when pedaling hard (say). Tony Oliver suggests that steep (73/74o) head angles are required, with longish offsets, typically 60-75mm. A road racing bike with 73o head angle would have a fork with an offset of 45mm to have steering which is neither too quick nor too slow. I hope this reproduction of the graph from Tony Oliver's book 'Touring Bikes' attached comes out."

As an exercise, perhaps you'd like to measure the offset of a few of your bikes. Just checked mine and the audax bike has 50mm offset and the 'racer' (1981) has 42mm but with a head tube angle a degree more.

 

[GrumpyGregry]

Buy some Surly forks, intended for the LHT. It's a no-brainer. DAHIKT

 

[Gravity Aided]

A bike with a fork like that will be borderline unrideable. Have a read of the other thread to which I linked (I've copied an extract below) and perhaps this compatriot site:
https://calfeedesign.com/geometry-of-bike-handling/

"There is a spectrum between 'twitchy'/fast response/racing and 'slow/stable response' (eg suitable for tandem) and the Tony Oliver graph of head tube angle (aka 'rake') against offset is the best representation I have seen. It shows limits of combinations outside which a frame builder/fork choice should only stray with due and deliberate consideration."
"A tandem must steer only where the handlebars dictate: you don't want a tandem to 'self-steer' like a road frame. The machine must not alter its line just because the stoker leans or sways when pedaling hard (say). Tony Oliver suggests that steep (73/74o) head angles are required, with longish offsets, typically 60-75mm. A road racing bike with 73o head angle would have a fork with an offset of 45mm to have steering which is neither too quick nor too slow. I hope this reproduction of the graph from Tony Oliver's book 'Touring Bikes' attached comes out." View attachment 466459
As an exercise, perhaps you'd like to measure the offset of a few of your bikes. Just checked mine and the audax bike has 50mm offset and the 'racer' (1981) has 42mm but with a head tube angle a degree more.

You forgot the critical word "almost"in your quote. Just thought I'd point that out, because it seems rather important to the verity of what was actually said.

 

[Ajax Bay]

You forgot the critical word "almost"in your quote.

Sorry - I should have included "almost" in your phrase I quoted.
I have amended the quote (above) and also edited my comment to suit.
Care to share, quantatively (ie mm or inches), what you mean by "short" "long" and "almost in line"? And what are the offsets* on a couple of your bikes?

*Perpendicular distance between two parallel lines: one an extension of the steerer tube axis and the other drawn through a dropout.

 

[Gravity Aided]

I would call racing geometry about a 40-45mm rake, and touring about 45-52 mm. That would put things on about a 50-60mm trail for road, 55-70 mm for touring, all depending on head tube angle and geometry considerations .

 

[mikeymustard]

Buy some Surly forks, intended for the LHT. It's a no-brainer. DAHIKT

https://surlybikes.com/parts/long_haul_trucker_fork
only $125 direct from Surly, so you might get them a bit cheaper if you look around.
It sounds like your free find is beginning to cost a lot of money , at least you'll have the satisfaction that you've saved the planet - twice (once from saving it from the tip and once from riding it); and you'll have learned some valuable skills on the way

 

[GrumpyGregry]

https://surlybikes.com/parts/long_haul_trucker_fork
only $125 direct from Surly, so you might get them a bit cheaper if you look around.
It sounds like your free find is beginning to cost a lot of money , at least you'll have the satisfaction that you've saved the planet - twice (once from saving it from the tip and once from riding it); and you'll have learned some valuable skills on the way

There's no such thing as a free bike