I am very interested in hearing details about extending the stern. Does anyone have a resource for reviewing this modification?
Pat
Stern Extension
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Pat Ross
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luigisante
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Stern Extension
Pat
I know that there is a write up of a stern extension in one of the old newsletters. I had all of the old newsletters at one time, but I lent them out for copying and they never came back. I think that Joe S. has a complete set and Mike Millerchip in England probably has a set. If they could dig out the old article, it is interesting. If I recall correctly, the author loved the extension and used a dagger-like, kick-up rudder under the extension instead of having a rudder hung off the back. It looked pretty cool as well.
Lou G.
I know that there is a write up of a stern extension in one of the old newsletters. I had all of the old newsletters at one time, but I lent them out for copying and they never came back. I think that Joe S. has a complete set and Mike Millerchip in England probably has a set. If they could dig out the old article, it is interesting. If I recall correctly, the author loved the extension and used a dagger-like, kick-up rudder under the extension instead of having a rudder hung off the back. It looked pretty cool as well.
Lou G.
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Pat Ross
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- Joined: Sun Jul 05, 2009 7:15 am
- Location: Panhandle Florida U. S. Gulf Coast
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Stern Extension
Lou,
I so agree with you and add one more mod to the extension with kick up rudder, a set of steps down tot he water. One cool boat.
Pat
I so agree with you and add one more mod to the extension with kick up rudder, a set of steps down tot he water. One cool boat.
Pat
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JoeWalling
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Stern Extension
Hi Pat,Lou and all
I have the article and the drawings for the referenced stern extension, sat in front of me. I also have some detailed pictures of a boat which this mod done and my local yard are going to embark upon the project on HUSH in the winter. Frustratingly, I have made the mistake of buying a new computer and my printer/scanner is not talking to it even though it is the same make (HP), so I can't upload and send to you at teh moment. I'll keep trying. Cheers. Joe
I have the article and the drawings for the referenced stern extension, sat in front of me. I also have some detailed pictures of a boat which this mod done and my local yard are going to embark upon the project on HUSH in the winter. Frustratingly, I have made the mistake of buying a new computer and my printer/scanner is not talking to it even though it is the same make (HP), so I can't upload and send to you at teh moment. I'll keep trying. Cheers. Joe
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JoeWalling
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- Joined: Sun Jun 28, 2009 1:33 am
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Stern Extension
I've managed to email this stuff to Ron. If you send me your email address I'll send to you also. Cheers.Joe
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Ron
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Stern Extension
The two diagrams or the stern extension are below - one in this message and the other following. I'm going to try to convert the 4 jpg based text pages to a doc file, or maybe a pdf.
Ron Marcuse
Telstar 28 #359 "Tri-Power"
Telstar 28 #359 "Tri-Power"
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Ron
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Ron
- Posts: 1136
- Joined: Mon Nov 24, 2008 6:15 pm
- Location: SW Florida
- Contact:
Stern Extension
I converted the 4 jpg images of typewritten pages (with x's and /'s typed over other letters to correct typing errors, and hand written changes) to a doc file. Hopefully we can get all of this onto the web site, but I'll try posting the doc file here. Tried a half dozen file types - none seem to work, so I'll try to copy it with the clipboard now - (some of the formatting may have gotten messed up by doing this). If anyone sees an error - let me know. I had to interpret some of the markings on the old typewritten pages, and some of it is not really english (as spoken in the colonies). The spelling checker really enjoyed doing this.
----------------------------------------------------------------------------------------------------------------------------------------------
How to modify a Telstar -- and why.
If we consider the design and development of the Trimaran over
the past half century, we find that the essential concepts haven’t changed. Each generation of designs being an improvement on its predecessor with a change of emphasis of certain functions. So the whole process has been one of gradual evolution.
Some designers have experimented with foils, both lifting and stabilizing, to replace the floats, but the current crop of boats still rely on the basic principles, culminating with the new breed of 60 footers which have beams of over GO ft. making them over square for the first time. The elegant parabola curves of the beams made possible now by technical processes denied to the early pioneers. All in the quest for yet greater speed.
