Why did the Royal Navy have to refit or condemn and scuttle most of the ships they captured from us during the American Revolution?

Why did the Royal Navy have to refit or condemn and scuttle most of the ships they captured from us during the American Revolution?
Lets face it, the facts of history are against Virginia and Maryland having a good reputation in regards to the construction and maintenance of larger trade and warships during the 18th century.
The more I researched what was the cause of this, the more confusion and misinformation I encountered.  As this is a big part of an upcoming presentation I felt it best to get my thoughts on paper. 

So, here in brief are the reasons why our ships were so terrible.

During the 18th century the plantations and the Glasgow/Liverpool/Bristol/London tobacco barons were not inclined to build vessels which were quick sailing ships or long lasting as those properties were not necessary for the trade that the Chesapeake vessels were employed in.  As a general rule the larger vessels followed the general lines of the West Indies traders built in Great Britain.  The colonial vessels built in the Chesapeake region were as a general rule in outward appearances similar to their British counterparts, but a lack of effort in their construction which would have allowed them to have longer service lives also set them apart.   Colonial vessels were most frequently built at the deep draft tobacco ports of the region such as Alexandria.  A vessel of 150-250 tons for the tobacco trade could be quickly and crudely assembled by a shipwright and crew of 75-150 men in three to four months from the time the keel was laid until the vessel was set in the water to receive deck planking, masts, and rigging.  

Often shipbuilders would use white oak which was not fully cured and still fairly green.  The quickness of the launch of colonial vessels was to prevent the ship from shrinking on the stocks.  Due to this the keel was quickly laid with poorly made table scarves held together by undesirable iron fastenings.  The transom and bow structure would be quickly laid, and whereas English vessels would have thick and sturdy deadwood rise blocks built upon the keel, colonial shipwrights often employed quickly and lightly built square blocking in the stem and stern rise.  These timbers were often held fast to these blocks and the keel by large iron drift pins, these however, were not for later structural integrity, but rather they helped these frames stay firm as the out planking was quickly wrapped around the hull.  The treenails, see Fig. 1, were quickly made on a sawhorse with a drawknife. Being sided treenails they often worked their way out of their fastening holes and needed constant attention and repair by the ships carpenter after launch.  

Once the roughly made hull was planked, her treenails, which had been left long all over the hull, would have been hammered home tight one last time, sawn off and the ship would have had its outer planking planed quickly flush.  The vessel was then quickly caulked, coated in a mixture of cow hair, tar, sulfur, and pitch.  Then a layer of sacrificial planking made of cedar or white pine would be affixed over with cedar nails.  All attempt was made to limit the exposure of iron fastenings to salt water.  The sacrificial planking helped protect the vulnerable white oak ships timbers from attack from the marine worms which would render an unprotected ship useless within a few months.

Once the lowest strake, the garboad was treenailed in place from bow to stern, prefabricated scantling sections would be  placed on the keel and garboard, often crudely notched with limber holes to let the water flow underneath them as these boats always leaked.  These pre-made sections would be quickly made by "rack of eye" and were made up of the floor timbers, first, and second futtocks held together longitudinally by drift pins.  For a 90 foot long vessel 7-9 of these pre-made sections would be placed in and held upright by leaned in posts as they quickly had their planking and ceiling treenailed on.  These scantling sections were not held to the keel by drift pins, but were allowed to float above the keel (Fig. 2)  

Often when a colonial tobacco ship was made, timber of undesirable shape would be used in the lower hull,  these areas would either be quickly trimmed off with a broad axe, or furring blocks would have to be added to cushion the hull planking.  In the center part of the ship as the planking and ceiling wrapped its way up the hull, loose futtocks would be treenailed in place to give the hull additional strength in a manner which is more similar to Dutch ship construction than English examples.  Whether this was due to a convergence in shipbuilding practices or that it was copied from Dutch vessels encountered by local shipwrights has yet to be illuminated.  

The ceiling and keelson would often be held in place by iron fastenings instead of being treenailed in place proper.  Often times the ceiling planking would only extend to the turn of the bilge.  As the hull was planked quickly the masts would be laid in the bottom of the boat before the hull was fully planked so that they could be raised with ease by block and tackle while the hull was in the water and having her decks finished.  

The fitting of  extra futtocks and frame members to the areas of the stern and bow rise would have made repair of the hull from within difficult Fig. 3.  While white oak trees could be found that were bifurcating, often times curving arms of oak trees would have been used blocking off access to the planking in those areas.  Once teredo or worm damage had occurred in these areas of a ship she was on the downhill side to being broken down.  The square blocking used in colonial vessels made the construction of drains and limbers in these areas problematic also increasing rot in the stem and stern.

Lastly, we need to discuss the life cycle of a colonial tobacco boat.  These boats were primarily employed in the direct tobacco and refined goods trade, or the triangle trade.  They returned to their homeports every 3-9 months, and were careened.  Careening was common throughout the Chesapeake and involved bringing the boat in on the highest tides to an area which had a hard sandy bottom so that a ships outer sacrificial planking could be replaced, her treenails could be tightened and repaired, and her roughly flat joint planking could be recaulked.  Royal Navy vessels and large English trading ships were often required to take much longer voyages with less access to careening yards.  Royal Navy vessels had beveled outer hull planking often with battens to hold their caulking in place.  This measure was almost never taken on American built commercial vessels Fig. 4.

All of the abovementioned construction deficiencies would have meant that for a colonial merchant vessel to get a broad arrow mark, she would have had to have been ripped apart piece by piece and put back together.  That is something the Royal Navy could not cost effectively do.  

I hope this answers some questions, and if you want send me an e-mail if you want to know where I have pulled this data from, both books and journal articles.

Best,

Jason