Arguably, monohulls HAVE GONE THROUGH A REVOLUTION in the last decade with their ultra light displacement planing hulls, coupled to swinging keels which provide more efficient righting moments, and coincidently allow them to escape 'Froudes law' which is loosely translated as ',AWL x 1.3 max velocity in knots. So a heavy displacement sailing yacht of 36 ft. would have a potential top speed of 7.8 kts. The modern lightweights do well over 20.
In the middle 50's the Amateur Yacht Research Society CAYRS) was founded by Dr. John Moriswood and quickly became the forum for designers and theorists to exchange their ideas and express opinions. More importantly the results of experiments were published. The great dilemma at that time as recorded in the journals, was " How buoyant should the outrigged floats be?. Should the roll moment be around a very buoyant float, or should the roll moment be around the hull with a submersible float ?.) Both conditions allowing action to be taken to avoid a full capsize.
In America, Arthur Piver, Norman Cross and others favored the full buoyant float which could support the weight of the whole craft -
or nearly so. The overall beam was relatively narrow usually with a solid wing deck. The hull and floats having deep V sections, and when at rest both floats were deeply immersed, thus sharing the displacement with the hill.
Arthur Pivers 'Nimble ' being a typical example of this type.
In Australia, Jock Crouther, Hedley Nichols et al. favored the submersible floats, supported by fabricated beams, enabling the floats to be spaced widely apart. When stationary the hull supported the weight of the floats and beams, allowing the floats to just
'kiss' the water.
Jock Crutherss 'Kraken' being a typical example. The underwater
sections being semi circular - which for a given volume has the least wetted surface area.
The great debate was Finally resolved through practical experience. Paradoxically modern designs are an amalgam of both types. Namely floats that can support the weight of the entire craft, spaced
very widely apart, and just kiss the water when stationary.
It was appreciated that when the floats were set high relative to the hull, it brought great benefits when sailing. With just a few degrees of heel, the windward float lifts from the water and in one stroke reduces wave making drag and surface friction resistance by nearly one third. The wider overall beam allowing more sail to be carried giving a higher power to weight ratio.
A little theory
William Froude 1810-1879 an English Naval Architect, observed from his experimental work that the 'chief components of resistance to motion were „wave Formation, skin friction and separation resistance'
The friction resistance is computed from a knowledge of the wetted area and friction value, derived from towing planes of various lengths/widths at various speeds. Pressure disturbances exist where there are changes in curvature at the extreme bow and stern and at the shoulder of maximum beam.
Using thin sections sharply pointed at each end wave making was all but eliminated.
Separation resistance is the drag due to the backward pressure et the transom. If submerged, the water literally sucks backwards causing disturbing eddies.
When a boat with its transom extended below the waterline is speeded up until the stern 'clears' or exposed to the atmosphere, the backwash pressure and eddying disappear.
On a Telstar this phenomenon occurs, usually in high winds and whilst running. What joy!. Hands up all those owners who have experienced this.
So how does a Telstar fit into these postulates?.
It has to be said that the Telstar is a very pretty craft. Voluminous and safe and a credit to her designer. We know that Tony Smith used to race a boat called :Startled Fawn' a Fiver derivative, so it is
no surprise to see its influence. Buoyant floats and a wing deck. Thank goodness it has proper underwater sections. The big question
is 'Could it be modernized to bring it in line with current thinking*,joy Raising the floats and Extending the transom?,
Theoretically yes. The hull would sink lower to support the weight of: the floats - by how much - and the lower edge of the transom would have to be sited on the water line.
Knowing that Peter Silcox an ex Telstar owner had made these two modifications, I contacted him for his assessment. He explained -He raised the floats by Birches and extended the transom by 3ft.
Actually - he raised the front of the floats by 5 inches and the rear by 6 inches, by fabricating completely new brackets, increasing the overall beam by 2 ft. As she floated the hull settled about
2 inches deeper in the water, as to be expected. The new transom follows the lines of the hull until it just clears the water.
I questioned him on any improvement in performance, and could he quantify it?. He said and I quote:-
one day, we saw another Telstar approach us.
They hailed as we passed, but could not hear them. So, we turned round, and were easily able to overhaul them - and they were flying a spinnaker IIIII "
It was that statement that decided me to make the same modifications. and I do not regret it. (I did not however increase the overall beam.)
When I bought my Mk 1 I was told that the metal brackets would need replacing, sooner rather than later. They were quite rusty. One day, off old Harry, force 6 the lower porthbracked snapped. No big deal. The wing flexed a bit due to the side of the hull twisting, so we ran into Poole and beached her. We replaced two bolts from the wing bracket, and two bolts from the strut, and replaced them with eye bolts which we lashed together. We then proceeded to Weymouth. We were one of the marker boats for the Sailing speed trials, and after a week sailed back to the mooring at Emsworth in Chichester Harbour. There she sat over winter until I could get her ashore in thalspring, which says a lot for the integrity of the design.
I decided to make four modifications while I had the opportunity.
1/. Raise Floats by 6"
2/. Extend Transom
3/. Add kick up rudder
4/. Reshape existing centre board
1/. Raising the floats is very easy. Remove the nuts/bolts from the hinges. Slacken the nuts/bolts joining the brackets at deck level. Undo one end of the lower struts, block up float, retighten nuts using wedges to fill the small gap. Add a distance piece to the lower struts with longer bolts. Done!!.
2/. Extending the transom is also easy. (I did it the hard way by making a female mould which took twice as long as laying up the extension). There is an easy way, and cheap too, as described to
me by Chris Evans - an entrant in the Speed Trials. I saw his results. Screw or bolt three KEY battens to the hull - see drawing - making
sure the top two battens are aligned it the extreme edge of the straight side of the hull before it starts to curve. The third batten is fixed to the centre of the hull at the base. The trick
is to have distance pieces/washers the same thickness as the material
being used to make the template, ie: thin ply, lino, Formica, or even stiff card. Slide the template over the hull sandwiched between the batten up to the distance piece. Use one template each side, with the join at the bottom. Cover the inside of the template with parcel tape to prevent the "glass fiber" sticking. Another trick. With an angle grinder cut three or four slots in the transom, some 8"xl" to enable the laying up cloth to go through
the slots and bond to the hull, making a very secure fixing. Any gaps can be filled from each side later. Remove templates and make good. The actual 'false transom' is made from 9mm ply faced with layers of cloth either side. A 9" wide doubler is then added to accept the rudder fixings.
3/. Reshaping existing centre board. Easy to cut new profile with a hand saw. More difficult to shape to an aerofoil section. The problem was getting the centre board out. Mike Barnsley a Telstar owner explained haw to do it. Cut away the opening in the centre board casing, and the board can be lifted up. When reassembled
two cheeks can be glassed over the cut away sides and stiffened.
4./. Rudder as described by Mike Millerchip in the last Newsletter, but the choice is yours.
Any Questions?.
I can only say that prior to these modifications, I used to join the queue of yachts making For the Chichester Bar. Now I can overtake everything. The real test will come , when we come up against other Telstars, when it will be assessed by others.
We shall see!.
If you will forgive the presumption, I have it in mind to rename my Telstar - éclat.
----------------------------------------------------------------------------------------------------------------------------------------------
How to modify a Telstar -- and why.
If we consider the design and development of the Trimaran over
the past half century, we find that the essential concepts haven’t changed. Each generation of designs being an improvement on its predecessor with a change of emphasis of certain functions. So the whole process has been one of gradual evolution.
Some designers have experimented with foils, both lifting and stabilizing, to replace the floats, but the current crop of boats still rely on the basic principles, culminating with the new breed of 60 footers which have beams of over GO ft. making them over square for the first time. The elegant parabola curves of the beams made possible now by technical processes denied to the early pioneers. All in the quest for yet greater speed.
Arguably, monohulls HAVE GONE THROUGH A REVOLUTION in the last decade with their ultra light displacement planing hulls, coupled to swinging keels which provide more efficient righting moments, and coincidently allow them to escape 'Froudes law' which is loosely translated as ',AWL x 1.3 max velocity in knots. So a heavy displacement sailing yacht of 36 ft. would have a potential top speed of 7.8 kts. The modern lightweights do well over 20.
In the middle 50's the Amateur Yacht Research Society CAYRS) was founded by Dr. John Moriswood and quickly became the forum for designers and theorists to exchange their ideas and express opinions. More importantly the results of experiments were published. The great dilemma at that time as recorded in the journals, was " How buoyant should the outrigged floats be?. Should the roll moment be around a very buoyant float, or should the roll moment be around the hull with a submersible float ?.) Both conditions allowing action to be taken to avoid a full capsize.
In America, Arthur Piver, Norman Cross and others favored the full buoyant float which could support the weight of the whole craft -
or nearly so. The overall beam was relatively narrow usually with a solid wing deck. The hull and floats having deep V sections, and when at rest both floats were deeply immersed, thus sharing the displacement with the hill.
Arthur Pivers 'Nimble ' being a typical example of this type.
In Australia, Jock Crouther, Hedley Nichols et al. favored the submersible floats, supported by fabricated beams, enabling the floats to be spaced widely apart. When stationary the hull supported the weight of the floats and beams, allowing the floats to just
'kiss' the water.
Jock Crutherss 'Kraken' being a typical example. The underwater
sections being semi circular - which for a given volume has the least wetted surface area.
The great debate was Finally resolved through practical experience. Paradoxically modern designs are an amalgam of both types. Namely floats that can support the weight of the entire craft, spaced
very widely apart, and just kiss the water when stationary.
It was appreciated that when the floats were set high relative to the hull, it brought great benefits when sailing. With just a few degrees of heel, the windward float lifts from the water and in one stroke reduces wave making drag and surface friction resistance by nearly one third. The wider overall beam allowing more sail to be carried giving a higher power to weight ratio.
A little theory
William Froude 1810-1879 an English Naval Architect, observed from his experimental work that the 'chief components of resistance to motion were „wave Formation, skin friction and separation resistance'
The friction resistance is computed from a knowledge of the wetted area and friction value, derived from towing planes of various lengths/widths at various speeds. Pressure disturbances exist where there are changes in curvature at the extreme bow and stern and at the shoulder of maximum beam.
Using thin sections sharply pointed at each end wave making was all but eliminated.
Separation resistance is the drag due to the backward pressure et the transom. If submerged, the water literally sucks backwards causing disturbing eddies.
When a boat with its transom extended below the waterline is speeded up until the stern 'clears' or exposed to the atmosphere, the backwash pressure and eddying disappear.
On a Telstar this phenomenon occurs, usually in high winds and whilst running. What joy!. Hands up all those owners who have experienced this.
So how does a Telstar fit into these postulates?.
It has to be said that the Telstar is a very pretty craft. Voluminous and safe and a credit to her designer. We know that Tony Smith used to race a boat called :Startled Fawn' a Fiver derivative, so it is
no surprise to see its influence. Buoyant floats and a wing deck. Thank goodness it has proper underwater sections. The big question
is 'Could it be modernized to bring it in line with current thinking*,joy Raising the floats and Extending the transom?,
Theoretically yes. The hull would sink lower to support the weight of: the floats - by how much - and the lower edge of the transom would have to be sited on the water line.
Knowing that Peter Silcox an ex Telstar owner had made these two modifications, I contacted him for his assessment. He explained -He raised the floats by Birches and extended the transom by 3ft.
Actually - he raised the front of the floats by 5 inches and the rear by 6 inches, by fabricating completely new brackets, increasing the overall beam by 2 ft. As she floated the hull settled about
2 inches deeper in the water, as to be expected. The new transom follows the lines of the hull until it just clears the water.
I questioned him on any improvement in performance, and could he quantify it?. He said and I quote:-
one day, we saw another Telstar approach us.
They hailed as we passed, but could not hear them. So, we turned round, and were easily able to overhaul them - and they were flying a spinnaker IIIII "
It was that statement that decided me to make the same modifications. and I do not regret it. (I did not however increase the overall beam.)
When I bought my Mk 1 I was told that the metal brackets would need replacing, sooner rather than later. They were quite rusty. One day, off old Harry, force 6 the lower porthbracked snapped. No big deal. The wing flexed a bit due to the side of the hull twisting, so we ran into Poole and beached her. We replaced two bolts from the wing bracket, and two bolts from the strut, and replaced them with eye bolts which we lashed together. We then proceeded to Weymouth. We were one of the marker boats for the Sailing speed trials, and after a week sailed back to the mooring at Emsworth in Chichester Harbour. There she sat over winter until I could get her ashore in thalspring, which says a lot for the integrity of the design.
I decided to make four modifications while I had the opportunity.
1/. Raise Floats by 6"
2/. Extend Transom
3/. Add kick up rudder
4/. Reshape existing centre board
1/. Raising the floats is very easy. Remove the nuts/bolts from the hinges. Slacken the nuts/bolts joining the brackets at deck level. Undo one end of the lower struts, block up float, retighten nuts using wedges to fill the small gap. Add a distance piece to the lower struts with longer bolts. Done!!.
2/. Extending the transom is also easy. (I did it the hard way by making a female mould which took twice as long as laying up the extension). There is an easy way, and cheap too, as described to
me by Chris Evans - an entrant in the Speed Trials. I saw his results. Screw or bolt three KEY battens to the hull - see drawing - making
sure the top two battens are aligned it the extreme edge of the straight side of the hull before it starts to curve. The third batten is fixed to the centre of the hull at the base. The trick
is to have distance pieces/washers the same thickness as the material
being used to make the template, ie: thin ply, lino, Formica, or even stiff card. Slide the template over the hull sandwiched between the batten up to the distance piece. Use one template each side, with the join at the bottom. Cover the inside of the template with parcel tape to prevent the "glass fiber" sticking. Another trick. With an angle grinder cut three or four slots in the transom, some 8"xl" to enable the laying up cloth to go through
the slots and bond to the hull, making a very secure fixing. Any gaps can be filled from each side later. Remove templates and make good. The actual 'false transom' is made from 9mm ply faced with layers of cloth either side. A 9" wide doubler is then added to accept the rudder fixings.
3/. Reshaping existing centre board. Easy to cut new profile with a hand saw. More difficult to shape to an aerofoil section. The problem was getting the centre board out. Mike Barnsley a Telstar owner explained haw to do it. Cut away the opening in the centre board casing, and the board can be lifted up. When reassembled
two cheeks can be glassed over the cut away sides and stiffened.
4./. Rudder as described by Mike Millerchip in the last Newsletter, but the choice is yours.
Any Questions?.
I can only say that prior to these modifications, I used to join the queue of yachts making For the Chichester Bar. Now I can overtake everything. The real test will come , when we come up against other Telstars, when it will be assessed by others.
We shall see!.
If you will forgive the presumption, I have it in mind to rename my Telstar - éclat.
Ron Marcuse
Telstar 28 #359 "Tri-Power"
Telstar 28 #359 "Tri-Power"
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Ron
- Posts: 1136
- Joined: Mon Nov 24, 2008 6:15 pm
- Location: SW Florida
- Contact:
Stern Extension
I found a temporary place to store documents that can't be physically attached to messages in this forum. When our website is further along we will probably move everything there. Instructions to get there are located in the members only portion of the forum, in the Member Info Center. Sorry about that, but I'll probably be putting other things like member lists there as well and we don't want to grant access to the world.
Ron Marcuse
Telstar 28 #359 "Tri-Power"
Telstar 28 #359 "Tri-Power"
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Pat Ross
- Posts: 185
- Joined: Sun Jul 05, 2009 7:15 am
- Location: Panhandle Florida U. S. Gulf Coast
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